AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1244 AM EST FRI DEC 5 2008 .SYNOPSIS... OVER THE NEXT FEW DAYS A SERIES OF FAST MOVING SYSTEMS WILL INFLUENCE OUR WEATHER. A COLD FRONT WILL SLIDE OFFSHORE THIS EVENING. HIGH PRESSURE WILL BUILD INTO THE OHIO VALLEY FRIDAY AND DRIFT OFFSHORE SATURDAY...BUT PRODUCE A COLD FLOW OF AIR ACROSS THE GREAT LAKES. SATURDAY NIGHT AND SUNDAY A CLIPPER TYPE LOW PRESSURE AREA WILL RACE ACROSS SOUTHEAST CANADA...DRAGGING YET ANOTHER COLD CDFNT THROUGH THE REGION...AND BRING SOME LIGHT SNOW. SUNDAY NIGHT INTO MONDAY AN ARCTIC HIGH PRESSURE AREA WILL MOVE EAST FROM THE GREAT LAKES ACROSS OUR REGION. MIDWEEK A RATHER COMPLEX STORM SYSTEM WILL HEAD OUR WAY FROM THE TENNESSEE VALLEY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... OVERNIGHT PER THE RUC13 AND NAM12/18Z SUGGESTS THAT SHEAR WILL NOT ONLY CONTINUE BUT BECOME MORE NORTHWEST OVERNIGHT. THIS HAS RESULTED IN A SHIFT SOUTHWARD OF THE EXPECTED LAKE BAND AND WILL EXPAND THE ADVISORY INTO SOUTHERN HERKIMER COUNTY. THIS BAND IS EXPECTED TO LIFT NORTHWARD AROUND SUNRISE AND COULD POSE AN ISSUE ALONG THE THRUWAY MORNING COMMUTE. && .SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/... FRIDAY AND FRI NIGHT THE BAND FLUCTUATES BTWN 280 AND 250 DEG...PUTTING MUCH OF N HERKIMER AND W HAMILTON COS IN PERIODS OF LAKE EFFECT SNOW. THIS FIRE HOUSE EFFECT WILL KEEP THE EVENT FROM REACHING WARNING CRITERIA AS THE SNOW IS SPREAD OVER A WIDER AREA. AWAY FROM THE LAKES UNDER HIGH PRESSURE AND SUBSIDENCE FAIR WEATHER EXPECTED...BUT MOISTURE AND CLOUDS OFF THE LAKES WILL KEEP IT MORE PARTLY CLOUDY THAN CLEAR. FRIDAY NIGHT SFC RIDGE SETS UP FM MAINE TO W VA. LAKE EFFECT DIMINISHES AS UPPER SUPPORT ENDS...AND THE WHATS LEFT IS TURNED TWRD SAINT LAWRENCE VALLEY AS H850 FLOW BCMS SW. JUST ABOUT IDEAL RADIATION CONDITIONS FRI NT AND WILL TAKE MINS SEVERAL DEGREES BLO MODEL BLEND. SAT WILL START FAIR...BUT CLOUDS ASSOC WITH WAA AHEAD OF APPROACHING CLIPPER SYSTEM WILL MOVE INTO REGION LATER IN THE DAY. THE NAM IS SLOWER WITH THIS BY 3-6 HOURS...BUT BOTH MDLS HOLD PCPN OFF TILL EVENING. THE CLIPPER SFC LOW MOVES THROUGH THE E GRTLKS AS A SERIES OF 500HPA SHORT WAVES CARVE OUT A NEGATIVELY TILED TROF AT THAT LEVEL FM THE GRTLKS TO MID ATLC. FCA IS IN WAA AREA BETWEEN SFC LOW OVER E GRTLKS AND DEVELOPING OFFSHORE COASTAL LOW SAT NT INTO SUNDAY. THE MAIN OCCLUDED AXIS IS EAST OF FCA SUNDAY MORNING. HWVR THE GFS/NAM SHOWS CONTINUING WIDESPREAD -SHSN IN CAA MAINLY N & W OF ALB. WHILE CONDS IN LOWER LEVELS ARE NOT INDICATIVE OF LK RESPONSE INTO OUR AREA...(N-NNW FLOW)...THIS PCPN IS MAINLY DRIVEN BY THE STRENGTH OF THE 500 HPA TROF. NAM IS STILL A TAD FASTER ENDING THIS EVENT. MUCH OF AREA WILL SEE -SN...WITH AN INCH OR SO POSSIBLE VALLEYS AND A FEW INCHES IN HIGHER ELEVATIONS...PARTICULARLY ADIRONDACKS. THE ENSEMBLES HAVE TWO OUTLIERS THAT WOULD INDICATE A 6 INCH SNOW STORM...BUT THEY ARE OUTLIERS. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... SFC LOW PRESSURE SYSTEM WILL MOVE OUT OF THE AREA WITH A MOSTLY DRY BUT COLD SUNDAY NIGHT...LEADING INTO A DRY MONDAY TO START OFF THE PERIOD. MONDAY TEMPS WILL TRY TO BREAK FREEZING...WITH 850 TEMPS IN THE NEGATIVE TEENS. HIGH PRESSURE WILL BUILD INTO THE NORTHEAST ON MONDAY ALLOWING FOR MOSTLY SUNNY SKIES. THIS WILL QUICKLY BE FOLLOWED BY ANOTHER LOW PRESSURE SYSTEM MONDAY NIGHT. INCREASED POPS TO SLGT CHC AND CHC OVERNIGHT. GFS A LITTLE FASTER THAN ECMWF AND DGEX WITH ONSET OF PRECIP. GFS HAS H500 CLOSED LOW IN MANITOBA WITH A TROUGH OVER THE PLAIN STATES HELPING TO FEED MOISTURE THE SFC LOW MOVING TOWARDS TENNESSEE. THE H500 LOW WILL DEEPEN AS THE SFC LOW CONTINUES TO MOVE NORTHEAST...SPLITTING BY WED MORNING...BECOMING A DOUBLE BARREL CLOSED LOW SYSTEM. THIS COMPLEX SYSTEM WILL LEAD TO ANOTHER MIXED PRECIP EVENT. THIS DEEP LOW WILL ALSO BRING STRONG COLD AIR...WITH MAX TEMPS ON THURSDAY IN THE M20S. 12Z ECMWF HAS LESS COMPLEX SYSTEM...WITH SLOWER PROGRESSION...AND WARMER TEMPS FROM A MORE BROAD TROUGH. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS EXPECTED AT ALL TAF SITES THROUGH 06Z SATURDAY WITH MAINLY SKC CONDITIONS EXPECTED FOR THE REMAINDER OF THE OVERNIGHT PERIOD AS ANY LAKE EFFECT CLOUDS AND SNOW SHOWERS REMAIN WELL WEST OF THE HUDSON VALLEY. KGFL MAY EXPERIENCE SOME SNOW FLURRIES ASSOCIATED WITH THE LAKE EFFECT THIS AFTERNOON MAINLY BETWEEN 17Z AND 22Z AND WILL CONTINUE VCSH WITH NO SNOW ACCUMULATION EXPECTED. THE LAKE EFFECT SNOWS WILL AFFECT MOSTLY THE ADIRONDACKS AND TUG HILL. GENERALLY EXPECT BKN035 BKN050 DURING DAYTIME HOURS WITH SKIES BECOMING SKC ONCE AGAIN THIS EVENING. WINDS WILL GENERALLY BE W-NW AT 5-8 KTS THROUGH THE PERIOD. OUTLOOK... FRI NGHT-SAT...VFR...NO SIG WX. SAT NGHT-SUN...MVFR/IFR...CHC -SN. MON...VFR...NO SIG WX. TUE...VFR/MVFR...CHC -SHSN/-SHRA. && .HYDROLOGY... NO HYDRO PROBLEMS ARE EXPECTED OVER THE NEXT 5 DAYS. IT WILL TURN MUCH COLDER STARTING LATER TODAY WITH PRECIPITATION CHANGING FROM RAIN TO SNOW. STARTING TONIGHT TEMPERATURES OVER THE REGION WILL AVERAGE WELL BELOW FREEZING INTO EARLY NEXT WEEK WITH HIGHS FROM THE MID TWENTIES TO THE MID THIRTIES AND LOWS FROM THE MID SINGLES TO THE MID TWENTIES. THIS WILL BE FAVORABLE FOR ICE TO FORM AND THICKEN ON RIVERS AND LAKES. FOR DETAILS ON THE RIVERS...PLEASE VISIT THE ADVANCED HYDROLOGIC PREDICTION SERVICE /AHPS/ GRAPHS ON OUR WEBSITE. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...LAKE EFFECT SNOW ADVISORY UNTIL 10 PM EST THIS EVENING FOR NYZ032-033-038. MA...NONE. VT...NONE. && $$ SYNOPSIS...SNYDER NEAR TERM...BGM/SNYDER SHORT TERM...BGM/SNYDER LONG TERM...KGS AVIATION...11 HYDROLOGY...RCK ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1015 AM EST SAT DEC 6 2008 .SYNOPSIS... HIGH PRESSURE WILL DRIFT ACROSS THE AREA TODAY, THEN RECEDE EAST AND WEAKEN. PRIMARY LOW PRESSURE WILL MOVE ACROSS THE GREAT LAKES REGION TONIGHT AND THEN BEGIN TO WEAKEN, WHILE SECONDARY LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST, LIFTS NORTHEAST TOWARD THE CANADIAN MARITIMES AND DEEPENS SHARPLY. BY LATE SUNDAY, DEEP LOW PRESSURE OVER THE CANADIAN MARITIMES WILL PULL A RUSH OF ARCTIC AIR INTO OUR REGION. HIGH PRESSURE WILL BUILD OVER THE REGION MONDAY. A COLD FRONT IS EXPECTED TO CROSS THE REGION WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HAVE MADE A FEW ADJUSTMENTS TO THE MORNING FCST PACKAGE. FIRST, HAVE INCREASED POPS A BIT OVER THE WHOLE AREA. THE LATEST RUC HAS SOME PRECIP REACHING THE ERN SHORE OF MD AND DELMARVA BY 00Z. THERE IS ALSO SOME WEAK ISENTROPIC LIFT. HOWEVER, THE NAM/WRF AND THE STAT GUIDANCE IS STILL VERY DRY. LATEST OBS HAVE DEW POINTS STILL IN THE TEENS, SO THE AMS REMAINS VERY DRY. SO, A SLIGHT INCREASE SEEMS REASONABLE FOR LATE AFTERNOON AND EARLY EVENING, WANTED TO TAKE THE PRUDENT COURSE AND NOT INCREASE THINGS TOO MUCH. OTHERWISE, HAVE ALSO INCREASED CLOUDS A BIT OVER THE AREA BASED ON LATEST SATELLITE TRENDS. MOST OF THE CURRENT CLOUDINESS IS CIRRUS, BUT CLOUDS SHOULD BEGIN TO LOWER AND THICKEN WITH TIME. WINDS SHOULD BE PRETTY LIGHT FOR MUCH OF THE DAY AS SURFACE HIGH PRESSURE MOVES BY US, BUT EVENTUALLY THEY SHOULD DEVELOP A SOUTHERLY COMPONENT WITH THE WEAKENING HIGH TO OUR EAST AND THE LOW TO OUR WEST. FORECAST TEMPERATURES ARE A BLEND OF CONTINUITY AND GUIDANCE. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... TONIGHT, THE APPROACHING MID LEVEL TROUGH WILL SHARPEN AS A JET STREAK, WHICH WAS DROPPING OUT OF CANADA EARLY THIS MORNING, DIGS AROUND THE TROUGH`S WESTERN SIDE, BOTTOMS OUT AND BEGINS TO LIFT AROUND THE EASTERN SIDE. THE SURFACE LOW MOVING THROUGH THE GREAT LAKES WILL NOT BENEFIT FROM THIS, BUT THE SECONDARY LOW OFF THE EASTERN SEABOARD WILL BEGIN TO DEEPEN. MODELS ARE IN FAIR AGREEMENT THROUGH 12Z SUNDAY WITH SOME PIVA, ALTHOUGH THE BRUNT OF THAT SEEMS FOCUSED FURTHER SOUTH. THEY ALSO AGREE ON THE BEGINNINGS OF SOME MID TO UPPER LEVEL Q-VECTOR CONVERGENCE AND SOME APPROACHING LOWER LEVEL FRONTOGENESIS, BUT THAT SEEMS TO COME TOGETHER AROUND 12Z. THEY DO PAINT SOME ISENTROPIC LIFT AT THE AFOREMENTIONED LEVEL LIFTING THROUGH OVERNIGHT. MODEL QPF EXISTS, BUT IS UNDER ONE-TENTH OF AN INCH AS THE BULK OF THE ACTION IS FORECAST WITH THE SECONDARY LOW. THIS DOESN`T SEEM LIKE A SCENARIO IN WHICH STAT GUIDANCE WOULD BE WOEFULLY UNDERDONE, AND WE CANNOT FIND ANY POPS FROM ANY PACKAGE IN OUR FORECAST AREA THAT EXCEEDS THE CHANCE LEVEL. WE WERE CARRYING HIGH LIKELY TO CATEGORICAL POPS, AND WE`VE BACKED OFF TO LOW LIKELY. OUR TEMPERATURES MAINTAIN CONTINUITY, AND BETWEEN THEM AND MODEL SOUNDINGS WE CARRY PRECIPITATION TYPES OF SNOW IN THE NORTHWEST AND A CHANGING MIXED BAG FURTHER SOUTH. ACCUMULATIONS IN THE NORTHWEST ARE NOT, AT PRESENT, THOUGHT TO AMOUNT TO MUCH. AFTER THAT, THINGS MAY GET INTERESTING. THE DEEPENING SECONDARY LOW COULD BECOME A BOMB AS IT LIFTS TOWARD THE CANADIAN MARITIMES DURING THE DAY ON SUNDAY. THE WARMTH AND MOISTURE THAT IT THROWS INTO THE EASTERN SIDE OF THE MID LEVEL TROUGH AND THE DECENT JET LIFTING UP SAME SIDE OF SAID TROUGH HAVE CONSISTENTLY BEEN FORECAST BY THE ECMWF, GFS AND NAM TO CAUSE IT TO DEVELOP A NEGATIVE TILT AS IT SWEEPS ACROSS US. ALL THREE MODELS HAVE A VERY NICE VORTICITY MAX MOVING ACROSS US WITH THE TROUGH AXIS. GFS H925 AND H8 WINDS ARE IN THE 40 TO 50 KT RANGE BY LATE SUNDAY, AND THE ECMWF WINDS ARE AT LEAST AS STRONG. THEIR TRAJECTORY IS OFF THE EASTERN GREAT LAKES, AND THE H8 TEMPERATURES OVER US BY 00Z MONDAY ARE EASILY BELOW -10 DEG C. THEY`RE EASILY BELOW -15 DEG C OVER THE EASTERN LAKES. MODEL SOUNDINGS IN THE WAKE OF THE SURFACE FRONTAL PASSAGE, WHICH HAPPENS AROUND OR A BIT BEFORE DAYBREAK, ARE DRY ADIABATIC THROUGH H8, AND THE SUBSIDENCE CAP IN THE COLD AIR IS UP AT AROUND 9K FT FOR THE FIRST HALF OF THE DAY. THE SURFACE FLOW IS CYCLONIC. THE WINDEX SCHEME THAT WE USE OFF THE OLD NGM FOUS DATA SUGGESTS THAT SNOW SQUALLS ARE A POSSIBILITY AT PHL. MEANWHILE, STAT GUIDANCE POPS ARE SLIGHT CHANCE AT BEST, AND THE HIGHEST ONES ARE FROM THE FWC GUIDANCE. REGARDING POPS, WE`VE DECIDED THAT THE PIVA, THE TRAJECTORY OF THE LOWER LEVEL WINDS, THE MORNING FRONTOGENESIS AND Q-VECTOR CONVERGENCE, THE CYCLONIC SURFACE FLOW, THE INITIALLY HIGH SUBSIDENCE CAPS AND THE INDICATIONS OF THE WINDEX TECHNIQUE ARE WORTH UPPING POPS TO HIGH CHANCE OVER THE NORTHWEST, MODERATE CHANCE AROUND THE I-95 CORRIDOR AND LOW END OF CHANCE SOUTHEAST OF THERE. WE ARE GOING FOR SNOW SHOWERS OVER LAND AND MUCH OF THE WATER, AND WE`RE GOING TO MENTION THE CHANCE OF SOME SNOW SQUALLS FROM THE FALL LINE NORTHWEST. WE CARRY A SLIGHT CHANCE OF THEM AROUND THE I-95 CORRIDOR. WE WILL MENTION THE POSSIBILITY OF THESE IN THE HWO. IF THE MODELS ARE CORRECT, ANY SNOW SHOULD BE ON THE DECLINE SUNDAY AFTERNOON. REGARDING WINDS, WE ARE FORECASTING WIND ADVISORY CRITERION WINDS TO DEVELOP DURING THE DAY ON SUNDAY AND DIMINISH SLOWLY SUNDAY NIGHT INTO MONDAY. WE WILL NOT PUT UP AN ADVISORY AT THIS POINT, BUT AGAIN WILL MENTION THIS IN THE HWO. FOR SUNDAY NIGHT INTO THE FIRST PART OF MONDAY, THE TRAJECTORIES ABOVE THE SURFACE MADE US KEEP LINGERING FLURRIES IN THE FAR NORTHWESTERN ZONES FOR A TIME. OTHERWISE, WE ARE PRECIPITATION FREE. WINDS, AS NOTED ABOVE, WILL DIMINISH GRADUALLY. REGARDING TEMPERATURES ON SUNDAY, WE STAYED CLOSER TO CONTINUITY THAN TO GUIDANCE ON THE COLD AIR ADVECTION AND EXPECTED CLOUDS, AND WE HAVE TEMPERATURES FALLING IN THE AFTERNOON. SUNDAY NIGHT AND MONDAY ARE A COLD BLEND OF GUIDANCE AND CONTINUITY. WIND CHILLS ON SUNDAY NIGHT LOOK TO TANK, AND THEY WILL BE MENTIONED IN THE HWO. FOR NOW, THEY DO NOT SHOW IN THE TEXT PRODUCT BUT ARE IN THE MATRICES. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... FOR MONDAY NIGHT AND TUESDAY...THE COLD HIGH MOVES OFF THE COAST AND A RETURN FLOW OF WARM ADVECTION DEVELOPS WITH THE UPPER TROUGH REFORMING AND DIGGING TO OUR WEST. THIS MEANS THE THREAT OF MORE PCPN. FOLLOWING HPC PROGS, IT LOOKS LIKE IT WILL WARM UP ENOUGH SO THAT MOST ANY PCPN SHOULD FALL AS RAIN. WEDNESDAY...A COLD FRONT COMES THROUGH FROM THE WEST ALLOWING ANY PCPN TO BECOME SHOWERY. HOWEVER, WITH MORE COLD AIR, ANY PCPN SHOULD CHANGE TO SNOW SHOWERS. THURSDAY AND FRIDAY...THIS IS THE PERIOD WITH THE LEAST AMOUNT OF CONFIDENCE. ANOTHER FRONT SHOULD CROSS THE REGION, BUT THERE IS THE POSSIBILITY OF LOW PRESSURE FORMING ON THE FRONT AND MOVING ACROSS OR EAST OF THE REGION. IF THIS IS TRUE, THE TIMING AND TRACK OF THE LOW WILL DETERMINE IF WE GET AN EAST COAST STORM WITH SNOW IN PARTS OF THE AREA OR NOT. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS WILL REMAIN THROUGH ALL, IF NOT MOST OF THE DAYLIGHT HOURS, COURTESY OF SURFACE HIGH PRESSURE AND A WEST-SOUTHWEST FLOW ALOFT. SOME CIRRUS HAS ALREADY BEGUN TO FORM AND CLOUDS WILL GRADUALLY THICKEN AND LOWER. DECENT ISENTROPIC LIFT WILL OCCUR AS THE LOW IN THE EASTERN GREAT LAKES INTERACTS WITH THE LOW DEVELOPING OFF THE EAST COAST. A QUASI-WARM FRONT IS CONTINUED ON THE MODELS TO LIFT SLOWLY THROUGH THE AREA TONIGHT. ALTHOUGH THE MOS STATISTICAL GUIDANCE CAPS PROBABILITIES IN THE CHANCE CATEGORY, THERE SHOULD BE MORE SUBSTANTIAL, ALBEIT LIGHT, PRECIPITATION AS THIS FEATURE LIFTS THROUGH THE AREA IN VIEW OF THE MODERATE UPWARD VERTICAL MOTION AND "JUST ENOUGH" MOISTURE. SO, CEILINGS AND VISIBILITIES ARE FORECAST TO DROP TO MARGINAL VFR TONIGHT. FOR THE PHILADELPHIA 30 HOUR TAF, CONDITIONS WERE IMPROVED TOWARD MORNING AS THE PRECIPITATION DIMINISHES TO PERHAPS SCATTERED SNOW SHOWERS. REGARDING PRECIPITATION TYPE, NORTHERN TAF SITES LOOK TO BE ALL SNOW. SOUTHERN TAF SITES, ON THE SOUTHERN SIDE OF THE 1300 METER 1000-850 HPA THICKNESS DEMARCATION, SHOULD BE WEIGHTED TOWARD RAIN. THE CENTRAL TAF SITES WILL LIKELY START OFF AS RAIN, OR A MIX OF RAIN AND SNOW, BEFORE CHANGING TO SNOW AS THE COLUMN COOLS FROM EVAPORATIVE EFFECTS AND DIURNAL TRENDS WHICH CAUSE SURFACE COOLING. LIGHT WINDS THIS MORNING UNDER THE HIGH WILL SHIFT AROUND TO SOUTH AT 5 TO 10 KNOTS BY LATE MORNING OR MIDDAY AS THE HIGH SHIFTS OFFSHORE. THEN, WINDS WILL SWITCH AROUND TO WEST-SOUTHWEST TOWARD SUNDAY MORNING IN THE WAKE OF THE FRONT. OUTLOOK... THE GREAT LAKES LOW AND THE COASTAL LOW WILL MERGE WELL OFF THE NEW ENGLAND COASTAL WATERS SUNDAY MORNING, AND THE RESULTANT INTENSIFICATION WILL CAUSE GUSTY WEST-NORTHWEST WINDS AND AN UNSTABLE FLOW REGIME OVER OUR AREA. THIS MAY CAUSE SCATTERED SNOW SHOWERS SUNDAY AFTERNOON, ALONG WITH STRONG AND VERY GUSTY WINDS, WHICH ARE VERY LIKELY TO NEGATIVELY IMPACT AIR TRAVEL SUNDAY AFTERNOON AND EVENING. HIGH PRESSURE WILL BUILD MONDAY BUT MOVE OFFSHORE MONDAY NIGHT. ANOTHER FRONT WILL HEAD IN FOR WEDNESDAY. && .MARINE... CONDITIONS WILL REMAIN BELOW ADVISORY OR WARNING CONDITIONS TODAY AND TONIGHT, BUT THEN LOOK ALIVE MATEY AS HIGH-END GALE CONDITIONS ARE EXPECTED BY SUNDAY AFTERNOON, CONTINUING INTO SUNDAY NIGHT. HIGH PRESSURE OVER THE AREA THIS MORNING WILL MOVE OFFSHORE THIS AFTERNOON. MARINE CONDITIONS SHOULD BE FINE, BUT COLD. RAIN AND SOME SNOW MOVING IN FOR TONIGHT WILL LOWER VISIBILITIES, BUT WINDS AND SEAS WILL REMAIN UNDER ADVISORY CRITERIA. LOW PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE EASTWARD TONIGHT AND MERGE WITH A LOW HEADING NORTHEASTWARD OFF THE EAST COAST. AS THEY MERGE SUNDAY, RAPID INTENSIFICATION WILL CAUSE A STRONG CIRCULATION OVER OUR AREA SUNDAY AFTERNOON AND NIGHT. WEST-NORTHWEST 925 HPA WINDS ARE FORECAST TO REACH 45 KNOTS, AND WITH MUCH COLDER AIR OVER RELATIVELY WARM WATER, DOWNWARD MOMENTUM TRANSFER SHOULD BE EXCELLENT. SO, THE INHERITED GALE WATCH WILL BE CHANGED TO A GALE WARNING, AND THE TIMES WILL BE ADJUSTED...BACKED UP TO 16Z SUNDAY FOR A START TIME, AND RUN THROUGH 11Z MONDAY. THE STRONG WEST-NORTHWEST FLOW WILL ALSO RESULT IN BELOW NORMAL TIDES. HOWEVER, AT THIS TIME IT DOES NOT APPEAR AS IF THEY WILL REACH THE BLOWOUT TIDE THRESHOLD, ACCORDING TO NGM AND AVIATION STORM SURGE GUIDANCE WHEN COUPLED WITH THE ASTRONOMICAL TIDES. HIGH PRESSURE WILL DOMINATE FOR MONDAY BUT MOVE OFFSHORE BY TUESDAY. THEN, ANOTHER FRONT IS FORECAST TO APPROACH TUESDAY NIGHT AND WEDNESDAY, PRECEDED BY STRONG SOUTHERLY WINDS. THIS WOULD BE A CASE OF WARMER AIR OVER COLDER WATER, SO THERE WOULD BE LESS MIXING OF MOMENTUM DOWN TO THE SURFACE. HOWEVER, SMALL CRAFT ADVISORY CONDITIONS ARE POSSIBLE WITH THIS SYSTEM AROUND THE MIDDLE OF NEXT WEEK. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...GALE WARNING FROM 9 AM SUNDAY TO 6 AM EST MONDAY FOR ANZ430- 431-450>455. && $$ SYNOPSIS...DELISI NEAR TERM...NIERENBERG/DELISI SHORT TERM...DELISI LONG TERM...STAUBER AVIATION...NIERENBERG MARINE... de AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 415 AM EST FRI DEC 5 2008 .SYNOPSIS... 07Z WATER VAPOR AND H4 RUC ANALYSIS SHOWING A RATHER UNEVENTFUL UPPER LEVEL PATTERN ACROSS THE CONUS EARLY THIS MORNING. NATION IS SPLIT ALOFT BY A STRUNG OUT UPPER TROUGH EXTENDING FROM EASTERN CANADA DOWN THROUGH THE GREAT LAKES AND THEN SOUTHWEST THROUGH THE FOUR CORNERS REGION. UPPER PATTERN ALONG THE CENTRAL/NORTHEAST GULF COAST IS ZONAL IN NATURE WITH OCCASIONAL FAST MOVING AND WEAK DISTURBANCES EMBEDDED WITHIN. ONE SUCH SHORTWAVE CROSSED OVERHEAD THIS PAST EVENING AND IS NOW SHEARING OUT TO THE NORTHEAST LEAVING LITTLE IN THE WAY OF LARGE SCALE FORCING OVERHEAD. AT THE SURFACE...SURFACE TROUGH ASSOCIATED WITH A WEAK COLD FRONT EXTENDS ACROSS THE EASTERN FORECAST AREA FROM THE CAROLINAS TO OUR OFFSHORE WATERS. THIS TROUGH IS MAKING PAINFULLY SLOW PROGRESS EASTWARD AND THIS SLOW MOTION SOUTH AND EAST WILL CONTINUE INTO THE DAYLIGHT HOURS. LOW DECK OF CLOUDS ASSOCIATED WITH THE FRONT COVERS THE ENTIRE FORECAST AREA EARLY THIS MORNING AND IS ALSO SHOWING THE SAME SLOW MOVEMENT EAST. WITH THE UPPER SUPPORT FOR LIFT VERY WEAK AT THIS POINT...REGIONAL RADARS ARE SHOWING ONLY A SCATTERING OF LIGHT SHOWERS ACROSS THE REGION. THESE SHOWERS ARE LARGELY IN A ZONE EAST OF A LINE FROM KPFN TO KABY AND WEST OF A LINE FROM PERRY TO TIFTON. && .SHORT TERM (TODAY THROUGH SUNDAY)... WEAK SURFACE FRONT WILL SLOWLY PUSH SOUTHEAST ACROSS THE EASTERN ZONES DURING THE MORNING HOURS AND EXIT SOUTHEAST OF THE FL BIG BEND EARLY THIS AFTERNOON. THIS FRONT IS UNLIKE SOME OF THE MORE POTENT SURGES SEEN OVER THE PAST FEW WEEKS IN TERMS OF COLD AIR WITH ONLY A SLIGHTLY COOLER AIRMASS IN ITS WAKE. AS WAS MENTIONED IN THE SYNOPSIS ABOVE...MID/UPPER LEVEL SYNOPTIC SUPPORT FOR LIFT IS LIMITED AT BEST THROUGH THE DAY. WITH THIS IN MIND...SUPPORT FOR SHOWERS WILL LARGELY HAVE TO COME FROM THE LOWER LEVELS. CURRENT SHOWERS ACROSS THE MIDDLE OF THE FORECAST AREA ARE FORMING IN A REGION OF WEAK FORCED ASCENT ALONG THE NOSE OF AN 850MB THETA-E RIDGE. GFS/NAM IN AGREEMENT SHOWING THIS RIDGE WEAKENING A BIT DURING THE DAY WHILE SLOWLY PROGRESSING EASTWARD WITH THE FRONT INTO THE EASTERN FLORIDA BIG BEND/SOUTH-CENTRAL GA. WITH THIS IN MIND WILL TAPER POPS OFF ACROSS THE NORTHWEST HALF OF THE AREA FOR THE AFTERNOON HOURS WITH HIGHEST SHOWER CHANCES SOUTH AND EAST OF A LINE FROM APALACHICOLA TO VALDOSTA AFTER 1 OR 2 PM. IF SHOULD BE MENTIONED THAT DESPITE THE RAIN CHANCES...THE OVERALL IMPACT WILL BE LIMITED WITH LIGHT RAINFALL ACCUMULATIONS OF GENERALLY ONLY AROUND ONE TENTH OF AN INCH AT BEST. WHILE THE SOUTHEAST HALF OF THE AREA IS LIKELY TO REMAIN MOSTLY CLOUDY THROUGH THE DAYLIGHT HOURS...FURTHER NORTHWEST WILL SEE IMPROVING CONDITIONS. MOISTURE LEVELS THROUGH THE COLUMN WILL BE SLOWLY SCOURING OUT ACROSS PORTIONS OF SOUTHEAST AL/SOUTHWEST GA AND THE FLORIDA PANHANDLE...ALLOWING FOR INCREASING AMOUNTS OF SUN...ESPECIALLY AFTER NOON. SURFACE FRONT STALLS ACROSS THE NORTH-CENTRAL FL PENINSULA THIS EVENING AND REMAIN IN THIS VICINITY THROUGH TONIGHT. MOST OF THE AREA WILL SEE DRY CONDITIONS TONIGHT WITH THE FRONT A MEMORY OFF TO THE SOUTHEAST. HOWEVER...IN CLOSER PROXIMITY TO THE STALLED FRONT (MAINLY SOUTH AND EAST OF TALLAHASSEE AND VALDOSTA) ACROSS THE EASTERN BIG BEND...LOW LEVEL ISENTROPIC LIFT ALONG THE 290-300K SURFACES SHOULD BE ENOUGH TO SUPPORT A CONTINUED CHANCE OF SCATTERED MAINLY LIGHT SHOWERS. ON TOP OF THIS LOWER LEVEL LIFT...WILL ALSO BE WATCHING ANOTHER WEAK DISTURBANCE ALOFT RACING EASTWARD ALONG THE NORTHEAST GULF COAST. GFS IS SHOWING A QUICK SHOT OF DEEP SYNOPTIC LIFT ASSOCIATED WITH THIS FEATURE TO ADD SUPPORT FOR THE SHOWERS. THIS ADDED LIFT MAY ALSO BE ADD JUST ENOUGH TO RESULT IN A RUMBLE OR TWO OF THUNDER DOWN TOWARD CROSS CITY. IN FACT SHOWALTER INDICES DO DROP TO AROUND ZERO OVER THE SOUTHEAST BIG BEND AFTER MIDNIGHT. A COOLER NIGHT IS IN STORE FOR ALL BEHIND THE FRONT. GRIDS NOW SHOWING 30S OVER THE NW ZONES AND LOWER TO MIDDLE 40S FURTHER SOUTHEAST. THERE ARE GUIDANCE MEMBERS SHOWING A LIGHT FREEZE OVER PORTIONS OF SE AL AND INLAND SECTIONS OF THE FL PANHANDLE. AM A BIT CONCERNED THAT SOME ADDITIONAL CLOUDCOVER ASSOCIATED WITH THE PASSING MID-LEVEL IMPULSE WILL PREVENT THESE TEMPERATURES FROM BEING ACHIEVED AND WILL KEEP THE LOWEST TEMPERATURES FROM DROPPING BELOW FREEZING. EVEN STILL MAY SEE SOME PATCHY FROST IN UNSHELTERED AREA OF THE WEST. SATURDAY AND SATURDAY NIGHT...IMPULSE IN THE MID-LEVELS EXITS TO OUR EAST EARLY ON SATURDAY. WEAK CYCLOGENESIS DURING THIS TIME OFF THE SOUTHEAST COAST WILL BEGIN PULLING THE BOUNDARY FORWARD AGAIN. WILL END POPS ACROSS THE SOUTHEAST BIG BEND BY SUNRISE ON SATURDAY FOR THIS REASON WITH A DRY DAY NOW FORECAST AREA WIDE. WILL BE WATCHING AN AMPLIFYING MID/UPPER LEVEL TROUGH DIGGING INTO THE EASTERN THIRD OF THE NATION LATER SATURDAY AND AT NIGHT. THIS TROUGH WILL FORCE THE NEXT COLD FRONT INTO THE AREA SATURDAY EVENING. MOISTURE WILL BE VERY LIMITED AND EXPECTING A RAPID AND DRY FRONTAL PASSAGE BY SUNRISE. WITH A MIX OF SUN AND CLOUDS IN THE FORECAST SHOULD BE ABLE TO GET AFTERNOON TEMPS UP IN TO THE LOWER 60S NORTH AND MIDDLE 60S SOUTH. COLD AIR ADVECTION BEHIND THE FRONT BRING A STEADY DROP IN TEMPS THROUGH THE OVERNIGHT PERIOD. CURRENT GRIDS SHOWING LOWER TO MIDDLE 30S NORTH AND MIDDLE 30S TO LOWER 40S SOUTH BY SUNRISE. AT THIS TIME THE RIDGE POSITION APPEARS TOO FAR NW TO ALLOW A GOOD RADIATIONAL COOLING SETUP...EVEN IN THE FAR WESTERN ZONES. WILL ONCE AGAIN NOT DROP LOW TEMPS BELOW THE FREEZING MARK. SUNDAY...PLEASANT AND COOL DAY LOOKS IN STORE FOR SUNDAY WITH MOSTLY SUNNY SKIES AND A STEADY NORTHERLY BREEZE. WEAK CAA WILL PREVENT HIGH TEMPERATURES FROM REACHING THE COLUMN POTENTIAL. HOWEVER... STILL FEEL THE MAV IS A TAD COOL AND WILL BUMP UP HIGHS A COUPLE OF DEGREES INTO THE UPPER 50S NORTH AND THE LOWER 60S SOUTH. && .LONG TERM (SUNDAY NIGHT THROUGH FRIDAY)... AFTER A COOL START TO THE DAY ON MONDAY...DEEP LAYER RIDGING WILL DEVELOP OVER THE EASTERN CONUS EARLY NEXT WEEK AS A 500 MB LONG WAVE TROUGH (AND ASSOCIATED FRONTAL SYSTEM) PROPAGATE TOWARD THE EAST. BOTH THE GFS MOS AND GFS BIAS CORRECTED GUIDANCE FORECAST A LIGHT FREEZE MONDAY...BUT THIS SEEMS SOMEWHAT UNLIKELY GIVEN THE POSITION OF THE SURFACE HIGH (ALONG THE VA COAST) AND THE POSSIBILITY OF INCREASING CS SUNDAY NIGHT. THERE ARE CONSIDERABLE DIFFERENCES AMONG THE VARIOUS MODEL SOLUTIONS ON THE TIMING AND INTENSITY OF THIS NEXT SYSTEM...BUT IT APPEARS THAT PORTIONS OF OUR AREA WILL RECEIVE 2 TO 3 INCHES OF RAIN WITHIN THE TUESDAY-THURSDAY MORNING TIME FRAME. THE OPERATIONAL GFS IS SLOWER AND FARTHER SOUTH WITH ITS SURFACE LOW (TRACKING ACROSS SOUTH GA WEDNESDAY) THAN THE GFS ENSEMBLE MEAN AND CMC SOLUTIONS. THE ECMWF SOLUTION IS SLOWER THAN THE OPERATIONAL GFS...AND THE UKMET IMPLIES THE FRONT MAY STALL BY MID WEEK. WE WILL FOLLOW THE OPERATIONAL GFS SOLUTION AS IT IS IN BETWEEN THESE VARYING SOLUTIONS...BUT FORECAST CONFIDENCE IS LOW WHEN IT COMES TO DETAILS BEYOND TUESDAY. ALL OF THE GUIDANCE INDICATE THAT THIS NEXT FRONTAL SYSTEM WILL BE FAIRLY ENERGETIC (REGARDLESS OF THE EXACT TIMING AND TRACK)...WHICH MEANS THERE MAY BE A SLIGHT CHANCE FOR SEVERE WEATHER ANYWHERE FROM TUESDAY NIGHT THROUGH THURSDAY MORNING. HOPEFULLY WE WILL BE ABLE TO PROVIDE MORE DETAIL WHEN (IF) THE MODEL SOLUTIONS CONVERGE. && .MARINE... A WEAK COLD FRONT WILL MOVE WEST TO EAST ACROSS THE FORECAST WATERS INTO THE AFTERNOON HOURS. IN THE WAKE OF THE FRONT EXPECT A WIND SHIFT TO THE NORTH AND NORTHEAST. EXPECTING WINDS IN THE CAUTIONARY LEVEL BEHIND THE FRONT WITH A FEW GUSTS UP OVER 20 KNOTS. OFFSHORE SEAS WILL ALSO BUILD UP TO AROUND 5 FEET...ESPECIALLY ACROSS THE WESTERN LEGS. FRONT WASHES OUT TO OUR SOUTH TONIGHT WITH WINDS AND SEAS DROPPING BELOW CAUTIONARY LEVELS INTO SATURDAY. THE NEXT COLD FRONT WILL RAPIDLY PUSH ACROSS THE WATERS LATER SATURDAY AND SATURDAY NIGHT WITH A PERIOD OF CAUTIONARY TO ADVISORY LEVEL WINDS AND SEAS. THESE ELEVATED WINDS AND SEAS LINGER INTO SUNDAY BEFORE HIGH PRESSURE BUILDS TO OUR NORTH INTO THE EARLY PART OF NEXT WEEK. && .AVIATION... THE 00 UTC GFS MOS APPEAR TO BE UNDER-ESTIMATING THE AMOUNT OF LOW CLOUD COVER OVER OUR REGION. THE BACK EDGE OF THIS MVFR-IFR CLOUD DECK EXTENDS FROM KFFC GA TO KCWF LA...AND WAS MAKING SLOW PROGRESS SOUTHEASTWARD. WE OPTED TO USE THE FORECAST RUC AND NAM SOUNDINGS FOR OUR CLOUD FORECAST AS THAT GUIDANCE HAS INITIALIZED REASONABLY WELL SO FAR...AND MOS SOMETIMES HAS A TENDENCY TO CLEAR LOW CLOUDS OUT TOO QUICKLY IN THESE SITUATIONS. MVFR-IFR CIGS ARE LIKELY AT ALL TAF SITES OVERNIGHT...WITH GRADUAL IMPROVEMENT TO VFR CIGS FROM NORTHWEST TO SOUTHEAST DURING THE MORNING AND EARLY AFTERNOON HOURS. LIGHT DRIZZLE AND/OR LIGHT RAIN WILL AFFECT KTLH...KPFN...AND KVLD DURING THE OVERNIGHT AND EARLY MORNING HOURS...WITH VIS OCCASIONALLY REDUCED TO MVFR. && .FIRE WEATHER... DRIER AIR WILL FILTER INTO WESTERN SECTIONS OF OUR FL PANHANDLE AND SOUTHEAST AL ZONES SATURDAY AFTERNOON...BUT WE DO NOT EXCPECT TO GET THE WIND OR DURATION OF LOW RELATIVE HUMIDITY TO WARRANT A FIRE WEATHER WATCH. RED FLAG CONDITIONS APPEAR POSSIBLE SUNDAY AFTERNOON FOR PORTIONS OF THE AREA...AND A FIRE WEATHER WATCH MAY BE ISSUED TODAY OR TONIGHT. && .PRELIMINARY POINT TEMPS/POPS... TALLAHASSEE 61 42 64 36 61 / 50 10 10 0 0 PANAMA CITY 60 43 63 41 61 / 30 10 10 0 0 DOTHAN 57 37 61 35 58 / 10 0 0 0 0 ALBANY 59 37 61 33 59 / 20 10 0 0 0 VALDOSTA 61 44 64 38 60 / 30 20 10 0 0 CROSS CITY 70 48 68 40 64 / 30 40 10 10 0 && .TAE WATCHES/WARNINGS/ADVISORIES... AL...NONE. GA...NONE. FL...NONE. GM...NONE. && $$ SYNOPSIS/SHORT TERM/MARINE...MROCZKA AVIATION/FIRE WEATHER/LONG TERM...FOURNIER fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 1245 PM EST SAT DEC 6 2008 .SYNOPSIS... A WAVE OF LOW PRESSURE WILL MOVE UP THE COAST TODAY THEN A REINFORCING COLD FRONT WILL CROSS THE REGION TONIGHT. DRY HIGH PRESSURE WILL BUILD IN SUNDAY THROUGH MONDAY. A COASTAL TROUGH WILL DEVELOP MONDAY NIGHT AND TUESDAY...THEN A COMPLEX STORM SYSTEM WILL AFFECT THE SOUTHEAST REGION DURING THE LATTER HALF OF THE WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THERE HAS DEFINITELY BEEN A PRONOUNCED WESTWARD SHIFT IN MOST MODELS WITH THE UPPER SHORTWAVE AND SURFACE TROUGH EXPECTED TO MOVE THROUGH THE COASTAL WATERS LATE THIS AFTERNOON. LOW-LEVEL MOISTURE HAS ALREADY BEGUN TO POOL AHEAD OF THE SHORTWAVE NOW LOCATED ALONG THE GULF COAST STATES WITH SFC DEWPOINTS INCREASING INTO THE MID 40S ALONG THE COAST. LIGHT RAIN WILL LIKELY BEGIN TO DEVELOP BY EARLY AFTERNOON ACROSS SOUTHEAST GEORGIA AND THE COASTAL WATERS. CONFIDENCE QUICKLY DECREASES WHEN ASSESSING POTENTIAL FOR RAIN ACROSS SOUTHEAST SOUTH CAROLINA. IF ANY RAIN OCCURS...IT WILL LIKELY BE AFTER 3 PM AND ACROSS COASTAL COUNTIES. THE 4 KM WRF SHOWS A FEW HOURS OF LIGHT RAIN LATE THIS AFTERNOON THROUGH THE EVENING IN COASTAL SC ALTHOUGH THE 12Z NAM-12 KEEPS ALL RAIN JUST OFFSHORE. THE GFS BRINGS RAIN TO COASTAL LAND AREAS...AS WELL AS THE 00Z ECMWF...ALTHOUGH THE RUC-13 IS DRIER. BASED ON THE CURRENT POSITION OF THE SHORTWAVE AND A BAROCLINIC LEAF APPEARING OFF THE GA COAST ON VIS SATELLITE...A FEW HOURS OF SCATTERED LIGHT RAIN SHOWERS WILL BE POSSIBLE ACROSS ABOUT TWO TIERS OF GA COASTAL COUNTIES AND MAYBE ONE LAYER OF COUNTIES ALONG THE SC COAST. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE LAST OF THE MAINLY LIGHT STRATIFORM RNFL WILL EXIT THE CENTRAL SOUTH CAROLINA COAST PRIOR TO MIDNIGHT WITH SKIES CLEARING AND WINDS STIRRING FROM THE NW TO W WITH THE ARRIVAL OF A MODIFIED CONTINENTAL POLAR AIR AIR MASS. SKIES WILL CLEAR ALL AREAS BEFORE DAWN ON SUNDAY AS THE UPPER TROF AXIS PASSES. WE HAVE CONTINUED TO FAVOR THE COOLER GFS MOS LOW TEMPERATURE SCHEME WHICH FITS IN REAL NICE WITH OUR FORECAST PERSISTENCE. && .LONG TERM /SUNDAY THROUGH FRIDAY/... MUCH UNCERTAINTY CONTINUES TO PLAGUE THE EXTENDED PERIODS THIS MORNING...BUT OVERALL THE MODELS AGREE THAT A FAIRLY UNSETTLED PERIOD CAN BE EXPECTED FROM MID TO LATE WEEK. GUIDANCE IS IN GOOD AGREEMENT THAT HIGH PRESSURE WILL BUILD NORTH OF THE REGION SUNDAY THROUGH MONDAY...AND WILL KEEP THE FORECAST RAIN FREE. THE RIDGE OF HIGH PRESSURE IS EXPECTED TO SLIDE EASTWARD AND INTO THE ATLANTIC MONDAY NIGHT THROUGH TUESDAY NIGHT. AS HIGH PRESSURE SHIFTS OFFSHORE...A COASTAL TROUGH WILL DEVELOP OFF THE SOUTH CAROLINA AND GEORGIA COAST MONDAY NIGHT AS SUGGESTED BY MOST OPERATIONAL GUIDANCE...WITH THE TROUGH SHIFTING NORTH OF THE AREA BY LATE IN THE DAY TUESDAY. WILL CONTINUE TO CARRY SLIGHT CHANCE/CHANCE POPS MONDAY NIGHT AND TUESDAY FOR PRIMARILY COASTAL ZONES...WITH A BIT FURTHER WESTWARD EXTENT INTO INTERIOR SOUTH CAROLINA ZONES GIVEN SOUTH-SOUTHEASTERLY LOW LEVEL STEERING FLOW OFF THE ATLANTIC. MAIN FORECAST CONCERN IN THE EXTENDED PERIODS REVOLVES AROUND THE HANDLING OF THE MID TO LATE WEEK STORM SYSTEM EXPECTED TO IMPACT THE FORECAST AREA. BOTH THE GFS AND ECMWF HAVE REMAINED FAIRLY CONSISTENT FROM ONE RUN TO THE NEXT. IT DOES APPEAR HOWEVER THAT THEY ARE BOTH BEGINNING TO CONVERGE ON A COMMON SOLUTION...BUT THIS WILL LIKELY TAKE SEVERAL MORE RUNS BEFORE A COMMON SOLUTION BECOMES CLEARLY APPARENT. THE GFS PUSHES A FRONT THROUGH THE AREA WEDNESDAY...THEN DEVELOPS A WAVE ALONG THE FRONT WEDNESDAY NIGHT AND LIFTS IT NORTHEASTWARD OFF THE SOUTH CAROLINA AND GEORGIA COAST ON THURSDAY. THE ECMWF ON THE OTHER HAND PUSHES A COLD FRONT THROUGH THE AREA ON THURSDAY...THEN LIFTS THE FRONT BACK NORTHWARD LATE THURSDAY NIGHT AS A WAVE OF LOW PRESSURE MOVES NORTHWARD OUT OF THE GULF OF MEXICO AND ACROSS THE FORECAST AREA ON FRIDAY. THE CANADIAN IS MORE SIMILAR TO THE GFS AND THE UKMET MORE SIMILAR TO THE ECMWF. GFS ENSEMBLE MEMBERS CONTINUE TO FAVOR A FASTER AND MORE PROGRESSIVE SOLUTION...WHICH AIDS IN FORECAST UNCERTAINTY CONSIDERING MOST OF THE OPERATIONAL GUIDANCE IS SLOWING THE SYSTEMS PROGRESSION DOWN. EXPECT THAT THE MOST PROBABLE SOLUTION LIES SOMEWHERE IN BETWEEN THE GFS AND ECMWF SOLUTIONS SO WILL TRY TO INCORPORATE IDEAS FROM EACH WITH THE MORNING PACKAGE TO REDUCE POTENTIAL FORECASTS BUSTS IN THE LATTER PERIODS AS THEY COULD BE QUITE LARGE. TO MAKE A LONG STORY SHORT...IT LOOKS LIKE A FAIRLY UNSETTLED PERIOD WEDNESDAY THROUGH FRIDAY...AND WILL CARRY CHANCE POPS THROUGHOUT. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... LOW CLOUDS WILL CONTINUE TO DEVELOP AND SPREAD NE THROUGH THE AREA DURING THE AFTERNOON HOURS AHEAD OF AN APPROACHING SHORTWAVE. SOME WARM ISENTROPIC ASCENT MAY PRODUCE PATCHY AREAS OF LIGHT RAIN ALONG COASTAL SECTIONS AS A SURFACE WAVE DEVELOPS ALONG A STALLED FRONT JUST OFF THE COAST. DO NOT EXPECT PROLONGED RAIN EVENT THUS CONFINED RAIN TO TEMPO GROUP AT BOTH TAF SITES. MVFR CEILINGS WILL BE THE PRIMARY ISSUE THROUGH THIS EVENING UNTIL A REINFORCING COLD FRONT MOVES THROUGH AND MUCH DRIER AIR FILTERS IN. GUSTY WINDS POSSIBLE ON SUNDAY DUE TO A DEEP MIXED LAYER AND 25-30 KT WINDS JUST OFF THE SURFACE. EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED SUNDAY THROUGH MONDAY. MVFR OR LOWER CONDITIONS ARE POSSIBLE AT THE TERMINALS MONDAY NIGHT THROUGH THURSDAY AS A COMPLEX STORM SYSTEM IMPACTS THE AREA. && .MARINE... A FAIRLY WEAK PRES PATTERN WILL KEEP RELATIVELY TRANQUIL MARINE CONDITIONS GOING FOR MOST OF TODAY. A COLD FRONT WILL MOVE THROUGH THE WATERS LATE THIS AFTERNOON...FOLLOWED BY A COOLER AND DRIER AIR AIR MASS PUNCHING IN TONIGHT. INCREASING W FLOW SHOULD JET OFF THE COAST AND WE HAVE ISSUED A SECOND PERIOD SMALL CRAFT ADVISORY FOR OUR 20-60 NM GEORGIA WATERS. AS USUAL...WE WILL NEED TO WATCH CONDITIONS AT GRAYS REEF FOR A PERIOD OF WINDS TOUCHING ADVISORY CRITERIA. OFFSHORE FLOW TONIGHT WILL BUILD SEAS TO 2-4 FT WITHING 20 NM...BUT HIGHER 4-6 FT SEAS ARE LIKELY AFTER MIDNIGHT BEYOND 30 NM E OF THE GEORGIA COAST. HIGH PRESSURE WILL BUILD NORTH OF THE REGION SUNDAY THROUGH MONDAY...THEN SHIFT OFFSHORE AND INTO THE ATLANTIC TUESDAY AND TUESDAY NIGHT. A COLD FRONT WILL APPROACH FROM THE WEST ON WEDNESDAY. SMALL CRAFT CONDITIONS ARE EXPECTED TO CONTINUE ACROSS THE OUTER GEORGIA WATERS SUNDAY MORNING. OTHERWISE WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT THRESHOLDS SUNDAY THROUGH MONDAY. THE COMBINATION OF PERSISTENT EASTERLY FLOW AND BUILDING SWELL MAY RESULT IN A NEED FOR SMALL CRAFT ADVISORIES ACROSS PORTIONS OF THE WATERS ONCE AGAIN MONDAY NIGHT THROUGH WEDNESDAY. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 12 PM EST SUNDAY FOR AMZ374. && $$ JRL ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL 607 AM CST FRI DEC 5 2008 .DISCUSSION... 402 AM CST SHORT WAVE TROUGH MOVING EAST OF THE AREA THIS MORNING...THOUGH ANOTHER WEAK SHORT WAVE DROPPING ACROSS THE NORTHERN LAKES AND UPPER MISSISSIPPI VALLEY THIS MORNING. WEAK LOW LEVEL WARM ADVECTION IN ADVANCE OF THIS FEATURE RESULTING IN SOME CLOUD COVER ACROSS MINNESOTA...IOWA AND WESTERN WISCONSIN EARLY THIS MORNING...AND WITH SOMEWHAT NEUTRAL VERTICAL MOTION FIELD DEPICTED BY BOTH WRF AND GFS UVM TIME/HEIGHT SECTIONS SUSPECT SOME OF THIS CLOUD COVER WILL WORK ITS WAY INTO NORTHERN IL LATE THIS MORNING. MID/HIGH LEVEL CLOUDS TO INCREASE LATER TODAY ANYWAY AS NEXT UPSTREAM SHORT WAVE TROUGH CURRENTLY OVER NORTHERN SASKATCHEWAN DIGS SOUTHEAST INTO MINNESOTA AND TRANSLATES ACROSS FORECAST AREA TONIGHT INTO SATURDAY MORNING. WINDS BACK SOUTH/SOUTHWEST BY EVENING IN ADVANCE OF THIS CLIPPER... WITH DEEP LAYERED VERTICAL MOTION INCREASING TONIGHT. LOOKING ISENTROPICALLY...APPEARS 285 KELVIN SURFACE INTERSECTS STRONGER UVM AND DENDRITIC GROWTH ZONE AROUND -15 C LATE TONIGHT WITH AVERAGE MIXING RATIO DURING THE 09-15Z PERIOD AROUND 2 G/KG. THUS MAX SNOW AMOUNTS AROUND 2 INCHES SEEM REASONABLE. SIMILAR QPF AMOUNTS FROM 00Z WRF/GFS...AND WITH ABOUT A 15:1 SNOW/LIQUID RATIO ALSO SUPPORT GENERALLY A 1-2 INCH OR 1-3 INCH TOTAL SNOWFALL BY THE TIME SHORT WAVE TROUGH AXIS MOVES THROUGH DURING SATURDAY MORNING. SECOND VORT NOTED DROPPING ACROSS NORTHERN LAKES AND WISCONSIN IN WAKE OF THE FIRST MIDDAY SATURDAY...WHICH MAY MAINTAIN SOME VERY WEAK FORCING ACROSS THE AREA INTO THE AFTERNOON HOURS. GIVEN DRYING OF MID/UPPER LEVELS NOTED IN TIME SECTIONS... SHALLOW NATURE OF MOISTURE AND WEAK UVM WOULD INDICATE MAINLY JUST SOME LINGERING FLURRIES OR LIGHT SNOW SHOWERS BEYOND THE MORNING HOURS WITH LITTLE IF ANY ADDITIONAL ACCUMULATION. COLD FRONT PUSHES ACROSS NORTH CENTRAL IL DURING THE MORNING AND THROUGH THE CHICAGO AREA AROUND MIDDAY...WITH GUSTY NORTHWEST WINDS PROVIDING STRONG LOW LEVEL COLD ADVECTION WITH FALLING TEMPS LIKELY IN THE AFTERNOON. UPPER TROUGH MOVES EAST SATURDAY NIGHT...WITH DEEP SUBSIDENCE DEVELOPING AND SURFACE RIDGE APPROACHING THE MISSISSIPPI BY SUNDAY MORNING. SNOW COVER...LOW LEVEL ARCTIC AIR AND POTENTIAL FOR PARTIAL CLEARING TO SEND TEMPS INTO THE SINGLE DIGITS SATURDAY NIGHT. HAVE UNDERCUT COOLEST GUIDANCE A BIT ESPECIALLY NORTH CENTRAL IL WHERE RADIATIVE COOLING CONDITIONS EXPECTED TO BE MOST FAVORABLE. SURFACE RIDGE THEN MOVES ACROSS AREA SUNDAY MORNING WITH SUNSHINE EXPECTED DURING THE MORNING. YET ANOTHER IN THIS RAPID FIRE SERIES OF SHORT WAVES RIPPLES SOUTHEAST ACROSS THE MIDWEST SUNDAY AFTERNOON HOWEVER...WITH BACKING LOW LEVEL FLOW AND RESULTING WARM ADVECTION TO INCREASE MID/HIGH CLOUDS RATHER QUICKLY. THIS WAVE CONTINUES TO DIG SOUTHEAST ACROSS THE AREA SUNDAY NIGHT BRINGING THE POTENTIAL FOR ANOTHER MEASURABLE SNOW. WHILE THIS SHORT WAVE DIGS ACROSS MIDWEST...LONG WAVE TROUGH AMPLIFIES ACROSS THE ROCKIES AND HIGH PLAINS TO OUR WEST. SURFACE LOW DEVELOPS ACROSS TX PANHANDLE REGION WITH INVERTED TROUGH EXTENDING NORTHEAST INTO THE MIDWEST ALONG LOW LEVEL BAROCLINIC ZONE ALONG SOUTHERN PERIPHERY OF ARCTIC AIR. POTENTIAL FOR LIGHT PRECIPITATION LINGERS MONDAY INTO TUESDAY IN VICINITY OF THERMAL GRADIENT AS SERIES OF WEAK NORTHERN STREAM WAVES PASS THROUGH LARGER SCALE TROUGH AXIS WHICH BECOMES QUITE SHEARED AS JET DIGS ACROSS THE WESTERN CONUS. SOME QUESTION AS TO PRECIP TYPE PROVIDED PRECIP DOES OCCUR ESPECIALLY IN MONDAY/MONDAY PERIOD AS SOUTH WINDS AHEAD OF SHEARED TROUGH AND RESULTING LOW LEVEL WARM ADVECTION RESULT IN THERMAL PROFILES WHICH BECOME MARGINAL FOR SNOW ACROSS SOUTHERN HALF OF CWA. GEM AND ECMWF PARTICULARLY MILD AND PUSH 1540 METER 850-700 THICKNESS CONTOUR UP TO AROUND I-88 MONDAY AFTERNOON. GFS REMAINS COOLER AND FORECASTS SNOW AS PREDOMINANT PRECIP TYPE EVEN IN SOUTHERN COUNTIES. FOR NOW WILL MAINTAIN CURRENT FORECAST GFS SLANT WITH CHANCE SNOW...THOUGH WILL HAVE TO MONITOR MODEL TRENDS NEXT FEW RUNS FOR BETTER HANDLE ON THERMAL PROFILES EARLY NEXT WEEK. RATZER && .AVIATION... 605 AM CST 1200 UTC TAFS...INCREASING SNOW POTENTIAL LATE TONIGHT AND BRISK WINDS WILL BE THE MAIN AVIATION FORECAST CONCERNS OVER THE NEXT 24 TO 36 HOURS. A BROAD RIDGE OF HIGH PRESSURE CENTERED ACROSS MISSOURI WILL CONTINUE TO SLOWLY SLIDE EASTWARD TODAY AS NEXT UPPER LEVEL SHORT WAVE TROUGH ACROSS SOUTHWEST CANADA DIGS INTO THE NORTHERN PLAINS THIS AFTERNOON. IN THE NEAR TERM...SOME HIGH END MVFR AND VFR CIGS BETWEEN 3-4K FT ACROSS EASTERN IOWA NOT HANDLED WELL IN NUMERICAL GUIDANCE WILL LIKELY MOVE ACROSS TERMINALS THIS MORNING AND BASED ON SFC OBS AND RUC SOUNDINGS WOULD EXPECTED GENERALLY VFR CIGS AROUND 3500 FT WITH THIS STRATOCU TO AFFECT RFD BY 13Z AND REMAINDER OF TERMINALS IN THE 15Z-16Z TIME FRAME. WEST WINDS AROUND 10 KNOTS THIS MORNING SHOULD BECOME WEST SOUTHWEST BY MID MORNING WITH SOME GUSTS TO 15 TO 20 KNOTS DEVELOPING. WINDS SHOULD CONTINUE TO BACK THIS AFTERNOON AS THE SFC TROUGH MOVES INTO THE NORTHERN PLAINS. AN AREA OF FAIRLY STRONG PRESSURE FALLS IS EXPECTED TO MOVE ACROSS NORTHERN ILLINOIS/SOUTHERN WISCONSIN LATE THIS EVENING AND EXPECTING A PERIOD OF HEIGHTENED GUSTS AS THIS OCCURS...ESPECIALLY AFTER 03Z WHEN SOME GUSTS TO AT LEAST 25 KNOTS WILL BE POSSIBLE. HAVE NOT MADE SIGNIFICANT CHANGES TO TIMING OF SNOW ASSOCIATED WITH THE SOUTHWEST CANADA TROUGH...AFFECTING RFD TOWARD 05Z AND REMAINDER OF TERMINALS BY 06Z OR 07Z. DURING PERIOD OF STEADIEST SNOW AFTER MIDNIGHT...WILL CONTINUE WITH IFR VSBYS AND LOW MVFR CIGS AROUND 1000 FT. CONDITIONS WILL BEGIN TO IMPROVE SATURDAY MORNING AS SFC FRONT PASSES THROUGH TAKING WINDS NORTHWEST...ALTHOUGH CONTINUED LIGHT SNOW IS EXPECTED THROUGH MID MORNING AS A SECONDARY SHORT WAVE DIGS INTO THE WESTERN GREAT LAKES. MARSILI && .MARINE... 310 AM CST THE PARADE OF WEATHER SYSTEMS WILL CONTINUE TO BRING STRONG WINDS TO LAKE MICHIGAN AT LEAST THROUGH EARLY SUNDAY. A BROAD SURFACE HIGH FROM THE CENTRAL/SOUTHERN PLAINS INTO THE MID MS RIVER VALLEY WILL CONTINUE TO SUPPORT A WESTERLY SFC PRESSURE GRADIENT WITH WINDS OF 15 TO 25 KNOTS THIS MORNING. STRONG SURFACE PRESSURE FALLS WILL DEVELOP THIS AFTERNOON ACROSS THE NORTHERN PLAINS AS AN AREA OF LOW PRESSURE MOVES ACROSS NORTHERN MINNESOTA THIS EVENING. THE PRESSURE FALLS WILL STRENGTHEN THE PRESSURE GRADIENT ACROSS LAKE MICHIGAN...AND EXPECTING SOUTHWEST GALES TO 35 KNOTS TO DEVELOP EARLY THIS EVENING ACROSS MOST OF LAKE MICHIGAN. AT THIS TIME WILL CONTINUE THE SMALL CRAFT ADVISORY FOR THE NEARSHORE WATERS...ALTHOUGH DUE TO THE STRENGTH OF THESE PRESSURE FALLS MOVING ACROSS THE REGION...SOME SOUTHWEST GALE GUSTS CANNOT BE RULED OUT EVEN FOR THE NEARSHORE WATERS TONIGHT. THE COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL TRACK ACROSS LAKE MICHIGAN SATURDAY MORNING BRINGING A POTENTIAL OF NORTHWEST GALES LATE SATURDAY MORNING THROUGH SATURDAY NIGHT...ESPECIALLY GIVEN SFC LOW WILL BE DEEPENING EAST OF LAKE MICHIGAN DURING THIS PERIOD. IN TERMS OF HEADLINES...HAVE UPGRADED THE OPEN WATERS GALE WATCH TO A GALE WARNING WHICH WILL BE IN EFFECT FROM EARLY THIS EVENING THROUGH SATURDAY NIGHT. AS MENTIONED...SMALL CRAFT ADVISORY FOR THE NEARSHORE WATERS WILL REMAIN IN EFFECT TONIGHT AND INTO SATURDAY MORNING...AND HAVE ISSUED GALE WATCH FOR THE NEARSHORE WATERS FOR SATURDAY AFTERNOON INTO SATURDAY EVENING FOR THE POTENTIAL OF NORTHWEST GALES. HAZARDOUS WAVES FOR SMALL CRAFT WILL THEN PERSIST INTO SUNDAY. WINDS AND WAVES WILL DIMINISH MORE SUBSTANTIALLY LATER SUNDAY AFTERNOON AND INTO SUNDAY EVENING AS A SFC RIDGE AXIS APPROACHES THE WESTERN GREAT LAKES. MARSILI && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868- LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...6 PM FRIDAY TO 3 AM SUNDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS UNTIL NOON SATURDAY. GALE WATCH...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...NOON SATURDAY TO MIDNIGHT SUNDAY. && $$ il AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 616 PM EST SAT DEC 6 2008 .AVIATION/UPDATE... SFC CDFNT IN ASSOCN/W SW TROUGH CLIPPING THROUGH CNTRL LWR MI ATTM ABT TO CLR NW OH. STG CAA IN WAKE OF SFC BNDRY W/RAPID VEERING OF FLW ACRS LK MI AND RAMPING SNOW STREAMERS DVLPG IN ITS WAKE. UPSTREAM TEMPS CRASHING W/SINGLE DIGITS NOTED OVR MOST OF MN. INITIAL LL FLW TRAJECTORY AT 320 DEGREES BUT VEERS FURTHER UPSTREAM TO 300 AND SIMILAR TO 21Z RUC/12Z 4KM ARW PROGS. WHILE THIS SUGGESTS GOING WSW HIGHLIGHTS ON THE MARK...IT ALSO RAISES SOME FLAGS FURTHER INLAND ESP IN LIGHT OF STG LL MEAN FLW AND INLAND CREEP XPCD W/INTENSE MULTIPLE SNOW BANDS. HIRES ARW OUTPUT CONFIRMED BY 21Z RUC MAKE A CASE FOR E/SE EXPANSION OF ADVISORY OVERNIGHT AND POTENTIAL UPGRADE TO WARNING FOR ST JOE MI/ELKHART. HWVR GIVEN DIMINISHING RESIDUAL CYCLONIC MSTR AND DECREASING INVERSION HGTS LT TONIGHT...DURATION OF HEAVIER SNOW LIMITED. WILL CONT TO MONITOR UPSTREAM DVLPMNTS THROUGH 7PM GIVEN EXISTING ADVISORY TIL THEN. GENERALLY MVFR CONDS THROUGH THE PD XCP AT KSBN WHERE IFR RESTRICTIONS TO VSBY/CIG WILL CONT OVERNIGHT BFR IMPRVG SOMEWHAT AFT DAYBREAK SUN. && .SHORT TERM... LOW OVER NRN MI WITH CDFNT EXTENDING SW ACROSS NRN INDIANA THIS AFTN. MID LEVEL DRY SLOT ASSOCIATED WITH THIS SYSTEM WAS ALSO PUSHING EAST ACROSS THE CWA THIS AFTN. CONTINUING TO GET SOME REPORTS OF FREEZING DRIZZLE IN THE DRY SLOT AND NORTHEAST OF THERE SNOWFALL WAS IN THE 1-3" RANGE WITH GUSTY WINDS AND SNOW SHOWERS ALONG THE COLD FRONT CAUSING SOME SGFNT WINTER WX HAZARDS SO EXTENDED ADVISORY ISSUED THIS MORNING TIL 7PM. MULT BAND LAKE EFFECT SNOW SHOWERS DVLPG OVER NW PORTION OF CWA ATTM. SHRTWV SEEN ON WATER VAPOR MOVG SE ACROSS NRN LM/NE WI THIS AFTN WILL MOVE SE ACRS THE CWA THIS EVE...LIKELY ENHANCING THE SNOW SHOWER ACTIVITY. 925MB OMEGA FCSTS SUGGEST BEST POTENTIAL FOR DOMINANT BAND OVERNIGHT WILL BE ACROSS BERRIEN/CASS SEWD THROUGH ELKHART/ST. JOE INDIANA. INVERSION FCST TO LOWER TO UNDER 5KFT LATE TONIGHT. WOULD EXPECT THIS TO DIMINISH INTENSITY OF SNOW SHOWERS CONSIDERABLY BY MORNING... HWVR AS GRADIENT WINDS DECREASE OVERNIGHT... THERE WILL BE A TENDENCY FOR LAND BREEZE COMPONENT TO WIND TO DVLP ENHANCING CONVERGENCE ALONG ERN SHORE...LIKELY CAUSING OR SUSTAINING A DOMINANT BAND IN THAT AREA THROUGH SUNDAY MORNING. NAM12 SHOWING WK SFC TROF MOVG SSE DOWN THE LAKE LATE TONIGHT... LIKELY AS A RESULT OF THIS LAND/LAKE WIND/CONVERGENCE INTERACTION. GOING FCST OF UP TO 6" OVERNIGHT IN ERN BERRIEN/CASS WITH LESSER AMOUNTS TO THE SE SEEMS REASONABLE AND NO CHANGES TO AMOUNTS/HEADLINES MADE ATTM. ADDITIONAL SNOWFALL IN THE WARNING/ADVISORY AREA AROUND AN INCH EXPECTED SUNDAY BEFORE SNOW SHOWERS TAPER END. LITTLE CHANGE MADE TO HIGHS FOR SUNDAY WHICH ARE AOB ALL 12Z MOS...BUT SEEM REASONABLE IF NOT A TOUCH TOO WARM BASED ON FCST -15C H85 TEMPS AND RECENT MOS WARM BIAS IN SIMILAR SITUATION ON FRI. SHRTWV TOPPING RIDGE OVER PAC NW THIS AFTN IS EXPECTED TO DROP SE INTO BACKSIDE OF LONGWAVE TROF OVER ERN US. THIS SYSTEM EXPECTED TO APPROACH OUR AREA SUNDAY NIGHT COINCIDING WITH WAA ON BACKSIDE OF SFC RIDGE RESULTING IN DECENT MID LEVEL ISENT LIFT WITH 2G/KG MIXING RATIO ON 290K ISENT SFC AROUND 700MB. LOW LEVELS REMAIN RATHER DRY THROUGH THIS PD SO STILL SOME DOUBT IF THIS WAA SNOW WILL FALL THIS FAR SOUTH...BUT DID BUMP UP POPS OVER ALL BUT SRN PORTION OF THE CWA. ALTHOUGH SKIES SHOULD BE MOSTLY CLOUDY SUNDAY NIGHT... LIGHT WINDS IN THE EVE WITH FRESH SNOW COVER AND RATHER DRY LOW LEVELS...ALONG WITH PRECEEDING COOLER DAY THAN FCST BY MOS...ALL SUGGEST GOING LOWS IN TEENS AND BLO ALL 12Z MOS GUIDANCE ARE REASONABLE AND NO CHANGES MADE. && LONG TERM...(MONDAY THROUGH SATURDAY)... EXTENDED PERIOD CONTINUES WITH AN ACTIVE BEGINNING AS MONDAY SEES WEAKENING CLIPPER WASH OUT AS IT APPROACHES THE AREA WITH ASSOCIATED AREA OF MOISTURE HEADING THROUGH THE GREAT LAKES. UPR LOW OVER SOUTHWEST OPENS AND PHASES WITH DEEPENING TROUGH OVER MOUNTAIN WEST AND SHIFTS EAST WITH SFC LOW EJECTING THROUGH THE OHIO VALLEY. WHILE DIFFERENCES EXITS IN SPEED AND INTENSITY OF THE LOW THE OPERATIONAL MODELS ARE TRENDING TOWARDS A BETTER CONSENSUS ON A WARMER SOLUTION WITH SFC LOW TRACKING ACROSS INDIANA. FOLLOWED A GFS/ECMWF BLEND FOR THIS SYSTEM WHILE NOTING THAT THE ENTIRE SUITE OF GFS ENSEMBLE MEMBERS IS SUBSTANTIALLY FURTHER SE WITH THIS SYSTEM PUTTING CWA IN A DECIDEDLY COLDER ENVIRONMENT. BASED ON A COMPROMISE BETWEEN OP GFS/ECMWF...THICKNESS FIELDS AND THERMAL PROFILES SUGGEST SNOW MONDAY NIGHT IN AN AREA OF WAA/ISENTROPIC LIFT INDICATED BY BRISK 40 KT FLOW ALONG MOIST 295K SFC. PROFILES DO NOT CURRENTLY SUGGEST A SUBSTANTIAL WINDOW FOR FREEZING RAIN BUT WILL NEED TO MONITOR WITH TIME AS SCENARIO OF WAA ALOFT OVER TRAPPED COLD AIR BELOW COULD YET PRODUCE A PERIOD WITH FZRA HAZARD. AS LOW DEEPENS AND MOVES NE ALONG BAROCLINIC ZONE COLUMN WARMS THROUGHOUT AND THERE IS CONSIDERABLE OPERATIONAL MODEL EVIDENCE TO SUGGEST CHANGING GRIDS OVER TO AN ALL RAIN TUESDAY. MODEL GUIDANCE NOW REACHING NEAR/ABV 40 FOR TUESDAY HIGHS AND BUFR SOUNDINGS SHOWING ABV FZ PROFILE THROUGH A SIGNIFICANT LAYER BY TUESDAY AFTERNOON. ALSO..GFS/EC NOW IN BASIC AGREEMENT WITH PTYPE SCENARIO...AND THE OP GFS HAS NUDGED FURTHER NORTH/WARMER WITH 3 SUCCESSIVE RUNS. HOWEVER..THE FACT THAT IT IS AN OUTLIER AMONG ITS OWN ENSEMBLE MEMBERS WARRANTS HOLDING ON TO CHC SNOW MENTION TUESDAY ALONG WITH LIKELY RAIN FOR THE TIME BEING. ECMWF IS FASTER/SHALLOWER WITH SFC LOW BUT HAS TRENDED TOWARDS GFS WITH 12Z RUN AND CURRENT WINDOW OF LIKELY POPS IS SLANTED TOWARDS SLOWER/DEEPER GFS. BEHIND SYSTEM COLDER AIR ONCE AGAIN FILTERS INTO THE CWA CHANGING EVERYONE BACK OVER TO A PD OF SNOW SHOWERS AS SFC LOW DEPARTS AND RETURNING TEMPS BACK BELOW NORMAL BY THE END OF THE WEEK. COLD H85 TEMPS AND NW FLOW ONCE AGAIN SIGNAL A CHANCE OF LAKE EFFECT AND HAVE CONSERVATIVELY ADDED CHC POPS IN BERRIEN COUNTY. MODELS THEN BRING IN ANOTHER WAVE AT THE END OF THE EXTENDED WITH SIGNIFICANT TIMING DIFFERENCES AND LARGE CONTRASTS IN DEPICTION OF UPPER LEVEL FLOW OVER NOAM. HAVE LEFT DAY 7 DRY FOR NOW TO LET THINGS SORT OUT WITH ANOTHER MODEL CYCLE. && .PREV DISCUSSION... /ISSUED 1233 PM EST SAT DEC 6 2008/ AVIATION... SYNOPTIC SCALE SNOW WITH ACCOMPANYING IFR VSBYS WILL BE MOVG OUT OF NRN INDIANA EARLY THIS AFTN AS CDFNT MOVES THROUGH THE AREA. WINDS WILL SHIFT TO NW BEHIND THE FRONT CAUSING LAKE EFFECT SNOW SHOWERS TO SPREAD INTO NRN INDIANA BY THIS EVE AND CONTINUING THROUGH SUNDAY MORNING. EXPECTING PREDOMINANTLY IFR CONDITIONS AT SBN DURING THE LAKE EFFECT EPISODE AND MVFR AT FWA. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY UNTIL 5 PM EST /4 PM CST/ THIS AFTERNOON FOR INZ003-006>009-012>018-020-022>027-032>034. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR INZ004-005. MI...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR MIZ080- 081. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ079. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ077-078. OH...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR OHZ001- 002-004-005-015-016-024-025. LM...GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...TAYLOR LONG TERM...LUDINGTON AVIATION...HOLSTEN UPDATE...HOLSTEN in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1233 PM EST SAT DEC 6 2008 .AVIATION... SYNOPTIC SCALE SNOW WITH ACCOMPANYING IFR VSBYS WILL BE MOVG OUT OF NRN INDIANA EARLY THIS AFTN AS CDFNT MOVES THROUGH THE AREA. WINDS WILL SHIFT TO NW BEHIND THE FRONT CAUSING LAKE EFFECT SNOW SHOWERS TO SPREAD INTO NRN INDIANA BY THIS EVE AND CONTINUING THROUGH SUNDAY MORNING. EXPECTING PREDOMINANTLY IFR CONDITIONS AT SBN DURING THE LAKE EFFECT EPISODE AND MVFR AT FWA. && .PREV DISCUSSION... /ISSUED 932 AM EST SAT DEC 6 2008/ UPDATE... AREA OF SNOW MOVG ACROSS CWA ATTM. SNOW FALLING IN WAA REGIME AHEAD OF LOW MOVG SE ACROSS NRN LM. WRN EDGE OF AREA OF PRECIP JUST AHEAD OF THE SYSTEMS COLD FRONT... LOOSES MID LEVEL MOISTURE RESULTING IN SOME FREEZING DRIZZLE...HAVE ADDED MENTION OF PATCHY FREEZING DRIZZLE TO SE 2/3 OF CWA AS FRONT MOVES THROUGH TODAY. UPSTREAM TEMPS AND CONTD WAA AHEAD OF FRONT SUGGEST GOING HIGHS FOR TODAY ARE A BIT ON THE COLD SIDE AND GENERALLY RAISED ABOUT 3F. OTRWS NO SGFNT CHANGES MADE ATTM. && SHORT TERM... .WINTER WEATHER TO IMPACT THE REGION TODAY AND TONIGHT... TODAY THROUGH SUNDAY NIGHT RATHER POTENT SHORTWAVE TROUGH AND ASSOCIATED SFC CYCLONE IS PUSHING INTO THE GREAT LAKES REGION. AN AREA ON LIGHT TO MODERATE SNOW IS ONGOING OVER PORTIONS OF IL/IN/WI IN THE WARM CONVEYOR BELT PORTION OF THE SYSTEM...WHERE A 50 KNOT LL JET IS AIDING IN WEAK MOISTURE ADVECTION AND CROSS ISOBARIC FLOW...LENDING TO UPGLIDE. VERY DRY COLUMN AS INDICATED BY ILX AND DVN SOUNDINGS IS ACTING TO LIMIT SNOWFALL SOMEWHAT...SUPPORTING WIDESPREAD VIRGA UNTIL SATURATION IS REACHED. THIS IS EVIDENT IN THE DONUT HOLE SIGNATURES THAT WERE OBSERVED AT DVN/ILX/AND LOT. REGARDLESS...ONCE SATURATION IS REACHED...EXPECTING A PERIOD OF LIGHT TO MODERATE SNOW TO OVERSPREAD THE REGION...SUPPORTING A QUICK BURST OF 1 TO 2 INCHES OF SNOW...WITH 1 INCH AMOUNTS MORE THE NORM. RATHER ROBUST TROPOPAUSE PRESSURE RISES COUPLED WITH STEEP MID LEVEL LAPSE RATES AND DECENT MOISTURE CONVERGENCE WILL CONTINUE TO SO SUPPORT BROAD LIFT THROUGH MUCH OF THE MORNING AND ACROSS THE FA. HAVE FAVORED THE SREF AND GFS WRT QPF GUIDANCE WITH THE CLIPPER SYSTEM...BUT OPTED FOR THE SUPPORT OF THE NAM12 FOR LAKE EFFECT PROCESSES. ALSO UTILIZED THE RUC13 FOR ADDED GUIDANCE. TODAY...CLIPPER SYSTEM WILL QUICKLY LEAVE GENERALLY 1 INCH OF SNOWFALL ACROSS THE MAJORITY OF THE FA. IN ADDITION STAUNCH FLOW/A RATHER TIGHT PRESSURE GRADIENT/STRONG FLOW ALOFT...45 TO 50 KNOTS OF H95 GEOSTROPHIC FLOW/AND LINKED MOMENTUM UNDER CAA WILL SUPPORT GUSTY WESTERLY WINDS. SUSTAINED WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS ARE EXPECTED THROUGH THE EVENING. THIS WILL ALLOW FOR AREAS OF BLOWING AND DRIFTING SNOW...MAKING TRAVEL DIFFICULT IN SOME AREAS. ROBUST CAA WITH H85 T/S DROPPING 5 TO 6C WILL HELP SUPPORT INCREASED INSTABILITY OVER LK MI THIS AFTERNOON. WESTERLY FLOW AT FIRST WILL LIMIT LK SNOW SHOWERS TO MAINLY MI THIS AFTERNOON. LL FLOW WILL CONTINUE TO VEER BEHIND THE COLD FRONT...INCREASING THE FLOW FETCH OVER LK MI...WITH PRECONDITIONED FLOW FROM LAKE SUPERIOR DEVELOPING. A SECONDARY UPPER IMPULSE WILL ACT TO FURTHER INCREASE INVERSION HEIGHTS ALREADY MODIFIED BY LAKE AGGREGATE EFFECTS FROM LK SUPERIOR. THE NET EFFECT WILL BE LAKE INDUCED CAPES OF 500 TO 700 J/KG WITH MAX UPWARD OMEGA IN THE DGZ. THIS WILL FAVOR THE DEVELOPMENT OF SEVERAL INTENSE BANDS OF LK EFFECT SNOW...CONGEALING INTO ONE DOMINATE BAND AS CONVECTIVE INFLUENCES EVENTUALLY OUTWEIGH WIND SHEAR EFFECTS. NAM12 AND RUC 13 PROGS HAVE CONSISTENTLY BEEN SUPPORTING THE PLACEMENT OF THIS BAND OVER EASTERN BERRIEN AND CASS COUNTIES. HIRES WRF SIMULATIONS FURTHER SUPPORT THIS IDEA. SNOWFALL RATES OF 2 TO 4 INCHES PER HOUR ARE WILL BE POSSIBLE WITH AN INTENSE DOMINATE BAND...ESPECIALLY IF THE LL MASS FIELD READJUSTS TO THE MESOSCALE PROCESS...ENHANCING LL CONVERGENCE. HAVE ISSUED A WINTER STORM WARNING FOR BERRIEN AND CASS COUNTIES...WITH 1 TO 2 INCHES OF SNOWFALL THIS MORNING/PERIODS OF LAKE EFFECT SNOW THIS AFTERNOON WITH AND ADDITIONAL 2 TO 3 INCHES POSSIBLE/BLOWING SNOW THROUGH THE DAY AND NIGHT SIGNIFICANTLY REDUCING VISIBILITIES/AND ADDITIONAL HEAVY LAKE EFFECT SNOW WITH AN ADDITIONAL 4 TO 8 INCHES POSSIBLE. OPTED FOR A WINTER WEATHER ADV FOR ST. JOE IN/MI AND ELKHART FOR COMBINATION OF LAKE EFFECT SNOW AND BLOWING SNOW WITH 3 TO 6 INCHES POSSIBLE BY SUNDAY MORNING. IT IS QUITE POSSIBLE THAT LAGRANGE AND MAYBE NOBLE COUNTIES MAY HAVE TO BE ADDED TO THE ADV AS CURRENT MODEL GUIDANCE CERTAINLY HINTS AT A PERIOD OF INTENSE LL OMEGA CENTERED OVER THESE COUNTIES. HEAVIEST LAKE SNOWS WILL OCCUR SAT EVENING AND BEGIN TO DIMINISH SUN MORNING WITH FALLING INVERSION HEIGHTS AND SFC RIDGING SHIFTING WINDS TO THE SW. TEMPS WILL REMAIN COLD THROUGH THE PERIOD WITH HIGHS RAGING 10 TO 15 DEGREES BELOW NORMAL. HAVE OPTED TO UNDERCUT GUIDANCE TEMPS GIVEN ANOMALOUSLY COLD CONDITIONS PRESENT. LONG TERM... .MONDAY THROUGH FRIDAY... COMPLICATED AND LOW CONFIDENCE LONG TERM FORECAST DUE TO HIGHLY ENERGETIC AND COMPLICATED MID AND UPPER LEVEL FLOW OVER PACIFIC AND WESTERN NORTH AMERICA. STILL EXPECT BELOW NORMAL TEMPERATURES FOR A LARGE PART OF THE PERIOD AND POTENTIAL FOR A MODERATE TO HEAVY PRECIPITATION EVENT MID WEEK. WATER VAPOR THIS MORNING SHOWS A VERY ENERGETIC PATTERN...SIMILAR TO LAST YEAR ABOUT THIS TIME. AS DISCUSSED LAST NIGHT...MODELS LIKELY NOT RESOLVING FEATURES OVER THE PACIFIC WELL GIVEN LIMITED SAMPLING MEASURES. FIRST AREA OF CONCERN IS WITH IMPRESSIVE LOOKING SUB-TROPICAL MOISTURE PLUME DEVELOPING NEAR 15N AND 120W. MODELS TRYING TO PICK UP ON THIS BUT CONCERNED THEY ARE NOT NEAR STRONG ENOUGH GIVEN DEPICTION IN WATER VAPOR. THIS AREA EXPECTED TO CONTINUE SPREADING NORTHEAST AND WILL FEED INTO DEVELOPING MID LEVEL LOW OFF OF CA COAST THAT WILL BECOME OUR WEATHER MAKER FOR MID WEEK. SECONDARY AREA OF CONCERN IS WITH STRONG JET CORE NEAR 40N AND 150W. MODELS DO SEEM TO HAVE A HANDLE ON THIS FEATURE...BUT GIVEN ITS STRENGTH THERE IS SOME CONCERN WITH HOW IT WILL EVOLVE OVER WESTERN CONUS. THIS IS A LARGE PART OF THE DIFFERENCES IN MODEL SOLUTIONS FOR MID WEEK. IT WILL BE THE INTERACTION OF THESE TWO PACIFIC FEATURES WITH THE MID LEVEL LOW ACROSS THE SOUTHWEST CONUS THAT DETERMINES ITS EVOLUTION AND IMPACT ON OUR AREA. AS MENTIONED LAST NIGHT...WE FELT MODELS WERE NOT HANDLING THIS ENERGY WELL AND A STRONGER SYSTEM WAS EXPECTED. LATEST MEDIUM RANGE SOLUTIONS ARE INDEED STRONGER...WITH GFS BEING THE STRONGEST. COMPLICATIONS FOR OUR FORECAST AREA WILL BE WITH AMOUNT OF WARM AIR ADVECTION AHEAD OF SYSTEM AND ITS ACTUAL TRACK. ECMWF WHILE WEAKER IS FURTHER NORTH WITH STRONG WAA AND MOISTURE INFLUX INTO THE AREA LATE MONDAY NIGHT AND TUESDAY...INDICATING A POSSIBLE HEAVY RAIN EVENT. GFS IS STRONGER AND FURTHER SOUTH WITH COLDER AIR OVER NORTHERN HALF OF FORECAST AREA...YIELDING A POSSIBLE RAIN EVENT SOUTH AND SNOW NORTH. BOTH SOLUTIONS PLAUSIBLE AND AGAIN WILL LIKELY NOT BE RESOLVED UNTIL SYSTEM GETS WITHIN RADIOSONDE NETWORK. AGREEMENT LIES WITH SOME TYPE OF PRECIPITATION EVENT WITH POTENTIAL FOR HEAVY PCPN SOMEWHERE IN THE WESTERN LAKES OR OHIO VALLEY REGION FROM LATE MONDAY NIGHT INTO EARLY WEDNESDAY. HAVE INCREASED POPS DURING THIS WINDOW WITH LIKELY POPS CENTERED ON TUESDAY. STAYED WITH ALL SNOW MONDAY NIGHT WITH INITIAL COLDER AIR IN PLACE AND LOWER WET BULB TEMPERATURES. ALSO STAYED WITH RAIN OR SNOW MENTION TUESDAY GIVEN UNCERTAINTY IN TRACK AND THERMAL FIELDS. BEYOND WEDNESDAY FEW CHANGES WERE MADE. MODELS CONTINUE TO INDICATE SOME TYPE OF COLDER AIR INTRUSION BUT NOT NEAR AS STRONG AS 48 HOURS AGO. THUS KEPT IDEA OF SLIGHTLY BELOW NORMAL TEMPERATURES. CLIPPER SYSTEM POSSIBLE BY END OF WEEK BUT AGAIN QUITE A BIT OF DISAGREEMENT IN MODELS SO NO CHANGES MADE. SOME SIGNALS TO A PATTERN CHANGE WELL BEYOND DAY 7...TOWARD MID MONTH. ENSEMBLES SHOWING WESTERN CONUS RIDGE BEING REPLACED BY DEEP TROUGH WITH FLOW OVER OUR AREA BECOMING MORE SOUTHWEST AND POSSIBLY ACTIVE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY UNTIL 5 PM EST /4 PM CST/ THIS AFTERNOON FOR INZ003-006>009-012>018-020-022>027-032>034. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR INZ004-005. MI...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR MIZ080- 081. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ079. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ077-078. OH...WINTER WEATHER ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR OHZ001- 002-004-005-015-016-024-025. LM...GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...TAYLOR UPDATE...TAYLOR in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 932 AM EST SAT DEC 6 2008 .UPDATE... AREA OF SNOW MOVG ACROSS CWA ATTM. SNOW FALLING IN WAA REGIME AHEAD OF LOW MOVG SE ACROSS NRN LM. WRN EDGE OF AREA OF PRECIP JUST AHEAD OF THE SYSTEMS COLD FRONT... LOOSES MID LEVEL MOISTURE RESULTING IN SOME FREEZING DRIZZLE...HAVE ADDED MENTION OF PATCHY FREEZING DRIZZLE TO SE 2/3 OF CWA AS FRONT MOVES THROUGH TODAY. UPSTREAM TEMPS AND CONTD WAA AHEAD OF FRONT SUGGEST GOING HIGHS FOR TODAY ARE A BIT ON THE COLD SIDE AND GENERALLY RAISED ABOUT 3F. OTRWS NO SGFNT CHANGES MADE ATTM. && .PREV DISCUSSION... /ISSUED 620 AM EST SAT DEC 6 2008/ AVIATION... SNOW WILL BE OVER THE AREA THIS MORNING AND DIMINISH BY AFTERNOON. VIS RESTRICTIONS AND LOWER CIGS EXPECTED. LAKE EFFECT SNOW SHOWERS WILL DEVELOP THIS AFTERNOON AND CONTINUE INTO SUNDAY. THIS WILL AFFECT MAINLY KSBN BUT TRAJECTORIES SUGGEST SOME SNOW SHOWERS COULD MAKE IT INTO KFWA. SHORT TERM... ..WINTER WEATHER TO IMPACT THE REGION TODAY AND TONIGHT... TODAY THROUGH SUNDAY NIGHT RATHER POTENT SHORTWAVE TROUGH AND ASSOCIATED SFC CYCLONE IS PUSHING INTO THE GREAT LAKES REGION. AN AREA ON LIGHT TO MODERATE SNOW IS ONGOING OVER PORTIONS OF IL/IN/WI IN THE WARM CONVEYOR BELT PORTION OF THE SYSTEM...WHERE A 50 KNOT LL JET IS AIDING IN WEAK MOISTURE ADVECTION AND CROSS ISOBARIC FLOW...LENDING TO UPGLIDE. VERY DRY COLUMN AS INDICATED BY ILX AND DVN SOUNDINGS IS ACTING TO LIMIT SNOWFALL SOMEWHAT...SUPPORTING WIDESPREAD VIRGA UNTIL SATURATION IS REACHED. THIS IS EVIDENT IN THE DONUT HOLE SIGNATURES THAT WERE OBSERVED AT DVN/ILX/AND LOT. REGARDLESS...ONCE SATURATION IS REACHED...EXPECTING A PERIOD OF LIGHT TO MODERATE SNOW TO OVERSPREAD THE REGION...SUPPORTING A QUICK BURST OF 1 TO 2 INCHES OF SNOW...WITH 1 INCH AMOUNTS MORE THE NORM. RATHER ROBUST TROPOPAUSE PRESSURE RISES COUPLED WITH STEEP MID LEVEL LAPSE RATES AND DECENT MOISTURE CONVERGENCE WILL CONTINUE TO SO SUPPORT BROAD LIFT THROUGH MUCH OF THE MORNING AND ACROSS THE FA. HAVE FAVORED THE SREF AND GFS WRT QPF GUIDANCE WITH THE CLIPPER SYSTEM...BUT OPTED FOR THE SUPPORT OF THE NAM12 FOR LAKE EFFECT PROCESSES. ALSO UTILIZED THE RUC13 FOR ADDED GUIDANCE. TODAY...CLIPPER SYSTEM WILL QUICKLY LEAVE GENERALLY 1 INCH OF SNOWFALL ACROSS THE MAJORITY OF THE FA. IN ADDITION STAUNCH FLOW/A RATHER TIGHT PRESSURE GRADIENT/STRONG FLOW ALOFT...45 TO 50 KNOTS OF H95 GEOSTROPHIC FLOW/AND LINKED MOMENTUM UNDER CAA WILL SUPPORT GUSTY WESTERLY WINDS. SUSTAINED WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS ARE EXPECTED THROUGH THE EVENING. THIS WILL ALLOW FOR AREAS OF BLOWING AND DRIFTING SNOW...MAKING TRAVEL DIFFICULT IN SOME AREAS. ROBUST CAA WITH H85 T/S DROPPING 5 TO 6C WILL HELP SUPPORT INCREASED INSTABILITY OVER LK MI THIS AFTERNOON. WESTERLY FLOW AT FIRST WILL LIMIT LK SNOW SHOWERS TO MAINLY MI THIS AFTERNOON. LL FLOW WILL CONTINUE TO VEER BEHIND THE COLD FRONT...INCREASING THE FLOW FETCH OVER LK MI...WITH PRECONDITIONED FLOW FROM LAKE SUPERIOR DEVELOPING. A SECONDARY UPPER IMPULSE WILL ACT TO FURTHER INCREASE INVERSION HEIGHTS ALREADY MODIFIED BY LAKE AGGREGATE EFFECTS FROM LK SUPERIOR. THE NET EFFECT WILL BE LAKE INDUCED CAPES OF 500 TO 700 J/KG WITH MAX UPWARD OMEGA IN THE DGZ. THIS WILL FAVOR THE DEVELOPMENT OF SEVERAL INTENSE BANDS OF LK EFFECT SNOW...CONGEALING INTO ONE DOMINATE BAND AS CONVECTIVE INFLUENCES EVENTUALLY OUTWEIGH WIND SHEAR EFFECTS. NAM12 AND RUC 13 PROGS HAVE CONSISTENTLY BEEN SUPPORTING THE PLACEMENT OF THIS BAND OVER EASTERN BERRIEN AND CASS COUNTIES. HIRES WRF SIMULATIONS FURTHER SUPPORT THIS IDEA. SNOWFALL RATES OF 2 TO 4 INCHES PER HOUR ARE WILL BE POSSIBLE WITH AN INTENSE DOMINATE BAND...ESPECIALLY IF THE LL MASS FIELD READJUSTS TO THE MESOSCALE PROCESS...ENHANCING LL CONVERGENCE. HAVE ISSUED A WINTER STORM WARNING FOR BERRIEN AND CASS COUNTIES...WITH 1 TO 2 INCHES OF SNOWFALL THIS MORNING/PERIODS OF LAKE EFFECT SNOW THIS AFTERNOON WITH AND ADDITIONAL 2 TO 3 INCHES POSSIBLE/BLOWING SNOW THROUGH THE DAY AND NIGHT SIGNIFICANTLY REDUCING VISIBILITIES/AND ADDITIONAL HEAVY LAKE EFFECT SNOW WITH AN ADDITIONAL 4 TO 8 INCHES POSSIBLE. OPTED FOR A WINTER WEATHER ADV FOR ST. JOE IN/MI AND ELKHART FOR COMBINATION OF LAKE EFFECT SNOW AND BLOWING SNOW WITH 3 TO 6 INCHES POSSIBLE BY SUNDAY MORNING. IT IS QUITE POSSIBLE THAT LAGRANGE AND MAYBE NOBLE COUNTIES MAY HAVE TO BE ADDED TO THE ADV AS CURRENT MODEL GUIDANCE CERTAINLY HINTS AT A PERIOD OF INTENSE LL OMEGA CENTERED OVER THESE COUNTIES. HEAVIEST LAKE SNOWS WILL OCCUR SAT EVENING AND BEGIN TO DIMINISH SUN MORNING WITH FALLING INVERSION HEIGHTS AND SFC RIDGING SHIFTING WINDS TO THE SW. TEMPS WILL REMAIN COLD THROUGH THE PERIOD WITH HIGHS RAGING 10 TO 15 DEGREES BELOW NORMAL. HAVE OPTED TO UNDERCUT GUIDANCE TEMPS GIVEN ANOMALOUSLY COLD CONDITIONS PRESENT. LONG TERM... ..MONDAY THROUGH FRIDAY... COMPLICATED AND LOW CONFIDENCE LONG TERM FORECAST DUE TO HIGHLY ENERGETIC AND COMPLICATED MID AND UPPER LEVEL FLOW OVER PACIFIC AND WESTERN NORTH AMERICA. STILL EXPECT BELOW NORMAL TEMPERATURES FOR A LARGE PART OF THE PERIOD AND POTENTIAL FOR A MODERATE TO HEAVY PRECIPITATION EVENT MID WEEK. WATER VAPOR THIS MORNING SHOWS A VERY ENERGETIC PATTERN...SIMILAR TO LAST YEAR ABOUT THIS TIME. AS DISCUSSED LAST NIGHT...MODELS LIKELY NOT RESOLVING FEATURES OVER THE PACIFIC WELL GIVEN LIMITED SAMPLING MEASURES. FIRST AREA OF CONCERN IS WITH IMPRESSIVE LOOKING SUB-TROPICAL MOISTURE PLUME DEVELOPING NEAR 15N AND 120W. MODELS TRYING TO PICK UP ON THIS BUT CONCERNED THEY ARE NOT NEAR STRONG ENOUGH GIVEN DEPICTION IN WATER VAPOR. THIS AREA EXPECTED TO CONTINUE SPREADING NORTHEAST AND WILL FEED INTO DEVELOPING MID LEVEL LOW OFF OF CA COAST THAT WILL BECOME OUR WEATHER MAKER FOR MID WEEK. SECONDARY AREA OF CONCERN IS WITH STRONG JET CORE NEAR 40N AND 150W. MODELS DO SEEM TO HAVE A HANDLE ON THIS FEATURE...BUT GIVEN ITS STRENGTH THERE IS SOME CONCERN WITH HOW IT WILL EVOLVE OVER WESTERN CONUS. THIS IS A LARGE PART OF THE DIFFERENCES IN MODEL SOLUTIONS FOR MID WEEK. IT WILL BE THE INTERACTION OF THESE TWO PACIFIC FEATURES WITH THE MID LEVEL LOW ACROSS THE SOUTHWEST CONUS THAT DETERMINES ITS EVOLUTION AND IMPACT ON OUR AREA. AS MENTIONED LAST NIGHT...WE FELT MODELS WERE NOT HANDLING THIS ENERGY WELL AND A STRONGER SYSTEM WAS EXPECTED. LATEST MEDIUM RANGE SOLUTIONS ARE INDEED STRONGER...WITH GFS BEING THE STRONGEST. COMPLICATIONS FOR OUR FORECAST AREA WILL BE WITH AMOUNT OF WARM AIR ADVECTION AHEAD OF SYSTEM AND ITS ACTUAL TRACK. ECMWF WHILE WEAKER IS FURTHER NORTH WITH STRONG WAA AND MOISTURE INFLUX INTO THE AREA LATE MONDAY NIGHT AND TUESDAY...INDICATING A POSSIBLE HEAVY RAIN EVENT. GFS IS STRONGER AND FURTHER SOUTH WITH COLDER AIR OVER NORTHERN HALF OF FORECAST AREA...YIELDING A POSSIBLE RAIN EVENT SOUTH AND SNOW NORTH. BOTH SOLUTIONS PLAUSIBLE AND AGAIN WILL LIKELY NOT BE RESOLVED UNTIL SYSTEM GETS WITHIN RADIOSONDE NETWORK. AGREEMENT LIES WITH SOME TYPE OF PRECIPITATION EVENT WITH POTENTIAL FOR HEAVY PCPN SOMEWHERE IN THE WESTERN LAKES OR OHIO VALLEY REGION FROM LATE MONDAY NIGHT INTO EARLY WEDNESDAY. HAVE INCREASED POPS DURING THIS WINDOW WITH LIKELY POPS CENTERED ON TUESDAY. STAYED WITH ALL SNOW MONDAY NIGHT WITH INITIAL COLDER AIR IN PLACE AND LOWER WET BULB TEMPERATURES. ALSO STAYED WITH RAIN OR SNOW MENTION TUESDAY GIVEN UNCERTAINTY IN TRACK AND THERMAL FIELDS. BEYOND WEDNESDAY FEW CHANGES WERE MADE. MODELS CONTINUE TO INDICATE SOME TYPE OF COLDER AIR INTRUSION BUT NOT NEAR AS STRONG AS 48 HOURS AGO. THUS KEPT IDEA OF SLIGHTLY BELOW NORMAL TEMPERATURES. CLIPPER SYSTEM POSSIBLE BY END OF WEEK BUT AGAIN QUITE A BIT OF DISAGREEMENT IN MODELS SO NO CHANGES MADE. SOME SIGNALS TO A PATTERN CHANGE WELL BEYOND DAY 7...TOWARD MID MONTH. ENSEMBLES SHOWING WESTERN CONUS RIDGE BEING REPLACED BY DEEP TROUGH WITH FLOW OVER OUR AREA BECOMING MORE SOUTHWEST AND POSSIBLY ACTIVE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 7 AM EST SUNDAY FOR INZ004-005. MI...WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ077-078. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ079. OH...NONE. LM...GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...JC UPDATE...TAYLOR in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 620 AM EST SAT DEC 6 2008 .AVIATION... SNOW WILL BE OVER THE AREA THIS MORNING AND DIMINISH BY AFTERNOON. VIS RESTRICTIONS AND LOWER CIGS EXPECTED. LAKE EFFECT SNOW SHOWERS WILL DEVELOP THIS AFTERNOON AND CONTINUE INTO SUNDAY. THIS WILL AFFECT MAINLY KSBN BUT TRAJECTORIES SUGGEST SOME SNOW SHOWERS COULD MAKE IT INTO KFWA. && .SHORT TERM... ...WINTER WEATHER TO IMPACT THE REGION TODAY AND TONIGHT... TODAY THROUGH SUNDAY NIGHT RATHER POTENT SHORTWAVE TROUGH AND ASSOCIATED SFC CYCLONE IS PUSHING INTO THE GREAT LAKES REGION. AN AREA ON LIGHT TO MODERATE SNOW IS ONGOING OVER PORTIONS OF IL/IN/WI IN THE WARM CONVEYOR BELT PORTION OF THE SYSTEM...WHERE A 50 KNOT LL JET IS AIDING IN WEAK MOISTURE ADVECTION AND CROSS ISOBARIC FLOW...LENDING TO UPGLIDE. VERY DRY COLUMN AS INDICATED BY ILX AND DVN SOUNDINGS IS ACTING TO LIMIT SNOWFALL SOMEWHAT...SUPPORTING WIDESPREAD VIRGA UNTIL SATURATION IS REACHED. THIS IS EVIDENT IN THE DONUT HOLE SIGNATURES THAT WERE OBSERVED AT DVN/ILX/AND LOT. REGARDLESS...ONCE SATURATION IS REACHED...EXPECTING A PERIOD OF LIGHT TO MODERATE SNOW TO OVERSPREAD THE REGION...SUPPORTING A QUICK BURST OF 1 TO 2 INCHES OF SNOW...WITH 1 INCH AMOUNTS MORE THE NORM. RATHER ROBUST TROPOPAUSE PRESSURE RISES COUPLED WITH STEEP MID LEVEL LAPSE RATES AND DECENT MOISTURE CONVERGENCE WILL CONTINUE TO SO SUPPORT BROAD LIFT THROUGH MUCH OF THE MORNING AND ACROSS THE FA. HAVE FAVORED THE SREF AND GFS WRT QPF GUIDANCE WITH THE CLIPPER SYSTEM...BUT OPTED FOR THE SUPPORT OF THE NAM12 FOR LAKE EFFECT PROCESSES. ALSO UTILIZED THE RUC13 FOR ADDED GUIDANCE. TODAY...CLIPPER SYSTEM WILL QUICKLY LEAVE GENERALLY 1 INCH OF SNOWFALL ACROSS THE MAJORITY OF THE FA. IN ADDITION STAUNCH FLOW/A RATHER TIGHT PRESSURE GRADIENT/STRONG FLOW ALOFT...45 TO 50 KNOTS OF H95 GEOSTROPHIC FLOW/AND LINKED MOMENTUM UNDER CAA WILL SUPPORT GUSTY WESTERLY WINDS. SUSTAINED WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS ARE EXPECTED THROUGH THE EVENING. THIS WILL ALLOW FOR AREAS OF BLOWING AND DRIFTING SNOW...MAKING TRAVEL DIFFICULT IN SOME AREAS. ROBUST CAA WITH H85 T/S DROPPING 5 TO 6C WILL HELP SUPPORT INCREASED INSTABILITY OVER LK MI THIS AFTERNOON. WESTERLY FLOW AT FIRST WILL LIMIT LK SNOW SHOWERS TO MAINLY MI THIS AFTERNOON. LL FLOW WILL CONTINUE TO VEER BEHIND THE COLD FRONT...INCREASING THE FLOW FETCH OVER LK MI...WITH PRECONDITIONED FLOW FROM LAKE SUPERIOR DEVELOPING. A SECONDARY UPPER IMPULSE WILL ACT TO FURTHER INCREASE INVERSION HEIGHTS ALREADY MODIFIED BY LAKE AGGREGATE EFFECTS FROM LK SUPERIOR. THE NET EFFECT WILL BE LAKE INDUCED CAPES OF 500 TO 700 J/KG WITH MAX UPWARD OMEGA IN THE DGZ. THIS WILL FAVOR THE DEVELOPMENT OF SEVERAL INTENSE BANDS OF LK EFFECT SNOW...CONGEALING INTO ONE DOMINATE BAND AS CONVECTIVE INFLUENCES EVENTUALLY OUTWEIGH WIND SHEAR EFFECTS. NAM12 AND RUC 13 PROGS HAVE CONSISTENTLY BEEN SUPPORTING THE PLACEMENT OF THIS BAND OVER EASTERN BERRIEN AND CASS COUNTIES. HIRES WRF SIMULATIONS FURTHER SUPPORT THIS IDEA. SNOWFALL RATES OF 2 TO 4 INCHES PER HOUR ARE WILL BE POSSIBLE WITH AN INTENSE DOMINATE BAND...ESPECIALLY IF THE LL MASS FIELD READJUSTS TO THE MESOSCALE PROCESS...ENHANCING LL CONVERGENCE. HAVE ISSUED A WINTER STORM WARNING FOR BERRIEN AND CASS COUNTIES...WITH 1 TO 2 INCHES OF SNOWFALL THIS MORNING/PERIODS OF LAKE EFFECT SNOW THIS AFTERNOON WITH AND ADDITIONAL 2 TO 3 INCHES POSSIBLE/BLOWING SNOW THROUGH THE DAY AND NIGHT SIGNIFICANTLY REDUCING VISIBILITIES/AND ADDITIONAL HEAVY LAKE EFFECT SNOW WITH AN ADDITIONAL 4 TO 8 INCHES POSSIBLE. OPTED FOR A WINTER WEATHER ADV FOR ST. JOE IN/MI AND ELKHART FOR COMBINATION OF LAKE EFFECT SNOW AND BLOWING SNOW WITH 3 TO 6 INCHES POSSIBLE BY SUNDAY MORNING. IT IS QUITE POSSIBLE THAT LAGRANGE AND MAYBE NOBLE COUNTIES MAY HAVE TO BE ADDED TO THE ADV AS CURRENT MODEL GUIDANCE CERTAINLY HINTS AT A PERIOD OF INTENSE LL OMEGA CENTERED OVER THESE COUNTIES. HEAVIEST LAKE SNOWS WILL OCCUR SAT EVENING AND BEGIN TO DIMINISH SUN MORNING WITH FALLING INVERSION HEIGHTS AND SFC RIDGING SHIFTING WINDS TO THE SW. TEMPS WILL REMAIN COLD THROUGH THE PERIOD WITH HIGHS RAGING 10 TO 15 DEGREES BELOW NORMAL. HAVE OPTED TO UNDERCUT GUIDANCE TEMPS GIVEN ANOMALOUSLY COLD CONDITIONS PRESENT. && .LONG TERM... ...MONDAY THROUGH FRIDAY... COMPLICATED AND LOW CONFIDENCE LONG TERM FORECAST DUE TO HIGHLY ENERGETIC AND COMPLICATED MID AND UPPER LEVEL FLOW OVER PACIFIC AND WESTERN NORTH AMERICA. STILL EXPECT BELOW NORMAL TEMPERATURES FOR A LARGE PART OF THE PERIOD AND POTENTIAL FOR A MODERATE TO HEAVY PRECIPITATION EVENT MID WEEK. WATER VAPOR THIS MORNING SHOWS A VERY ENERGETIC PATTERN...SIMILAR TO LAST YEAR ABOUT THIS TIME. AS DISCUSSED LAST NIGHT...MODELS LIKELY NOT RESOLVING FEATURES OVER THE PACIFIC WELL GIVEN LIMITED SAMPLING MEASURES. FIRST AREA OF CONCERN IS WITH IMPRESSIVE LOOKING SUB-TROPICAL MOISTURE PLUME DEVELOPING NEAR 15N AND 120W. MODELS TRYING TO PICK UP ON THIS BUT CONCERNED THEY ARE NOT NEAR STRONG ENOUGH GIVEN DEPICTION IN WATER VAPOR. THIS AREA EXPECTED TO CONTINUE SPREADING NORTHEAST AND WILL FEED INTO DEVELOPING MID LEVEL LOW OFF OF CA COAST THAT WILL BECOME OUR WEATHER MAKER FOR MID WEEK. SECONDARY AREA OF CONCERN IS WITH STRONG JET CORE NEAR 40N AND 150W. MODELS DO SEEM TO HAVE A HANDLE ON THIS FEATURE...BUT GIVEN ITS STRENGTH THERE IS SOME CONCERN WITH HOW IT WILL EVOLVE OVER WESTERN CONUS. THIS IS A LARGE PART OF THE DIFFERENCES IN MODEL SOLUTIONS FOR MID WEEK. IT WILL BE THE INTERACTION OF THESE TWO PACIFIC FEATURES WITH THE MID LEVEL LOW ACROSS THE SOUTHWEST CONUS THAT DETERMINES ITS EVOLUTION AND IMPACT ON OUR AREA. AS MENTIONED LAST NIGHT...WE FELT MODELS WERE NOT HANDLING THIS ENERGY WELL AND A STRONGER SYSTEM WAS EXPECTED. LATEST MEDIUM RANGE SOLUTIONS ARE INDEED STRONGER...WITH GFS BEING THE STRONGEST. COMPLICATIONS FOR OUR FORECAST AREA WILL BE WITH AMOUNT OF WARM AIR ADVECTION AHEAD OF SYSTEM AND ITS ACTUAL TRACK. ECMWF WHILE WEAKER IS FURTHER NORTH WITH STRONG WAA AND MOISTURE INFLUX INTO THE AREA LATE MONDAY NIGHT AND TUESDAY...INDICATING A POSSIBLE HEAVY RAIN EVENT. GFS IS STRONGER AND FURTHER SOUTH WITH COLDER AIR OVER NORTHERN HALF OF FORECAST AREA...YIELDING A POSSIBLE RAIN EVENT SOUTH AND SNOW NORTH. BOTH SOLUTIONS PLAUSIBLE AND AGAIN WILL LIKELY NOT BE RESOLVED UNTIL SYSTEM GETS WITHIN RADIOSONDE NETWORK. AGREEMENT LIES WITH SOME TYPE OF PRECIPITATION EVENT WITH POTENTIAL FOR HEAVY PCPN SOMEWHERE IN THE WESTERN LAKES OR OHIO VALLEY REGION FROM LATE MONDAY NIGHT INTO EARLY WEDNESDAY. HAVE INCREASED POPS DURING THIS WINDOW WITH LIKELY POPS CENTERED ON TUESDAY. STAYED WITH ALL SNOW MONDAY NIGHT WITH INITIAL COLDER AIR IN PLACE AND LOWER WET BULB TEMPERATURES. ALSO STAYED WITH RAIN OR SNOW MENTION TUESDAY GIVEN UNCERTAINTY IN TRACK AND THERMAL FIELDS. BEYOND WEDNESDAY FEW CHANGES WERE MADE. MODELS CONTINUE TO INDICATE SOME TYPE OF COLDER AIR INTRUSION BUT NOT NEAR AS STRONG AS 48 HOURS AGO. THUS KEPT IDEA OF SLIGHTLY BELOW NORMAL TEMPERATURES. CLIPPER SYSTEM POSSIBLE BY END OF WEEK BUT AGAIN QUITE A BIT OF DISAGREEMENT IN MODELS SO NO CHANGES MADE. SOME SIGNALS TO A PATTERN CHANGE WELL BEYOND DAY 7...TOWARD MID MONTH. ENSEMBLES SHOWING WESTERN CONUS RIDGE BEING REPLACED BY DEEP TROUGH WITH FLOW OVER OUR AREA BECOMING MORE SOUTHWEST AND POSSIBLY ACTIVE. && AVIATION.../06Z TAFS/ CLIPPER SYSTEM WILL MOVE THROUGH THE REGION DURING THE PERIOD...BRINGING DETERIORATING FLIGHT CONDITIONS TO THE REGION. EXPECTING A PERIOD OF MVFR CIGS/VISBY WITH THE SYNOPTIC SYSTEM AT SBN AND FWA. THIS LINES UP WELL WITH MOS AND UPSTREAM OBS. STRONG GUSTY SOUTHERLY WINDS WILL BE EXPECTED GIVEN VERY STRONG FLOW OFF THE SFC AND A TIGHT PRESSURE GRADIENT IN PLACE. COLD FRONT WILL PUSH THROUGH THE REGION LATE MORNING AND EARLY AFTERNOON...ALLOWING WINDS TO VEER WESTERLY. GUSTS OF 25 TO 30 KNOTS WILL SUPPORT AREAS OF BLOWING SNOW...WHICH COULD ALLOW FOR BRIEF VISBY REDUCTIONS ACROSS THE FA. LAKE EFFECT SNOWS WILL DEVELOP AND SHIFT SOUTH INTO THE NORTHWEST FA...WITH IFR/LIFR CONDITIONS LIKELY THERE BY EVENING IN A COMBINATION OF BLOWING SNOW AND HEAVY LAKE SNOWS. HAVE TRENDED SBN IN THIS DIRECTION. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 7 AM EST SUNDAY FOR INZ004-005. MI...WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ077-078. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ079. OH...NONE. LM...GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...JC in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 400 AM EST SAT DEC 6 2008 .SHORT TERM... ...WINTER WEATHER TO IMPACT THE REGION TODAY AND TONIGHT... TODAY THROUGH SUNDAY NIGHT RATHER POTENT SHORTWAVE TROUGH AND ASSOCIATED SFC CYCLONE IS PUSHING INTO THE GREAT LAKES REGION. AN AREA ON LIGHT TO MODERATE SNOW IS ONGOING OVER PORTIONS OF IL/IN/WI IN THE WARM CONVEYOR BELT PORTION OF THE SYSTEM...WHERE A 50 KNOT LL JET IS AIDING IN WEAK MOISTURE ADVECTION AND CROSS ISOBARIC FLOW...LENDING TO UPGLIDE. VERY DRY COLUMN AS INDICATED BY ILX AND DVN SOUNDINGS IS ACTING TO LIMIT SNOWFALL SOMEWHAT...SUPPORTING WIDESPREAD VIRGA UNTIL SATURATION IS REACHED. THIS IS EVIDENT IN THE DONUT HOLE SIGNATURES THAT WERE OBSERVED AT DVN/ILX/AND LOT. REGARDLESS...ONCE SATURATION IS REACHED...EXPECTING A PERIOD OF LIGHT TO MODERATE SNOW TO OVERSPREAD THE REGION...SUPPORTING A QUICK BURST OF 1 TO 2 INCHES OF SNOW...WITH 1 INCH AMOUNTS MORE THE NORM. RATHER ROBUST TROPOPAUSE PRESSURE RISES COUPLED WITH STEEP MID LEVEL LAPSE RATES AND DECENT MOISTURE CONVERGENCE WILL CONTINUE TO SO SUPPORT BROAD LIFT THROUGH MUCH OF THE MORNING AND ACROSS THE FA. HAVE FAVORED THE SREF AND GFS WRT QPF GUIDANCE WITH THE CLIPPER SYSTEM...BUT OPTED FOR THE SUPPORT OF THE NAM12 FOR LAKE EFFECT PROCESSES. ALSO UTILIZED THE RUC13 FOR ADDED GUIDANCE. TODAY...CLIPPER SYSTEM WILL QUICKLY LEAVE GENERALLY 1 INCH OF SNOWFALL ACROSS THE MAJORITY OF THE FA. IN ADDITION STAUNCH FLOW/A RATHER TIGHT PRESSURE GRADIENT/STRONG FLOW ALOFT...45 TO 50 KNOTS OF H95 GEOSTROPHIC FLOW/AND LINKED MOMENTUM UNDER CAA WILL SUPPORT GUSTY WESTERLY WINDS. SUSTAINED WINDS OF 15 TO 25 MPH WITH HIGHER GUSTS ARE EXPECTED THROUGH THE EVENING. THIS WILL ALLOW FOR AREAS OF BLOWING AND DRIFTING SNOW...MAKING TRAVEL DIFFICULT IN SOME AREAS. ROBUST CAA WITH H85 T/S DROPPING 5 TO 6C WILL HELP SUPPORT INCREASED INSTABILITY OVER LK MI THIS AFTERNOON. WESTERLY FLOW AT FIRST WILL LIMIT LK SNOW SHOWERS TO MAINLY MI THIS AFTERNOON. LL FLOW WILL CONTINUE TO VEER BEHIND THE COLD FRONT...INCREASING THE FLOW FETCH OVER LK MI...WITH PRECONDITIONED FLOW FROM LAKE SUPERIOR DEVELOPING. A SECONDARY UPPER IMPULSE WILL ACT TO FURTHER INCREASE INVERSION HEIGHTS ALREADY MODIFIED BY LAKE AGGREGATE EFFECTS FROM LK SUPERIOR. THE NET EFFECT WILL BE LAKE INDUCED CAPES OF 500 TO 700 J/KG WITH MAX UPWARD OMEGA IN THE DGZ. THIS WILL FAVOR THE DEVELOPMENT OF SEVERAL INTENSE BANDS OF LK EFFECT SNOW...CONGEALING INTO ONE DOMINATE BAND AS CONVECTIVE INFLUENCES EVENTUALLY OUTWEIGH WIND SHEAR EFFECTS. NAM12 AND RUC 13 PROGS HAVE CONSISTENTLY BEEN SUPPORTING THE PLACEMENT OF THIS BAND OVER EASTERN BERRIEN AND CASS COUNTIES. HIRES WRF SIMULATIONS FURTHER SUPPORT THIS IDEA. SNOWFALL RATES OF 2 TO 4 INCHES PER HOUR ARE WILL BE POSSIBLE WITH AN INTENSE DOMINATE BAND...ESPECIALLY IF THE LL MASS FIELD READJUSTS TO THE MESOSCALE PROCESS...ENHANCING LL CONVERGENCE. HAVE ISSUED A WINTER STORM WARNING FOR BERRIEN AND CASS COUNTIES...WITH 1 TO 2 INCHES OF SNOWFALL THIS MORNING/PERIODS OF LAKE EFFECT SNOW THIS AFTERNOON WITH AND ADDITIONAL 2 TO 3 INCHES POSSIBLE/BLOWING SNOW THROUGH THE DAY AND NIGHT SIGNIFICANTLY REDUCING VISIBILITIES/AND ADDITIONAL HEAVY LAKE EFFECT SNOW WITH AN ADDITIONAL 4 TO 8 INCHES POSSIBLE. OPTED FOR A WINTER WEATHER ADV FOR ST. JOE IN/MI AND ELKHART FOR COMBINATION OF LAKE EFFECT SNOW AND BLOWING SNOW WITH 3 TO 6 INCHES POSSIBLE BY SUNDAY MORNING. IT IS QUITE POSSIBLE THAT LAGRANGE AND MAYBE NOBLE COUNTIES MAY HAVE TO BE ADDED TO THE ADV AS CURRENT MODEL GUIDANCE CERTAINLY HINTS AT A PERIOD OF INTENSE LL OMEGA CENTERED OVER THESE COUNTIES. HEAVIEST LAKE SNOWS WILL OCCUR SAT EVENING AND BEGIN TO DIMINISH SUN MORNING WITH FALLING INVERSION HEIGHTS AND SFC RIDGING SHIFTING WINDS TO THE SW. TEMPS WILL REMAIN COLD THROUGH THE PERIOD WITH HIGHS RAGING 10 TO 15 DEGREES BELOW NORMAL. HAVE OPTED TO UNDERCUT GUIDANCE TEMPS GIVEN ANOMALOUSLY COLD CONDITIONS PRESENT. && .LONG TERM... ...MONDAY THROUGH FRIDAY... COMPLICATED AND LOW CONFIDENCE LONG TERM FORECAST DUE TO HIGHLY ENERGETIC AND COMPLICATED MID AND UPPER LEVEL FLOW OVER PACIFIC AND WESTERN NORTH AMERICA. STILL EXPECT BELOW NORMAL TEMPERATURES FOR A LARGE PART OF THE PERIOD AND POTENTIAL FOR A MODERATE TO HEAVY PRECIPITATION EVENT MID WEEK. WATER VAPOR THIS MORNING SHOWS A VERY ENERGETIC PATTERN...SIMILAR TO LAST YEAR ABOUT THIS TIME. AS DISCUSSED LAST NIGHT...MODELS LIKELY NOT RESOLVING FEATURES OVER THE PACIFIC WELL GIVEN LIMITED SAMPLING MEASURES. FIRST AREA OF CONCERN IS WITH IMPRESSIVE LOOKING SUB-TROPICAL MOISTURE PLUME DEVELOPING NEAR 15N AND 120W. MODELS TRYING TO PICK UP ON THIS BUT CONCERNED THEY ARE NOT NEAR STRONG ENOUGH GIVEN DEPICTION IN WATER VAPOR. THIS AREA EXPECTED TO CONTINUE SPREADING NORTHEAST AND WILL FEED INTO DEVELOPING MID LEVEL LOW OFF OF CA COAST THAT WILL BECOME OUR WEATHER MAKER FOR MID WEEK. SECONDARY AREA OF CONCERN IS WITH STRONG JET CORE NEAR 40N AND 150W. MODELS DO SEEM TO HAVE A HANDLE ON THIS FEATURE...BUT GIVEN ITS STRENGTH THERE IS SOME CONCERN WITH HOW IT WILL EVOLVE OVER WESTERN CONUS. THIS IS A LARGE PART OF THE DIFFERENCES IN MODEL SOLUTIONS FOR MID WEEK. IT WILL BE THE INTERACTION OF THESE TWO PACIFIC FEATURES WITH THE MID LEVEL LOW ACROSS THE SOUTHWEST CONUS THAT DETERMINES ITS EVOLUTION AND IMPACT ON OUR AREA. AS MENTIONED LAST NIGHT...WE FELT MODELS WERE NOT HANDLING THIS ENERGY WELL AND A STRONGER SYSTEM WAS EXPECTED. LATEST MEDIUM RANGE SOLUTIONS ARE INDEED STRONGER...WITH GFS BEING THE STRONGEST. COMPLICATIONS FOR OUR FORECAST AREA WILL BE WITH AMOUNT OF WARM AIR ADVECTION AHEAD OF SYSTEM AND ITS ACTUAL TRACK. ECMWF WHILE WEAKER IS FURTHER NORTH WITH STRONG WAA AND MOISTURE INFLUX INTO THE AREA LATE MONDAY NIGHT AND TUESDAY...INDICATING A POSSIBLE HEAVY RAIN EVENT. GFS IS STRONGER AND FURTHER SOUTH WITH COLDER AIR OVER NORTHERN HALF OF FORECAST AREA...YIELDING A POSSIBLE RAIN EVENT SOUTH AND SNOW NORTH. BOTH SOLUTIONS PLAUSIBLE AND AGAIN WILL LIKELY NOT BE RESOLVED UNTIL SYSTEM GETS WITHIN RADIOSONDE NETWORK. AGREEMENT LIES WITH SOME TYPE OF PRECIPITATION EVENT WITH POTENTIAL FOR HEAVY PCPN SOMEWHERE IN THE WESTERN LAKES OR OHIO VALLEY REGION FROM LATE MONDAY NIGHT INTO EARLY WEDNESDAY. HAVE INCREASED POPS DURING THIS WINDOW WITH LIKELY POPS CENTERED ON TUESDAY. STAYED WITH ALL SNOW MONDAY NIGHT WITH INITIAL COLDER AIR IN PLACE AND LOWER WET BULB TEMPERATURES. ALSO STAYED WITH RAIN OR SNOW MENTION TUESDAY GIVEN UNCERTAINTY IN TRACK AND THERMAL FIELDS. BEYOND WEDNESDAY FEW CHANGES WERE MADE. MODELS CONTINUE TO INDICATE SOME TYPE OF COLDER AIR INTRUSION BUT NOT NEAR AS STRONG AS 48 HOURS AGO. THUS KEPT IDEA OF SLIGHTLY BELOW NORMAL TEMPERATURES. CLIPPER SYSTEM POSSIBLE BY END OF WEEK BUT AGAIN QUITE A BIT OF DISAGREEMENT IN MODELS SO NO CHANGES MADE. SOME SIGNALS TO A PATTERN CHANGE WELL BEYOND DAY 7...TOWARD MID MONTH. ENSEMBLES SHOWING WESTERN CONUS RIDGE BEING REPLACED BY DEEP TROUGH WITH FLOW OVER OUR AREA BECOMING MORE SOUTHWEST AND POSSIBLY ACTIVE. && AVIATION.../06Z TAFS/ CLIPPER SYSTEM WILL MOVE THROUGH THE REGION DURING THE PERIOD...BRINGING DETERIORATING FLIGHT CONDITIONS TO THE REGION. EXPECTING A PERIOD OF MVFR CIGS/VISBY WITH THE SYNOPTIC SYSTEM AT SBN AND FWA. THIS LINES UP WELL WITH MOS AND UPSTREAM OBS. STRONG GUSTY SOUTHERLY WINDS WILL BE EXPECTED GIVEN VERY STRONG FLOW OFF THE SFC AND A TIGHT PRESSURE GRADIENT IN PLACE. COLD FRONT WILL PUSH THROUGH THE REGION LATE MORNING AND EARLY AFTERNOON...ALLOWING WINDS TO VEER WESTERLY. GUSTS OF 25 TO 30 KNOTS WILL SUPPORT AREAS OF BLOWING SNOW...WHICH COULD ALLOW FOR BRIEF VISBY REDUCTIONS ACROSS THE FA. LAKE EFFECT SNOWS WILL DEVELOP AND SHIFT SOUTH INTO THE NORTHWEST FA...WITH IFR/LIFR CONDITIONS LIKELY THERE BY EVENING IN A COMBINATION OF BLOWING SNOW AND HEAVY LAKE SNOWS. HAVE TRENDED SBN IN THIS DIRECTION. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY FROM 5 PM THIS AFTERNOON TO 7 AM EST SUNDAY FOR INZ004-005. MI...WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ077-078. WINTER WEATHER ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ079. OH...NONE. LM...GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...JC in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1209 PM EST FRI DEC 5 2008 .AVIATION... MVFR/LOW VFR STRATO CU OVER THE AREA EXPECTED TO PERSIST UNTIL AFTER DARK WHEN INCRSG SWLY FLOW WILL ADVECT THE LOW CLOUDS OUT OF THE AREA. SOME FLURRIES ACCOMPANYING THE LOW CLOUDS SHOULD MAINLY IMPACT SBN EARLY IN THE PD WITH BACKING WINDS TAKING LAKE EFFECT NORTH OF THE TERMINAL BY 20Z. LOW PRESSURE SYSTEM CENTERED OVER SASK WILL MOVE SE TO LS WITH ASSOCIATED CDFNT MOVG INTO NW INDIANA BY 18Z SAT. HIGH CLOUDS WILL OVERSPREAD THE AREA THIS EVE IN ADVANCE OF THIS SYSTEM AND GRADUALLY LOWER OVERNIGHT WITH CONDITIONS THEN LOWERING TO IFR TOWARD MORNING AS A BAND OF SNOW ACCOMPANYING FRONTAL PASSAGE MOVES THROUGH. && SHORT TERM... TODAY THROUGH SATURDAY LAKE EFFECT SNOW SHOWERS CONTINUE TO IMPACT SW MI THIS MORNING...WITH DOPPLER RADAR ESTIMATIONS OF 2 TO 4 INCHES ACROSS A NARROW SWATH OF BERRIEN AND CASS COUNTIES. OTHERWISE...GENERALLY CLEAR SKIES RE PREVAILING ACROSS THE REGION WITH JUST A FEW CLOUDS AND FLURRIES ARE IN PLACE ACROSS THE FAR SOUTH WHERE A SUBTLE WIND SHIFT IS OCCURRING WITH A WEAK UPPER WAVE. TEMPS ARE GENERALLY IN THE TEENS...SAVE FOR THE FAR NW WHERE LOW 20S ARE PRESENT WITH LAKE MODIFIED AIR IN PLACE. THE OVERALL SYNOPTIC PICTURE CONTINUES TO DISPLAY A BLOCKING TYPE PATTERN WITH A LONG WAVE RIDGE PRESENT OVER THE EASTERN PACIFIC...WITH EASTERN CONUS TROUGHING ONGOING...BEING REINFORCED BY SEVERAL FAST MOVING NORTHWEST FLOW DISTURBANCES .THE NEXT RATHER POTENT UPPER LEVEL SHORTWAVE TAKING AIM ON THE REGION...IS EVIDENT IN WATER VAPOR AND 00Z UPPER AIR ANALYSIS OVER NORTHERN BC AND ALBERTA...AS 150 KNOTS PLUS OF FLOW IS PRESENT IN THE UPPER JET CORE ASSOCIATED WITH THIS SYSTEM. TODAY...LAKE EFFECT SNOW SHOWERS WILL CONTINUE THEIR SLOW DEMISE AS INVERSION HEIGHTS FALL INTO THE DGZ/FLOW TURNS MORE SOUTHWESTERLY/AND DRY AIR CONTINUES TO INFILTRATE THE REGION UPWIND OF THE LAKE. WILL LET THE ADV RIDE...AS CONDITIONS WILL REMAIN FAVORABLE FOR ANOTHER INCH OR TWO THIS MORNING...AND GIVEN THE MORNING COMMUTE JUST AHEAD. OTHERWISE...NAM12/RUC 13 BOTH INDICATE VERY LITTLE QPF BEYOND 15Z. HAVE OPTED FOR DIMINISHING POPS IN THE AFTERNOON. LINGERING LL MOISTURE IN THE H9-H85 LAYER WILL ALLOW CU DEVELOPMENT ONCE INSOLATION OCCUR THIS MORNING...CLOUDS SHOULD MIX OUT INTO THE AFTERNOON WITH A PT SUNNY CONDITIONS POSSIBLE BY THEN. TONIGHT THROUGH SATURDAY...POTENT CLIPPER SYSTEM WILL TAKE AIM ON THE REGION. MOISTURE LOOKS TO BE LIMITED WITH THIS SYSTEM AS GULF INFLUENCES WILL BE NONEXISTENT. HOWEVER...THE BIGGEST IMPACT MAY BE THE COMBINATION OF THE 1 TO 2 INCH SNOWFALL AND GUSTY WINDS...CREATING POSSIBLE NEAR ZERO VISIBILITY CONDITIONS...ESPECIALLY SAT NIGHT WHEN CAA AND DOWNWARD MOMENTUM TRANSPORT WILL MAXIMIZED. FORECAST MODELS HAVE PUSHED UP THE ARRIVAL TIME OF THIS SYSTEM COMPARED WOT PREVIOUS RUNS...OPTING FOR A SNOW ARRIVAL BEFORE 12Z SAT. THIS IS CONFIRMED BY THE GEFS/SREF/AND NAEFS ENSEMBLE RUNS WHICH ALSO PREFER THE EARLIER TREND. POTENT ISENTROPIC LIFT NOTED ON THE 285K SFC WITH 50 KNOTS CROSS ISOBARIC FLOW UNDER TROPOPAUSE PRESSURE RISES AND RATHER STEEP MD LEVEL LAPSE RATES CONFIRM THE SETUP FOR A PERIOD OF DECENT SNOW GIVEN OMEGA MAXIMIZED IN THE DGZ. HAVE BLENDED FORECAST POPS UP IN LINE WITH MOS NUMBERS. THINGS CERTAINLY GET INTERESTING IN THE NW FA AS LAKE ENHANCEMENT OF THE SYNOPTIC SNOW WILL BE LIKELY. FORECAST MODELS PROG THE GREATEST IMPACTS FROM LAKE ENHANCEMENT OVER PORTIONS OF WEST CENTRAL MI WHERE SNOWFALL RATES COULD BE DOUBLED. NAM H925 OMEGA PLOTS DO CONFIRM THAT AS CAA ENSUES AND THE LL FLOW VEERS NW...LAKE EFFECT ENHANCEMENT COULD AFFECT PORTIONS OF THE NW FA...WITH PURE LAKE EFFECT SHOWERS/BANDING LIKELY BY EVENING...LASTING INTO THE OVERNIGHT. THIS AREA WILL NEED TO BE WATCH FOR A POTENTIAL ADV OR WATCH/WARNING WITH HEAVY SNOW AND BLOWING SNOW THE BIGGEST CONCERNS. A PERIOD OF DECENT LAKE EFFECT SNOW MAY AFFECT THE REMAINDER OF THE LAKE BELT REGION INTO SUNDAY GIVEN NNW FLOW TENDING TO FAVOR LAKE SUPERIOR AGGREGATE EFFECTS. OTHERWISE...EXPECT BELOW TEMPS THROUGHOUT THE PERIOD WITH HIGHS IN THE 20S AND LOWS IN THE TEENS TO POSSIBLE SINGLE DIGITS BY SUN MORNING. LONG TERM... ..SUNDAY THROUGH THURSDAY... THE LONG TERM PICTURE CONTINUES TO BE FRAMED IN A BELOW NORMAL TEMPERATURE PORTRAIT. NUMEROUS SHORT WAVES WILL IMPACT THE AREA OVER THE LONG TERM PERIOD AND KEEP COLDER AIR IN PLACE ALONG WITH SEVERAL CHANCES FOR SNOWFALL. SUNDAY WILL SEE NORTHWEST FLOW AND DELTA T VALUES IN LOWER 20S WHICH WILL AID IN LAKE EFFECT SNOW SHOWERS THROUGH MID AFTERNOON BEFORE HIGH PRESSURE FINALLY MOVES IN AND ENDS LAKE EFFECT. SIMILAR TO CURRENT EVENT...COULD SEE SEVERAL INCHES OF ACCUMULATION STRUNG OUT OVER SEVERAL HOURS FROM SATURDAY NIGHT INTO SUNDAY AFTERNOON. THIS WILL BE DEPENDENT ON ORIENTATION AND MOVEMENT OF BANDS. NO HEADLINES PLANNED AT THIS TIME. NEXT SYSTEM BEGINS TO TAKE SHAPE TO OUR WEST SUNDAY NIGHT AND APPROACHES MONDAY NIGHT INTO TUESDAY. WARM AIR ADVECTION BEGINS AHEAD OF THIS WAVE SUNDAY NIGHT WITH INCREASING MOISTURE AND WEAK LIFT. MAYBE SOME LIGHT SNOW OR FLURRIES INTO WESTERN AREAS LATE SUNDAY NIGHT BUT STAYED WITH WELL COLLABORATED MONDAY POPS FOR NOW. THIS APPROACHING SHORT WAVE STILL HAS MUCH UNCERTAINTY WITH EVOLUTION AND MOVEMENT. THIS WAVE APPEARS TO DEVELOP OFF THE CA COAST TODAY AND EVENTUALLY MOVES INTO PLAINS ON MONDAY. QUESTION REMAINS ON DEGREE OF PHASING WITH NORTHERN STREAM AND STRENGTH OF DEVELOPMENT. MEDIUM RANGE MODELS COMING INTO AGREEMENT ON A WEAKER SYSTEM MOVING THROUGH OUR AREA BUT THERE HAVE BEEN SOME EARLIER SOLUTIONS SHOWING A STRONGER SYSTEM. SIMILAR PATTERN LAST YEAR SAW A TROPICAL MOISTURE PLUME ASSOCIATED WITH THESE WAVES AND MODELS WERE SLOW TO CATCH ON. CURRENT WATER VAPOR SHOWS AN ESTABLISHED TROPICAL PACIFIC PLUME INTO THE BAJA AREA...SOUTH OF WHERE THIS WAVE IS EXPECTED TO DEVELOP TODAY. THIS WILL BE WATCHED CLOSELY BUT CURRENT GRIDS HAVE RAIN OR SNOW FOR TUESDAY WITH BAROCLINIC ZONE IN VICINITY OF FA. PLAN TO KEEP THIS FOR NOW AND INCREASED POPS INTO MID CHANCE CATEGORY. BELOW NORMAL CONFIDENCE EXISTS FOR TUE THROUGH THURSDAY TIME FRAME WITH EVOLUTION OF THIS WAVE AND STRONGER ENERGY DIGGING INTO PLAINS TOWARD END OF PERIOD. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 11 PM EST THIS EVENING FOR LMZ043-046. GALE WARNING FROM 11 PM THIS EVENING TO 3 AM EST SUNDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...TAYLOR in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 419 AM EST FRI DEC 5 2008 .SHORT TERM... ODAY THROUGH SATURDAY LAKE EFFECT SNOW SHOWERS CONTINUE TO IMPACT SW MI THIS MORNING...WITH DOPPLER RADAR ESTIMATIONS OF 2 TO 4 INCHES ACROSS A NARROW SWATH OF BERRIEN AND CASS COUNTIES. OTHERWISE...GENERALLY CLEAR SKIES RE PREVAILING ACROSS THE REGION WITH JUST A FEW CLOUDS AND FLURRIES ARE IN PLACE ACROSS THE FAR SOUTH WHERE A SUBTLE WIND SHIFT IS OCCURRING WITH A WEAK UPPER WAVE. TEMPS ARE GENERALLY IN THE TEENS...SAVE FOR THE FAR NW WHERE LOW 20S ARE PRESENT WITH LAKE MODIFIED AIR IN PLACE. THE OVERALL SYNOPTIC PICTURE CONTINUES TO DISPLAY A BLOCKING TYPE PATTERN WITH A LONG WAVE RIDGE PRESENT OVER THE EASTERN PACIFIC...WITH EASTERN CONUS TROUGHING ONGOING...BEING REINFORCED BY SEVERAL FAST MOVING NORTHWEST FLOW DISTURBANCES .THE NEXT RATHER POTENT UPPER LEVEL SHORTWAVE TAKING AIM ON THE REGION...IS EVIDENT IN WATER VAPOR AND 00Z UPPER AIR ANALYSIS OVER NORTHERN BC AND ALBERTA...AS 150 KNOTS PLUS OF FLOW IS PRESENT IN THE UPPER JET CORE ASSOCIATED WITH THIS SYSTEM. TODAY...LAKE EFFECT SNOW SHOWERS WILL CONTINUE THEIR SLOW DEMISE AS INVERSION HEIGHTS FALL INTO THE DGZ/FLOW TURNS MORE SOUTHWESTERLY/AND DRY AIR CONTINUES TO INFILTRATE THE REGION UPWIND OF THE LAKE. WILL LET THE ADV RIDE...AS CONDITIONS WILL REMAIN FAVORABLE FOR ANOTHER INCH OR TWO THIS MORNING...AND GIVEN THE MORNING COMMUTE JUST AHEAD. OTHERWISE...NAM12/RUC 13 BOTH INDICATE VERY LITTLE QPF BEYOND 15Z. HAVE OPTED FOR DIMINISHING POPS IN THE AFTERNOON. LINGERING LL MOISTURE IN THE H9-H85 LAYER WILL ALLOW CU DEVELOPMENT ONCE INSOLATION OCCUR THIS MORNING...CLOUDS SHOULD MIX OUT INTO THE AFTERNOON WITH A PT SUNNY CONDITIONS POSSIBLE BY THEN. TONIGHT THROUGH SATURDAY...POTENT CLIPPER SYSTEM WILL TAKE AIM ON THE REGION. MOISTURE LOOKS TO BE LIMITED WITH THIS SYSTEM AS GULF INFLUENCES WILL BE NONEXISTENT. HOWEVER...THE BIGGEST IMPACT MAY BE THE COMBINATION OF THE 1 TO 2 INCH SNOWFALL AND GUSTY WINDS...CREATING POSSIBLE NEAR ZERO VISIBILITY CONDITIONS...ESPECIALLY SAT NIGHT WHEN CAA AND DOWNWARD MOMENTUM TRANSPORT WILL MAXIMIZED. FORECAST MODELS HAVE PUSHED UP THE ARRIVAL TIME OF THIS SYSTEM COMPARED WOT PREVIOUS RUNS...OPTING FOR A SNOW ARRIVAL BEFORE 12Z SAT. THIS IS CONFIRMED BY THE GEFS/SREF/AND NAEFS ENSEMBLE RUNS WHICH ALSO PREFER THE EARLIER TREND. POTENT ISENTROPIC LIFT NOTED ON THE 285K SFC WITH 50 KNOTS CROSS ISOBARIC FLOW UNDER TROPOPAUSE PRESSURE RISES AND RATHER STEEP MD LEVEL LAPSE RATES CONFIRM THE SETUP FOR A PERIOD OF DECENT SNOW GIVEN OMEGA MAXIMIZED IN THE DGZ. HAVE BLENDED FORECAST POPS UP IN LINE WITH MOS NUMBERS. THINGS CERTAINLY GET INTERESTING IN THE NW FA AS LAKE ENHANCEMENT OF THE SYNOPTIC SNOW WILL BE LIKELY. FORECAST MODELS PROG THE GREATEST IMPACTS FROM LAKE ENHANCEMENT OVER PORTIONS OF WEST CENTRAL MI WHERE SNOWFALL RATES COULD BE DOUBLED. NAM H925 OMEGA PLOTS DO CONFIRM THAT AS CAA ENSUES AND THE LL FLOW VEERS NW...LAKE EFFECT ENHANCEMENT COULD AFFECT PORTIONS OF THE NW FA...WITH PURE LAKE EFFECT SHOWERS/BANDING LIKELY BY EVENING...LASTING INTO THE OVERNIGHT. THIS AREA WILL NEED TO BE WATCH FOR A POTENTIAL ADV OR WATCH/WARNING WITH HEAVY SNOW AND BLOWING SNOW THE BIGGEST CONCERNS. A PERIOD OF DECENT LAKE EFFECT SNOW MAY AFFECT THE REMAINDER OF THE LAKE BELT REGION INTO SUNDAY GIVEN NNW FLOW TENDING TO FAVOR LAKE SUPERIOR AGGREGATE EFFECTS. OTHERWISE...EXPECT BELOW TEMPS THROUGHOUT THE PERIOD WITH HIGHS IN THE 20S AND LOWS IN THE TEENS TO POSSIBLE SINGLE DIGITS BY SUN MORNING. && .LONG TERM... ...SUNDAY THROUGH THURSDAY... THE LONG TERM PICTURE CONTINUES TO BE FRAMED IN A BELOW NORMAL TEMPERATURE PORTRAIT. NUMEROUS SHORT WAVES WILL IMPACT THE AREA OVER THE LONG TERM PERIOD AND KEEP COLDER AIR IN PLACE ALONG WITH SEVERAL CHANCES FOR SNOWFALL. SUNDAY WILL SEE NORTHWEST FLOW AND DELTA T VALUES IN LOWER 20S WHICH WILL AID IN LAKE EFFECT SNOW SHOWERS THROUGH MID AFTERNOON BEFORE HIGH PRESSURE FINALLY MOVES IN AND ENDS LAKE EFFECT. SIMILAR TO CURRENT EVENT...COULD SEE SEVERAL INCHES OF ACCUMULATION STRUNG OUT OVER SEVERAL HOURS FROM SATURDAY NIGHT INTO SUNDAY AFTERNOON. THIS WILL BE DEPENDENT ON ORIENTATION AND MOVEMENT OF BANDS. NO HEADLINES PLANNED AT THIS TIME. NEXT SYSTEM BEGINS TO TAKE SHAPE TO OUR WEST SUNDAY NIGHT AND APPROACHES MONDAY NIGHT INTO TUESDAY. WARM AIR ADVECTION BEGINS AHEAD OF THIS WAVE SUNDAY NIGHT WITH INCREASING MOISTURE AND WEAK LIFT. MAYBE SOME LIGHT SNOW OR FLURRIES INTO WESTERN AREAS LATE SUNDAY NIGHT BUT STAYED WITH WELL COLLABORATED MONDAY POPS FOR NOW. THIS APPROACHING SHORT WAVE STILL HAS MUCH UNCERTAINTY WITH EVOLUTION AND MOVEMENT. THIS WAVE APPEARS TO DEVELOP OFF THE CA COAST TODAY AND EVENTUALLY MOVES INTO PLAINS ON MONDAY. QUESTION REMAINS ON DEGREE OF PHASING WITH NORTHERN STREAM AND STRENGTH OF DEVELOPMENT. MEDIUM RANGE MODELS COMING INTO AGREEMENT ON A WEAKER SYSTEM MOVING THROUGH OUR AREA BUT THERE HAVE BEEN SOME EARLIER SOLUTIONS SHOWING A STRONGER SYSTEM. SIMILAR PATTERN LAST YEAR SAW A TROPICAL MOISTURE PLUME ASSOCIATED WITH THESE WAVES AND MODELS WERE SLOW TO CATCH ON. CURRENT WATER VAPOR SHOWS AN ESTABLISHED TROPICAL PACIFIC PLUME INTO THE BAJA AREA...SOUTH OF WHERE THIS WAVE IS EXPECTED TO DEVELOP TODAY. THIS WILL BE WATCHED CLOSELY BUT CURRENT GRIDS HAVE RAIN OR SNOW FOR TUESDAY WITH BAROCLINIC ZONE IN VICINITY OF FA. PLAN TO KEEP THIS FOR NOW AND INCREASED POPS INTO MID CHANCE CATEGORY. BELOW NORMAL CONFIDENCE EXISTS FOR TUE THROUGH THURSDAY TIME FRAME WITH EVOLUTION OF THIS WAVE AND STRONGER ENERGY DIGGING INTO PLAINS TOWARD END OF PERIOD. && .AVIATION.../06Z TAFS/ FLIGHT RESTRICTIONS WILL BE LIMITED TO LAKE EFFECT SNOW SHOWERS ACROSS THE FAR NORTH. VARYING CIGS DOWN TO 1.5KFT AND VISBYS DOWN TO 1/2 MILE ARE POSSIBLE IN THE HEAVIER BANDS...WHICH WILL BE CONFINED TO SOUTHERN MI. SBN WILL BE ON THE EDGE OF THE ACTIVITY WITH A PERIOD OF MVFR CIGS AND VISBYS POSSIBLE EARLY THIS MORNING. OTHERWISE...SCT MVFR CIGS WILL BE POSSIBLE ACROSS THE SOUTH AND WEST...WITH A WEAK UPPER WAVE PASSING THROUGH THE REGION. WINDS WILL BACK SOUTHERLY THROUGH THE PERIOD...IN RESPONSE TO THE NEXT LOW PRESSURE SYSTEM APPROACHING THE REGION. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...LAKE EFFECT SNOW ADVISORY UNTIL NOON EST TODAY FOR MIZ077>079. OH...NONE. LM...GALE WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR LMZ043-046. SMALL CRAFT ADVISORY UNTIL 1 PM EST SATURDAY FOR LMZ043-046. && $$ SHORT TERM...JC LONG TERM...LASHLEY AVIATION...JC in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1229 AM EST FRI DEC 5 2008 .AVIATION.../06Z TAFS/ FLIGHT RESTRICTIONS WILL BE LIMITED TO LAKE EFFECT SNOW SHOWERS ACROSS THE FAR NORTH. VARYING CIGS DOWN TO 1.5KFT AND VISBYS DOWN TO 1/2 MILE ARE POSSIBLE IN THE HEAVIER BANDS...WHICH WILL BE CONFINED TO SOUTHERN MI. SBN WILL BE ON THE EDGE OF THE ACTIVITY WITH A PERIOD OF MVFR CIGS AND VISBYS POSSIBLE EARLY THIS MORNING. OTHERWISE...SCT MVFR CIGS WILL BE POSSIBLE ACROSS THE SOUTH AND WEST...WITH A WEAK UPPER WAVE PASSING THROUGH THE REGION. WINDS WILL BACK SOUTHERLY THROUGH THE PERIOD...IN RESPONSE TO THE NEXT LOW PRESSURE SYSTEM APPROACHING THE REGION. && .PREV DISCUSSION... /ISSUED 1141 PM EST THU DEC 4 2008/ UPDATE... LAKE EFFECT SNOW SHOWERS ARE ONGOING ACROSS SW LOWER MI...WITH SOME INTENSE SQUALLS PRODUCING ONE INCH PER HOUR SNOW RATES PER SPOTTER REPORTS. SNOW SHOWERS HAVE INCREASED IN COVERAGE AND INTENSITY PER COOLING ALOFT PER AN ADVANCING UPPER WAVE...ALLOWING LAKE INDUCED CAPES TO RISE TO NEARLY 600 J/KG...WITH MAX UPWARD OMEGA IN THE DGZ. WITH BUFR PROGS SUPPORTING CAPES AROUND 400-600 J/KG THROUGH ABOUT NOON WITH FAVORABLE FETCH AND LL UPWIND RH OF AT LEAST 60 PERCENT...HAVE ISSUED A LAKE SNOW ADV FOR ACCUMS OF 2-4 INCHES WITH IMPACTS TO TRAVEL. INVERSION HEIGHTS WILL FALL FRIDAY MORNING...TRENDING SHOWER ACTIVITY TO JUST FLURRIES BY AFTERNOON. HAVE OPTED FOR A BLEND OF THE RUC13 AND NAM12 QPF...WHICH PLACES MAXIMUM VALUES IN CASS AND WESTERN SAINT JOSEPH /MI/...WHERE 5 INCHES MAY BE POSSIBLE BASED ON A 23:1 RATIO. OTHERWISE...JUST SOME TWEAKS TO SKY GRIDS...ALL ELSE IN GOOD SHAPE. PREV DISCUSSION... /ISSUED 343 PM EST THU DEC 4 2008/ SHORT TERM... CAA/LAKE EFFECT CLOUDINESS CONTS OVER THE GRTLKS REGION...INCLUDING NE 1/2 OF OUR CWA THIS AFTN. SOME LAKE EFFECT SNOW HAS OCCURRED MUCH OF THE DAY ACROSS MUCH OF SRN MI AND ADJACENT NRN INDIANA COUNTIES...HWVR INVERSION WHICH TAMDAR SOUNDINGS INDICATE IS BASED AROUND 3-5KFT...ALONG WITH SHORT WNW FETCH HAS LIMITED INTENSITY OF SNOW SHOWERS IN OUR AREA. COLDER AIR WILL CONTINUE TO ADVECT INTO THE REGION TONIGHT. SHRTWV SEEN ON WATER VAPOR OVER THE UPR MS VALLEY WITH A SFC REFLECTION SEEN IN SFC OBS MOVG INTO NW IL ACCOMPANIED BY A FEW FLURRIES IS EXPECTED TO MOVE EAST ACROSS OUR CWA TONIGHT PSBLY CAUSING SOME FLURRIES OUTSIDE OF LAKE EFFECT AREAS. ALSO INVERSION WILL RISE OVERNIGHT AS THE TROF MOVES THROUGH WHICH SHOULD INCREASE INTENSITY OF LAKE EFFECT SNOW SHOWERS... THOUGH CONTD SHORT FETCH WILL STILL BE LIMITING FACTOR TO SGFNT ACCUMS...WENT WITH 1-2" OVER SRN MI WITH <1" IN ADJACENT IN/OH COUNTIES. H85 TEMPS EXPECTED TO FALL TO AROUND -15C IN OUR CWA OVERNIGHT. UPSTREAM TEMPS THIS MORNING IN THIS AIRMASS IN SINGLE DIGITS/TEENS. WITH LESS SNOW COVER IN OUR AREA THAN IA/NRN IL AND PARTLY TO MOSTLY CLOUDY SKIES EXPECTED OVERNIGHT...KEPT LOWS IN THE TEENS. WITH THERMAL TROF MOVG ACROSS THE AREA ON FRIDAY...TEMPS ONLY EXPECTED TO RISE INTO THE L-M20S. SFC RIDGE WILL MOVE ACROSS THE AREA DURING THE DAY CAUSING WINDS TO BACK TO SW BRINGING LAKE EFFECT TO AN END ACROSS OUR CWA BY EVE WITH THE PSBL EXCEPTION OF NRN BERRIEN COUNTY. AMOUNT OF CLOUDS QUESTIONABLE. BOTH NAM AND GFS INDICATE H925 WILL BE SATURATED...BUT THIS LAYER WAS TOO MOIST IN MODELS TODAY...SO OPTIMISTICALLY WENT WITH PARTLY SUNNY SKIES AGAIN ACROSS SRN PORTION OF THE CWA. ANOTHER STRONG CDFNT WILL DROP SE INTO THE WRN GRTLKS FRI NIGHT. ANY REMAINING LOW CLOUDS EXPECTED TO ADVECT NE OUT OF THE AREA IN THE EVE AS SWLY LOW LEVEL FLOW INCREASES. HIGH CLOUDS WILL BE SPREADING INTO THE AREA AHD OF THE UPR TROF SO EXPECTING MOSTLY CLOUDY SKIES WITH LITTLE TEMP DROP. CONTD WITH SMALL CHC OF SNOW FOR LATE FRI NIGHT AS FRONT APPROACHES...BUT STILL APPEARS BEST CHC OF SNOW WITH THE FRONT WILL BE SATURDAY. LONG TERM...(SATURDAY THROUGH THURSDAY)... CONTINUED COLD AND ACTIVE PATTERN THROUGH THE EXTENDED PERIOD WITH QUICK CLIPPER AND LAKE EFFECT SAT NITE/SUN FOLLOWED BY ANOTHER POTENTIAL STRONG SYSTEM MOVING THROUGH THE EASTERN US MIDWEEK. EXTENDED BEGINS WITH CLIPPER SYSTEM IMPACTING NW CWA AS SFC LOW MOVES THROUGH THE UPPER GREAT LAKES. SIGNIFICANT TIMING DIFFERENCES BETWEEN SLOWER NAM/FASTER GFS BRINGING PRECIP INTO THE CWA ON SATURDAY AND HAVE SIDED WITH THE TIMING OF 09Z SREF AS A COMPROMISE. HWVR AS AN ADDNL NOD TO MODEL PERFORMANCE WITH THE PREV SYSTEM HAVE MAINTAINED EARLIER POPS INDICATED BY THE GFS AND UNDERCUT THE MODEL CONSENSUS QPF BY A MARGINAL AMOUNT AS THE 12Z GFS DECREASED QPF FROM 00Z/06Z RUNS POSSIBLY FORESHADOWING SIMILAR OUTCOME OF REALIZING LESSER AMOUNTS. NET RESULT IS LIGHT/MOD SNOW SETTLING IN SATURDAY MORNING AND EXPANDING ACROSS THE CWA WITH RELATIVELY MINOR SYNOPTIC QPF AMOUNTS. ZONE-OMEGA TECHNIQUE INDICATES SNOW RATIOS ON THE ORDER OF 15:1 TRANSLATING TO 2-3 INCH SNOW TOTALS TAPERING OFF FROM NW TOWARDS THE SE. AS SYNOPTIC FORCING WANES IN WAKE OF SFC LOW WINDS TURNING NW PRODUCE LAKE EFFECT SETUP BEGINNING AROUND 00Z SAT AND CONTINUING INTO SUNDAY. BUFR SOUNDINGS SHOW DELTA-T`S PEAKING AT 20 DEG WITH INVERSION LOCATED IN LOW END OF GROWTH ZONE AND UNIDIRECTIONAL 20KT WINDS THROUGH THE LAYER. HAVE REMAINED CONSERVATIVE WITH SNOW AMOUNTS GIVEN LOCATION OF EQL LEVELS HWVR POTENTIAL EXITS FOR MORE SIGNIFICANT SNOW WITH SMALL CHANGE IN THERMAL PROFILE FAVORING BETTER SNOW GROWTH. UPR TROF SHIFTS EASTWARD WITH FLOW RETURNING TO SOUTHERLY BY MONDAY SHUTTING DOWN ANY LEFTOVER LAKE EFFECT MECHANISM AND WARMING TEMPS BACK TO UPPER 20S AND INTO LOW 30S FOR TUESDAY. RELIEF IS POTENTIALLY SHORT LIVED HOWEVER AS MODELS CONTINUE TO SHOW STRONG MID WEEK STORM TAKING SHAPE AS SFC LOW EJECTS NE THROUGH THE EASTERN US WHILE SECOND DEEPER LOW WRAPS UP NEAR BASE OF MID LEVEL TROF ALONG GOMEX WHILE A PUSH OF ARCTIC AIR INTO THE US FOLLOWS. CONSIDERABLE SPREAD AMONG OPERATIONAL MODELS AND ENSEMBLES AS ONE WOULD EXPECT THIS FAR OUT SO HAVE NOT ATTEMPTED TO GO BEYOND THE BIG PICTURE WHICH PAINTS POPS MON-WED AND COLDER TEMPS BEHIND FRONT ON WEDNESDAY. HAVE KEPT LATE WEEK TEMPS ABOVE GUIDANCE AS GFS TENDS TO CONSISTENTLY OVERDO COLD AIR INTRUSIONS SEVERAL DAYS OUT AND ECMWF IS NOT AS AGGRESSIVE WITH ADVANCEMENT OF COLD AIR INTO THE UPPER MISSISSIPPI VALLEY. STAY TUNED. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...LAKE EFFECT SNOW ADVISORY UNTIL NOON EST TODAY FOR MIZ077>079. OH...NONE. LM...SMALL CRAFT ADVISORY UNTIL 7 PM EST SATURDAY FOR LMZ043-046. && $$ SHORT TERM...TAYLOR LONG TERM...LUDINGTON AVIATION...JC UPDATE...JC in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 950 PM CST FRI DEC 5 2008 .UPDATE... ANOTHER ROUND OF UPDATES WERE SENT OUT AROUND 9 PM. THE MAIN CHANGES WERE TO REDUCE SNOWFALL AMOUNTS OVER SOUTHEAST IOWA AND WEST CENTRAL ILLINOIS AND TO TWEAK HOURLY TEMP TRENDS AND INCREASE WINDS TONIGHT. 00Z ANALYSIS SHOWED A SURFACE WARM FROM EXTENDING SOUTH THROUGH CENTRAL IOWA WITH THE H8 FRONT OVER EASTERN IA AND THE ARCTIC SURFACE FRONT JUST CROSSING INTO NORTH DAKOTA. SNOW RAPIDLY DEVELOPED FROM MN SE INTO NORTHEAST IA THIS EVENING IN ISENTROPIC LIFT ACROSS THE WARM FRONT. ONE BAND OF SNOW WAS MOVING THROUGH THE NORTHERN CWA AND HAS PRODUCED VSBYS AROUND 1 MILE FOR A BRIEF TIME. REGIONAL RADAR COMPOSITE WAS SHOWING ANOTHER BAND OF SNOW MOVING THROUGH NORTH CENTRAL IOWA WHICH SHOULD SPREAD OVER THE NRN CWA AROUND MIDNIGHT. CURRENT PCPN TRENDS COMBINED WITH RUC/NAM ISENTROPIC PROGS SUGGEST MOST OF THE SNOW TONIGHT WILL BE NORTH OF I80. SO AMOUNTS AND POPS WERE TRIMMED BACK SOME OVER THE SOUTHERN CWA WITH LITTLE CHANGE MADE TO PREVIOUS SNOWFALL AMOUNTS IN THE NORTH. CWA WILL ALSO BE IN THE WARM SECTOR MOST OF THE NIGHT WITH STRONG SOUTHWEST WINDS AND CLOUDS HELPING TEMPS RISE SLOWLY MOST OF THE NIGHT. ...DLF... && .AVIATION... SNOW MOVING THROUGH NRN CWFA CURRENTLY WILL PRODUCE OCCASIONAL MVFR CIGS/VSBYS WITH BRIEF IFR CONDITIONS AT KCID/KDBQ/KMLI THROUGH EARLY SATURDAY MORNING. MAINLY VFR CONDITIONS ARE EXPECTED AT KBRL OVERNIGHT. SOUTH TO SOUTHWEST WINDS WILL BE SUSTAINED AT 15 TO 20KTS WITH GUSTS IN THE 25KTS TO 30KTS RANGE MOST OF THE NIGHT. ARCTIC FRONT WILL MOVE SOUTH THROUGH ALL TAF SITES BETWEEN 12Z AND 18Z SATURDAY EXPECT STRONG NW WINDS BEHIND THE FRONT...WHICH MAY CAUSE SOME REDUCED VSBYS IN BLOWING SNOW. ALSO EXPECTING MVFR CIGS MOST OF THE DAY. ...DLF... && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ HAASE/NICHOLS ia AREA FORECAST DISCUSSION...CORRECTED NATIONAL WEATHER SERVICE JACKSON KY 850 PM EST SAT DEC 6 2008 .SHORT TERM.../THE REST OF TONIGHT/...UPDATED SCATTERED TO NUMEROUS LIGHT SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA. THESE ARE ALL OUT AHEAD OF THE APPROACHING COLD FRONT. MUCH OF THESE WILL BE WINDING DOWN OVER THE NEXT COUPLE OF HOURS. THE NEXT BATCH OF PRECIP THAT WILL BE AFFECTING OUR AREA IS OVER INDIANA. THIS IS POST FRONTAL...AND ASSOCIATED WITH A SUBTLE H5 VORT MAX...VISIBLE ON THE RUC13 AND WATER VAPOR IMAGERY. VISIBILITIES IN THIS PRECIP ARE ALL 3 TO 5 MILES ATTM...BUT AM CONCERNED THIS COULD BE ENHANCED JUST A LITTLE AS IT MOVES OVER THE HIGHER TERRAIN OF EASTERN KENTUCKY. FOR THIS REASON...INCREASED POPS TONIGHT AND MENTIONED NUMEROUS LIGHT SNOW SHOWERS AS OPPOSED TO FLURRIES FOR MUCH OF OUR AREA. TAPERED POPS DOWN RAPIDLY IN THE SOUTHWESTERN CWA...WHERE THEY REMAIN IN THE LEAST FAVORABLE MOISTURE FOR SIGNIFICANT SHSN COVERAGE. FROPA SHOULD OCCUR WITHIN A COUPLE HOURS OF MIDNIGHT ACROSS THE CWA. MEAN RH DECREASES...BUT LOW LEVEL MOISTURE LINGERS IN THE SNOW GROWTH REGION. STILL THINK ANY ACCUMULATIONS WILL BE LESS THAN A HALF INCH...WITH AROUND A HALF INCH POSSIBLE IN FAR SOUTHEAST KENTUCKY. BEST UPSLOPE FLOW WILL NOT LIKELY OCCUR UNTIL 08 OR 09Z AS WINDS SHIFT AROUND TO THE NORTHWEST. BY THEN...MOISTURE SHOULD BE BEGINNING TO DECREASE. LOW TEMPS LOOKED GOOD...SO NO MAJOR ADJUSTMENTS THERE. DID TWEAK THE HOURLY TEMPS...AS TEMPS RANGE FROM THE UPPER 20S TO THE MID 30S ACROSS OUR CWA JUST AHEAD OF THE FRONT. THESE WILL DROP OFF AFTER FROPA. STILL THE MAJOR TRAVEL CONCERN OVERNIGHT IS REFREEZING WATER ON ROADWAYS. WILL CONTINUE TO HIGHLIGHT THIS IN SPECIAL WEATHER STATEMENTS...WEB HEADLINES...AND IN THE HWO. UPDATED FORECAST PRODUCTS ARE ALREADY OUT. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TONIGHT THROUGH MONDAY NIGHT/ AN UPPER LEVEL TROUGH IS IN PLACE OVER MUCH OF THE EASTERN CONUS...WITH A RELATIVELY POTENT SW/V CURRENTLY WORKING THROUGH THE OH VALLEY. THE SFC AREA OF LOW PRESSURE IS WORKING INTO MI AND ONTARIO...WITH THE COLD FRONT TRAILING SOUTH INTO THE OH VALLEY. THE EARLIER BAND OF LIGHT SNOW HAS GENERALLY MOVED EAST OF THE AREA WITH SOME WARMER AND DRIER AIR ATTEMPTING TO ADVECT IN IN THE WARM SECTOR. A FEW ISOLATED SNOW SHOWERS WERE OVER INDIANA AND ILLINOIS IN ADVANCE OF THE FRONT. THE COLD FRONT WILL WORK ACROSS WESTERN AND INTO CENTRAL KY THIS EVENING AND THEN CROSS THE JKL CWA GENERALLY BETWEEN 0Z AND 4Z. IN ADDITION AS THE SW/V MOVES THROUGH THE OH VALLEY...THE LAPSE RATES WILL INCREASE AND THERE SHOULD BE REDEVELOPMENT OF SNOW SHOWERS DURING THE EVENING HOURS OVER THE NE PART OF THE CWA AND ALONG THE VA BORDER AREA THIS MORNING. WENT WITH SCATTERED POPS OVER MUCH OF THE CWA...WITH SLIGHT CHANCE IN THE SW AND LIKELY NEAR THE VA BORDER. ALTHOUGH QPF WILL BE VERY MINIMAL...A DUSTING TO ONE HALF OF AN INCH OF SNOW CANNOT BE RULED OUT FROM THIS EVENING INTO THE OVERNIGHT HOURS GIVEN HIGH SNOW TO LIQUID RATIOS. THE SUBSIDENCE INVERSION WILL LOWER AND THE BL IS EXPECTED TO DRY OUT TOWARD 12Z SUN...SO WE WENT WITH ONLY ISOLATED FLURRIES AND SNOW SHOWERS OVER THE SE ON SUN. AS FAR AS TEMPS...WITH A COLDER START THAN WAS EXPECTED EARLIER...OPTED TO LOWER MIN T TONIGHT. 8H TEMPS ARE EXPECTED TO REMAIN COLD FOR MUCH OF TOMORROW...EVEN AS HEIGHTS BEGIN TO INCREASE AND SFC HIGH PRESSURE BUILDS INTO THE TN AND OH VALLEYS. BY THE END OF THE DAY -4C IS FORECAST IN THE SW...WITH COLDER...-10 OR -11C IN THE EAST. WITH THAT IN MIND...OPTED TO LEAN TOWARD THE COLDER END OF MOS GUIDANCE. DEPENDING ON THE EXACT TIMING OUT OF THE EXPECTED CU AND SC...TEMPS COULD END UP EVEN COLDER THAN THAT...ESPECIALLY SINCE THERE SHOULD BE SOME CIRRUS FROM TIME TO TIME IN NW FLOW ALOFT. HOWEVER...MUCH OF THE AREA WILL STRUGGLE TO REACH THE FREEZING MARK. HIGH PRESSURE WILL BEGIN TO SHIFT EAST ACROSS THE APPALACHIANS AND REACH THE EAST COAST PIEDMONT REGION BY EARLY MON. MID AND HIGH CLOUDS LATE MAY LIMIT THE TEMP FALL...BUT WITH DRIER DEWPOINTS IN THE TEENS EXPECTED BY LATE ON SUN AND EXPECTED EARLY DECOUPLING DUE TO CLEARING SKIES...KEPT THE SLIGHTLY COOLER THAN GUIDANCE TEMPS FOR VALLEYS ON SUN NIGHT. SOUTHERLY FLOW ON THE RIDGES SHOULD LEAD TO A MODERATE RIDGE/VALLEY SPLIT. MON APPEARS TO BE A TRANSITION DAY AS WEAK UPPER RIDGING WORKS ACROSS THE AREA...WITH WARMER TEMPERATURES. GUIDANCE HAS TRENDED WARMER OVERALL AND UPPED MAX T FOR MON. HOWEVER...TWO SHORTWAVES...ONE OVER THE NORTHERN ROCKIES AND ANOTHER OVER THE SOUTHERN ROCKIES WILL BEGIN TO CARVE OUT A PLAINS TROUGH. LEE CYCLOGENESIS SHOULD TAKE PLACE LATER IN THE PERIOD...WITH AN INCREASING LOW LEVEL JET LATE ON TUE NIGHT AS WELL AS INCREASING PRESS GRADIENT. ISENTROPIC LIFT SHOULD PRODUCE CLOUDS AT THE VERY LEAST...WITH BETTER LIFT AND ASSOCIATED PRECIP LIKELY REMAINING WEST AND NORTH OF THE AREA. .LONG TERM.../TUESDAY THROUGH SATURDAY/ THE LONG RANGE MODELS ARE IN DECENT AGREEMENT WITH REGARDS TO NEXT WEEKS WEATHER. A FRONT WILL PUSH ACROSS THE OHIO VALLEY ON TUESDAY. PRECIPITATION AHEAD OF THE FRONT WILL LIKELY BE IN THE FORM OF RAIN...AS BOTH GFS MODELS SOUNDINGS AND TIME HEIGHT CROSS SECTIONS ARE KEEPING TEMPERATURES ABOVE FREEZING FOR THE ENTIRE DAY. IT APPEARS AT THIS TIME THAT THE SUB FREEZING AIR WILL NOT MAKES ITS WAY INTO THE REGION UNTIL AFTER THE FRONT PASSES BY AND WINDS SHIFT TO THE WEST AND NORTHWEST. WITH THAT IT MIND...IT LOOKS LIKE THERE WILL BE A PERIOD OF LIGHT SNOW SHOWERS BEGINNING AT 7Z WEDNESDAY AND LASTING THROUGH 15 OR 16Z ON WEDNESDAY. LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED. IT IS LOOKING MORE AND MORE LIKE NEXT WEEKS SYSTEM WILL BRING GOOD SOAKING RAINS TO THE FORECAST AREA. THE LATEST GFS MODEL HAS A 60-70KT LOW LEVEL JET MOVING ACROSS KENTUCKY TUESDAY AFTERNOON AND NIGHT...WHICH WILL ACT TO REALLY ENHANCE THE RAINFALL AHEAD OF THE FRONT. BY THE TIME ENOUGH COLD AIR MAKES IT INTO THE AREA FOR SNOW TO FORM...THE BEST JET DYNAMICS WILL BE WELL EAST OF THE AREA. TEMPERATURES WERE A MAJOR CHALLENGE FOR NEXT WEEK AS ALL OF THE MODEL DATA IS HAVING A VERY DIFFICULT TIME COMING INTO ANY SORT OF AGREEMENT WITH REGARD TO HOW WARM OR COLD IT IS GOING TO BE. MODEL SOUNDINGS ARE PAINTING A PICTURE OF VERY COLD DAYTIME HIGHS NEAR FREEZING ON THURSDAY AND FRIDAY...WHILE AT THE SAME TIME THE LATEST MEXMOS HAS HIGH TEMPERATURES AROUND 40 ON THU AND FRI...WITH HPC COMING IN WITH TEMPS IN THE UPPER 40S FOR THU AND AROUND 40 ON FRIDAY. WHAT I ULTIMATELY DECIDED TO DO WAS ADJUST TEMPERATURES DOWN A BIT ACROSS THE BOARD WITH THE EXCEPTION OF TUESDAY AFTERNOON...WHERE I ADJUSTED TEMPS UP A BIT MORE TOWARD THE VERY WARM MEXMOS AND HPC NUMBERS AND TO MATCH UP WITH SURROUNDING OFFICES BETTER. A FEW ADJUSTMENTS WERE ALSO MADE TO SKY COVER TO ACCOUNT FOR TIMING CHANGES MADE TO NEXT WEEKS FRONTAL PASSAGE. DEWPOINTS ARE ALSO OUT OF SORTS WITH SURROUNDING OFFICES FOR LATE NEXT WEEK...SO ADJUSTMENTS WERE NEEDED THERE AS WELL. && .AVIATION.../00Z TO 24Z/ BANDS OF SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA AHEAD OF A COLD FRONT. EXPECTING PREDOMINANT VFR THROUGH 03-04Z...WITH TEMPO IFR IN -SHSN NORTH OF LOZ AND SME. AS THE FRONT PASSES THROUGH...EXPECT A WSHFT TO THE NW WITH MVFR CIGS. COULD STILL BE SOME ISOLATED -SHSN AROUND THE SME AND LOZ TAF SITES...WITH MORE NUMEROUS -SHSN FROM JKL AND POINTS EAST AS UPSLOPE FLOW GENERATES ADDITIONAL -SHSN. COULD STILL BE SOME ISOLATED IFR CONDITIONS IN ANY OF THE HEAVIER SHSN. MVFR CONDITIONS SHOULD LINGER UNTIL 13 TO 14Z AS CLOUDS SCATTER OUT AT LOZ AND SME. CIGS WILL REMAIN AT JKL...BUT WILL GRADUALLY LIFT TO VFR BY AROUND 14Z. PRECIP SHOULD BE WINDING DOWN AND ENDING EARLY SUNDAY MORNING. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JP/WJM LONG TERM....AR AVIATION...WJM ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSON KY 850 PM EST SAT DEC 6 2008 .SHORT TERM.../THE REST OF TODAY/...UPDATED SCATTERED TO NUMEROUS LIGHT SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA. THESE ARE ALL OUT AHEAD OF THE APPROACHING COLD FRONT. MUCH OF THESE WILL BE WINDING DOWN OVER THE NEXT COUPLE OF HOURS. THE NEXT BATCH OF PRECIP THAT WILL BE AFFECTING OUR AREA IS OVER INDIANA. THIS IS POST FRONTAL...AND ASSOCIATED WITH A SUBTLE H5 VORT MAX...VISIBLE ON THE RUC13 AND WATER VAPOR IMAGERY. VISIBILITIES IN THIS PRECIP ARE ALL 3 TO 5 MILES ATTM...BUT AM CONCERNED THIS COULD BE ENHANCED JUST A LITTLE AS IT MOVES OVER THE HIGHER TERRAIN OF EASTERN KENTUCKY. FOR THIS REASON...INCREASED POPS TONIGHT AND MENTIONED NUMEROUS LIGHT SNOW SHOWERS AS OPPOSED TO FLURRIES FOR MUCH OF OUR AREA. TAPERED POPS DOWN RAPIDLY IN THE SOUTHWESTERN CWA...WHERE THEY REMAIN IN THE LEAST FAVORABLE MOISTURE FOR SIGNIFICANT SHSN COVERAGE. FROPA SHOULD OCCUR WITHIN A COUPLE HOURS OF MIDNIGHT ACROSS THE CWA. MEAN RH DECREASES...BUT LOW LEVEL MOISTURE LINGERS IN THE SNOW GROWTH REGION. STILL THINK ANY ACCUMULATIONS WILL BE LESS THAN A HALF INCH...WITH AROUND A HALF INCH POSSIBLE IN FAR SOUTHEAST KENTUCKY. BEST UPSLOPE FLOW WILL NOT LIKELY OCCUR UNTIL 08 OR 09Z AS WINDS SHIFT AROUND TO THE NORTHWEST. BY THEN...MOISTURE SHOULD BE BEGINNING TO DECREASE. LOW TEMPS LOOKED GOOD...SO NO MAJOR ADJUSTMENTS THERE. DID TWEAK THE HOURLY TEMPS...AS TEMPS RANGE FROM THE UPPER 20S TO THE MID 30S ACROSS OUR CWA JUST AHEAD OF THE FRONT. THESE WILL DROP OFF AFTER FROPA. STILL THE MAJOR TRAVEL CONCERN OVERNIGHT IS REFREEZING WATER ON ROADWAYS. WILL CONTINUE TO HIGHLIGHT THIS IN SPECIAL WEATHER STATEMENTS...WEB HEADLINES...AND IN THE HWO. UPDATED FORECAST PRODUCTS ARE ALREADY OUT. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TONIGHT THROUGH MONDAY NIGHT/ AN UPPER LEVEL TROUGH IS IN PLACE OVER MUCH OF THE EASTERN CONUS...WITH A RELATIVELY POTENT SW/V CURRENTLY WORKING THROUGH THE OH VALLEY. THE SFC AREA OF LOW PRESSURE IS WORKING INTO MI AND ONTARIO...WITH THE COLD FRONT TRAILING SOUTH INTO THE OH VALLEY. THE EARLIER BAND OF LIGHT SNOW HAS GENERALLY MOVED EAST OF THE AREA WITH SOME WARMER AND DRIER AIR ATTEMPTING TO ADVECT IN IN THE WARM SECTOR. A FEW ISOLATED SNOW SHOWERS WERE OVER INDIANA AND ILLINOIS IN ADVANCE OF THE FRONT. THE COLD FRONT WILL WORK ACROSS WESTERN AND INTO CENTRAL KY THIS EVENING AND THEN CROSS THE JKL CWA GENERALLY BETWEEN 0Z AND 4Z. IN ADDITION AS THE SW/V MOVES THROUGH THE OH VALLEY...THE LAPSE RATES WILL INCREASE AND THERE SHOULD BE REDEVELOPMENT OF SNOW SHOWERS DURING THE EVENING HOURS OVER THE NE PART OF THE CWA AND ALONG THE VA BORDER AREA THIS MORNING. WENT WITH SCATTERED POPS OVER MUCH OF THE CWA...WITH SLIGHT CHANCE IN THE SW AND LIKELY NEAR THE VA BORDER. ALTHOUGH QPF WILL BE VERY MINIMAL...A DUSTING TO ONE HALF OF AN INCH OF SNOW CANNOT BE RULED OUT FROM THIS EVENING INTO THE OVERNIGHT HOURS GIVEN HIGH SNOW TO LIQUID RATIOS. THE SUBSIDENCE INVERSION WILL LOWER AND THE BL IS EXPECTED TO DRY OUT TOWARD 12Z SUN...SO WE WENT WITH ONLY ISOLATED FLURRIES AND SNOW SHOWERS OVER THE SE ON SUN. AS FAR AS TEMPS...WITH A COLDER START THAN WAS EXPECTED EARLIER...OPTED TO LOWER MIN T TONIGHT. 8H TEMPS ARE EXPECTED TO REMAIN COLD FOR MUCH OF TOMORROW...EVEN AS HEIGHTS BEGIN TO INCREASE AND SFC HIGH PRESSURE BUILDS INTO THE TN AND OH VALLEYS. BY THE END OF THE DAY -4C IS FORECAST IN THE SW...WITH COLDER...-10 OR -11C IN THE EAST. WITH THAT IN MIND...OPTED TO LEAN TOWARD THE COLDER END OF MOS GUIDANCE. DEPENDING ON THE EXACT TIMING OUT OF THE EXPECTED CU AND SC...TEMPS COULD END UP EVEN COLDER THAN THAT...ESPECIALLY SINCE THERE SHOULD BE SOME CIRRUS FROM TIME TO TIME IN NW FLOW ALOFT. HOWEVER...MUCH OF THE AREA WILL STRUGGLE TO REACH THE FREEZING MARK. HIGH PRESSURE WILL BEGIN TO SHIFT EAST ACROSS THE APPALACHIANS AND REACH THE EAST COAST PIEDMONT REGION BY EARLY MON. MID AND HIGH CLOUDS LATE MAY LIMIT THE TEMP FALL...BUT WITH DRIER DEWPOINTS IN THE TEENS EXPECTED BY LATE ON SUN AND EXPECTED EARLY DECOUPLING DUE TO CLEARING SKIES...KEPT THE SLIGHTLY COOLER THAN GUIDANCE TEMPS FOR VALLEYS ON SUN NIGHT. SOUTHERLY FLOW ON THE RIDGES SHOULD LEAD TO A MODERATE RIDGE/VALLEY SPLIT. MON APPEARS TO BE A TRANSITION DAY AS WEAK UPPER RIDGING WORKS ACROSS THE AREA...WITH WARMER TEMPERATURES. GUIDANCE HAS TRENDED WARMER OVERALL AND UPPED MAX T FOR MON. HOWEVER...TWO SHORTWAVES...ONE OVER THE NORTHERN ROCKIES AND ANOTHER OVER THE SOUTHERN ROCKIES WILL BEGIN TO CARVE OUT A PLAINS TROUGH. LEE CYCLOGENESIS SHOULD TAKE PLACE LATER IN THE PERIOD...WITH AN INCREASING LOW LEVEL JET LATE ON TUE NIGHT AS WELL AS INCREASING PRESS GRADIENT. ISENTROPIC LIFT SHOULD PRODUCE CLOUDS AT THE VERY LEAST...WITH BETTER LIFT AND ASSOCIATED PRECIP LIKELY REMAINING WEST AND NORTH OF THE AREA. .LONG TERM.../TUESDAY THROUGH SATURDAY/ THE LONG RANGE MODELS ARE IN DECENT AGREEMENT WITH REGARDS TO NEXT WEEKS WEATHER. A FRONT WILL PUSH ACROSS THE OHIO VALLEY ON TUESDAY. PRECIPITATION AHEAD OF THE FRONT WILL LIKELY BE IN THE FORM OF RAIN...AS BOTH GFS MODELS SOUNDINGS AND TIME HEIGHT CROSS SECTIONS ARE KEEPING TEMPERATURES ABOVE FREEZING FOR THE ENTIRE DAY. IT APPEARS AT THIS TIME THAT THE SUB FREEZING AIR WILL NOT MAKES ITS WAY INTO THE REGION UNTIL AFTER THE FRONT PASSES BY AND WINDS SHIFT TO THE WEST AND NORTHWEST. WITH THAT IT MIND...IT LOOKS LIKE THERE WILL BE A PERIOD OF LIGHT SNOW SHOWERS BEGINNING AT 7Z WEDNESDAY AND LASTING THROUGH 15 OR 16Z ON WEDNESDAY. LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED. IT IS LOOKING MORE AND MORE LIKE NEXT WEEKS SYSTEM WILL BRING GOOD SOAKING RAINS TO THE FORECAST AREA. THE LATEST GFS MODEL HAS A 60-70KT LOW LEVEL JET MOVING ACROSS KENTUCKY TUESDAY AFTERNOON AND NIGHT...WHICH WILL ACT TO REALLY ENHANCE THE RAINFALL AHEAD OF THE FRONT. BY THE TIME ENOUGH COLD AIR MAKES IT INTO THE AREA FOR SNOW TO FORM...THE BEST JET DYNAMICS WILL BE WELL EAST OF THE AREA. TEMPERATURES WERE A MAJOR CHALLENGE FOR NEXT WEEK AS ALL OF THE MODEL DATA IS HAVING A VERY DIFFICULT TIME COMING INTO ANY SORT OF AGREEMENT WITH REGARD TO HOW WARM OR COLD IT IS GOING TO BE. MODEL SOUNDINGS ARE PAINTING A PICTURE OF VERY COLD DAYTIME HIGHS NEAR FREEZING ON THURSDAY AND FRIDAY...WHILE AT THE SAME TIME THE LATEST MEXMOS HAS HIGH TEMPERATURES AROUND 40 ON THU AND FRI...WITH HPC COMING IN WITH TEMPS IN THE UPPER 40S FOR THU AND AROUND 40 ON FRIDAY. WHAT I ULTIMATELY DECIDED TO DO WAS ADJUST TEMPERATURES DOWN A BIT ACROSS THE BOARD WITH THE EXCEPTION OF TUESDAY AFTERNOON...WHERE I ADJUSTED TEMPS UP A BIT MORE TOWARD THE VERY WARM MEXMOS AND HPC NUMBERS AND TO MATCH UP WITH SURROUNDING OFFICES BETTER. A FEW ADJUSTMENTS WERE ALSO MADE TO SKY COVER TO ACCOUNT FOR TIMING CHANGES MADE TO NEXT WEEKS FRONTAL PASSAGE. DEWPOINTS ARE ALSO OUT OF SORTS WITH SURROUNDING OFFICES FOR LATE NEXT WEEK...SO ADJUSTMENTS WERE NEEDED THERE AS WELL. && .AVIATION.../00Z TO 24Z/ BANDS OF SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA AHEAD OF A COLD FRONT. EXPECTING PREDOMINANT VFR THROUGH 03-04Z...WITH TEMPO IFR IN -SHSN NORTH OF LOZ AND SME. AS THE FRONT PASSES THROUGH...EXPECT A WSHFT TO THE NW WITH MVFR CIGS. COULD STILL BE SOME ISOLATED -SHSN AROUND THE SME AND LOZ TAF SITES...WITH MORE NUMEROUS -SHSN FROM JKL AND POINTS EAST AS UPSLOPE FLOW GENERATES ADDITIONAL -SHSN. COULD STILL BE SOME ISOLATED IFR CONDITIONS IN ANY OF THE HEAVIER SHSN. MVFR CONDITIONS SHOULD LINGER UNTIL 13 TO 14Z AS CLOUDS SCATTER OUT AT LOZ AND SME. CIGS WILL REMAIN AT JKL...BUT WILL GRADUALLY LIFT TO VFR BY AROUND 14Z. PRECIP SHOULD BE WINDING DOWN AND ENDING EARLY SUNDAY MORNING. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JP/WJM LONG TERM....AR AVIATION...WJM ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CARIBOU ME 535 AM EST FRI DEC 5 2008 .SYNOPSIS... HIGH PRESSURE WILL BUILD IN FROM THE WEST THIS AFTERNOON AND CREST OVER THE AREA TONIGHT. A TROUGH OF LOW PRESSURE WILL APPROACH FROM THE WEST SATURDAY INTO SATURDAY NIGHT. THE TROUGH WILL DEVELOP ONE LOW CENTER NEAR THE GULF OF MAINE AND ANOTHER OVER EASTERN NOVA SCOTIA ON SUNDAY. THE TWO LOWS WILL CONSOLIDATE OVER THE MARITIMES SUNDAY NIGHT AND LIFT NORTH ACROSS LABRADOR ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... MAIN CONCERNS WILL BE CLOUDS AND THE SCA FOR THE MARINE SECTION. A QUICK UPDATE TO ADD SOME ACCUMULATION ACROSS THE FAR N (MEZ002,005-006) DUE TO A BAND OF SNOW IN ASSOCN W/SOME PVA FROM THAT UPPER LEVEL FEATURE MOVING IN FROM QUEBEC. LESS THAN AN INCH OF SNOW IS EXPECTED. SNOW RATIO AROUND 20:1. BOOSTED POPS A BIT TO ACCOUNT FOR WHAT THE LATEST RADAR WAS SHOWING. SOME TWEAKS WERE MADE TO THE TEMPS. THE CARWRF AND RUC CONTINUE TO HANDLE THE LATEST CONDITIONS QUITE WELL AND THEREFORE FOLLOWED THIS BLEND THROUGH TODAY. KEPT MORE CLOUDS ACROSS THE NORTHERN 1/2 OF THE CWA TODAY. MDL SOUNDINGS SHOW DEEP MOISTURE FROM 925-850MBS IN THE AFOREMENTIONED REGION. DECIDED ON GOINGS CLOUDY ACROSS THE NORTH AND WEST AND PARTLY CLOUDY CONDITIONS FOR THE INTERIOR DOWNEAST AND COASTAL REGIONS. A VORT MAX MOVING ACROSS SOUTHERN QUEBEC THIS MORNING IS FCST TO MOVE ACROSS THE NORTHERN PORTION OF THE CWA TODAY AIDING IN SOME FLURRY OR SNOW SHOWER ACTIVITY. KEPT 20-30% POPS ACROSS THE NORTH AND WEST THROUGH THE AFTERNOON. MADE ADJUSTMENTS TO THE HRLY TEMPS/DWPTS USING THE RTMA AND GMOS BC. GMOS AND NAM12 TEMPS NOT CATCHING TO COOLER TEMPS ACROSS THE NORTH AND WEST. TWEAKED MAX TEMPS TODAY AS WELL KNOCKING THEM DOWN BY 3 DEGS WHICH PUTS LOW TO MID 20S ACROSS THE NORTH AND WEST. MID/UPPER 30S EXPECTED FOR THE DOWNEAST AND COAST. CLOUDS ARE EXPECTED TO DISSIPATE TONIGHT AS THE MDL SOUNDINGS DRYING THROUGH 850 MBS WHICH SHOULD LEAD TO SOME CLEARING. THE EXCEPTION TO THIS WILL BE THE WESTERN AREAS AS UPSLOPE EFFECTS COULD KEEP MORE CLOUDS AROUND LONGER. TIRED TO ACCOUNT FOR THIS IN THE GRIDS USING THE BTV_SKY TOOL WHICH GAVE PARTLY SKIES. TEMPERATURES WILL BE SOME 5 TO 10 DEGS COLDER THAN THEY WERE SOME 24 HRS AGO AT THIS TIME SATURDAY MORNING. OVERNIGHT MINS ARE EXPECTED TO DROP BACK INTO THE MID TEENS ACROSS THE NORTH AND UPPER TEENS AND LOWER 20S FOR THE DOWNEAST AND THE COAST. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... A LARGE TROUGH WILL BE DIGGING INTO THE MIDWEST ON SATURDAY. ONE BUNDLE OF ENERGY WILL BE ROUNDING THE BOTTOM OF THE TROUGH THROUGH THE SOUTHERN BRANCH AND OFF THE SOUTHEAST COAST LATE SATURDAY AS ANOTHER BUNDLE OF ENERGY ACROSS THE NORTHERN BRANCH WILL BE DIGGING INTO THE GREAT LAKES. THE SOUTHERN BRANCH ENERGY WILL BE FORMING A LOW SOUTH OF NOVA SCOTIA LATER SUNDAY NIGHT INTO MONDAY WHILE THE NORTHERN BRANCH FORMS A LOW IN THE GULF OF MAINE. THIS BRINGS A CHALLENGING FORECAST. THE INTERIOR LOW CARRIES LOTS OF UPPER LEVEL ENERGY BUT MOISTURE MAY BE LIMITED IF THE OUTER LOW WELL TO THE EAST OBSTRUCTS SIGNIFICANT INFLOW OF ATLANTIC MOISTURE. THIS WOULD BRING A LIGHT SNOWFALL OF 2 TO 3 INCHES ACROSS THE AREA. HOWEVER...THE CANADIAN...ECMWF AND SREF CONSOLIDATE THE TWO LOWS INTO ONE OVER THE MARITIMES MORE RAPIDLY THAN EITHER THE NAM OR THE GFS. A QUICKER CONSOLIDATION WOULD ALLOW A MORE ORGANIZED AREA OF SNOW TO BACK IN FROM THE EAST BRINGING HEAVIER SNOW TO THE REGION...ESPECIALLY OVER THE EAST. FOR NOW VERY CONFIDENT WE`LL SEE SNOW SO WILL GO CAT POPS SUNDAY AFTERNOON...WITH AMOUNTS STILL HAVING TO BE RESOLVED. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... SNOW ACROSS THE AREA WILL LIFT OUT TO THE NORTHEAST SUNDAY NIGHT AS THE LOW LIFTS AWAY INTO EASTERN CANADA. THE LOW WILL LIKELY INTENSIFY AS IT CONSOLIDATES TO OUR NORTHEAST. NORTHWEST WINDS BEHIND THE LOW WILL LIKELY RESULT IN BLOWING AND DRIFTING. HIGH PRESSURE WILL BUILD IN ON MONDAY AND CREST OVER THE AREA MONDAY NIGHT. A MOIST BUT SOMEWHAT DISORGANIZED SYSTEM WILL APPROACH TUESDAY BRINGING A CHANCE FOR SNOW NORTH AND SNOW OR RAIN CENTRAL AND DOWNEAST TUESDAY INTO TUESDAY NIGHT. SOME COLD ARCTIC AIR MAY THEN APPROACH FOR MID WEEK. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... NEAR TERM: MVFR CIGS ACROSS THE NORTHERN TAF SITES INTO EARLY AFTERNOON AND THEN CONDITIONS LOOK TO IMPROVE TO VFR THROUGH TONIGHT. KBGR AND KBHB WILL STAY VFR. SHORT TERM: VFR TO MVFR CONDITIONS SATURDAY WILL LOWER TO IFR SATURDAY NIGHT INTO SUNDAY EVENING AS SNOW MOVES ACROSS THE AREA. CONDITIONS WILL IMPROVE TO VFR DOWNEAST EARLY MONDAY MORNING AND ACROSS THE NORTH LATER MONDAY. VFR CONDITIONS ARE THEN EXPECTED INTO MONDAY NIGHT BEFORE LOWERING TO IFR IN LOW CLOUDS AND PRECIPITATION ON TUESDAY. && .MARINE... NEAR TERM: THE SCA WAS EXTENDED THROUGH LATE MORNING AS WINDS/SEAS STILL W/IN SCA RANGE ESP THE SEAS. USED A BLEND OF THE NAM12/GFS FOR THE WINDS WHICH GIVES 15-20 KT INTO THE AFTERNOON. GUSTS UP TO 25 KT WERE ADDED. THE SWANNAM WAVE HEIGHTS MATCHING VERY WELL THIS MORNING AND DECIDED TO USE IT TO INITIALIZE THE GRIDS AND THEN BLENDED THE WNAWAVE4 FOR THIS AFTERNOON INTO TONIGHT. THIS SHOWS CONDITIONS GOING BELOW SCA AFT 18Z OR SO. SHORT TERM: WINDS WILL BE LIGHT AS THE LOW APPROACHES THROUGH SUNDAY. STRONG WINDS POSSIBLY REQUIRING A GALE ARE THEN LIKELY BEHIND THE LOW SUNDAY EVENING INTO MONDAY AS THE LOW INTENSIFIES TO OUR NORTHEAST. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR ANZ050>052. && $$ NEAR TERM...HEWITT SHORT TERM...BLOOMER LONG TERM...BLOOMER AVIATION...HEWITT MARINE...HEWITT/BLOOMER me AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WAKEFIELD VA 946 PM EST SAT DEC 6 2008 .SYNOPSIS... HIGH PRESSURE PUSHES FURTHER OFFSHORE AS A COLD FRONT QUICKLY MOVES THROUGH THE AREA OVERNIGHT...THEN OFF THE COAST BY EARLY SUNDAY MORNING. MEANWHILE...A LOW PRESSURE SYSTEM CONTINUES TO DEVELOP OFF THE CAROLINA COAST...PUSHING WELL OFF THE MID ATLANTIC COAST SUNDAY MORNING. HIGH PRESSURE BUILDS INTO THE MID ATLANTIC SUNDAY AND MONDAY. AN AREA OF LOW PRESSURE WILL AFFECT THE REGION TUESDAY THROUGH THURSDAY. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... DIFFUSE REGION OF HIGHER CLOUD TOPS ALONG WITH LIGHT PRECIPITATION SHIELD AHEAD OF MID/UPR LVL DEFORMATION AXIS CONTINUES TO PIVOT EWRD ACROSS THE FCST AREA. RIDGING DEFORMATION AT LLVLS BTWN THE LOW E OF LAKE HURON AND THE WEAK LOW OFF THE COAST SE OF ILM IS HAVING AN EFFECT ON LIMITING THE DEGREE/DEPTH OF VERTICAL ASCENT AND MOISTENING. THUS THE INTENSITY OF THE PRECIP HAS BEEN LIGHT...EVEN VERY LIGHT (DRIZZLE) AT TIMES GIVEN THE LACK OF FVRBL UVM/MOISTURE ABOVE THE -10C ISOTHERM...WHICH IN TURN LIMITS THE AMOUNT OF ICE SEEDING AND DENDRITIC GROWTH INTO THE LOWER MOIST LAYERS. SO...BECAUSE OF THE LIGHT NATURE OF THE PRECIP...TEMPS IN MOST AREAS HAVE HAD A REAL DIFFICULT DROPPING TO THE WET BULB READINGS... THUS ALLOWING FOR MORE OF A LIGHT RAIN/DRIZZLE/SNOW MIX VS. ALL SNOW. SNOW ACCUMULATIONS THUS FAR HAVE BEEN GENERALLY LESS THAN A QUARTER INCH TOPS...MAINLY ON ELEVATED OR NON-PAVED SURFACES W OF I-95 WHERE THE ELEVATION CLIMBS TO ABOVE 200 FT. FOR THE OVERNIGHT...THE RUC (WHICH HAS DONE WELL THUS FAR WITH THIS SYSTEM) CONTINUES TO PIVOT THE AXIS OF LIGHT PRECIP E THROUGH THE FCST AREA. ORIENTATION OF THE PRECIP SHIELD SHOULD BECOME MORE N-S ORIENTED (VS. THE CURRENT NE-SW ORIENTATION) AS THE MID LVL TROUGH (DEFORMATION AXIS) BECOMES MORE NEGATIVELY TILTED. STILL A BIT CONCERNED ABOUT THE POTENTIAL FOR LIGHT (LESS THAN HALF INCH) WET SNOW ACCUMULATIONS ACROSS THE NRN NECK OF VA AND THE LOWER MD ERN SHORE. THIS GIVEN THE LOW LEVEL THERMAL PROFILE IN THAT REGION...AS SFC WET BULB TEMPS SLOWLY DROP TO AROUND FREEZING THROUGH MIDNIGHT AS THE FVRBL DYNAMICS/DEEPER MOISTURE CONTINUE TO MOVE INTO THESE AREAS. ALSO...EXPECT A LONGER PERIOD OF PRECIPITATION AS WELL... GIVEN THE AMPLIFICATION (NEG TILT) OF THE MID LEVEL TROUGH AND THUS TRANSITION TOWARD N-S PRECIP AREAS (WHICH TENDS TO ALLOW THE PRECIP TO LINGER A WHILE LONGER). FOR NOW...BASED ON THE SFC LAYER WARMTH CURRENTLY (SFC TEMPS/WET BULB TEMPS STILL ABOVE FREEZING) ALONG WITH ABOVE FREEZING GROUND/PAVEMENT TEMPS...WILL MAINTAIN FCST ACCUMULATION UNDER AN INCH. PREVIOUS DISCUSSION BELOW... && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/... THE FRONTAL SYSTEM WILL PUSH OFF THE COAST SUNDAY MORNING AS HIGH PRESSURE REBUILDS IN FROM THE W. AGAIN MAINTAINED SLIGHT CHANCE POPS OVER MD/VA ERN SHORE SUN MORNING...WITH DRY/CLEARING CONDITIONS EXPECTED ELSEWHERE. SUN HIGH TEMPS LWR TO MID 40S WITH CAA LOWERING H85 TEMPS TO -10C TO -14C. EXPECT BREEZY CONDITIONS...SUST AROUND 20 MPH...GUSTS TO 30 MPH (35 MPH FOR THE ERN SHRE...BELOW WIND ADVSRY) MID MORNING THROUGH THE AFTERNOON SUN ACROSS THE FA. WINDINESS DUE TO A TIGHT PRES GRADIENT FROM THE DEEPENING LOW OFF THE MID ATLANTIC THEN NEW ENGLAND COAST AND HIGH CENTERED OVER THE SRN MS VLY. RESULTANT WIND CHILL VALUES WILL BE FROM 25 NW TO 32 SE DURING THE DAYTIME HOURS. HIGH PRESSURE SHIFTS OVERHEAD LATE SUNDAY INTO EARLY MONDAY. THE GFS IS A LITTLE FASTER IN MVG THE HIGH TO THE COAST BY MONDAY MORNING WHILE THE NAM LAGS BEHIND...BUT SINCE THE GFS IS CURRENTLY DEPICTING THE CENTER OF THIS HIGH RATHER ACCURATELY...WILL STICK WITH THE SLIGHTLY COOLER TEMPS SUNDAY NIGHT THAT THIS SOLN WOULD WARRANT. TEMPS WILL PLUMMET RAPIDLY AFTER SUNSET AND BASED ON LOCAL THICKNESS SCHEMES LOOK TO BOTTOM OUT IN THE UPR TEENS TO LWR 20S. SOUTHERLY FLOW RETURNS TO THE AREA ON MONDAY BUT NOT STRONG ENOUGH TO GET TEMPS MUCH ABOVE THE UPR 30S TO LWR 40 RANGE IN THE AFTN...ESP CONSIDERING THAT CLOUDS WILL ALSO BE ON THE INCREASE THROUGHOUT THE DAY AS THE HIGH SHIFTS OFFSHORE AND SOME WEAK ENERGY MVS TOWARDS THE AREA FROM A SYSTEM MVG THROUGH THE CNTRL PLAINS. RAIN CHANCES PICK UP ON TUESDAY AS THE AFOREMENTIONED SYSTEM CONTINUES TO PUSH EASTWARD INTO THE MS VALLEY. A GOOD OVERRUNNING PATTERN SETTING UP AT THAT TIME WILL MEAN LIKELY POPS FOR AT LEAST OUR PIEDMONT COUNTIES...ALTHOUGH QPF AMOUNTS NOT THAT IMPRESSIVE FOR THE TIME PERIOD. THE SFC LOW MVS INTO THE OH VALLEY BY WED MORNING AND LIGHT RAIN CONTINUES THROUGH THIS TIME FOR MUCH OF OUR AREA. WITH ALL THE WARM AIR BEING PUMPED INTO THE REGION...NOT EXPECTING TUES NIGHT TO BE THAT COLD (MID 40S TO LWR 50S). CONTINUED RAIN CHANCES INTO ERY WEDNESDAY AS THE FRONT MVS THROUGH...LEFT POPS AT LIKELY FOR NOW FOR THE ENTIRE AREA AND ADDED MENTION OF AN ISOLD TS. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... THE EXTENDED PERIOD CONTINUES TO HV DIFFICULTY RESOLVING INTERACTIONS BETWEEN NORTHERN AND SOUTHERN STREAM SYSTEMS. AS A RESULT...MODELS ONCE AGAIN HV DIVERGENT SOLNS IN THE THU-SAT TIME FRAME. DEEPENING UPR LOW WL PUSH AFOREMENTIONED FRONTAL BNDRY THRU THE MID-ATLANTIC AS IT RIDES FROM SERN TX TO THE FL PANHANDLE ON WED. DECENT AGREEMENT NOW AMONGST 12Z OPERATIONAL GFS/EURO IN BRINGING THIS FEATURE UP THE SERN COAST THU/FRI. MEANWHILE...ANOTHER LO PRES AREA LKS TO TRACK NE JUST OFF THE SE AND MID ATLC CST. IT APPEARS AS IF COLD AIR ARRIVES LATER THAN PRVSLY EXPECTED...WITH COLDER AIR QUICKLY MOVING IN BEHIND THR FRONT ON THU. THIS MAY MAKE FOR SOME P-TYPE ISSUES FOR THU. HOWEVER GIVEN LACK OF MODEL CONTINUITY RUN TO RUN...WL KEEP FORECAST SIMPLE AND STICK WITH LIQUID PHASE PCPN FOR NOW AND CONTINUE TO AWAIT BETTER MODEL AGREEMENT. HI PRES WILL BLD IN FM THE W DURING FRI...WITH UPR FLOW BECOMING DRIER (QUASI-ZONAL) LTR FRIDAY THROUGH THE END OF THE PERIOD. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... CLOUDS HAVE BEEN THICKENING AND LOWERING THROUGHOUT THE DAY AT ALL TAF SITES. EXPECT EVEN LOWER CLOUDS OVERNIGHT AS THE FRONT MVS THROUGH. LOOKING UPSTREAM...MOST CIGS SHOULD REMAIN VFR ALTHOUGH THERE WILL PROBABLY BE A FEW SPOTS WHERE THEY COULD GET AS LOW AS 1500 TO 2000FT AT TIMES. NOT CONFIDENT ENOUGH TO PUT IT IN AS A PREDOMINANT OR TEMPO GROUP FOR NOW. INCLUDED RAIN IN THE ORF AND PHF TAFS ALTHOUGH THERE WILL BE A BETTER CHANCE FOR RAIN AT ECG AND SBY (ALTHOUGH AT SBY THE RAIN WILL SWITCH OVER TO SNOW JUST BEFORE MIDNIGHT). RAIN CLEARS OUT OF ALL TAF SITES BY EARLY MORNING AND CLOUDS ARE QUICK TO FOLLOW SO LOOKING FOR CLEAR SKIES ON SUNDAY. WINDS WILL PICK UP IN THE MORNING HOWEVER AND BE PRETTY GUSTY THROUGHOUT THE DAY. VFR CONDS CONTINUE THROUGH MONDAY. && .MARINE... WINDS HAVE SLOWLY TURNED TO THE S/SE THIS AFTN AHEAD OF STRG COLD FRONT APPROACHING FROM THE WEST THIS EVENING. KEPT INHERITED HEADLINES AS IS...WITH GRADIENT TIGHTENING IN EARNEST AFTER 06Z TONIGHT AS SFC LOW DEVELOPS AND RIDES NORTHEASTWARD ACROSS CAROLINA COASTAL PLAIN TOMORROW. H85 TEMPS PLUNGE TO -11 TO -13C BY SUNDAY AFTN/EVENG WHICH SHOULD ALLOW FOR OPTIMAL MIXING OVER THE RELATIVELY WARM WATERS. NAM/GFS BUFKIT DATA SHOWING ADEQUATE MOMENTUM XFER TO YIELD WND GUSTS IN THE 35 TO 40 KT RANGE TOMORROW AFTN INTO TOMORROW NIGHT AS LOW INTENSIFIES RAPIDLY WELL OFF THE NEW ENGLAND COAST. H85-92 WINDS PROGGED AT 35-40KTS NORTH AND 30-35KTS SOUTH. WL ADD WORDING FOR BREEZY TO WINDY CONDITIONS OVER LAND AREAS TOMORROW. OTW...SMALL CRAFT FLAGS REMAIN FLYING FOR ERLY SUNDAY MRNG...WITH GALE WRNGS (FOR GUSTS) OVER THE BAY AND VA/MD CSTL WATERS IN EFFECT FOR SUN AFTN/EVENING. WNDS/WAVES MORE MARGINAL FARTHER SOUTH AND IN THE BAY BUT CONSIDERING HOW COLD IT WILL BE HAVE DECIDED TO GO A BIT STRONGER THAN THE MODEL DATA SUGGESTS. SEAS WILL NOT BUILD TOO HIGH GIVEN OFFSHORE WNW WIND DIRECTION (MAINLY 5-6 FT...BUT UP TO 7 FT NORTH). SEAS/WINDS SUBSIDE LATER SUNDAY EVENG INTO MON MRNG...AND MUCH MORE TRANQUIL WEATHER SHOULD TAKE HOLD BY LATE MORNING/MIDDAY MONDAY. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...NONE. NC...NONE. VA...NONE. MARINE...SMALL CRAFT ADVISORY FROM 6 AM TO 12 PM EST SUNDAY FOR ANZ630>632-650-652-654-656. GALE WARNING FROM 12 PM TO 10 PM EST SUNDAY FOR ANZ630>632-654- 656. SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO 6 AM EST MONDAY FOR ANZ633-658. GALE WARNING FROM 12 PM SUNDAY TO 1 AM EST MONDAY FOR ANZ650- 652. && $$ SYNOPSIS...BAJ NEAR TERM...BKH SHORT TERM...BAJ LONG TERM...MAM AVIATION...JEF MARINE...JEF md AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1043 PM EST SAT DEC 6 2008 .UPDATE... BIGGEST CHANGE ON UPDATE WAS TO DROP BLIZZARD WARNINGS FOR ALGER AND NRN SCHOOLCRAFT AND PUT UP WINTER STORM WARNINGS INTO SUNDAY MORNING AS STRONG NNW WINDS SHOWING SIGNS OF WEAKENING SOME WITH BUILDING RDG FROM THE WEST. STILL EXPECT ENHANCED LLVL CONV TO FOCUS HEAVIER LES BANDS INTO THESE COUNTIES OVERNIGHT INTO SUNDAY AND WIND GUSTS TO 30 MPH AT TIMES WILL ALSO CONTRIBUTE TO BLOWING/DRIFTING AND OCCASIONAL WHITEOUT CONDITIONS. ALSO DROPPED LES ADVISORY FOR BARAGA AS DRIER AIR HAS REALLY DIMINISHED LES BANDS OVER WRN LAKE SUPERIOR. REST OF FCST STILL OF TRACK SO DIDN`T MAKE ANY OTHER BIG CHANGES. && .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. AND A TROUGH EXTENDING FROM HUDSON BAY SOUTHWARD INTO THE TENNESSEE VALLEY. UPPER MI SITS IN THE MIDDLE OF THE TROUGH AXIS...AND RIGHT UNDERNEATH A SHRTWV AT 500MB. DPVA FORCING WITH THE SHRTWV COMBINED WITH LAKE EFFECT AND A COLD FRONT TO GENERATE A BAND OF HEAVY SNOWFALL THAT MOVED THROUGH UPPER MI EARLY THIS AFTN. THE COLD FRONT IS ASSOCIATED WITH A 1001 MB LOW...LOCATED NOW NEAR DRUMMOND ISLAND. WITH THE SHRTWV OVER UPPER MI...THE CWA IS BEGINNING TO SEE DNVA AND LOWERING INVERSIONS...AS NOTED BY 12Z SOUNDINGS FROM INL AND CWPL. NUMEROUS LAKE EFFECT MULTI-PARALLEL BANDS HAVE DEVELOPED WITH COLD AIR FLOWING IN UNDERNEATH THE INVERSION...MOST INTENSE OVER THE NORTH CENTRAL AND EAST WITH THE LONGER FETCH OF NW WINDS. 850MB TEMPS PER RUC ANALYSIS RANGED FROM -20C WEST TO -15C EAST. DESPITE THE COLD AIRMASS...LAKE EFFECT IS DIMINISHING OVER WESTERN LAKE SUPERIOR THANKS TO DRIER AIR ADVECTING IN OUT OF MN. THIS DRIER AIR IS NOTED BY THE 12Z INL AND CWPL SOUNDINGS HAVING PRECIPITABLE WATER VALUES LESS THAN 0.10 OF AN INCH AND SFC DEWPOINTS BELOW ZERO F. THE DRIER AIR IS ALSO ASSOCIATED WITH A HIGH PRESSURE RIDGE THAT COVERS MANITOBA AND NORTH DAKOTA. FARTHER TO THE WEST...MID AND HIGH CLOUDS ARE MOVING ACROSS THE WESTERN DAKOTAS AND EASTERN MONTANA...ASSOCIATED WITH WARM ADVECTION AHEAD OF A SHRTWV MOVING THROUGH CENTRAL BRITISH COLUMBIA AND ALBERTA. FOR LATEST SNOWFALL REPORTS AND BLOWING SNOW IMPACTS...SEE ARBLSRMQT. && .SHORT TERM (TONIGHT AND SUN)... UPPER LEVEL HEIGHTS ARE PROGGED TO RISE DURING THE NEXT 24 HOURS AS THE TROUGH AXIS PUSHES OFF TO THE EAST. THEREFORE...INVERSIONS WILL CONTINUE TO LOWER ACROSS THE CWA WHILE DRIER AIR ADVECTS IN FROM THE WEST. THE COMBINATION OF BOTH FACTORS SHOULD ALLOW SNOW SHOWERS TO BECOME SCATTERED OVER WESTERN UPPER MI TONIGHT WITH MUCH LESS ACCUMULATION. GOING END TIMES FOR THE WARNINGS FOR WESTERN UPPER MICHIGAN AT 7 PM EST THIS EVENING LOOK GOOD. FOR NORTH CENTRAL AND EASTERN UPPER MICHIGAN...THE LONGER FETCH OF NW WINDS COMBINED WITH LAND BREEZES COMING OUT OF WESTERN UPPER MI SHOULD KEEP THE LAKE EFFECT GOING LONGER. IN ADDITION...UPSTREAM MOISTENING OFF LAKE NIPIGON IS EXPECTED...AS IS OCCURRING ATTM. IN FACT...LAST FEW RUC RUNS AND OUR LOCAL WRF-ARW RUNS SUGGEST A SINGLE BAND FROM LAKE NIPIGON...OFF THE TIP OF THE KEWEENAW AND INTO THE ALGER/DELTA/MARQUETTE COUNTY LINES. THIS SEEMS REASONABLE AS THE LAND BREEZE DEVELOPS AND CONVERGES ON THE GENERAL NNW TO NW FLOW BEHIND THE DEPARTING SFC LOW. SHOULD THE BAND STAY IN PLACE... SOUNDINGS AND MODEL DERIVED QPF AMOUNTS SUGGEST THAT 1 INCH PER HOUR RATES ARE REASONABLE. THEREFORE...WILL CONTINUE WARNINGS FOR ALGER...DELTA AND MARQUETTE COUNTIES. SCHOOLCRAFT AND LUCE COUNTIES ARE A LITTLE MORE TROUBLESOME...AND WAS TEMPTED TO DROP THE WARNINGS AS ONLY THE MULTI-PARALLEL BANDS ARE EXPECTED THERE. HOWEVER...WITH THE WIND BLOWING THE SNOW THIS EVENING AND THE WARNING ONLY BEING UP FOR ABOUT 3 TO 4 HOURS SO FAR...HAVE DECIDED TO LEAVE IT UP FOR NOW. LAKE EFFECT OVER THE NORTH CENTRAL AND EAST SHOULD GRADUALLY DIMINISH ON SUNDAY AS THE DRIER AIR OVER WESTERN UPPER MI BUILDS IN THERE. STILL MAINTAINED LIKELY POPS SUNDAY AFTN FOR NORTHERN SCHOOLCRAFT/LUCE AS IT LOOKS LIKE THE LAKE NIPIGON ENHANCED BAND WILL SHIFT IN THERE. BESIDES THE LAKE EFFECT...ANOTHER POSSIBLE PCPN IMPACT IS SOME WARM ADVECTION -SN MOVING IN SUNDAY AFTN. THIS WARM ADVECTION PCPN IS ASSOCIATED WITH THE MID/HIGH CLOUD IN THE WESTERN DAKOTAS AND EASTERN MONTANA. THE CANADIAN MODEL WAS VERY AGGRESSIVE BRINGING THIS PCPN INTO UPPER MI...MAKING ITS WAY INTO THE CENTRAL U.P.. HOWEVER...IT IS AN OUTLIER AND PROBABLY TOO FAST GIVEN THAT SOUNDINGS SHOW PLENTY OF DRY AIR. INSTEAD...FOLLOWED THE GFS/LOCAL WRF-ARW RUNS WHICH ONLY BRING A HUNDREDTH OF QPF INTO FAR WESTERN UPPER MI. ANOTHER ISSUE FOR THE FORECAST IS TEMPS TONIGHT. IT APPEARS SOME OF THE WI BORDER AREAS COULD CLEAR OUT. GIVEN FRESH SNOW AND THE DRY AIRMASS MOVING IN...TEMPS WOULD PLUMMET ASSUMING WINDS BECOME CALM. LOWERED MINS ALONG THE WI BORDER OF GOGEBIC AND IRON COUNTIES TO 0 TO 5 BELOW ZERO...BUT MAY NOT BE LOW ENOUGH IF CLOUDS CLEAR SOONER. FOR SUNDAY...WITH THE HIGH CLOUDS MOVING IN DURING THE AFTERNOON AND A COLD AIRMASS IN PLACE (850MB TEMPS ONLY REACHING -16C AT 18Z)...FOLLOWED SIMILARLY TO THE MIDNIGHT SHIFT OF STAYING WITH THE COLDER MAV GUIDANCE READINGS FOR HIGHS. .LONG TERM (SUN NIGHT THROUGH NEXT SATURDAY)... UPPER FLOW CONTINUES TO BE FROM THE NW THROUGH THE PERIOD WITH TROUGHING IN THE AREA WITH MORE TROUGHING DIGGING TOWARDS THE AREA FOR TUE. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE AND MOISTURE MOVING THROUGH THE AREA SUN NIGHT INTO MON MORNING BEFORE BOTH MOVE OUT BY MON AFTERNOON. NAM SHOWING ISENTROPIC LIFT ON I280K-I295K SURFACES WITH SOME MOISTURE MOVING ACROSS THE CWA SUN NIGHT WITH THE MOISTURE MOVING OUT MON MORNING EXCEPT IN THE LOWEST LEVELS ON I280K SURFACE WHICH LINGERS. GFS SHOWS SOME ISENTROPIC LIFT ON I280K SURFACE WITH MOISTURE AS WELL SUN NIGHT AND THE MOISTURE MOVES OUT ON MON. BASICALLY...LOOKS LIKE RIGHT NOW...THIS SYSTEM FOR SUN NIGHT GOES MOSTLY TO THE SOUTH OF CWA AND DOES NOT LOOK LIKE HEADLINES WILL BE NEEDED. ONLY EXCEPTION AND WILL NEED TO BE WATCHED IS LUCE AND SCHOOLCRAFT COUNTIES WHERE THERE COULD BE A LAKE MICHIGAN BAND THAT FORMS FROM THE SOUTH WINDS THAT OCCUR AND THIS COULD POSSIBLY BE ACROSS THE EASTERN PORTIONS OF THOSE TWO COUNTIES. IT IS COLD ENOUGH FOR LAKE EFFECT TO FORM AND WITH WINDS CONVERGING ACROSS EASTERN LAKE MICHIGAN...A LONG FETCH WOULD FORM. ONLY THING IS THERE COULD BE ENOUGH OF A LAND BREEZE TO PUSH THIS BAND A BIT FURTHER EAST AND KEEP OUT OF THOSE TWO COUNTIES AS WELL. THE LAND BREEZE COULD ALSO DISRUPT THE BAND AS WELL. WILL MENTION THIS IN THE HWO PRODUCT FOR NOW AND NOT HIGHLIGHT...BUT THIS POSSIBILITY OF A HEAVY LAKE EFFECT BAND WILL HAVE TO BE WATCHED. CHANGE FOR THIS FORECAST WAS ALSO TO GO LIKELY POPS LATE SUNDAY NIGHT FOR ALL OF CWA WITH DEEP MOISTURE. FOR TUESDAY...SIGNIFICANT TROUGH DIGGING CAUSES A SYSTEM TO COME UP FROM THE SW. SOUTHERN CWA IS ON THE NORTHERN END OF THIS SYSTEM WITH LAKE EFFECT ACROSS THE REST OF THE CWA. SIGNIFICANT SYSTEM SNOW WOULD BE ACROSS THE SOUTHERN CWA AND BUMPED POPS UP TO LIKELY FOR THIS AREA. IF THIS SYSTEM COMES A BIT FURTHER NORTH...THEN WILL HAVE TO BE WATCHED AS WELL. SUBSEQUENT MODEL RUNS WILL HELP TO DETERMINE IF THIS SYSTEM WILL AFFECT US MORE WITH HEAVIER SNOW OR NOT. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A 500 MB TROUGH ACROSS THE CENTRAL U.S. WITH RIDGING IN THE WESTERN U.S. 00Z WED. MORE TROUGHING COMES IN FOR 00Z THU AND REMAINS THROUGH 00Z SUN. LOOKS PRETTY ACTIVE IN THE EXTENDED AND LOOKS LIKE REPEAT LAKE EFFECT EVENT EPISODES WITH ALBERTA CLIPPER TYPE SYSTEMS MOVING THROUGH EVERY SO OFTEN. BROADBRUSHED THE EXTENDED AND KEPT SOME POPS IN NEAR LAKE SUPERIOR EVERY DAY WITH COLD ENOUGH AIR AROUND AND SOME SHORTWAVES NEAR THE AREA AS WELL. TEMPERATURES LOOK TO STAY BELOW NORMAL.USED THE ECMWF AS GUIDANCE FOR THIS EXTENDED FORECAST AND DID NOT STRAY TOO MUCH FROM IT. CLIPPER SYSTEM MOVES THROUGH WED NIGHT AND THIS LOOKS TO BE THE BEST CHANCE FOR WIDEPSREAD SNOW THEN. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... MULTI-PARALLEL BAND LAKE EFFECT SNOW WINDING DOWN FROM THE WEST THIS EVENING. VERY DRY AIR UPSTREAM GREATLY DIMINISHING LES OVER WRN LAKE SUPERIOR THIS EVENING. HAVE DECIDED TO GO WITH VFR VBSY AT KCMX THROUGH THE PERIOD BUT WILL KEEP MVFR CIGS UNTIL WINDS BACK SW BY 20Z SUN. NNW WINDS WILL MAINTAIN MVFR TO OCCASIONAL IFR CONDITIONS AT KSAW THIS EVENING AS THEY REMAIN ON THE EDGE OF INTENSE LES BANDS. WINDS BACKING NW BY LATE EVENING WILL QUICKLY IMPROVE VSBY TO VFR. WINDS BACKING W LATE TONIGHT WILL BREAK UP MVFR CIGS AND KEEP SKIES VFR THROUGH THE REST OF THE FCST PD. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... NORTH GALES OF UP TO 45 KNOTS...STRONGEST ON EASTERN SUPERIOR...WILL DIMINISH BELOW 30 KT AFTER MIDNIGHT AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM THE DAKOTAS. EXPECT WINDS TO GENERALLY REMAIN AT OR BELOW 30 KNOTS THEN THROUGH MONDAY NIGHT. ON TUESDAY...AN AREA OF LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS IS EXPECTED TO MOVE NORTHEAST...REACHING THE EASTERN GREAT LAKES ON WEDNESDAY. A PERIOD OF NORTH GALES TO 35 KNOTS ARE POSSIBLE BEHIND THE LOW OVER EASTERN LAKE SUPERIOR TUESDAY NIGHT...THEN WINDS WILL DROP BACK DOWN BELOW 30 KNOTS FOR WEDNESDAY AND THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... WINTER STORM WARNING UNTIL 11 AM EST SUNDAY FOR MIZ006-085. WINTER STORM WARNING UNTIL 10 AM EST SUNDAY FOR MIZ007. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005-013-014. LAKE SUPERIOR... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LSZ242>245. LAKE MICHIGAN... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ221-250. && $$ UPDATE...VOSS SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...JV MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 802 PM EST SAT DEC 6 2008 UPDATED FOR 00Z AVIATION DISCUSSION .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. AND A TROUGH EXTENDING FROM HUDSON BAY SOUTHWARD INTO THE TENNESSEE VALLEY. UPPER MI SITS IN THE MIDDLE OF THE TROUGH AXIS...AND RIGHT UNDERNEATH A SHRTWV AT 500MB. DPVA FORCING WITH THE SHRTWV COMBINED WITH LAKE EFFECT AND A COLD FRONT TO GENERATE A BAND OF HEAVY SNOWFALL THAT MOVED THROUGH UPPER MI EARLY THIS AFTN. THE COLD FRONT IS ASSOCIATED WITH A 1001 MB LOW...LOCATED NOW NEAR DRUMMOND ISLAND. WITH THE SHRTWV OVER UPPER MI...THE CWA IS BEGINNING TO SEE DNVA AND LOWERING INVERSIONS...AS NOTED BY 12Z SOUNDINGS FROM INL AND CWPL. NUMEROUS LAKE EFFECT MULTI-PARALLEL BANDS HAVE DEVELOPED WITH COLD AIR FLOWING IN UNDERNEATH THE INVERSION...MOST INTENSE OVER THE NORTH CENTRAL AND EAST WITH THE LONGER FETCH OF NW WINDS. 850MB TEMPS PER RUC ANALYSIS RANGED FROM -20C WEST TO -15C EAST. DESPITE THE COLD AIRMASS...LAKE EFFECT IS DIMINISHING OVER WESTERN LAKE SUPERIOR THANKS TO DRIER AIR ADVECTING IN OUT OF MN. THIS DRIER AIR IS NOTED BY THE 12Z INL AND CWPL SOUNDINGS HAVING PRECIPITABLE WATER VALUES LESS THAN 0.10 OF AN INCH AND SFC DEWPOINTS BELOW ZERO F. THE DRIER AIR IS ALSO ASSOCIATED WITH A HIGH PRESSURE RIDGE THAT COVERS MANITOBA AND NORTH DAKOTA. FARTHER TO THE WEST...MID AND HIGH CLOUDS ARE MOVING ACROSS THE WESTERN DAKOTAS AND EASTERN MONTANA...ASSOCIATED WITH WARM ADVECTION AHEAD OF A SHRTWV MOVING THROUGH CENTRAL BRITISH COLUMBIA AND ALBERTA. FOR LATEST SNOWFALL REPORTS AND BLOWING SNOW IMPACTS...SEE ARBLSRMQT. && .SHORT TERM (TONIGHT AND SUN)... UPPER LEVEL HEIGHTS ARE PROGGED TO RISE DURING THE NEXT 24 HOURS AS THE TROUGH AXIS PUSHES OFF TO THE EAST. THEREFORE...INVERSIONS WILL CONTINUE TO LOWER ACROSS THE CWA WHILE DRIER AIR ADVECTS IN FROM THE WEST. THE COMBINATION OF BOTH FACTORS SHOULD ALLOW SNOW SHOWERS TO BECOME SCATTERED OVER WESTERN UPPER MI TONIGHT WITH MUCH LESS ACCUMULATION. GOING END TIMES FOR THE WARNINGS FOR WESTERN UPPER MICHIGAN AT 7 PM EST THIS EVENING LOOK GOOD. FOR NORTH CENTRAL AND EASTERN UPPER MICHIGAN...THE LONGER FETCH OF NW WINDS COMBINED WITH LAND BREEZES COMING OUT OF WESTERN UPPER MI SHOULD KEEP THE LAKE EFFECT GOING LONGER. IN ADDITION...UPSTREAM MOISTENING OFF LAKE NIPIGON IS EXPECTED...AS IS OCCURRING ATTM. IN FACT...LAST FEW RUC RUNS AND OUR LOCAL WRF-ARW RUNS SUGGEST A SINGLE BAND FROM LAKE NIPIGON...OFF THE TIP OF THE KEWEENAW AND INTO THE ALGER/DELTA/MARQUETTE COUNTY LINES. THIS SEEMS REASONABLE AS THE LAND BREEZE DEVELOPS AND CONVERGES ON THE GENERAL NNW TO NW FLOW BEHIND THE DEPARTING SFC LOW. SHOULD THE BAND STAY IN PLACE... SOUNDINGS AND MODEL DERIVED QPF AMOUNTS SUGGEST THAT 1 INCH PER HOUR RATES ARE REASONABLE. THEREFORE...WILL CONTINUE WARNINGS FOR ALGER...DELTA AND MARQUETTE COUNTIES. SCHOOLCRAFT AND LUCE COUNTIES ARE A LITTLE MORE TROUBLESOME...AND WAS TEMPTED TO DROP THE WARNINGS AS ONLY THE MULTI-PARALLEL BANDS ARE EXPECTED THERE. HOWEVER...WITH THE WIND BLOWING THE SNOW THIS EVENING AND THE WARNING ONLY BEING UP FOR ABOUT 3 TO 4 HOURS SO FAR...HAVE DECIDED TO LEAVE IT UP FOR NOW. LAKE EFFECT OVER THE NORTH CENTRAL AND EAST SHOULD GRADUALLY DIMINISH ON SUNDAY AS THE DRIER AIR OVER WESTERN UPPER MI BUILDS IN THERE. STILL MAINTAINED LIKELY POPS SUNDAY AFTN FOR NORTHERN SCHOOLCRAFT/LUCE AS IT LOOKS LIKE THE LAKE NIPIGON ENHANCED BAND WILL SHIFT IN THERE. BESIDES THE LAKE EFFECT...ANOTHER POSSIBLE PCPN IMPACT IS SOME WARM ADVECTION -SN MOVING IN SUNDAY AFTN. THIS WARM ADVECTION PCPN IS ASSOCIATED WITH THE MID/HIGH CLOUD IN THE WESTERN DAKOTAS AND EASTERN MONTANA. THE CANADIAN MODEL WAS VERY AGGRESSIVE BRINGING THIS PCPN INTO UPPER MI...MAKING ITS WAY INTO THE CENTRAL U.P.. HOWEVER...IT IS AN OUTLIER AND PROBABLY TOO FAST GIVEN THAT SOUNDINGS SHOW PLENTY OF DRY AIR. INSTEAD...FOLLOWED THE GFS/LOCAL WRF-ARW RUNS WHICH ONLY BRING A HUNDREDTH OF QPF INTO FAR WESTERN UPPER MI. ANOTHER ISSUE FOR THE FORECAST IS TEMPS TONIGHT. IT APPEARS SOME OF THE WI BORDER AREAS COULD CLEAR OUT. GIVEN FRESH SNOW AND THE DRY AIRMASS MOVING IN...TEMPS WOULD PLUMMET ASSUMING WINDS BECOME CALM. LOWERED MINS ALONG THE WI BORDER OF GOGEBIC AND IRON COUNTIES TO 0 TO 5 BELOW ZERO...BUT MAY NOT BE LOW ENOUGH IF CLOUDS CLEAR SOONER. FOR SUNDAY...WITH THE HIGH CLOUDS MOVING IN DURING THE AFTERNOON AND A COLD AIRMASS IN PLACE (850MB TEMPS ONLY REACHING -16C AT 18Z)...FOLLOWED SIMILARLY TO THE MIDNIGHT SHIFT OF STAYING WITH THE COLDER MAV GUIDANCE READINGS FOR HIGHS. .LONG TERM (SUN NIGHT THROUGH NEXT SATURDAY)... UPPER FLOW CONTINUES TO BE FROM THE NW THROUGH THE PERIOD WITH TROUGHING IN THE AREA WITH MORE TROUGHING DIGGING TOWARDS THE AREA FOR TUE. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE AND MOISTURE MOVING THROUGH THE AREA SUN NIGHT INTO MON MORNING BEFORE BOTH MOVE OUT BY MON AFTERNOON. NAM SHOWING ISENTROPIC LIFT ON I280K-I295K SURFACES WITH SOME MOISTURE MOVING ACROSS THE CWA SUN NIGHT WITH THE MOISTURE MOVING OUT MON MORNING EXCEPT IN THE LOWEST LEVELS ON I280K SURFACE WHICH LINGERS. GFS SHOWS SOME ISENTROPIC LIFT ON I280K SURFACE WITH MOISTURE AS WELL SUN NIGHT AND THE MOISTURE MOVES OUT ON MON. BASICALLY...LOOKS LIKE RIGHT NOW...THIS SYSTEM FOR SUN NIGHT GOES MOSTLY TO THE SOUTH OF CWA AND DOES NOT LOOK LIKE HEADLINES WILL BE NEEDED. ONLY EXCEPTION AND WILL NEED TO BE WATCHED IS LUCE AND SCHOOLCRAFT COUNTIES WHERE THERE COULD BE A LAKE MICHIGAN BAND THAT FORMS FROM THE SOUTH WINDS THAT OCCUR AND THIS COULD POSSIBLY BE ACROSS THE EASTERN PORTIONS OF THOSE TWO COUNTIES. IT IS COLD ENOUGH FOR LAKE EFFECT TO FORM AND WITH WINDS CONVERGING ACROSS EASTERN LAKE MICHIGAN...A LONG FETCH WOULD FORM. ONLY THING IS THERE COULD BE ENOUGH OF A LAND BREEZE TO PUSH THIS BAND A BIT FURTHER EAST AND KEEP OUT OF THOSE TWO COUNTIES AS WELL. THE LAND BREEZE COULD ALSO DISRUPT THE BAND AS WELL. WILL MENTION THIS IN THE HWO PRODUCT FOR NOW AND NOT HIGHLIGHT...BUT THIS POSSIBILITY OF A HEAVY LAKE EFFECT BAND WILL HAVE TO BE WATCHED. CHANGE FOR THIS FORECAST WAS ALSO TO GO LIKELY POPS LATE SUNDAY NIGHT FOR ALL OF CWA WITH DEEP MOISTURE. FOR TUESDAY...SIGNIFICANT TROUGH DIGGING CAUSES A SYSTEM TO COME UP FROM THE SW. SOUTHERN CWA IS ON THE NORTHERN END OF THIS SYSTEM WITH LAKE EFFECT ACROSS THE REST OF THE CWA. SIGNIFICANT SYSTEM SNOW WOULD BE ACROSS THE SOUTHERN CWA AND BUMPED POPS UP TO LIKELY FOR THIS AREA. IF THIS SYSTEM COMES A BIT FURTHER NORTH...THEN WILL HAVE TO BE WATCHED AS WELL. SUBSEQUENT MODEL RUNS WILL HELP TO DETERMINE IF THIS SYSTEM WILL AFFECT US MORE WITH HEAVIER SNOW OR NOT. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A 500 MB TROUGH ACROSS THE CENTRAL U.S. WITH RIDGING IN THE WESTERN U.S. 00Z WED. MORE TROUGHING COMES IN FOR 00Z THU AND REMAINS THROUGH 00Z SUN. LOOKS PRETTY ACTIVE IN THE EXTENDED AND LOOKS LIKE REPEAT LAKE EFFECT EVENT EPISODES WITH ALBERTA CLIPPER TYPE SYSTEMS MOVING THROUGH EVERY SO OFTEN. BROADBRUSHED THE EXTENDED AND KEPT SOME POPS IN NEAR LAKE SUPERIOR EVERY DAY WITH COLD ENOUGH AIR AROUND AND SOME SHORTWAVES NEAR THE AREA AS WELL. TEMPERATURES LOOK TO STAY BELOW NORMAL.USED THE ECMWF AS GUIDANCE FOR THIS EXTENDED FORECAST AND DID NOT STRAY TOO MUCH FROM IT. CLIPPER SYSTEM MOVES THROUGH WED NIGHT AND THIS LOOKS TO BE THE BEST CHANCE FOR WIDEPSREAD SNOW THEN. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... MULTI-PARALLEL BAND LAKE EFFECT SNOW WINDING DOWN FROM THE WEST THIS EVENING. VERY DRY AIR UPSTREAM GREATLY DIMINISHING LES OVER WRN LAKE SUPERIOR THIS EVENING. HAVE DECIDED TO GO WITH VFR VBSY AT KCMX THROUGH THE PERIOD BUT WILL KEEP MVFR CIGS UNTIL WINDS BACK SW BY 20Z SUN. NNW WINDS WILL MAINTAIN MVFR TO OCCASIONAL IFR CONDITIONS AT KSAW THIS EVENING AS THEY REMAIN ON THE EDGE OF INTENSE LES BANDS. WINDS BACKING NW BY LATE EVENING WILL QUICKLY IMPROVE VSBY TO VFR. WINDS BACKING W LATE TONIGHT WILL BREAK UP MVFR CIGS AND KEEP SKIES VFR THROUGH THE REST OF THE FCST PD. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... NORTH GALES OF UP TO 45 KNOTS...STRONGEST ON EASTERN SUPERIOR...WILL DIMINISH BELOW 30 KT AFTER MIDNIGHT AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM THE DAKOTAS. EXPECT WINDS TO GENERALLY REMAIN AT OR BELOW 30 KNOTS THEN THROUGH MONDAY NIGHT. ON TUESDAY...AN AREA OF LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS IS EXPECTED TO MOVE NORTHEAST...REACHING THE EASTERN GREAT LAKES ON WEDNESDAY. A PERIOD OF NORTH GALES TO 35 KNOTS ARE POSSIBLE BEHIND THE LOW OVER EASTERN LAKE SUPERIOR TUESDAY NIGHT...THEN WINDS WILL DROP BACK DOWN BELOW 30 KNOTS FOR WEDNESDAY AND THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... BLIZZARD WARNING UNTIL 10 AM EST SUNDAY FOR MIZ006-085. BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ001-003. WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR MIZ002-009. WINTER STORM WARNING UNTIL 10 AM EST SUNDAY FOR MIZ007. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005-013-014. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ084. LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ004. LAKE SUPERIOR... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LSZ242>245. LAKE MICHIGAN... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ221-250. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...JV MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 442 PM EST SAT DEC 6 2008 .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. AND A TROUGH EXTENDING FROM HUDSON BAY SOUTHWARD INTO THE TENNESSEE VALLEY. UPPER MI SITS IN THE MIDDLE OF THE TROUGH AXIS...AND RIGHT UNDERNEATH A SHRTWV AT 500MB. DPVA FORCING WITH THE SHRTWV COMBINED WITH LAKE EFFECT AND A COLD FRONT TO GENERATE A BAND OF HEAVY SNOWFALL THAT MOVED THROUGH UPPER MI EARLY THIS AFTN. THE COLD FRONT IS ASSOCIATED WITH A 1001 MB LOW...LOCATED NOW NEAR DRUMMOND ISLAND. WITH THE SHRTWV OVER UPPER MI...THE CWA IS BEGINNING TO SEE DNVA AND LOWERING INVERSIONS...AS NOTED BY 12Z SOUNDINGS FROM INL AND CWPL. NUMEROUS LAKE EFFECT MULTI-PARALLEL BANDS HAVE DEVELOPED WITH COLD AIR FLOWING IN UNDERNEATH THE INVERSION...MOST INTENSE OVER THE NORTH CENTRAL AND EAST WITH THE LONGER FETCH OF NW WINDS. 850MB TEMPS PER RUC ANALYSIS RANGED FROM -20C WEST TO -15C EAST. DESPITE THE COLD AIRMASS...LAKE EFFECT IS DIMINISHING OVER WESTERN LAKE SUPERIOR THANKS TO DRIER AIR ADVECTING IN OUT OF MN. THIS DRIER AIR IS NOTED BY THE 12Z INL AND CWPL SOUNDINGS HAVING PRECIPITABLE WATER VALUES LESS THAN 0.10 OF AN INCH AND SFC DEWPOINTS BELOW ZERO F. THE DRIER AIR IS ALSO ASSOCIATED WITH A HIGH PRESSURE RIDGE THAT COVERS MANITOBA AND NORTH DAKOTA. FARTHER TO THE WEST...MID AND HIGH CLOUDS ARE MOVING ACROSS THE WESTERN DAKOTAS AND EASTERN MONTANA...ASSOCIATED WITH WARM ADVECTION AHEAD OF A SHRTWV MOVING THROUGH CENTRAL BRITISH COLUMBIA AND ALBERTA. FOR LATEST SNOWFALL REPORTS AND BLOWING SNOW IMPACTS...SEE ARBLSRMQT. && .SHORT TERM (TONIGHT AND SUN)... UPPER LEVEL HEIGHTS ARE PROGGED TO RISE DURING THE NEXT 24 HOURS AS THE TROUGH AXIS PUSHES OFF TO THE EAST. THEREFORE...INVERSIONS WILL CONTINUE TO LOWER ACROSS THE CWA WHILE DRIER AIR ADVECTS IN FROM THE WEST. THE COMBINATION OF BOTH FACTORS SHOULD ALLOW SNOW SHOWERS TO BECOME SCATTERED OVER WESTERN UPPER MI TONIGHT WITH MUCH LESS ACCUMULATION. GOING END TIMES FOR THE WARNINGS FOR WESTERN UPPER MICHIGAN AT 7 PM EST THIS EVENING LOOK GOOD. FOR NORTH CENTRAL AND EASTERN UPPER MICHIGAN...THE LONGER FETCH OF NW WINDS COMBINED WITH LAND BREEZES COMING OUT OF WESTERN UPPER MI SHOULD KEEP THE LAKE EFFECT GOING LONGER. IN ADDITION...UPSTREAM MOISTENING OFF LAKE NIPIGON IS EXPECTED...AS IS OCCURRING ATTM. IN FACT...LAST FEW RUC RUNS AND OUR LOCAL WRF-ARW RUNS SUGGEST A SINGLE BAND FROM LAKE NIPIGON...OFF THE TIP OF THE KEWEENAW AND INTO THE ALGER/DELTA/MARQUETTE COUNTY LINES. THIS SEEMS REASONABLE AS THE LAND BREEZE DEVELOPS AND CONVERGES ON THE GENERAL NNW TO NW FLOW BEHIND THE DEPARTING SFC LOW. SHOULD THE BAND STAY IN PLACE... SOUNDINGS AND MODEL DERIVED QPF AMOUNTS SUGGEST THAT 1 INCH PER HOUR RATES ARE REASONABLE. THEREFORE...WILL CONTINUE WARNINGS FOR ALGER...DELTA AND MARQUETTE COUNTIES. SCHOOLCRAFT AND LUCE COUNTIES ARE A LITTLE MORE TROUBLESOME...AND WAS TEMPTED TO DROP THE WARNINGS AS ONLY THE MULTI-PARALLEL BANDS ARE EXPECTED THERE. HOWEVER...WITH THE WIND BLOWING THE SNOW THIS EVENING AND THE WARNING ONLY BEING UP FOR ABOUT 3 TO 4 HOURS SO FAR...HAVE DECIDED TO LEAVE IT UP FOR NOW. LAKE EFFECT OVER THE NORTH CENTRAL AND EAST SHOULD GRADUALLY DIMINISH ON SUNDAY AS THE DRIER AIR OVER WESTERN UPPER MI BUILDS IN THERE. STILL MAINTAINED LIKELY POPS SUNDAY AFTN FOR NORTHERN SCHOOLCRAFT/LUCE AS IT LOOKS LIKE THE LAKE NIPIGON ENHANCED BAND WILL SHIFT IN THERE. BESIDES THE LAKE EFFECT...ANOTHER POSSIBLE PCPN IMPACT IS SOME WARM ADVECTION -SN MOVING IN SUNDAY AFTN. THIS WARM ADVECTION PCPN IS ASSOCIATED WITH THE MID/HIGH CLOUD IN THE WESTERN DAKOTAS AND EASTERN MONTANA. THE CANADIAN MODEL WAS VERY AGGRESSIVE BRINGING THIS PCPN INTO UPPER MI...MAKING ITS WAY INTO THE CENTRAL U.P.. HOWEVER...IT IS AN OUTLIER AND PROBABLY TOO FAST GIVEN THAT SOUNDINGS SHOW PLENTY OF DRY AIR. INSTEAD...FOLLOWED THE GFS/LOCAL WRF-ARW RUNS WHICH ONLY BRING A HUNDREDTH OF QPF INTO FAR WESTERN UPPER MI. ANOTHER ISSUE FOR THE FORECAST IS TEMPS TONIGHT. IT APPEARS SOME OF THE WI BORDER AREAS COULD CLEAR OUT. GIVEN FRESH SNOW AND THE DRY AIRMASS MOVING IN...TEMPS WOULD PLUMMET ASSUMING WINDS BECOME CALM. LOWERED MINS ALONG THE WI BORDER OF GOGEBIC AND IRON COUNTIES TO 0 TO 5 BELOW ZERO...BUT MAY NOT BE LOW ENOUGH IF CLOUDS CLEAR SOONER. FOR SUNDAY...WITH THE HIGH CLOUDS MOVING IN DURING THE AFTERNOON AND A COLD AIRMASS IN PLACE (850MB TEMPS ONLY REACHING -16C AT 18Z)...FOLLOWED SIMILARLY TO THE MIDNIGHT SHIFT OF STAYING WITH THE COLDER MAV GUIDANCE READINGS FOR HIGHS. .LONG TERM (SUN NIGHT THROUGH NEXT SATURDAY)... UPPER FLOW CONTINUES TO BE FROM THE NW THROUGH THE PERIOD WITH TROUGHING IN THE AREA WITH MORE TROUGHING DIGGING TOWARDS THE AREA FOR TUE. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE AND MOISTURE MOVING THROUGH THE AREA SUN NIGHT INTO MON MORNING BEFORE BOTH MOVE OUT BY MON AFTERNOON. NAM SHOWING ISENTROPIC LIFT ON I280K-I295K SURFACES WITH SOME MOISTURE MOVING ACROSS THE CWA SUN NIGHT WITH THE MOISTURE MOVING OUT MON MORNING EXCEPT IN THE LOWEST LEVELS ON I280K SURFACE WHICH LINGERS. GFS SHOWS SOME ISENTROPIC LIFT ON I280K SURFACE WITH MOISTURE AS WELL SUN NIGHT AND THE MOISTURE MOVES OUT ON MON. BASICALLY...LOOKS LIKE RIGHT NOW...THIS SYSTEM FOR SUN NIGHT GOES MOSTLY TO THE SOUTH OF CWA AND DOES NOT LOOK LIKE HEADLINES WILL BE NEEDED. ONLY EXCEPTION AND WILL NEED TO BE WATCHED IS LUCE AND SCHOOLCRAFT COUNTIES WHERE THERE COULD BE A LAKE MICHIGAN BAND THAT FORMS FROM THE SOUTH WINDS THAT OCCUR AND THIS COULD POSSIBLY BE ACROSS THE EASTERN PORTIONS OF THOSE TWO COUNTIES. IT IS COLD ENOUGH FOR LAKE EFFECT TO FORM AND WITH WINDS CONVERGING ACROSS EASTERN LAKE MICHIGAN...A LONG FETCH WOULD FORM. ONLY THING IS THERE COULD BE ENOUGH OF A LAND BREEZE TO PUSH THIS BAND A BIT FURTHER EAST AND KEEP OUT OF THOSE TWO COUNTIES AS WELL. THE LAND BREEZE COULD ALSO DISRUPT THE BAND AS WELL. WILL MENTION THIS IN THE HWO PRODUCT FOR NOW AND NOT HIGHLIGHT...BUT THIS POSSIBILITY OF A HEAVY LAKE EFFECT BAND WILL HAVE TO BE WATCHED. CHANGE FOR THIS FORECAST WAS ALSO TO GO LIKELY POPS LATE SUNDAY NIGHT FOR ALL OF CWA WITH DEEP MOISTURE. FOR TUESDAY...SIGNIFICANT TROUGH DIGGING CAUSES A SYSTEM TO COME UP FROM THE SW. SOUTHERN CWA IS ON THE NORTHERN END OF THIS SYSTEM WITH LAKE EFFECT ACROSS THE REST OF THE CWA. SIGNIFICANT SYSTEM SNOW WOULD BE ACROSS THE SOUTHERN CWA AND BUMPED POPS UP TO LIKELY FOR THIS AREA. IF THIS SYSTEM COMES A BIT FURTHER NORTH...THEN WILL HAVE TO BE WATCHED AS WELL. SUBSEQUENT MODEL RUNS WILL HELP TO DETERMINE IF THIS SYSTEM WILL AFFECT US MORE WITH HEAVIER SNOW OR NOT. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A 500 MB TROUGH ACROSS THE CENTRAL U.S. WITH RIDGING IN THE WESTERN U.S. 00Z WED. MORE TROUGHING COMES IN FOR 00Z THU AND REMAINS THROUGH 00Z SUN. LOOKS PRETTY ACTIVE IN THE EXTENDED AND LOOKS LIKE REPEAT LAKE EFFECT EVENT EPISODES WITH ALBERTA CLIPPER TYPE SYSTEMS MOVING THROUGH EVERY SO OFTEN. BROADBRUSHED THE EXTENDED AND KEPT SOME POPS IN NEAR LAKE SUPERIOR EVERY DAY WITH COLD ENOUGH AIR AROUND AND SOME SHORTWAVES NEAR THE AREA AS WELL. TEMPERATURES LOOK TO STAY BELOW NORMAL.USED THE ECMWF AS GUIDANCE FOR THIS EXTENDED FORECAST AND DID NOT STRAY TOO MUCH FROM IT. CLIPPER SYSTEM MOVES THROUGH WED NIGHT AND THIS LOOKS TO BE THE BEST CHANCE FOR WIDEPSREAD SNOW THEN. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... ARCTIC FRONT HAS PUSHED THROUGH BOTH TAF SITES...WITH BLUSTERY MULTI-PARALLEL BAND LAKE EFFECT SNOW SET UP IN ITS WAKE. WOULD EXPECT CONDITIONS TO BOUNCE BACK AND FORTH BTWN IFR AND LIFR AND BOTH TAF SITES THROUGH THE REST OF THE AFTN AS BANDS MOVE THROUGH. THERE IS A CHANCE VSBYS COULD DROP TO VLIFR BUT NOT HIGH ENOUGH TO INCLUDE EVEN IN A TEMPO GROUP ATTM. TONIGHT...A SINGLE BAND OF SNOW FROM LAKE NIPIGON ACROSS CENTRAL LAKE SUPERIOR MAY BECOME STATIONARY FOR A FEW HOURS AT SAW...WITH ENOUGH CONFIDENCE TO AT LEAST INCLUDE LIFR CONDITIONS. OTHERWISE...IMPROVEMENT IS EXPECTED THROUGH THE NIGHT AS WINDS DIMINISH AND DRIER AIR WORKS IN FROM MN...WITH VSBYS REACHING VFR BY SUNRISE. CIGS WILL REACH VFR LATE SUNDAY MORNING AS THE DRIER AIR AND WINDS BACKING TOWARDS THE WEST AND EVENTUALLY SW HELP TO BREAK UP THE CLOUDS. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... NORTH GALES OF UP TO 45 KNOTS...STRONGEST ON EASTERN SUPERIOR...WILL DIMINISH BELOW 30 KT AFTER MIDNIGHT AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM THE DAKOTAS. EXPECT WINDS TO GENERALLY REMAIN AT OR BELOW 30 KNOTS THEN THROUGH MONDAY NIGHT. ON TUESDAY...AN AREA OF LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS IS EXPECTED TO MOVE NORTHEAST...REACHING THE EASTERN GREAT LAKES ON WEDNESDAY. A PERIOD OF NORTH GALES TO 35 KNOTS ARE POSSIBLE BEHIND THE LOW OVER EASTERN LAKE SUPERIOR TUESDAY NIGHT...THEN WINDS WILL DROP BACK DOWN BELOW 30 KNOTS FOR WEDNESDAY AND THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... BLIZZARD WARNING UNTIL 10 AM EST SUNDAY FOR MIZ006-085. BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ001-003. WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR MIZ002-009. WINTER STORM WARNING UNTIL 10 AM EST SUNDAY FOR MIZ007. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005-013-014. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ084. LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ004. LAKE SUPERIOR... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LSZ242>245. LAKE MICHIGAN... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ221-250. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...AJ MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1242 PM EST SAT DEC 6 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE .UPDATE... GOING FORECAST LOOKS IN PRETTY GOOD SHAPE BASED ON THE LAST FEW HOURS OF RADAR IMAGERY. ARCTIC/POLAR FRONT MOVING SE THROUGH UPPER MI ABOUT AN HOUR TO TWO FASTER COMPARED TO PREVIOUS RUNS...BUT IT WORKS OUT ALRIGHT AS THE STRONGER WINDS SEEM TO BE LAGGING THE ARCTIC FRONT BY AN HOUR. WHITEOUT CONDITIONS HAVE BEEN OBSERVED HERE AT OUR OFFICE...IN THE CITY OF MARQUETTE AND ELSEWHERE THAT HAVE BEEN IMPACTED BY THE CONVERGENT BAND OF LAKE EFFECT SNOW ALONG THE FRONT. A FEW VEHICLE ACCIDENTS HAVE ALSO OCCURRED DUE TO THE WHITEOUT CONDITIONS. HAVE BEEN ISSUING SPECIAL WEATHER STATEMENTS TO EMPHASIZE THE HEAVY SNOW BURST ACCOMPANYING THE FRONT. IN THE WAKE OF THE FRONT...LAKE EFFECT BANDS ARE SETTING UP...BUT ARE NOT ALL THAT IMPRESSIVE. HOWEVER...STRONG NORTHERLY FLOW IS HELPING TO INCREASE UPSLOPE...AND THEREFORE A LOT OF THE HEAVIER SNOW SHOWERS ARE BEING OBSERVED OVER THE HIGHER TERRAIN. RECENTLY RECEIVED A REPORT OF 8 INCHES SO FAR IN IRONWOOD AND STILL SNOWING HEAVILY. WINDS SHOULD REMAIN CONVERGENT IN THE IRONWOOD AREA THROUGH THE AFTERNOON...SO THE WARNING FOR THE FAR WEST LOOKS GOOD. ONLY AREA OF CONCERN THAT IS NOT PANNING OUT TOO WELL IS THE BLIZZARD WARNING OF THE KEWEENAW PENINSULA. WINDS HAVE BEEN GUSTING TO BLIZZARD CRITERIA...ESPECIALLY AT P59...BUT THE SNOWFALL HAS BEEN FAIRLY BENIGN OUTSIDE OF THE INITIAL CONVERGENT BAND THAT MOVED THROUGH EARLY THIS MORNING. THIS IS PROBABLY DUE TO THE FACT THAT WINDS ARE NOT CONVERGENT AT ALL...AND LIKELY THE ONLY AREA SEEING HEAVIER SNOW IS THE HIGHEST TERRAIN OF KEWEENAW COUNTY (I.E. DELAWARE AND PHOENIX). WEBCAMS SEEM TO CONFIRM THIS AS WELL. WILL KEEP THE BLIZZARD WARNING GOING...IN CASE SNOW TRIES TO PICK UP A BIT THIS AFTERNOON AS COLDER AIR FILTERS IN. HOWEVER...THIS COLDER AIR WILL ALSO BE DRIER...AS EVIDENCED BY PRECIPITABLE WATER VALUES OF LESS THAN 0.10 OF AN INCH ON THE 12Z SOUNDINGS FROM CWPL AND KINL. UPDATED GRID FORECAST AND WINTER STORM STATEMENT HAVE BEEN ISSUED. NO CHANGES NEEDED TO THE ZFP. && .DISCUSSION... (ISSUED AT 355 AM EST) 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW ERN TROF/WRN RDG CONFIGURATION OVER NAMERICA. A PAIR OF STRONG SHRTWVS NOTED DIGGING SEWD INTO THE TROF IN THE NW FLOW ALF BTWN THESE TWO LARGER SCALE FEATURES. THE FIRST SHRTWV IS SLIDING INTO IA...AND THE SECOND IS MOVING THRU NW ONTARIO. STRONG NW WINDS ALF WITH 00Z H3/H5/H7 WINDS AS HI AS 150KT/90KT/60KT NOTED ON ACYC SIDE OF FIRST SHRTWV. GENERAL LLVL SW FLOW AHEAD OF ACCOMPANYING SFC-H85 TROF IN MN AND ARCTIC COLD FNT MOVING THRU NW MN/ADJOINING ONTARIO HAS CAUSED AREAS OF -SN ACRS NE MN/UPR MI AS ISENTROPIC LIFT/DPVA/H85-5 QVECTOR CNVGC HAS GRDLY SATURATED INITIALLY DRY AIRMASS OVER THE UPR GRT LK AS SHOWN ON THE 00Z GRB RAOB. 00Z INL SDNG SHOWS DEEP SATURATION THRU H3. THE HEAVIEST SN APPEARS TO BE JUST S OF UPR MI IN WI...WHERE DPVA/UPR DVGC AHEAD OF SRN SHRTWV/IN LEFT EXIT OF SUPPORTING JET MAX APPEAR TO BE SHARPEST. THERE IS EVIDENCE AN LES BAND IS FORMING OVER LK MI IN THE SW FLOW AHEAD OF THE SHRTWV COMPLEX. WINDS APPEAR TO HAVE ENUF OF A WLY COMPONENT TO FORCE THIS SN BAND INTO CHIP/MACK COUNTIES OF FAR ERN UPR MI...BUT WL HAVE TO MONITOR IN CASE THE BAND DRIFTS MORE TO THE W. FARTHER UPSTREAM...00Z H85 TEMPS AS LO AS -21C AT YQD BEHIND ARCTIC COLD FNT. THE AIRMASS ALSO DRIEST OUT QUITE A BIT AS WELL WITH SFC DWPTS NEAR -10F/CLRG OF LINGERING LO CLD BEHIND FNT PUSHING SWD NEAR LK WINNIPEG IN NLY FLOW AHEAD OF ARCTIC HI PRES BLDG INTO SASKATCHEWAN. 00Z PWAT WAS 0.07 INCH AT YQD. MAIN FCST CONCERNS THIS PACKAGE ARE GOING HEADLINES/EXPECTED LES AND BLSN INTO SUN. FOR TDAY...THE SECOND SHRTWV IN ONTARIO/ACCOMPANYING ARCTIC COLD FNT WL BE THE MAIN INFLUENCE ON WX ACRS CWA AS FIRST SHRTWV/ACCOMPANYING DYNAMICS WL BE PASSING TO THE S INTO THE LOWER LKS BY 12Z. IN ITS WAKE...THE ONTARIO SHRTWV WL DIG ACRS THE FA WITH ARCTIC COLD FROPA SOON AFT 12Z OVER THE NW AND ARND 18Z OVER THE SE. STILL EXPECTING A PD OF LK ENHANCED HEAVIER SHSN TO ACCOMPANY THE ARRIVAL OF THIS FEATURE OVER AT LEAST THE ZNS NEAR LK SUP AS GUIDANCE SHOWS DPVA/ H85-5 QVECTOR CNVGC/UPR DVGC/DEEP MSTR LINGERING UNTIL DYNAMICS/DEEP MSTR PASS TO THE E AFT 18Z. THE PRESENCE OF SHARP UVV WITHIN THE PRIME SN GROWTH LYR ALSO SUGS A PD OF HEAVY SN. CYC NLY FLOW PROGGED TO INCREASE IN THE WAKE OF THE FNT...WITH H925 WINDS RISING TO 35-40KT PRODUCING STRONG CAD/LLVL DESTABILIZATION. THESE STRONG WINDS WILL FRAGMENT THE SNOW FLAKES INTO A MORE POWDERY SN WITH ARRIVAL OF COLDER/DRIER AIR IN THE AFTN. THE RESULT WILL BE A MORE EFFICIENT REDUCTION IN VSBY...WITH WDSPRD BLSN EVEN AFT THE SN INTENSITY BEGINS TO DIMINISH. LK ENHANCED SN WL EVOLVE TO PURE LES BY LATER IN THE DAY AS H85 TEMPS BOTTOM OUT ARND -18C OVER LK SUP BY 00Z SUN. THE STRONG NNW WINDS...STRONGEST OVER THE CNTRL ZNS...WL PUSH THE SHSN FARTHER INLAND INTO DELTA/SRN SCHOOLCRAFT COUNTIES. OTRW...EXPECT HI TEMPS IN THE MRNG OVER THE W HALF...WITH THE MERCURY FALLING OFF IN THE AFTN WITH ARRIVAL OF COLDER AIR. LOOK FOR PURE LES TNGT WITH RISING HGTS/DNVA/H85-5 QVECTOR DVGC IN WAKE OF DEPARTING SHRTWV/SFC LO. THE INTENSITY OF THE LES/BLSN OVER THE W SHOULD DIMINISH THRU THE NGT WITH THE ARRIVAL OF MUCH DRIER AIR FM THE NW AND APPROACH OF HI PRES RDG AS INVERSION HGTS FCST TO LOWER TO 3K FT DURING THE NGT FM IWD-CMX. BUT STILL EXPECT HI SN/WATER RATIOS THROUGH THE END OF THE EVENT OVER THE W WITH TEMPS WITHIN THE INCRSGLY SHALLOW MOIST LYR ARND A FAVORABLE TEMP OF -15C...ESPECIALLY WITH DIMINISHING WINDS/SN FLAKE FRAGMENTATION. BLIZZARD CONDITIONS OVER ALGER/NRN SCHOOLRAFT COUNTY SHOULD EASE AFT THE EVNG WITH H925 WINDS FCST TO DIMINISH TO ARND 25 KT BY 12Z SUN. LES BANDS SHOULD CONTINUE TO DRIFT FAR INTO DELTA/SRN SCHOOLCRAFT ZNS. OTRW...LONGER FETCH LENGTH ACRS ERN LK SUP WL MITIGATE IMPACT OF DRYING SOMEWHAT. LES CHART WOULD SUG 3-6 INCHES OF SN THRU THE NGT OVER THE E...WITH THE HEAVIER AMTS MOST LIKELY OVER ALGER/NRN SCHOOLCRAFT IN MOST PERSISTENT...FOCUSED LLVL CNVGC SHOWN BY NAM12/LOCAL HI RES WRF-ARW ON E EDGE OF LAND BREEZE OFF THE INTERIOR W HALF. WL TEND TOWARD THE LO END OF MOS GUIDANCE FOR MIN TEMPS FCST CONSIDERING INTENSITY OF THIS SHRTWV/DRYNESS OF AIR UPSTREAM. GOING HEADLINES SEEM TO HAVE THE SITUATION IN HAND FOR TDAY...BUT OPTED TO END THE WRNGS BY 00Z SUN OVER THE W ONCE STRONGEST WINDS (H925 WINDS ABV 25 KTS) ARE FCST TO DIMINISH FOLLOWING PASSAGE OF PRES RISE MAX TO THE SE. WL MAINTAIN GOING HEADLINES AS IS FOR THE E HALF. LES WL DIMINISH W-E ON SUN WITH ARRIVAL OF HI PRES RDG UNDER CONTINUED RISING HGTS. AS LLVL FLOW BACKS AHEAD OF THIS FEATURE... THE LES OVER THE E WL TEND TO SHIFT TO THE E BUT END COMPLETELY FM MQT AND W. HOWEVER...LARGER SCALE NAM/GFS MIGHT BE TOO AGGRESSIVE WITH THIS SHIFT OVER THE E CONSIDERING STRONGER LLVL CNVGC SHOWN BY HIER RES CNDN/WRF-ARW RUNS TO BE MORE PERSISTENT OVER ALGER/NRN SCHOOLCRAFT WITH LAND BREEZE OFF ONTARIO HOLDING UP THE PROGRESS. BUT SINCE WINDS/BLSN WL NO LONGER BE AN ISSUE...WL NOT EXTEND GOING HEADLINE EXPIRATION OF 15Z FOR THESE ZNS. OTRW...SUN WL BE ANOTHER VERY COLD DAY UNDER ARRIVING RDG AXIS AND 850 MB THERMAL TROF WITH H85 TEMPS RANGING FM ABOUT -15C OVER THE W TO -18C OVER THE E BY 00Z MON. MAX TEMPS SHOULD REMAIN IN THE TEENS AT MOST SPOTS EVEN THOUGH THERE WL BE SOME SUNSHINE OVER THE W AND CNTRL BEFORE MORE HI CLDS AHEAD OF NEXT SHRTWV APRCHG FM THE W INVADE LATER IN THE DAY. AS FLOW BACKS TO MORE SSW ON SUN NGT AHEAD OF INCOMING SHRTWV FM THE PLAINS...LINGERING LES OFF LK SUP WL DIMINISH AND END OVER THE E WHILE MID CLD THICKENS WITH DVLPG ISENTROPIC LIFT SHOWN ON THE 275K-285K SFCS (H8 THRU H7). GFS AND ESPECIALLY THE NAM SHOW SHARPER ISENTROPIC LIFT/H85-5 QVECTOR CNVGC PASSING TO THE S OF THE FA. WITH SUPPORT FM THE CNDN MODEL AND NCEP PREFERENCE...WL FOLLOW THE GFS/CNDN SOLN MOST CLOSELY. THESE MODELS SUG A SOMEWHAT HIER POP OVER THE SRN TIER...WITH BOTH ACTUALLY SHOWING SOME UPR DVGC IN LEFT EXIT OF SUPPORTING UPR JET STREAK. LOOKS LIKE MUCH OF THESE DYNAMICS WL BE NECESSARY TO SATURATE INITIALLY DRY AIRMASS...SO WL KEEP POPS IN THE CHC RANGE (20 OVER THE N TO 50 ACRS THE S) EXCEPT OVER SRN MNM COUNTY (60 THERE). ONE OTHER INTERESTING ASPECT OF THE FCST IS THE POTENTIAL FOR AN LES BAND TO DVLP OVER LK MI AND PUSH INTO THE ERN ZNS ON THE HEELS OF A SSW WIND AND H85 TEMPS ARND -13C OVER NRN LK MI AT 12Z MON. WL MAINTAIN GOING HIER POPS TO REFLECT THIS POTENTIAL DOWNWIND OF LK MI. DIMINISHED POPS A BIT ON MON AFTN AS GFS/CNDN SHOW BETTER DYNAMICS SHIFTING TO THE E AND SOME DRYING ALF. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... ARCTIC FRONT HAS PUSHED THROUGH BOTH TAF SITES...WITH BLUSTERY MULTI-PARALLEL BAND LAKE EFFECT SNOW SET UP IN ITS WAKE. WOULD EXPECT CONDITIONS TO BOUNCE BACK AND FORTH BTWN IFR AND LIFR AND BOTH TAF SITES THROUGH THE REST OF THE AFTN AS BANDS MOVE THROUGH. THERE IS A CHANCE VSBYS COULD DROP TO VLIFR BUT NOT HIGH ENOUGH TO INCLUDE EVEN IN A TEMPO GROUP ATTM. TONIGHT...A SINGLE BAND OF SNOW FROM LAKE NIPIGON ACROSS CENTRAL LAKE SUPERIOR MAY BECOME STATIONARY FOR A FEW HOURS AT SAW...WITH ENOUGH CONFIDENCE TO AT LEAST INCLUDE LIFR CONDITIONS. OTHERWISE...IMPROVEMENT IS EXPECTED THROUGH THE NIGHT AS WINDS DIMINISH AND DRIER AIR WORKS IN FROM MN...WITH VSBYS REACHING VFR BY SUNRISE. CIGS WILL REACH VFR LATE SUNDAY MORNING AS THE DRIER AIR AND WINDS BACKING TOWARDS THE WEST AND EVENTUALLY SW HELP TO BREAK UP THE CLOUDS. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... STRONG COLD FRONT PLOWING THROUGH ALONG WITH SFC LOW DEEPENING JUST EAST OF LK SUPERIOR RESULTS IN GALES 40-45 KNOTS FOR THE E 2/3 OF LAKE SUPERIOR THROUGH TONIGHT. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE MOVES ACROSS THE GREAT LAKES. SRLY WINDS ON MONDAY AHEAD OF LOW PRESSURE TROUGH SHOULD REACH 30 KNOTS...MAINLY OVER E 1/2 OF LAKE SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ084. BLIZZARD WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SUNDAY FOR MIZ006-085. BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ001-003. WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR MIZ002-009. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SUNDAY FOR MIZ007. LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ004. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST SUNDAY FOR MIZ013-014. LAKE SUPERIOR... GALE WARNING UNTIL 7 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL 1 AM EST SUNDAY FOR LSZ242>245. GALE WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR LSZ241. LAKE MICHIGAN... GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 AM EST SUNDAY FOR LMZ221-250. && $$ UPDATE...AJ DISCUSSION...KC AVIATION...AJ MARINE...JLA mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1133 AM EST SAT DEC 6 2008 .UPDATE... GOING FORECAST LOOKS IN PRETTY GOOD SHAPE BASED ON THE LAST FEW HOURS OF RADAR IMAGERY. ARCTIC/POLAR FRONT MOVING SE THROUGH UPPER MI ABOUT AN HOUR TO TWO FASTER COMPARED TO PREVIOUS RUNS...BUT IT WORKS OUT ALRIGHT AS THE STRONGER WINDS SEEM TO BE LAGGING THE ARCTIC FRONT BY AN HOUR. WHITEOUT CONDITIONS HAVE BEEN OBSERVED HERE AT OUR OFFICE...IN THE CITY OF MARQUETTE AND ELSEWHERE THAT HAVE BEEN IMPACTED BY THE CONVERGENT BAND OF LAKE EFFECT SNOW ALONG THE FRONT. A FEW VEHICLE ACCIDENTS HAVE ALSO OCCURRED DUE TO THE WHITEOUT CONDITIONS. HAVE BEEN ISSUING SPECIAL WEATHER STATEMENTS TO EMPHASIZE THE HEAVY SNOW BURST ACCOMPANYING THE FRONT. IN THE WAKE OF THE FRONT...LAKE EFFECT BANDS ARE SETTING UP...BUT ARE NOT ALL THAT IMPRESSIVE. HOWEVER...STRONG NORTHERLY FLOW IS HELPING TO INCREASE UPSLOPE...AND THEREFORE A LOT OF THE HEAVIER SNOW SHOWERS ARE BEING OBSERVED OVER THE HIGHER TERRAIN. RECENTLY RECEIVED A REPORT OF 8 INCHES SO FAR IN IRONWOOD AND STILL SNOWING HEAVILY. WINDS SHOULD REMAIN CONVERGENT IN THE IRONWOOD AREA THROUGH THE AFTERNOON...SO THE WARNING FOR THE FAR WEST LOOKS GOOD. ONLY AREA OF CONCERN THAT IS NOT PANNING OUT TOO WELL IS THE BLIZZARD WARNING OF THE KEWEENAW PENINSULA. WINDS HAVE BEEN GUSTING TO BLIZZARD CRITERIA...ESPECIALLY AT P59...BUT THE SNOWFALL HAS BEEN FAIRLY BENIGN OUTSIDE OF THE INITIAL CONVERGENT BAND THAT MOVED THROUGH EARLY THIS MORNING. THIS IS PROBABLY DUE TO THE FACT THAT WINDS ARE NOT CONVERGENT AT ALL...AND LIKELY THE ONLY AREA SEEING HEAVIER SNOW IS THE HIGHEST TERRAIN OF KEWEENAW COUNTY (I.E. DELAWARE AND PHOENIX). WEBCAMS SEEM TO CONFIRM THIS AS WELL. WILL KEEP THE BLIZZARD WARNING GOING...IN CASE SNOW TRIES TO PICK UP A BIT THIS AFTERNOON AS COLDER AIR FILTERS IN. HOWEVER...THIS COLDER AIR WILL ALSO BE DRIER...AS EVIDENCED BY PRECIPITABLE WATER VALUES OF LESS THAN 0.10 OF AN INCH ON THE 12Z SOUNDINGS FROM CWPL AND KINL. UPDATED GRID FORECAST AND WINTER STORM STATEMENT HAVE BEEN ISSUED. NO CHANGES NEEDED TO THE ZFP. && .DISCUSSION... (ISSUED AT 355 AM EST) 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW ERN TROF/WRN RDG CONFIGURATION OVER NAMERICA. A PAIR OF STRONG SHRTWVS NOTED DIGGING SEWD INTO THE TROF IN THE NW FLOW ALF BTWN THESE TWO LARGER SCALE FEATURES. THE FIRST SHRTWV IS SLIDING INTO IA...AND THE SECOND IS MOVING THRU NW ONTARIO. STRONG NW WINDS ALF WITH 00Z H3/H5/H7 WINDS AS HI AS 150KT/90KT/60KT NOTED ON ACYC SIDE OF FIRST SHRTWV. GENERAL LLVL SW FLOW AHEAD OF ACCOMPANYING SFC-H85 TROF IN MN AND ARCTIC COLD FNT MOVING THRU NW MN/ADJOINING ONTARIO HAS CAUSED AREAS OF -SN ACRS NE MN/UPR MI AS ISENTROPIC LIFT/DPVA/H85-5 QVECTOR CNVGC HAS GRDLY SATURATED INITIALLY DRY AIRMASS OVER THE UPR GRT LK AS SHOWN ON THE 00Z GRB RAOB. 00Z INL SDNG SHOWS DEEP SATURATION THRU H3. THE HEAVIEST SN APPEARS TO BE JUST S OF UPR MI IN WI...WHERE DPVA/UPR DVGC AHEAD OF SRN SHRTWV/IN LEFT EXIT OF SUPPORTING JET MAX APPEAR TO BE SHARPEST. THERE IS EVIDENCE AN LES BAND IS FORMING OVER LK MI IN THE SW FLOW AHEAD OF THE SHRTWV COMPLEX. WINDS APPEAR TO HAVE ENUF OF A WLY COMPONENT TO FORCE THIS SN BAND INTO CHIP/MACK COUNTIES OF FAR ERN UPR MI...BUT WL HAVE TO MONITOR IN CASE THE BAND DRIFTS MORE TO THE W. FARTHER UPSTREAM...00Z H85 TEMPS AS LO AS -21C AT YQD BEHIND ARCTIC COLD FNT. THE AIRMASS ALSO DRIEST OUT QUITE A BIT AS WELL WITH SFC DWPTS NEAR -10F/CLRG OF LINGERING LO CLD BEHIND FNT PUSHING SWD NEAR LK WINNIPEG IN NLY FLOW AHEAD OF ARCTIC HI PRES BLDG INTO SASKATCHEWAN. 00Z PWAT WAS 0.07 INCH AT YQD. MAIN FCST CONCERNS THIS PACKAGE ARE GOING HEADLINES/EXPECTED LES AND BLSN INTO SUN. FOR TDAY...THE SECOND SHRTWV IN ONTARIO/ACCOMPANYING ARCTIC COLD FNT WL BE THE MAIN INFLUENCE ON WX ACRS CWA AS FIRST SHRTWV/ACCOMPANYING DYNAMICS WL BE PASSING TO THE S INTO THE LOWER LKS BY 12Z. IN ITS WAKE...THE ONTARIO SHRTWV WL DIG ACRS THE FA WITH ARCTIC COLD FROPA SOON AFT 12Z OVER THE NW AND ARND 18Z OVER THE SE. STILL EXPECTING A PD OF LK ENHANCED HEAVIER SHSN TO ACCOMPANY THE ARRIVAL OF THIS FEATURE OVER AT LEAST THE ZNS NEAR LK SUP AS GUIDANCE SHOWS DPVA/ H85-5 QVECTOR CNVGC/UPR DVGC/DEEP MSTR LINGERING UNTIL DYNAMICS/DEEP MSTR PASS TO THE E AFT 18Z. THE PRESENCE OF SHARP UVV WITHIN THE PRIME SN GROWTH LYR ALSO SUGS A PD OF HEAVY SN. CYC NLY FLOW PROGGED TO INCREASE IN THE WAKE OF THE FNT...WITH H925 WINDS RISING TO 35-40KT PRODUCING STRONG CAD/LLVL DESTABILIZATION. THESE STRONG WINDS WILL FRAGMENT THE SNOW FLAKES INTO A MORE POWDERY SN WITH ARRIVAL OF COLDER/DRIER AIR IN THE AFTN. THE RESULT WILL BE A MORE EFFICIENT REDUCTION IN VSBY...WITH WDSPRD BLSN EVEN AFT THE SN INTENSITY BEGINS TO DIMINISH. LK ENHANCED SN WL EVOLVE TO PURE LES BY LATER IN THE DAY AS H85 TEMPS BOTTOM OUT ARND -18C OVER LK SUP BY 00Z SUN. THE STRONG NNW WINDS...STRONGEST OVER THE CNTRL ZNS...WL PUSH THE SHSN FARTHER INLAND INTO DELTA/SRN SCHOOLCRAFT COUNTIES. OTRW...EXPECT HI TEMPS IN THE MRNG OVER THE W HALF...WITH THE MERCURY FALLING OFF IN THE AFTN WITH ARRIVAL OF COLDER AIR. LOOK FOR PURE LES TNGT WITH RISING HGTS/DNVA/H85-5 QVECTOR DVGC IN WAKE OF DEPARTING SHRTWV/SFC LO. THE INTENSITY OF THE LES/BLSN OVER THE W SHOULD DIMINISH THRU THE NGT WITH THE ARRIVAL OF MUCH DRIER AIR FM THE NW AND APPROACH OF HI PRES RDG AS INVERSION HGTS FCST TO LOWER TO 3K FT DURING THE NGT FM IWD-CMX. BUT STILL EXPECT HI SN/WATER RATIOS THROUGH THE END OF THE EVENT OVER THE W WITH TEMPS WITHIN THE INCRSGLY SHALLOW MOIST LYR ARND A FAVORABLE TEMP OF -15C...ESPECIALLY WITH DIMINISHING WINDS/SN FLAKE FRAGMENTATION. BLIZZARD CONDITIONS OVER ALGER/NRN SCHOOLRAFT COUNTY SHOULD EASE AFT THE EVNG WITH H925 WINDS FCST TO DIMINISH TO ARND 25 KT BY 12Z SUN. LES BANDS SHOULD CONTINUE TO DRIFT FAR INTO DELTA/SRN SCHOOLCRAFT ZNS. OTRW...LONGER FETCH LENGTH ACRS ERN LK SUP WL MITIGATE IMPACT OF DRYING SOMEWHAT. LES CHART WOULD SUG 3-6 INCHES OF SN THRU THE NGT OVER THE E...WITH THE HEAVIER AMTS MOST LIKELY OVER ALGER/NRN SCHOOLCRAFT IN MOST PERSISTENT...FOCUSED LLVL CNVGC SHOWN BY NAM12/LOCAL HI RES WRF-ARW ON E EDGE OF LAND BREEZE OFF THE INTERIOR W HALF. WL TEND TOWARD THE LO END OF MOS GUIDANCE FOR MIN TEMPS FCST CONSIDERING INTENSITY OF THIS SHRTWV/DRYNESS OF AIR UPSTREAM. GOING HEADLINES SEEM TO HAVE THE SITUATION IN HAND FOR TDAY...BUT OPTED TO END THE WRNGS BY 00Z SUN OVER THE W ONCE STRONGEST WINDS (H925 WINDS ABV 25 KTS) ARE FCST TO DIMINISH FOLLOWING PASSAGE OF PRES RISE MAX TO THE SE. WL MAINTAIN GOING HEADLINES AS IS FOR THE E HALF. LES WL DIMINISH W-E ON SUN WITH ARRIVAL OF HI PRES RDG UNDER CONTINUED RISING HGTS. AS LLVL FLOW BACKS AHEAD OF THIS FEATURE... THE LES OVER THE E WL TEND TO SHIFT TO THE E BUT END COMPLETELY FM MQT AND W. HOWEVER...LARGER SCALE NAM/GFS MIGHT BE TOO AGGRESSIVE WITH THIS SHIFT OVER THE E CONSIDERING STRONGER LLVL CNVGC SHOWN BY HIER RES CNDN/WRF-ARW RUNS TO BE MORE PERSISTENT OVER ALGER/NRN SCHOOLCRAFT WITH LAND BREEZE OFF ONTARIO HOLDING UP THE PROGRESS. BUT SINCE WINDS/BLSN WL NO LONGER BE AN ISSUE...WL NOT EXTEND GOING HEADLINE EXPIRATION OF 15Z FOR THESE ZNS. OTRW...SUN WL BE ANOTHER VERY COLD DAY UNDER ARRIVING RDG AXIS AND 850 MB THERMAL TROF WITH H85 TEMPS RANGING FM ABOUT -15C OVER THE W TO -18C OVER THE E BY 00Z MON. MAX TEMPS SHOULD REMAIN IN THE TEENS AT MOST SPOTS EVEN THOUGH THERE WL BE SOME SUNSHINE OVER THE W AND CNTRL BEFORE MORE HI CLDS AHEAD OF NEXT SHRTWV APRCHG FM THE W INVADE LATER IN THE DAY. AS FLOW BACKS TO MORE SSW ON SUN NGT AHEAD OF INCOMING SHRTWV FM THE PLAINS...LINGERING LES OFF LK SUP WL DIMINISH AND END OVER THE E WHILE MID CLD THICKENS WITH DVLPG ISENTROPIC LIFT SHOWN ON THE 275K-285K SFCS (H8 THRU H7). GFS AND ESPECIALLY THE NAM SHOW SHARPER ISENTROPIC LIFT/H85-5 QVECTOR CNVGC PASSING TO THE S OF THE FA. WITH SUPPORT FM THE CNDN MODEL AND NCEP PREFERENCE...WL FOLLOW THE GFS/CNDN SOLN MOST CLOSELY. THESE MODELS SUG A SOMEWHAT HIER POP OVER THE SRN TIER...WITH BOTH ACTUALLY SHOWING SOME UPR DVGC IN LEFT EXIT OF SUPPORTING UPR JET STREAK. LOOKS LIKE MUCH OF THESE DYNAMICS WL BE NECESSARY TO SATURATE INITIALLY DRY AIRMASS...SO WL KEEP POPS IN THE CHC RANGE (20 OVER THE N TO 50 ACRS THE S) EXCEPT OVER SRN MNM COUNTY (60 THERE). ONE OTHER INTERESTING ASPECT OF THE FCST IS THE POTENTIAL FOR AN LES BAND TO DVLP OVER LK MI AND PUSH INTO THE ERN ZNS ON THE HEELS OF A SSW WIND AND H85 TEMPS ARND -13C OVER NRN LK MI AT 12Z MON. WL MAINTAIN GOING HIER POPS TO REFLECT THIS POTENTIAL DOWNWIND OF LK MI. DIMINISHED POPS A BIT ON MON AFTN AS GFS/CNDN SHOW BETTER DYNAMICS SHIFTING TO THE E AND SOME DRYING ALF. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... ARCTIC FRONT ON VERGE OF PUSHING THROUGH KEWEENAW. AS THE FRONT SWEEPS THROUGH THE REST OF UPPER MICHIGAN THROUGH EARLY AFTN...EXPECT PERIOD OF HVY LAKE ENHANCED SHSN AND BLSN AS WINDS SHIFT SHARPLY TO STRONG NRLY. VLIFR CONDITIONS IN SHSN/BLSN WILL OCCUR AT BOTH SITES...ALREADY HAPPENING AT CMX...AND DUE INTO SAW EARLY THIS AFTN. EVENTUALLY...IMPROVEMENT TO LIFR EXPECTED...BUT THIS MAY TAKE A WHILE AS STRONG WINDS/BLSN HANG ON INTO THE EARLY EVENING. FURTHER IMPROVEMENT TO IFR AT KCMX AND TO MVFR AT KSAW SHOULD OCCUR LATER TONIGHT AS AIRMASS BECOMES DRIER...CAUSING SHSN TO DIMINISH...AND WINDS DECREASE...RESULTING IN LESS BLSN. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... STRONG COLD FRONT PLOWING THROUGH ALONG WITH SFC LOW DEEPENING JUST EAST OF LK SUPERIOR RESULTS IN GALES 40-45 KNOTS FOR THE E 2/3 OF LAKE SUPERIOR THROUGH TONIGHT. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE MOVES ACROSS THE GREAT LAKES. SRLY WINDS ON MONDAY AHEAD OF LOW PRESSURE TROUGH SHOULD REACH 30 KNOTS...MAINLY OVER E 1/2 OF LAKE SUPERIOR. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST THIS EVENING FOR MIZ084. BLIZZARD WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SUNDAY FOR MIZ006-085. BLIZZARD WARNING UNTIL 7 PM EST THIS EVENING FOR MIZ001-003. WINTER STORM WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR MIZ002-009. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 10 AM EST SUNDAY FOR MIZ007. LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SUNDAY FOR MIZ004. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST SUNDAY FOR MIZ013-014. LAKE SUPERIOR... GALE WARNING UNTIL 7 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL 1 AM EST SUNDAY FOR LSZ242>245. GALE WARNING UNTIL 7 PM EST /6 PM CST/ THIS EVENING FOR LSZ241. LAKE MICHIGAN... GALE WARNING FROM 4 PM THIS AFTERNOON TO 1 AM EST SUNDAY FOR LMZ221-250. && $$ UPDATE...AJ DISCUSSION...KC AVIATION...JLA MARINE...JLA mi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mi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mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1247 PM EST FRI DEC 5 2008 LATEST UPDATE...AVIATION... .SYNOPSIS...(459 AM EST FRI DEC 5 2008) LAKE EFFECT SNOW SHOWERS WILL GRADUALLY DIMINISH ACROSS THE AREA DURING THE DAY TODAY AS A PORTION OF A RIDGE OF HIGH PRESSURE MOVES ACROSS THE AREA TODAY. SNOW IS EXPECTED TO INTENSIFY ACROSS THE AREA THEN OVERNIGHT TONIGHT AS AN AREA OF LOW PRESSURE OVER ALBERTA THIS MORNING APPROACHES THE AREA. MOST AREAS WILL SEE AT LEAST A COUPLE OF INCHES OF SNOW FROM TONIGHT THROUGH SATURDAY NIGHT. HEAVIER AMOUNTS OF SNOW ARE LIKELY NORTHWEST OF A LINE FROM HOLLAND TO BALDWIN AS SOUTHWEST WINDS WILL ALLOW LAKE MICHIGAN TO ENHANCE SNOWFALL. && .SHORT TERM...(1015 AM EST FRI DEC 5 2008) (REST OF TODAY THROUGH SUNDAY) I HAVE UPGRADED THE LAKE EFFECT SNOW ADVISORY TO A LAKE EFFECT SNOW WARNING SINCE WE HAVE HAD SEVERAL REPORTS OF BETWEEN 8 TO 10 INCHES IN EXTREME SOUTHWESTERN KENT...EASTERN OTTAWA AND NORTHEAST ALLEGAN COUNTIES IN THE PAST THREE HOURS. ALSO...SINCE THE LATEST RUC SHOWS THE LOW LEVEL WIND CONVERGENCE CONTINUES THROUGH MID AFTERNOON AND SHIFTS NORTH ONLY SLIGHTLY... I EXPECTED THE TIME OF THE HEADLINES UNTIL 5 PM FOR BOTH THE WARNING AND ADVISORY COUNTIES. OUR 88D RADAR CONTINUES TO SHOW ECHO INTENSITIES OVER 30 DBZ CONTINUING TO DEVELOP OVER THE LAKE SHORE AREAS OF OTTAWA AND ALLEGAN COUNTIES THAT THEN MOVE INLAND. GIVEN THE RUC KEEPS THE LIFT AND CONVERGENCE GOING INTO MID AFTERNOON OVER THE HEADLINE COUNTIES I THROUGH IT BEST TO KEEP THE HEADLINES GOING THROUGH 5 PM. I DO EXPECT THE SUNSHINE TO TURN THIS INTO A MORE CELLULAR EVENT BY LATE THIS MORNING. THAT WILL ONLY HELP BRING THE CONVECTION FARTHER EAST ACROSS THE CWA. ONE WAY OR THE OTHER ONLY OUR EXTREME NORTHEAST AND SOUTHERN COUNTIES WILL HAVE NEGLIGIBLE SNOWFALL THROUGH THE AFTERNOON. PREVIOUS DISCUSSION....THERE WILL BE A BREAK IN THE ACCUMULATION POTENTIAL LATE THIS AFTERNOON AND EARLY THIS EVENING AS THE INVERSION HEIGHTS DROP WITH SHORT WAVE RIDGING ALOFT AND SFC RIDGING MOVING OVERHEAD. THIS WILL BE SHORT LIVED AS A SHORT WAVE OVER NRN ALBERTA THIS MORNING...WILL RACE SE TO ERN WI BY 12Z SAT. MID AND HIGH CLOUDS WILL MOVE IN AHEAD OF THE WAVE...ALLOWING FOR A DEEP LAYER OF MOISTURE OVERHEAD. SNOW IS EXPECTED TO DEVELOP ACROSS THE AREA FROM THE WNW AFTER MIDNIGHT. SW FLOW AHEAD OF THE SYSTEM WILL TRY TO ADVECT SOME WARMER AIR IN...HOWEVER H850 TEMPS ARE EXPECTED TO WARM ONLY TO AROUND -9 TO -10C. PLENTY OF OVER-LAKE INSTABILITY WILL REMAIN AND WILL COMBINE WITH THE SYNOPTIC FORCING TO ENHANCE SNOWFALL ACROSS THE NW CORNER OF THE CWFA. PAST CASES OF A SW FLOW SUCH AS THIS AND A GOOD DEAL OF LOW LEVEL CONVERGENCE...BOTH SUPPORT HEAVIER SNOW ALONG AND NW OF A LINE FROM HOLLAND TO BALDWIN. MODELS SUPPORT A GENERAL 1-3/2-4 INCH TYPE OF EVENT ACROSS MOST OF THE CWFA. WITH THE DEEP MOISTURE... MODERATE OVER-LAKE INSTABILITY...AND THE BEST FORCING CLOSE TO THE DGZ...WARNING CRITERIA SNOWS ARE VERY POSSIBLE OVER THE NW. WE EXPECT THAT AN ADVISORY WILL EVENTUALLY BE NEEDED SURROUNDING THE WATCH AREA. THE WINDOW OF BEST SNOW OVER THE NW LOOKS TO BE AFTER 06Z TONIGHT AND THROUGH 18Z TOMORROW. AFTER 18Z SAT...THE FLOW BECOMES NW BEHIND THE FRONT. ADDITIONAL SNOWS WILL REMAIN POSSIBLE AFTER 18Z AS THE SNOW TRANSITIONS TO LAKE EFFECT. ENOUGH MOISTURE AND A FAVORABLE FLOW WILL KEEP THE POTENTIAL OF ACCUMULATING SNOW IN THROUGH THE EVENING SAT EVENING. AS THE FLOW BECOMES NW...THE SW COUNTIES WILL BEGIN TO SEE LAKE EFFECT TAKE CHARGE. H850 TEMPS WILL FALL BACK DOWN TO AROUND -17C OR SO BY 12Z SUN. INVERSION HEIGHTS ARE EXPECTED TO REMAIN UP THROUGH 10K FEET THROUGH A GOOD PORTION OF SAT NIGHT. THIS COMBINATION WILL BRING POTENTIAL FOR SOME HEAVIER LAKE EFFECT SNOW ACCUMULATIONS SOUTHWEST OF A LINE FROM HOLLAND TO KALAMAZOO. WE CONTEMPLATED ISSUING A WATCH FOR THIS AREA. HOWEVER WITH THE POTENTIAL OF SIGNIFICANT ACCUMS HOLDING OFF UNTIL MAINLY SAT NIGHT...WE FELT IT WAS BEST TO HOLD OFF FOR NOW WITH EVERYTHING ELSE GOING ON. LAKE EFFECT WILL THEN DIMINISH THROUGH THE DAY ON SUNDAY AS THE UPPER TROUGH PULLS AWAY AND SFC RIDGING MOVES IN. && .LONG TERM...(459 AM EST FRI DEC 5 2008) (SUNDAY NIGHT THROUGH THURSDAY) LONG TERM BEGINS WITH HIGH PRESSURE IN PLACE FOR SUNDAY NIGHT. MODELS HAVE SHIFTED SOMEWHAT FOR NEXT WEEK...YIELDING A LESS CONFIDENT FORECAST. FOR THAT REASON DID NOT MAKE MANY CHANGES TO THE GOING FORECAST. MODELS WERE BRINGING A HEALTHY CLIPPER THROUGH THE REGION ON MONDAY...NOW IT IS MORE OF AN INVERTED TROUGH. IN ADDITION...THE STRONG LOW THAT THE GFS WAS ROLLING UP INTO EASTERN CANADA MID WEEK (WHICH WAS TUGGING VERY COLD AIR SOUTH OUT OF CANADA INTO THE GREAT LAKES) IS NO LONGER THERE. TO ADD FURTHER COMPLEXITY...ON THURSDAY MORNING...THE GFS HAS A 1004MB LOW DROPPING OUT OF THE NORTHERN PLAINS...WHEREAS THE EURO HAS A SPRAWLING HIGH BUILDING IN. SUFFICE IT TO SAY CONFIDENCE IS LOW. IT DOES STILL LOOK TO BE A COLDER THAN NORMAL PERIOD...WITH CHANCES AT LAKE EFFECT SNOW. HOPING FOR MORE IN THE WAY OF MODEL CONSISTENCY OFF THE 12Z MODEL RUNS. && .MARINE...(459 AM EST FRI DEC 5 2008) HAVE GONE AHEAD AND HOISTED A GALE WARNING FOR THE PERIOD FROM OVERNIGHT TONIGHT THROUGH MOST OF SATURDAY NIGHT. WINDS REMAIN IN THE 15 TO 25 KNOT RANGE THIS MORNING AT THE OBSERVATION SITES AT BIG SABLE AND THE MUSKEGON GLERL. WINDS WILL PICK UP THIS EVENING AHEAD OF THE INCOMING SYSTEM THAT WILL MOVE THROUGH ON SATURDAY. MODELS INDICATE THAT WE WILL BE ABLE TO MIX A PORTION OF THE 40+ KNOT SOUTHWEST WIND CORE AROUND 2K FEET BEGINNING AFTER 00Z THIS EVENING. THERE MAY BE A BRIEF LULL WHERE WINDS DROP DOWN TO AROUND 25 KNOTS FOR A FEW HOURS ON SAT WHEN THE FRONT COMES THROUGH. HOWEVER NORTHWEST WINDS WILL KICK UP TO GALES ONCE AGAIN AS THE FRONT PASSES AND COLDER AIR ADVECTS IN. FREEZING SPRAY WILL BE POSSIBLE ON SATURDAY NIGHT...HOWEVER WATER TEMPS MAY BE A TAD TOO WARM PER LOCAL STUDIES. THIS CAN BE ADDRESSED MORE BY LATER SHIFTS. && .AVIATION...(1247 PM EST FRI DEC 5 2008) THE LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO VERY SLOWLY DIMINISH TOWARD EVENING AS INVERSION HEIGHTS LOWER AND LIFT WITHIN THE SNOW GROWTH REGION WEAKENS. HOWEVER...IFR OR EVEN PATCHY LIFR WILL PERSIST IN THIS ACTIVITY UNTIL AROUND 02Z. ALSO OF NOTE WILL BE THE BACKING WINDS...FROM WESTERLY TO SOUTHWEST BY EVENING. THIS WILL HELP TAKE THE HEAVIER SNOW SHOWERS AWAY FROM ALL THE TAF SITES EXCEPT MKG BY SUNSET. THERE SHOULD BE A LULL IN THE SNOWFALL FROM MID EVENING UNTIL THE WEE HOURS OF SATURDAY MORNING. HOWEVER BY 08-10Z MORE SNOW WILL MOVE BACK IN AS A CLIPPER SYSTEM MOVES TOWARD THE GREAT LAKES. THIS WILL BRING A BURST OF SNOW TO ALL TAF SITES THROUGH MUCH OF SATURDAY MORNING. THE SNOWFALL WILL PERSIST INTO THE AFTERNOON ALONG THE LAKESHORE AS ANOTHER OF ROUND OF LAKE EFFECT IS GENERATED. && .HYDROLOGY...(459 AM EST FRI DEC 5 2008) NO SIGNIFICANT HYDRO ISSUES IN THE NEXT FEW DAYS AS TEMPERATURES EXPECTED TO GENERALLY BE BELOW FREEZING THROUGH THE NEXT WEEK. LITTLE TO NO RUNOFF CAN BE EXPECTED INTO AREA STREAMS AND RIVERS. IT DOES APPEAR THAT WE WILL BUILD A SNOWPACK WITH LAKE EFFECT SNOW SHOWERS EXPECTED MOST DAYS AND A FEW SYSTEMS MOVING THROUGH. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...LAKE EFFECT SNOW WARNING THROUGH 5 PM FOR KENT...OTTAWA AND ALLEGAN COUNTIES. LAKE EFFECT SNOW ADVISORY THROUGH 5 PM FOR BARRY...VAN BUREN AND KALAMAZOO COUNTIES. WINTER STORM WATCH FOR OTTAWA...MUSKEGON...OCEANA...MASON... LAKE...AND NEWAYGO COUNTIES FROM 06Z SAT THROUGH 06Z SUN. LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH 00Z SATURDAY. GALE WARNING IN EFFECT 00Z SATURDAY THROUGH 09Z SUNDAY. && $$ SYNOPSIS: NJJ SHORT TERM: NJJ WDM LONG TERM: DUKE MARINE: NJJ AVIATION: JK HYDROLOGY: NJJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1207 PM EST FRI DEC 5 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAFS .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEP UPR TROF CENTERED OVER ERN NAMERICA DOWNWIND OF RDG ALG THE W COAST. CORE OF ARCTIC COLD UNDER THE TROF AT 00Z WAS CENTERED NEAR THE CWA...WITH 00Z H85 TEMP -22C AT INL AND H7 TEMP -25C AT GRB/APX. AT YQD...THE 00Z H8/H7 TEMPS WERE -16C/-19C. OBVIOUSLY WITH THE LARGE AIR/LK SUP WATER TEMP DIFFERENTIAL...QUITE A BIT OF LES HAS BEEN FALLING IN THE FVRD SN BELTS IN THE LLVL WNW FLOW BTWN HI PRES OVER THE CNTRL PLAINS AND LO PRES OVER NRN QUEBEC. MORE WSW LAND BREEZE WIND COMPONENT WITHIN THE RELATIVELY UNMODIFIED ARCTIR AIRMASS OVER LAND APPEARS TO BE INTENSIFYING THE LLVL CNVGC WITH THE MORE NW FLOW OVER THE OPEN WATERS OF LK SUP AND INTENSIFIED THE SRN MOST BANDS STREAMING INTO THE CWA NEAR THE PORCUPINE MTNS AND ALONG THE LK SUP SHORE E OF GRAND MARAIS. PRESENCE OF SOME MID LVL MSTR NOTED BY MID CLD/H85-75 MSTR SHOWN ON THE 00Z INL RAOB ASSOCIATED WITH A PAIR OF SHRTWVS DROPPING SEWD THRU ONTARIO MAY ALSO BE ENHANCING THE BANDS. ANOTHER SHRTWV APPEARS TO BE RIDING OVER THE WRN RDG WITH QUITE A BIT OF MSTR SHOWN ON WV IMAGERY IN ADVANCE OF THIS SYS SPILLING INTO THE NRN PLAINS/MN. MAIN FCST CONCERNS THIS PACKAGE INCLUDE LES TRENDS/COVG/AMTS/GOING HEADLINES THRU TDAY. FOCUS FOR TNGT INTO THE WEEKEND CONCERNS TIMING/IMPACT OF SHRTWV NOW MOVING OVER WRN RDG AND ANOTHER DIGGING SEWD FM NRN CAN. FOR TDAY...HGTS ARE FCST TO RISE SLOWLY OVER THE UPR LKS WITH WARMER AIR TO THE NW GRDLY INFILTRATING THE AREA. IN TANDEM WITH FALLING MSLP OVER SCNTRL CAN AHEAD OF SHRTWV RIDING OVER THE WRN RDG...THE LLVL FLOW IS FCST TO BACK MORE SW. SO LES BANDS WL BEGIN TO DRIFT MORE TO THE N...EXITING ALL BUT THE KEWEENAW BY THE AFTN. MAY BE ABLE TO CANX GOING WRNGS FOR ALGER/LUCE COUNTIES EARLY IF THE BANDS SHIFT N INTO THE LK...WL CHECK RADAR TRENDS AT FCST ISSUANCE. GFS/NAM/LOCAL WRF-ARW RUNS ALSO SUG FLOW WL BACK ENUF TO END HEADLINES FOR THE KEWEENAW EARLY AS WELL. THE FLOW DOES NOT APPEAR TO BACK ENUF TO RAISE CONCERNS ABOUT AN LES BAND OFF LK IMPACTING LUCE/SRN SCHOOLCRAFT COUNTIES. OTRW...LOOKS LIKE ANOTHER DRY COLD DAY OVER THE INTERIOR. BUT HI CLDS NOW SPILLING INTO THE PLAINS/MN WL ARRIVE IN THE AFTN. CONSIDERING THE FRIGID HI TEMPS OBSVD IN THE NRN PLAINS YDAY AND THE LACK OF LK MODERATION WITH BACKING LLVL FLOW...WL TEND TOWARD THE LO END OF MOS GUIANCE FOR HI TEMPS AS SUGD BY GFS FCST SDNGS. TNGT...SW FLOW AHEAD OF SHRTWV NOW TOPPING WRN RDG AND DIGGING SHARPLY SEWD TO IA BY 12Z SAT IS FCST TO DOMINATE. MEANWHILE... ANOTHER SHRTWV MOVING QUICKLY SEWD THRU NW ONTARIO/ASSOCIATED SFC LO AND ARCTIC COLD FNT WL APRCH FM THE NW LATE. EXPECT SOME -SN ASSOCIATED WITH ISENTROPIC LIFT ON THE 275K-285K SFC (H8-65) TO BREAK OUT NW-SE IN ADVANCE OF THESE FEATURES. WITH ABOUT 1.0-1.5 G/KG SPECIFIC HUMIDITY IN THE H7-75 LYR...EXPECT 1 TO 3 INCHES OF -SN TO FALL ACRS THE FA THRU THE NGT. A LAKE ENHANCED SN BAND OFF LK MI IS LIKELY TO DVLP...BUT THE FLOW APPEARS TO HAVE ENUF OF A WLY COMPONENT TO FOCUS THE HEAVIER SN INTO MACKINAC COUNTY SE OF ERY. FAIRLY SHARP DPVA/H85-5 QVECTOR CNVGC IS ALSO FCST TO ARRIVE AFT 06Z AHEAD OF THE NRN SHRTWV. SOME HEAVIER SN MAY DVLP LATE OVER THE W TOWARD 12Z WITH ARRIVAL OF ACCOMPANYING ARCTIC COLD FNT. ALTHOUGH THE TOTAL PCPN APPEARS WL BE RELATIVELY LGT...THE DEEP SATURATION SHOWN ON THE FCST SDNGS SUGS BUMPING UP POPS CLOSER TO THE HIER GFS MOS NUMBERS. SAT LOOKS TO BE A WINTRY DAY WITH BLIZZARD CONDITIONS PSBL FOR AT LEAST A TIME IN THE STRONG NLY FLOW FOLLOWING THE PASSAGE OF CLIPPER LO/ACCOMPANYING COLD FNT. LOCAL WRF-ARW RUN SUGS AN INTENSE SN BAND WL ACCOMPANY THE COLD FROPA...ESPECIALLY OVER THE NRN TIER WHERE THERE WL BE ENHANCEMENT OFF LK SUP/UPSLOPE COMPONENT TO THE NNW FLOW...WITH H925 WINDS PROGGED TO PEAK AT 40 KTS IN THE WAKE OF THE FNT. STRONG WINDS WL LIKELY FRAGMENT THE SN FLAKES THAT WL BECOME INCRSGLY POWDERY WITH ARRIVAL OF COLDER/DRIER AIR IN THE AFTN. THE RESULT WL BE A MORE EFFICIENT REDUCTION IN VSBY. SUSPECT A BLIZZARD WRNG MIGHT BE NECESSARY FOR ALGER COUNTY...WHICH WL BE MOST EXPOSED TO FCST NNW FLOW FOR THE LONGEST PD OF TIME. OTRW...HOISTED WATCH FOR GOGEBIC AND MQT COUNTIES WHILE CONTINUING OTHER GOING WATCHES. ADVYS WL LIKELY BE NECESSARY FOR DELTA/SRN SCHOOLCRAFT ZNS WITH STRG NNW FLOW BLOWING THE LES WELL INLAND.EXPECT MAX TEMPS ON SAT OVER THE W HALF IN THE MRNG...WITH SLOWLY FALLING TEMPS IN THE AFTN. SAT NGT WL FEATURE PURE LES WITH RISING HGTS/DNVA/H85-5 QVECTOR DVGC IN WAKE OF DEPARTING SHRTWV/SFC LO. INTENSITY OF THE LES OVER THE FAR W SHOULD DIMINISH OVERNGT WITH APRCH OF HI PRES RDG/FCST INVRN BASE PROGGED TO SUBSIDE TO ARND H9 BY 12Z SUN AT IWD...BUT EXPECT HI SN/WATER RATIOS UNTIL THE END WITH TEMPS WITHIN THE INCRSGLY SHALLOW MOIST LYR ARND -15C. GOING EXPIRATION OF WATCH FOR THE WRN ZNS SEEMS APPROPRIATE. MAGNITUDE OF THE BLSN SHOULD ALSO DIMINISH W TO E WITH GRDL WEAKENING OF THE PRES GRADIENT W TO E. BUT EXPECTED BLIZZARD CONDITIONS OVER ALGER COUNTY SHOULD LIKELY PERSIST INTO THE EVNG WITH H925 WINDS IN THE 35-40KT RANGE UNTIL ABOUT 03Z. LES WL DIMINISH OVER THE E HALF ON SUN WITH ARRIVAL OF HI PRES RDG. SUN WL BE ANOTHER VERY COLD DAY UNDER ARRIVING RDG AXIS WITH H85 TEMPS IN THE -15C TO -18C RANGE. END OF WATCH LATE ON SUN APPEARS CONSISTENT WITH RECENT GUIDANCE. HI CLDS AHEAD OF YET ANOTHER CLIPPER LO WL INVADE DURING THE DAY. ADDED LO CHC POPS ON SUN NGT TO REFLECT DVLPG ISENTROPIC LIFT/MODEL QPF IN ADVANCE OF THIS CLIPPER. HIEST CHC POPS DOWNWIND OF LK MI WITH SOME MOISTENING/DESTABILATION PSBL OFF THE WATER. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... AT KCMX...LK EFFECT WILL CONTINUE TO LIFT NORTH AND CONDITIONS IMPROVE TO VFR FOR A TIME. NEXT LOW PRES SYSTEM DROPPING INTO THE UPPER LAKES REGION BRINGS MORE SNOW INTO THE REGION BY THIS EVENING. UPSTREAM OBS SUGGEST IFR VSBY WITH THE SNOW...THEN AS ARCTIC FRONT NEARS AND WINDS SHIFT TO NW...HEAVY LK EFFECT MAY RETURN YET AGAIN LATE TONIGHT. CONDITIONS DETERIORATE RAPIDLY TO VLIFR SAT MORNING WITH BLOWING SNOW/SNOW WITH WIND SHIFT AND STRONG WINDS BEHIND THE ARCTIC FRONT AND WILL LOOK TO STAY DOWN ALL DAY. AT KSAW...EXPECT VFR CONDITIONS TO PREVAIL THRU THIS AFTN. MVFR/IFR CONDITIONS DEVELOP IN THE EVENING AS -SN SPREADS INTO THE AREA IN ASSOCIATION WITH APPROACHING LOW PRES SYSTEM. SNOW/WINDS DIMINISH ONLY VERY LATE TONIGHT. CONDITIONS WILL DETERIORATE FROM MVFR LATE SAT MORNING TO VLIFR WITH BLOWING SNOW AND STRONG WINDS BEHIND THE ARCTIC FRONT THAT COME THROUGH SAT MORNING AND WILL LOOK TO STAY LOW FOR A WHILE. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SW WINDS TODAY MAY REACH GALES BUT SHOULD ONLY BE A FEW GUSTS. ON SATURDAY...STRONG COLD FRONT PLOWING THROUGH WITH DEEPENING SFC LOW LEADS TO HIGH POTENTIAL OF GALES. WENT AHEAD WITH GALE WARNINGS AS CONFIDENCE IS HIGH FOR AT LEAST MARGINAL GALES. STRONG GALES TO 45 KNOTS COULD OCCUR. IF TEMPS GET COLD ENOUGH...COULD SEE NEED FOR FREEZING SPRAY AS WELL. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE MOVES ACROSS THE GREAT LAKES. SRLY WINDS ON MONDAY NOW LOOK TO STAY BLO GALES. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 1 PM EST THIS AFTERNOON FOR MIZ003. LAKE EFFECT SNOW ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR MIZ001. WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY MORNING FOR MIZ001>003-005-009. WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON FOR MIZ006-007-085. LAKE SUPERIOR... GALE WARNING FROM 10 AM SATURDAY TO 7 AM EST SUNDAY FOR LSZ265>267. GALE WARNING FROM 7 AM TO 10 PM EST SATURDAY FOR LSZ263-264. GALE WARNING FROM 10 AM SATURDAY TO 6 AM EST SUNDAY FOR LSZ248>251. LAKE MICHIGAN... GALE WARNING FROM 7 PM THIS EVENING TO 4 AM EST SUNDAY FOR LMZ248-250. GALE WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR LMZ221. && $$ DISCUSSION...KC AVIATION...GM MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1015 AM EST FRI DEC 5 2008 LATEST UPDATE...SHORT TERM AND HEADLINE SECTION... .SYNOPSIS...(459 AM EST FRI DEC 5 2008) LAKE EFFECT SNOW SHOWERS WILL GRADUALLY DIMINISH ACROSS THE AREA DURING THE DAY TODAY AS A PORTION OF A RIDGE OF HIGH PRESSURE MOVES ACROSS THE AREA TODAY. SNOW IS EXPECTED TO INTENSIFY ACROSS THE AREA THEN OVERNIGHT TONIGHT AS AN AREA OF LOW PRESSURE OVER ALBERTA THIS MORNING APPROACHES THE AREA. MOST AREAS WILL SEE AT LEAST A COUPLE OF INCHES OF SNOW FROM TONIGHT THROUGH SATURDAY NIGHT. HEAVIER AMOUNTS OF SNOW ARE LIKELY NORTHWEST OF A LINE FROM HOLLAND TO BALDWIN AS SOUTHWEST WINDS WILL ALLOW LAKE MICHIGAN TO ENHANCE SNOWFALL. && .SHORT TERM...(1015 AM EST FRI DEC 5 2008) (REST OF TODAY THROUGH SUNDAY) I HAVE UPGRADED THE LAKE EFFECT SNOW ADVISORY TO A LAKE EFFECT SNOW WARNING SINCE WE HAVE HAD SEVERAL REPORTS OF BETWEEN 8 TO 10 INCHES IN EXTREME SOUTHWESTERN KENT...EASTERN OTTAWA AND NORTHEAST ALLEGAN COUNTIES IN THE PAST THREE HOURS. ALSO...SINCE THE LATEST RUC SHOWS THE LOW LEVEL WIND CONVERGENCE CONTINUES THROUGH MID AFTERNOON AND SHIFTS NORTH ONLY SLIGHTLY... I EXPECTED THE TIME OF THE HEADLINES UNTIL 5 PM FOR BOTH THE WARNING AND ADVISORY COUNTIES. OUR 88D RADAR CONTINUES TO SHOW ECHO INTENSITIES OVER 30 DBZ CONTINUING TO DEVELOP OVER THE LAKE SHORE AREAS OF OTTAWA AND ALLEGAN COUNTIES THAT THEN MOVE INLAND. GIVEN THE RUC KEEPS THE LIFT AND CONVERGENCE GOING INTO MID AFTERNOON OVER THE HEADLINE COUNTIES I THROUGH IT BEST TO KEEP THE HEADLINES GOING THROUGH 5 PM. I DO EXPECT THE SUNSHINE TO TURN THIS INTO A MORE CELLULAR EVENT BY LATE THIS MORNING. THAT WILL ONLY HELP BRING THE CONVECTION FARTHER EAST ACROSS THE CWA. ONE WAY OR THE OTHER ONLY OUR EXTREME NORTHEAST AND SOUTHERN COUNTIES WILL HAVE NEGLIGIBLE SNOWFALL THROUGH THE AFTERNOON. PREVIOUS DISCUSSION....THERE WILL BE A BREAK IN THE ACCUMULATION POTENTIAL LATE THIS AFTERNOON AND EARLY THIS EVENING AS THE INVERSION HEIGHTS DROP WITH SHORT WAVE RIDGING ALOFT AND SFC RIDGING MOVING OVERHEAD. THIS WILL BE SHORT LIVED AS A SHORT WAVE OVER NRN ALBERTA THIS MORNING...WILL RACE SE TO ERN WI BY 12Z SAT. MID AND HIGH CLOUDS WILL MOVE IN AHEAD OF THE WAVE...ALLOWING FOR A DEEP LAYER OF MOISTURE OVERHEAD. SNOW IS EXPECTED TO DEVELOP ACROSS THE AREA FROM THE WNW AFTER MIDNIGHT. SW FLOW AHEAD OF THE SYSTEM WILL TRY TO ADVECT SOME WARMER AIR IN...HOWEVER H850 TEMPS ARE EXPECTED TO WARM ONLY TO AROUND -9 TO -10C. PLENTY OF OVER-LAKE INSTABILITY WILL REMAIN AND WILL COMBINE WITH THE SYNOPTIC FORCING TO ENHANCE SNOWFALL ACROSS THE NW CORNER OF THE CWFA. PAST CASES OF A SW FLOW SUCH AS THIS AND A GOOD DEAL OF LOW LEVEL CONVERGENCE...BOTH SUPPORT HEAVIER SNOW ALONG AND NW OF A LINE FROM HOLLAND TO BALDWIN. MODELS SUPPORT A GENERAL 1-3/2-4 INCH TYPE OF EVENT ACROSS MOST OF THE CWFA. WITH THE DEEP MOISTURE... MODERATE OVER-LAKE INSTABILITY...AND THE BEST FORCING CLOSE TO THE DGZ...WARNING CRITERIA SNOWS ARE VERY POSSIBLE OVER THE NW. WE EXPECT THAT AN ADVISORY WILL EVENTUALLY BE NEEDED SURROUNDING THE WATCH AREA. THE WINDOW OF BEST SNOW OVER THE NW LOOKS TO BE AFTER 06Z TONIGHT AND THROUGH 18Z TOMORROW. AFTER 18Z SAT...THE FLOW BECOMES NW BEHIND THE FRONT. ADDITIONAL SNOWS WILL REMAIN POSSIBLE AFTER 18Z AS THE SNOW TRANSITIONS TO LAKE EFFECT. ENOUGH MOISTURE AND A FAVORABLE FLOW WILL KEEP THE POTENTIAL OF ACCUMULATING SNOW IN THROUGH THE EVENING SAT EVENING. AS THE FLOW BECOMES NW...THE SW COUNTIES WILL BEGIN TO SEE LAKE EFFECT TAKE CHARGE. H850 TEMPS WILL FALL BACK DOWN TO AROUND -17C OR SO BY 12Z SUN. INVERSION HEIGHTS ARE EXPECTED TO REMAIN UP THROUGH 10K FEET THROUGH A GOOD PORTION OF SAT NIGHT. THIS COMBINATION WILL BRING POTENTIAL FOR SOME HEAVIER LAKE EFFECT SNOW ACCUMULATIONS SOUTHWEST OF A LINE FROM HOLLAND TO KALAMAZOO. WE CONTEMPLATED ISSUING A WATCH FOR THIS AREA. HOWEVER WITH THE POTENTIAL OF SIGNIFICANT ACCUMS HOLDING OFF UNTIL MAINLY SAT NIGHT...WE FELT IT WAS BEST TO HOLD OFF FOR NOW WITH EVERYTHING ELSE GOING ON. LAKE EFFECT WILL THEN DIMINISH THROUGH THE DAY ON SUNDAY AS THE UPPER TROUGH PULLS AWAY AND SFC RIDGING MOVES IN. && .LONG TERM...(459 AM EST FRI DEC 5 2008) (SUNDAY NIGHT THROUGH THURSDAY) LONG TERM BEGINS WITH HIGH PRESSURE IN PLACE FOR SUNDAY NIGHT. MODELS HAVE SHIFTED SOMEWHAT FOR NEXT WEEK...YIELDING A LESS CONFIDENT FORECAST. FOR THAT REASON DID NOT MAKE MANY CHANGES TO THE GOING FORECAST. MODELS WERE BRINGING A HEALTHY CLIPPER THROUGH THE REGION ON MONDAY...NOW IT IS MORE OF AN INVERTED TROUGH. IN ADDITION...THE STRONG LOW THAT THE GFS WAS ROLLING UP INTO EASTERN CANADA MID WEEK (WHICH WAS TUGGING VERY COLD AIR SOUTH OUT OF CANADA INTO THE GREAT LAKES) IS NO LONGER THERE. TO ADD FURTHER COMPLEXITY...ON THURSDAY MORNING...THE GFS HAS A 1004MB LOW DROPPING OUT OF THE NORTHERN PLAINS...WHEREAS THE EURO HAS A SPRAWLING HIGH BUILDING IN. SUFFICE IT TO SAY CONFIDENCE IS LOW. IT DOES STILL LOOK TO BE A COLDER THAN NORMAL PERIOD...WITH CHANCES AT LAKE EFFECT SNOW. HOPING FOR MORE IN THE WAY OF MODEL CONSISTENCY OFF THE 12Z MODEL RUNS. && .MARINE...(459 AM EST FRI DEC 5 2008) HAVE GONE AHEAD AND HOISTED A GALE WARNING FOR THE PERIOD FROM OVERNIGHT TONIGHT THROUGH MOST OF SATURDAY NIGHT. WINDS REMAIN IN THE 15 TO 25 KNOT RANGE THIS MORNING AT THE OBSERVATION SITES AT BIG SABLE AND THE MUSKEGON GLERL. WINDS WILL PICK UP THIS EVENING AHEAD OF THE INCOMING SYSTEM THAT WILL MOVE THROUGH ON SATURDAY. MODELS INDICATE THAT WE WILL BE ABLE TO MIX A PORTION OF THE 40+ KNOT SOUTHWEST WIND CORE AROUND 2K FEET BEGINNING AFTER 00Z THIS EVENING. THERE MAY BE A BRIEF LULL WHERE WINDS DROP DOWN TO AROUND 25 KNOTS FOR A FEW HOURS ON SAT WHEN THE FRONT COMES THROUGH. HOWEVER NORTHWEST WINDS WILL KICK UP TO GALES ONCE AGAIN AS THE FRONT PASSES AND COLDER AIR ADVECTS IN. FREEZING SPRAY WILL BE POSSIBLE ON SATURDAY NIGHT...HOWEVER WATER TEMPS MAY BE A TAD TOO WARM PER LOCAL STUDIES. THIS CAN BE ADDRESSED MORE BY LATER SHIFTS. && .AVIATION...(650 AM EST FRI DEC 5 2008) LAKE EFFECT SNOW SHOWERS CONTINUE THIS MORNING...WITH CONDITIONS VARYING BETWEEN VFR (FLURRIES AND CEILINGS ABOVE 3000FT) AND MVFR (3-5SM -SHSN AND CEILINGS BETWEEN 1000 AND 3000FT). BRIEFLY IN THE HEAVIER SNOW SHOWERS VISIBILITIES WILL DIP BELOW 3SM. EXPECT A GRADUAL DOWNTURN IN SNOW INTENSITY TODAY WITH TAFS SITES MAINLY SEEING VFR CONDITIONS THIS AFTERNOON. THE SNOW SHOWERS SHOULD LOSE BOTH COVERAGE AND INTENSITY THIS AFTERNOON. FOCUS WILL THEN SHIFT TO A CLIPPER SYSTEM DROPPING TOWARD THE GREAT LAKES FROM THE NORTHWEST TONIGHT. A WIDESPREAD LIGHT SNOW WILL MOVE ACROSS THE AREA BETWEEN 06Z AND 12Z. A LAKE ENHANCEMENT IS EXPECTED AT KMKG THOUGH LATE TONIGHT...WHICH WILL DIP VISIBILITIES BELOW A MILE. SIGNIFICANT BLOWING SNOW MAY DEVELOP THERE AS WELL WITH VERY GUSTY SOUTHWEST WINDS. && .HYDROLOGY...(459 AM EST FRI DEC 5 2008) NO SIGNIFICANT HYDRO ISSUES IN THE NEXT FEW DAYS AS TEMPERATURES EXPECTED TO GENERALLY BE BELOW FREEZING THROUGH THE NEXT WEEK. LITTLE TO NO RUNOFF CAN BE EXPECTED INTO AREA STREAMS AND RIVERS. IT DOES APPEAR THAT WE WILL BUILD A SNOWPACK WITH LAKE EFFECT SNOW SHOWERS EXPECTED MOST DAYS AND A FEW SYSTEMS MOVING THROUGH. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...LAKE EFFECT SNOW WARNING THROUGH 5 PM FOR KENT...OTTAWA AND ALLEGAN COUNTIES. LAKE EFFECT SNOW ADVISORY THROUGH 5 PM FOR BARRY...VAN BUREN AND KALAMAZOO COUNTIES. WINTER STORM WATCH FOR OTTAWA...MUSKEGON...OCEANA...MASON... LAKE...AND NEWAYGO COUNTIES FROM 06Z SAT THROUGH 06Z SUN. LM...SMALL CRAFT ADVISORY IN EFFECT THROUGH 00Z SATURDAY. GALE WARNING IN EFFECT 00Z SATURDAY THROUGH 09Z SUNDAY. && $$ SYNOPSIS: NJJ SHORT TERM: NJJ WDM LONG TERM: DUKE MARINE: NJJ AVIATION: DUKE HYDROLOGY: NJJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 455 AM EST FRI DEC 5 2008 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW DEEP UPR TROF CENTERED OVER ERN NAMERICA DOWNWIND OF RDG ALG THE W COAST. CORE OF ARCTIC COLD UNDER THE TROF AT 00Z WAS CENTERED NEAR THE CWA...WITH 00Z H85 TEMP -22C AT INL AND H7 TEMP -25C AT GRB/APX. AT YQD...THE 00Z H8/H7 TEMPS WERE -16C/-19C. OBVIOUSLY WITH THE LARGE AIR/LK SUP WATER TEMP DIFFERENTIAL...QUITE A BIT OF LES HAS BEEN FALLING IN THE FVRD SN BELTS IN THE LLVL WNW FLOW BTWN HI PRES OVER THE CNTRL PLAINS AND LO PRES OVER NRN QUEBEC. MORE WSW LAND BREEZE WIND COMPONENT WITHIN THE RELATIVELY UNMODIFIED ARCTIR AIRMASS OVER LAND APPEARS TO BE INTENSIFYING THE LLVL CNVGC WITH THE MORE NW FLOW OVER THE OPEN WATERS OF LK SUP AND INTENSIFIED THE SRN MOST BANDS STREAMING INTO THE CWA NEAR THE PORCUPINE MTNS AND ALONG THE LK SUP SHORE E OF GRAND MARAIS. PRESENCE OF SOME MID LVL MSTR NOTED BY MID CLD/H85-75 MSTR SHOWN ON THE 00Z INL RAOB ASSOCIATED WITH A PAIR OF SHRTWVS DROPPING SEWD THRU ONTARIO MAY ALSO BE ENHANCING THE BANDS. ANOTHER SHRTWV APPEARS TO BE RIDING OVER THE WRN RDG WITH QUITE A BIT OF MSTR SHOWN ON WV IMAGERY IN ADVANCE OF THIS SYS SPILLING INTO THE NRN PLAINS/MN. MAIN FCST CONCERNS THIS PACKAGE INCLUDE LES TRENDS/COVG/AMTS/GOING HEADLINES THRU TDAY. FOCUS FOR TNGT INTO THE WEEKEND CONCERNS TIMING/IMPACT OF SHRTWV NOW MOVING OVER WRN RDG AND ANOTHER DIGGING SEWD FM NRN CAN. FOR TDAY...HGTS ARE FCST TO RISE SLOWLY OVER THE UPR LKS WITH WARMER AIR TO THE NW GRDLY INFILTRATING THE AREA. IN TANDEM WITH FALLING MSLP OVER SCNTRL CAN AHEAD OF SHRTWV RIDING OVER THE WRN RDG...THE LLVL FLOW IS FCST TO BACK MORE SW. SO LES BANDS WL BEGIN TO DRIFT MORE TO THE N...EXITING ALL BUT THE KEWEENAW BY THE AFTN. MAY BE ABLE TO CANX GOING WRNGS FOR ALGER/LUCE COUNTIES EARLY IF THE BANDS SHIFT N INTO THE LK...WL CHECK RADAR TRENDS AT FCST ISSUANCE. GFS/NAM/LOCAL WRF-ARW RUNS ALSO SUG FLOW WL BACK ENUF TO END HEADLINES FOR THE KEWEENAW EARLY AS WELL. THE FLOW DOES NOT APPEAR TO BACK ENUF TO RAISE CONCERNS ABOUT AN LES BAND OFF LK IMPACTING LUCE/SRN SCHOOLCRAFT COUNTIES. OTRW...LOOKS LIKE ANOTHER DRY COLD DAY OVER THE INTERIOR. BUT HI CLDS NOW SPILLING INTO THE PLAINS/MN WL ARRIVE IN THE AFTN. CONSIDERING THE FRIGID HI TEMPS OBSVD IN THE NRN PLAINS YDAY AND THE LACK OF LK MODERATION WITH BACKING LLVL FLOW...WL TEND TOWARD THE LO END OF MOS GUIANCE FOR HI TEMPS AS SUGD BY GFS FCST SDNGS. TNGT...SW FLOW AHEAD OF SHRTWV NOW TOPPING WRN RDG AND DIGGING SHARPLY SEWD TO IA BY 12Z SAT IS FCST TO DOMINATE. MEANWHILE... ANOTHER SHRTWV MOVING QUICKLY SEWD THRU NW ONTARIO/ASSOCIATED SFC LO AND ARCTIC COLD FNT WL APRCH FM THE NW LATE. EXPECT SOME -SN ASSOCIATED WITH ISENTROPIC LIFT ON THE 275K-285K SFC (H8-65) TO BREAK OUT NW-SE IN ADVANCE OF THESE FEATURES. WITH ABOUT 1.0-1.5 G/KG SPECIFIC HUMIDITY IN THE H7-75 LYR...EXPECT 1 TO 3 INCHES OF -SN TO FALL ACRS THE FA THRU THE NGT. A LAKE ENHANCED SN BAND OFF LK MI IS LIKELY TO DVLP...BUT THE FLOW APPEARS TO HAVE ENUF OF A WLY COMPONENT TO FOCUS THE HEAVIER SN INTO MACKINAC COUNTY SE OF ERY. FAIRLY SHARP DPVA/H85-5 QVECTOR CNVGC IS ALSO FCST TO ARRIVE AFT 06Z AHEAD OF THE NRN SHRTWV. SOME HEAVIER SN MAY DVLP LATE OVER THE W TOWARD 12Z WITH ARRIVAL OF ACCOMPANYING ARCTIC COLD FNT. ALTHOUGH THE TOTAL PCPN APPEARS WL BE RELATIVELY LGT...THE DEEP SATURATION SHOWN ON THE FCST SDNGS SUGS BUMPING UP POPS CLOSER TO THE HIER GFS MOS NUMBERS. SAT LOOKS TO BE A WINTRY DAY WITH BLIZZARD CONDITIONS PSBL FOR AT LEAST A TIME IN THE STRONG NLY FLOW FOLLOWING THE PASSAGE OF CLIPPER LO/ACCOMPANYING COLD FNT. LOCAL WRF-ARW RUN SUGS AN INTENSE SN BAND WL ACCOMPANY THE COLD FROPA...ESPECIALLY OVER THE NRN TIER WHERE THERE WL BE ENHANCEMENT OFF LK SUP/UPSLOPE COMPONENT TO THE NNW FLOW...WITH H925 WINDS PROGGED TO PEAK AT 40 KTS IN THE WAKE OF THE FNT. STRONG WINDS WL LIKELY FRAGMENT THE SN FLAKES THAT WL BECOME INCRSGLY POWDERY WITH ARRIVAL OF COLDER/DRIER AIR IN THE AFTN. THE RESULT WL BE A MORE EFFICIENT REDUCTION IN VSBY. SUSPECT A BLIZZARD WRNG MIGHT BE NECESSARY FOR ALGER COUNTY...WHICH WL BE MOST EXPOSED TO FCST NNW FLOW FOR THE LONGEST PD OF TIME. OTRW...HOISTED WATCH FOR GOGEBIC AND MQT COUNTIES WHILE CONTINUING OTHER GOING WATCHES. ADVYS WL LIKELY BE NECESSARY FOR DELTA/SRN SCHOOLCRAFT ZNS WITH STRG NNW FLOW BLOWING THE LES WELL INLAND.EXPECT MAX TEMPS ON SAT OVER THE W HALF IN THE MRNG...WITH SLOWLY FALLING TEMPS IN THE AFTN. SAT NGT WL FEATURE PURE LES WITH RISING HGTS/DNVA/H85-5 QVECTOR DVGC IN WAKE OF DEPARTING SHRTWV/SFC LO. INTENSITY OF THE LES OVER THE FAR W SHOULD DIMINISH OVERNGT WITH APRCH OF HI PRES RDG/FCST INVRN BASE PROGGED TO SUBSIDE TO ARND H9 BY 12Z SUN AT IWD...BUT EXPECT HI SN/WATER RATIOS UNTIL THE END WITH TEMPS WITHIN THE INCRSGLY SHALLOW MOIST LYR ARND -15C. GOING EXPIRATION OF WATCH FOR THE WRN ZNS SEEMS APPROPRIATE. MAGNITUDE OF THE BLSN SHOULD ALSO DIMINISH W TO E WITH GRDL WEAKENING OF THE PRES GRADIENT W TO E. BUT EXPECTED BLIZZARD CONDITIONS OVER ALGER COUNTY SHOULD LIKELY PERSIST INTO THE EVNG WITH H925 WINDS IN THE 35-40KT RANGE UNTIL ABOUT 03Z. LES WL DIMINISH OVER THE E HALF ON SUN WITH ARRIVAL OF HI PRES RDG. SUN WL BE ANOTHER VERY COLD DAY UNDER ARRIVING RDG AXIS WITH H85 TEMPS IN THE -15C TO -18C RANGE. END OF WATCH LATE ON SUN APPEARS CONSISTENT WITH RECENT GUIDANCE. HI CLDS AHEAD OF YET ANOTHER CLIPPER LO WL INVADE DURING THE DAY. ADDED LO CHC POPS ON SUN NGT TO REFLECT DVLPG ISENTROPIC LIFT/MODEL QPF IN ADVANCE OF THIS CLIPPER. HIEST CHC POPS DOWNWIND OF LK MI WITH SOME MOISTENING/DESTABILATION PSBL OFF THE WATER. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... WITH LAKE EFFECT -SHSN CONTINUING AT KCMX...EXPECT CONDITIONS TO VARY BTWN IFR AND LIFR THRU THE MORNING. THERE MAY BE SOME BRIEF PERIODS OF MVFR AND PERHAPS VFR...BUT THOSE PERIODS WILL BE VERY INFREQUENT. AS WINDS BACK MORE TO THE SW VERY LATE IN THE NIGHT INTO THE MORNING...ENHANCING LOW-LEVEL CONVERGENCE...EXPECT A PREVAILING PERIOD OF VLIFR CONDITIONS IN HEAVIER SHSN. AS WINDS CONTINUE TO BACK...EXPECT CONDITIONS TO IMPROVE TO MVFR LATE MORNING AND TO VFR IN THE AFTN. NEXT LOW PRES SYSTEM DROPPING INTO THE UPPER LAKES REGION WILL BRING A RETURN TO MVFR CONDITIONS WITH -SN DURING THE EVENING. AT KSAW...WITH LOW-LEVEL W TO SW WINDS...LAKE EFFECT -SHSN WILL NOT BE AN ISSUE. EXPECT VFR CONDITIONS TO PREVAIL OVERNIGHT THRU THE AFTN. MVFR CONDITIONS SHOULD DEVELOP IN THE EVENING AS -SN SPREADS INTO THE AREA IN ASSOCIATION WITH APPROACHING LOW PRES SYSTEM. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... SW WINDS TODAY MAY REACH GALES BUT SHOULD ONLY BE A FEW GUSTS. ON SATURDAY...STRONG COLD FRONT PLOWING THROUGH WITH DEEPENING SFC LOW LEADS TO HIGH POTENTIAL OF GALES. WENT AHEAD WITH GALE WARNINGS AS CONFIDENCE IS HIGH FOR AT LEAST MARGINAL GALES. STRONG GALES TO 45 KNOTS COULD OCCUR. IF TEMPS GET COLD ENOUGH...COULD SEE NEED FOR FREEZING SPRAY AS WELL. WINDS DIMINISH BY SUNDAY AS HIGH PRESSURE MOVES ACROSS THE GREAT LAKES. SRLY WINDS ON MONDAY NOW LOOK TO STAY BLO GALES. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WARNING UNTIL 7 AM EST THIS MORNING FOR MIZ002. LAKE EFFECT SNOW WARNING UNTIL 1 PM EST THIS AFTERNOON FOR MIZ003. LAKE EFFECT SNOW ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR MIZ001. WINTER STORM WATCH FROM SATURDAY MORNING THROUGH SUNDAY MORNING FOR MIZ001>003-005-009. WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON FOR MIZ006-007-085. LAKE SUPERIOR... GALE WARNING FROM 10 AM SATURDAY TO 7 AM EST SUNDAY FOR LSZ265>267. GALE WARNING FROM 7 AM TO 10 PM EST SATURDAY FOR LSZ263-264. GALE WARNING FROM 10 AM SATURDAY TO 6 AM EST SUNDAY FOR LSZ248>251. LAKE MICHIGAN... GALE WARNING FROM 7 PM THIS EVENING TO 4 AM EST SUNDAY FOR LMZ248-250. GALE WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR LMZ221. && $$ DISCUSSION...KC AVIATION...JLA MARINE...JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1155 AM CST FRI DEC 5 2008 .UPDATE...FOR 18Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED 234 AM CST FRI DEC 5 2008/ MAIN FORECAST CONCERN THIS MORNING IS THE ALBERTA CLIPPER WHICH WILL MOVE THROUGH THE AREA TONIGHT AND ITS ASSOCIATED SNOWFALL AND GUSTY WINDS. THE GOING FORECAST HAD A GOOD HANDLE ON THE SITUATION... WITH THE MAIN ADJUSTMENT BEING A BIT QUICKER TIMING OF THINGS. LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES SHOW THE DEPARTING UPPER TROUGH AND SHORTWAVE TO OUR EAST WITH A PROMINENT UPPER RIDGE OFF THE WEST COAST. A SHORTWAVE FEATURE IS EVIDENT ON THE DOWNSTREAM SIDE OF THE RIDGE MOVING INTO CENTRAL SASKATCHEWAN. THIS SHORTWAVE WILL DIVE SOUTHEAST OVER THE UPCOMING 24 HOURS... WORKING TO PUSH A SURFACE LOW ACROSS CENTRAL AND SOUTHERN CANADA WHILE DRIVING A COLD FRONT THROUGH OUR AREA. THE GFS AND NAM ARE REASONABLY SIMILAR ON THE OVERALL MASS FIELDS... BUT PREFERRED THE GFS MOISTURE FIELDS... PARTICULARLY ITS DEPICTION OF SATURATION ON THE ISENTROPIC SURFACES. ESSENTIALLY USED A BLEND OF THE GFS AND SREF GUIDANCE FOR THE FORECAST OVER THE NEXT FEW DAYS. ONCE TONIGHT/S SYSTEM MOVES BY... THE NEXT FEATURE OF INTEREST WILL BE ANOTHER SHORTWAVE MOVING IN ON NORTHWEST UPPER FLOW AND ITS ASSOCIATED ALBERTA CLIPPER SURFACE FEATURE... WHICH WILL SWING THROUGH THE AREA DURING THE LATE SUNDAY THROUGH MONDAY TIME FRAME. THE GOING FORECAST HAD A GOOD HANDLE ON THE EXPECTATIONS FOR THAT SYSTEM IN COMPARISON TO THE LATEST GUIDANCE... WITH ONCE AGAIN JUST SOME MINOR TWEAKS TO SPEED THE TIMING OF THINGS. SCT-BKN LOW CLOUDS WERE PRESENT OVER MUCH OF THE AREA THIS MORNING... LINGERING ON THE BACKSIDE OF THE LOW LEVEL THERMAL TROUGH. AS WARM ADVECTION CONTINUES TO INCREASE THESE LOW CLOUDS WILL MOVE EAST AND/OR SCOUR OUT. HOWEVER... THEY WILL BE QUICKLY REPLACED BY RAPIDLY INCREASING MID AND HIGH CLOUDS THIS MORNING DUE TO THE WARM ADVECTION AHEAD OF THE NEXT SHORTWAVE. THIS SYSTEM WILL BE A QUICK HITTER... IMPACTING THE CWFA FROM NORTHWEST TO SOUTHEAST... PRIMARILY BETWEEN 21Z AND 06Z. DEEP LAYER SATURATION COMES INTO BETTER ALIGNMENT AS THE SYSTEM MOVES THROUGH THE AREA... SO THE BETTER CHANCES FOR PCPN AND HIGHER SNOWFALL TOTALS WILL BE OVER THE NORTHEAST AND EASTERN PORTION OF THE AREA. THE BULK OF THE FORCING WILL BE DUE TO ISENTROPIC ASCENT OWING TO PRESSURE ADVECTION... ALONG AND AHEAD OF THE 925-500MB TROUGH AXIS. USED THE 285K ISENTROPIC SURFACE AS A PROXY FOR THE ARRIVAL OF PCPN AND THE LOCATION OF HIGHEST POPS AND GREATEST PCPN. MIXING RATIOS ON THIS SURFACE NEAR 700MB LOOK TO BE ON THE ORDER OF 1-2 G/KG... WHICH WOULD SUGGEST 2-4 INCHES FOR A 12-HOUR EVENT... BUT THE WINDOW OF OPPORTUNITY FOR THIS SYSTEM IS AROUND 4 OR 5 HOURS WHICH SUGGESTS MORE OF A 1-2 INCH EVENT FOR MOST LOCATIONS. QPF FROM THE GFS IS GENERALLY BETWEEN ONE AND TWO TENTHS OF AN INCH... WHICH WOULD ALSO FALL INTO THAT BALLPARK. A LOOK AT FORECAST SOUNDINGS AND LAPSE RATES... AS WELL AS EPV... DOES NOT SUGGEST A GREAT DEAL OF POTENTIAL ENHANCEMENT FROM STABILITY ARGUMENTS... WITH THE BETTER INSTABILITY LOCATED AOA 15K FEET... WHICH IS WELL ABOVE THE DENDRITIC GROWTH LAYER WHICH IS AROUND 10K FT. LAPSE RATES ARE ACTUALLY FAIRLY POOR IN THAT LAYER... WHICH DOES RESULT IN A DEEPER DENDRITIC GROWTH LAYER BUT ONE WHICH MAY NOT HAVE AUGMENTED UPWARD MOTION DUE TO INSTABILITY. SO... IN TERMS OF SNOWFALL RATIOS... WOULD BE TOUGH TO STRAY TO FAR FROM A CLIMATOLOGICAL OR EXPECTED VALUE FOR THE GIVEN AIRMASS... WHICH IS PROBABLY CLOSER TO 14 TO 1. SO... WILL GENERALLY PAINT 1 TO 2 INCHES OF SNOWFALL... WITH SOME MAXES BETWEEN 2 AND 3 OVER THE EASTERN PORTION OF THE FORECAST AREA WHERE THE WINDOW OF OPPORTUNITY WILL BE SLIGHTLY LONGER GIVEN A BETTER PERIOD OF DEEP LAYER SATURATION. SOUTHWEST WINDS WILL INCREASE THROUGH THE DAY TODAY AS THE GRADIENT STRENGTHENS... ALTHOUGH THE STRONGEST WINDS WILL BE WITH THE POST-FRONTAL COLD ADVECTION LATER TONIGHT AND SATURDAY MORNING WHEN NORTHWEST WINDS WILL GUST NEAR 30 MPH WORKING TO BLOW AROUND THE NEW FALLEN SNOW. AT THIS POINT SNOWFALL TOTALS AND EXPECTED WINDS DURING THE TIME OF FALLING SNOW LOOK LIKE THEY WILL NOT NECESSITATE AN ADVISORY... ALTHOUGH THIS WILL NEED TO BE MONITORED BY LATER SHIFTS. RIDGING AND ANTICYCLONIC FLOW LOOK TO BUILD IN QUICKLY BEHIND THE SYSTEM ON SATURDAY... WITH JUST SOME MORNING FLURRIES OVER THE EAST AND OTHERWISE DECREASING CLOUDS THROUGH THE DAY. HOWEVER... IT WON/T TAKE LONG FOR RETURN FLOW TO SET BACK UP... WITH WARM ADVECTION WORKING BACK IN BY SUNDAY AFTERNOON AND INCREASING MARKEDLY SUNDAY NIGHT AS THINGS SATURATE THROUGH THE COLUMN. WILL MAINTAIN THE IDEA OF INCREASING POPS FROM WEST TO EAST SUNDAY AFTERNOON AND SUNDAY NIGHT WITH HIGH CHANCE POPS. LATER FORECASTS WILL PROBABLY BE ABLE TO BUMP THE POPS UP FURTHER ONCE THE TIMING IS NAILED DOWN A BIT BETTER. THIS SHORTWAVE WILL SWING THROUGH ON MONDAY... DRIVING THE COLD FRONT THROUGH THE CWFA MONDAY AFTERNOON AND EVENING... WITH THE BOUNDARY LAYER FLOW QUICKLY BECOMING ANTICYCLONIC ONCE AGAIN WHICH SHOULD BRING A QUICK END TO PCPN MONDAY NIGHT. MADE NO ADJUSTMENTS TO THE GOING FORECAST BEYOND MONDAY. && .AVIATION.../18Z TAF ISSUANCE/ VIGOROUS SHORT WAVE RACING SOUTHEAST ACROSS NORTH DAKOTA THIS AFTERNOON...SHOULD AFFECT MUCH OF MN FA BY 00Z SAT. CIGS ALREADY BEGINNING TO LOWER WESTERN AREAS. PREVIOUS FCST LOOKED GOOD FOR TIMING...COMING IN THIS AFTERNOON KAXN-KRWF-KSTC AREAS AND MAINLY AFTER 00Z TO THE EAST. WILL SEE 1-3 INCH SNOW ACROSS THE AREA DURING THE LATE AFTERNOON/OVERNIGHT...WITH OCNL LIFR DURING THE HEAVIER SNOW PERIODS OVER EASTERN AREAS. WIND TO INCREASE WITH FROPA FIRST AT KAXN...LAST AT KEAU. SOME GUSTS TO 28-30KT PSBL WITH FROPA KAXN-KRWF AND WITH FRESH SNOW BLSN COULD BECOME A PROBLEM. SNOW SHOULD END IN THOSE AREAS WITH SOME MVFR VSBYS PSBL FOR A TIME. LOW CLOUDS TO REMAIN THROUGH 18Z ACROSS THE REGION...POSSIBLY BREAKING OUT OVER THE WEST INTO CENTRAL FA DURING THE AFTERNOON SAT. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ DWE/TRH mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 602 AM CST FRI DEC 5 2008 .UPDATE...FOR 12Z AVIATION DISCUSSION BELOW && .DISCUSSION.../ISSUED 234 AM CST FRI DEC 5 2008/ MAIN FORECAST CONCERN THIS MORNING IS THE ALBERTA CLIPPER WHICH WILL MOVE THROUGH THE AREA TONIGHT AND ITS ASSOCIATED SNOWFALL AND GUSTY WINDS. THE GOING FORECAST HAD A GOOD HANDLE ON THE SITUATION... WITH THE MAIN ADJUSTMENT BEING A BIT QUICKER TIMING OF THINGS. LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES SHOW THE DEPARTING UPPER TROUGH AND SHORTWAVE TO OUR EAST WITH A PROMINENT UPPER RIDGE OFF THE WEST COAST. A SHORTWAVE FEATURE IS EVIDENT ON THE DOWNSTREAM SIDE OF THE RIDGE MOVING INTO CENTRAL SASKATCHEWAN. THIS SHORTWAVE WILL DIVE SOUTHEAST OVER THE UPCOMING 24 HOURS... WORKING TO PUSH A SURFACE LOW ACROSS CENTRAL AND SOUTHERN CANADA WHILE DRIVING A COLD FRONT THROUGH OUR AREA. THE GFS AND NAM ARE REASONABLY SIMILAR ON THE OVERALL MASS FIELDS... BUT PREFERRED THE GFS MOISTURE FIELDS... PARTICULARLY ITS DEPICTION OF SATURATION ON THE ISENTROPIC SURFACES. ESSENTIALLY USED A BLEND OF THE GFS AND SREF GUIDANCE FOR THE FORECAST OVER THE NEXT FEW DAYS. ONCE TONIGHT/S SYSTEM MOVES BY... THE NEXT FEATURE OF INTEREST WILL BE ANOTHER SHORTWAVE MOVING IN ON NORTHWEST UPPER FLOW AND ITS ASSOCIATED ALBERTA CLIPPER SURFACE FEATURE... WHICH WILL SWING THROUGH THE AREA DURING THE LATE SUNDAY THROUGH MONDAY TIME FRAME. THE GOING FORECAST HAD A GOOD HANDLE ON THE EXPECTATIONS FOR THAT SYSTEM IN COMPARISON TO THE LATEST GUIDANCE... WITH ONCE AGAIN JUST SOME MINOR TWEAKS TO SPEED THE TIMING OF THINGS. SCT-BKN LOW CLOUDS WERE PRESENT OVER MUCH OF THE AREA THIS MORNING... LINGERING ON THE BACKSIDE OF THE LOW LEVEL THERMAL TROUGH. AS WARM ADVECTION CONTINUES TO INCREASE THESE LOW CLOUDS WILL MOVE EAST AND/OR SCOUR OUT. HOWEVER... THEY WILL BE QUICKLY REPLACED BY RAPIDLY INCREASING MID AND HIGH CLOUDS THIS MORNING DUE TO THE WARM ADVECTION AHEAD OF THE NEXT SHORTWAVE. THIS SYSTEM WILL BE A QUICK HITTER... IMPACTING THE CWFA FROM NORTHWEST TO SOUTHEAST... PRIMARILY BETWEEN 21Z AND 06Z. DEEP LAYER SATURATION COMES INTO BETTER ALIGNMENT AS THE SYSTEM MOVES THROUGH THE AREA... SO THE BETTER CHANCES FOR PCPN AND HIGHER SNOWFALL TOTALS WILL BE OVER THE NORTHEAST AND EASTERN PORTION OF THE AREA. THE BULK OF THE FORCING WILL BE DUE TO ISENTROPIC ASCENT OWING TO PRESSURE ADVECTION... ALONG AND AHEAD OF THE 925-500MB TROUGH AXIS. USED THE 285K ISENTROPIC SURFACE AS A PROXY FOR THE ARRIVAL OF PCPN AND THE LOCATION OF HIGHEST POPS AND GREATEST PCPN. MIXING RATIOS ON THIS SURFACE NEAR 700MB LOOK TO BE ON THE ORDER OF 1-2 G/KG... WHICH WOULD SUGGEST 2-4 INCHES FOR A 12-HOUR EVENT... BUT THE WINDOW OF OPPORTUNITY FOR THIS SYSTEM IS AROUND 4 OR 5 HOURS WHICH SUGGESTS MORE OF A 1-2 INCH EVENT FOR MOST LOCATIONS. QPF FROM THE GFS IS GENERALLY BETWEEN ONE AND TWO TENTHS OF AN INCH... WHICH WOULD ALSO FALL INTO THAT BALLPARK. A LOOK AT FORECAST SOUNDINGS AND LAPSE RATES... AS WELL AS EPV... DOES NOT SUGGEST A GREAT DEAL OF POTENTIAL ENHANCEMENT FROM STABILITY ARGUMENTS... WITH THE BETTER INSTABILITY LOCATED AOA 15K FEET... WHICH IS WELL ABOVE THE DENDRITIC GROWTH LAYER WHICH IS AROUND 10K FT. LAPSE RATES ARE ACTUALLY FAIRLY POOR IN THAT LAYER... WHICH DOES RESULT IN A DEEPER DENDRITIC GROWTH LAYER BUT ONE WHICH MAY NOT HAVE AUGMENTED UPWARD MOTION DUE TO INSTABILITY. SO... IN TERMS OF SNOWFALL RATIOS... WOULD BE TOUGH TO STRAY TO FAR FROM A CLIMATOLOGICAL OR EXPECTED VALUE FOR THE GIVEN AIRMASS... WHICH IS PROBABLY CLOSER TO 14 TO 1. SO... WILL GENERALLY PAINT 1 TO 2 INCHES OF SNOWFALL... WITH SOME MAXES BETWEEN 2 AND 3 OVER THE EASTERN PORTION OF THE FORECAST AREA WHERE THE WINDOW OF OPPORTUNITY WILL BE SLIGHTLY LONGER GIVEN A BETTER PERIOD OF DEEP LAYER SATURATION. SOUTHWEST WINDS WILL INCREASE THROUGH THE DAY TODAY AS THE GRADIENT STRENGTHENS... ALTHOUGH THE STRONGEST WINDS WILL BE WITH THE POST-FRONTAL COLD ADVECTION LATER TONIGHT AND SATURDAY MORNING WHEN NORTHWEST WINDS WILL GUST NEAR 30 MPH WORKING TO BLOW AROUND THE NEW FALLEN SNOW. AT THIS POINT SNOWFALL TOTALS AND EXPECTED WINDS DURING THE TIME OF FALLING SNOW LOOK LIKE THEY WILL NOT NECESSITATE AN ADVISORY... ALTHOUGH THIS WILL NEED TO BE MONITORED BY LATER SHIFTS. RIDGING AND ANTICYCLONIC FLOW LOOK TO BUILD IN QUICKLY BEHIND THE SYSTEM ON SATURDAY... WITH JUST SOME MORNING FLURRIES OVER THE EAST AND OTHERWISE DECREASING CLOUDS THROUGH THE DAY. HOWEVER... IT WON/T TAKE LONG FOR RETURN FLOW TO SET BACK UP... WITH WARM ADVECTION WORKING BACK IN BY SUNDAY AFTERNOON AND INCREASING MARKEDLY SUNDAY NIGHT AS THINGS SATURATE THROUGH THE COLUMN. WILL MAINTAIN THE IDEA OF INCREASING POPS FROM WEST TO EAST SUNDAY AFTERNOON AND SUNDAY NIGHT WITH HIGH CHANCE POPS. LATER FORECASTS WILL PROBABLY BE ABLE TO BUMP THE POPS UP FURTHER ONCE THE TIMING IS NAILED DOWN A BIT BETTER. THIS SHORTWAVE WILL SWING THROUGH ON MONDAY... DRIVING THE COLD FRONT THROUGH THE CWFA MONDAY AFTERNOON AND EVENING... WITH THE BOUNDARY LAYER FLOW QUICKLY BECOMING ANTICYCLONIC ONCE AGAIN WHICH SHOULD BRING A QUICK END TO PCPN MONDAY NIGHT. MADE NO ADJUSTMENTS TO THE GOING FORECAST BEYOND MONDAY. && .AVIATION.../12Z TAF ISSUANCE/ LOW-END VFR CIGS WILL SHIFT EAST OF THE TAF SITES THIS MORNING...BUT BE REPLACED BY MID/HIGH CLOUDS SHORTLY AFTERWARD...AS THE NEXT CLIPPER SYSTEM DRAWS NEAR. HAVE SPED UP THE ARRIVAL OF THE ASSOCIATED SNOWFALL WITH THIS SYSTEM...CONSISTENT WITH MODEL TRENDS. EXPECT SNOW TO REACH KAXN/KSTC AROUND 20Z...KRWF/KSMP AROUND 22Z...AND KRNH/KEAU BY 00Z. EXPECT IFR VSBYS WITH THE SNOWFALL...WITH OCCASIONAL DIPS TO THE LIFR CATEGORY THIS EVENING. EXPECT MAINLY MVFR CIGS WITH THE SNOWFALL. GUSTY NORTHWEST WINDS BEHIND THE FROPA WILL LIKELY RESULT IN SOME BLOWING SNOW TONIGHT AS WELL. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ LS/TRH mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 234 AM CST FRI DEC 5 2008 .DISCUSSION... MAIN FORECAST CONCERN THIS MORNING IS THE ALBERTA CLIPPER WHICH WILL MOVE THROUGH THE AREA TONIGHT AND ITS ASSOCIATED SNOWFALL AND GUSTY WINDS. THE GOING FORECAST HAD A GOOD HANDLE ON THE SITUATION... WITH THE MAIN ADJUSTMENT BEING A BIT QUICKER TIMING OF THINGS. LATEST WATER VAPOR IMAGERY AND RUC UPPER AIR ANALYSES SHOW THE DEPARTING UPPER TROUGH AND SHORTWAVE TO OUR EAST WITH A PROMINENT UPPER RIDGE OFF THE WEST COAST. A SHORTWAVE FEATURE IS EVIDENT ON THE DOWNSTREAM SIDE OF THE RIDGE MOVING INTO CENTRAL SASKATCHEWAN. THIS SHORTWAVE WILL DIVE SOUTHEAST OVER THE UPCOMING 24 HOURS... WORKING TO PUSH A SURFACE LOW ACROSS CENTRAL AND SOUTHERN CANADA WHILE DRIVING A COLD FRONT THROUGH OUR AREA. THE GFS AND NAM ARE REASONABLY SIMILAR ON THE OVERALL MASS FIELDS... BUT PREFERRED THE GFS MOISTURE FIELDS... PARTICULARLY ITS DEPICTION OF SATURATION ON THE ISENTROPIC SURFACES. ESSENTIALLY USED A BLEND OF THE GFS AND SREF GUIDANCE FOR THE FORECAST OVER THE NEXT FEW DAYS. ONCE TONIGHT/S SYSTEM MOVES BY... THE NEXT FEATURE OF INTEREST WILL BE ANOTHER SHORTWAVE MOVING IN ON NORTHWEST UPPER FLOW AND ITS ASSOCIATED ALBERTA CLIPPER SURFACE FEATURE... WHICH WILL SWING THROUGH THE AREA DURING THE LATE SUNDAY THROUGH MONDAY TIME FRAME. THE GOING FORECAST HAD A GOOD HANDLE ON THE EXPECTATIONS FOR THAT SYSTEM IN COMPARISON TO THE LATEST GUIDANCE... WITH ONCE AGAIN JUST SOME MINOR TWEAKS TO SPEED THE TIMING OF THINGS. SCT-BKN LOW CLOUDS WERE PRESENT OVER MUCH OF THE AREA THIS MORNING... LINGERING ON THE BACKSIDE OF THE LOW LEVEL THERMAL TROUGH. AS WARM ADVECTION CONTINUES TO INCREASE THESE LOW CLOUDS WILL MOVE EAST AND/OR SCOUR OUT. HOWEVER... THEY WILL BE QUICKLY REPLACED BY RAPIDLY INCREASING MID AND HIGH CLOUDS THIS MORNING DUE TO THE WARM ADVECTION AHEAD OF THE NEXT SHORTWAVE. THIS SYSTEM WILL BE A QUICK HITTER... IMPACTING THE CWFA FROM NORTHWEST TO SOUTHEAST... PRIMARILY BETWEEN 21Z AND 06Z. DEEP LAYER SATURATION COMES INTO BETTER ALIGNMENT AS THE SYSTEM MOVES THROUGH THE AREA... SO THE BETTER CHANCES FOR PCPN AND HIGHER SNOWFALL TOTALS WILL BE OVER THE NORTHEAST AND EASTERN PORTION OF THE AREA. THE BULK OF THE FORCING WILL BE DUE TO ISENTROPIC ASCENT OWING TO PRESSURE ADVECTION... ALONG AND AHEAD OF THE 925-500MB TROUGH AXIS. USED THE 285K ISENTROPIC SURFACE AS A PROXY FOR THE ARRIVAL OF PCPN AND THE LOCATION OF HIGHEST POPS AND GREATEST PCPN. MIXING RATIOS ON THIS SURFACE NEAR 700MB LOOK TO BE ON THE ORDER OF 1-2 G/KG... WHICH WOULD SUGGEST 2-4 INCHES FOR A 12-HOUR EVENT... BUT THE WINDOW OF OPPORTUNITY FOR THIS SYSTEM IS AROUND 4 OR 5 HOURS WHICH SUGGESTS MORE OF A 1-2 INCH EVENT FOR MOST LOCATIONS. QPF FROM THE GFS IS GENERALLY BETWEEN ONE AND TWO TENTHS OF AN INCH... WHICH WOULD ALSO FALL INTO THAT BALLPARK. A LOOK AT FORECAST SOUNDINGS AND LAPSE RATES... AS WELL AS EPV... DOES NOT SUGGEST A GREAT DEAL OF POTENTIAL ENHANCEMENT FROM STABILITY ARGUMENTS... WITH THE BETTER INSTABILITY LOCATED AOA 15K FEET... WHICH IS WELL ABOVE THE DENDRITIC GROWTH LAYER WHICH IS AROUND 10K FT. LAPSE RATES ARE ACTUALLY FAIRLY POOR IN THAT LAYER... WHICH DOES RESULT IN A DEEPER DENDRITIC GROWTH LAYER BUT ONE WHICH MAY NOT HAVE AUGMENTED UPWARD MOTION DUE TO INSTABILITY. SO... IN TERMS OF SNOWFALL RATIOS... WOULD BE TOUGH TO STRAY TO FAR FROM A CLIMATOLOGICAL OR EXPECTED VALUE FOR THE GIVEN AIRMASS... WHICH IS PROBABLY CLOSER TO 14 TO 1. SO... WILL GENERALLY PAINT 1 TO 2 INCHES OF SNOWFALL... WITH SOME MAXES BETWEEN 2 AND 3 OVER THE EASTERN PORTION OF THE FORECAST AREA WHERE THE WINDOW OF OPPORTUNITY WILL BE SLIGHTLY LONGER GIVEN A BETTER PERIOD OF DEEP LAYER SATURATION. SOUTHWEST WINDS WILL INCREASE THROUGH THE DAY TODAY AS THE GRADIENT STRENGTHENS... ALTHOUGH THE STRONGEST WINDS WILL BE WITH THE POST-FRONTAL COLD ADVECTION LATER TONIGHT AND SATURDAY MORNING WHEN NORTHWEST WINDS WILL GUST NEAR 30 MPH WORKING TO BLOW AROUND THE NEW FALLEN SNOW. AT THIS POINT SNOWFALL TOTALS AND EXPECTED WINDS DURING THE TIME OF FALLING SNOW LOOK LIKE THEY WILL NOT NECESSITATE AN ADVISORY... ALTHOUGH THIS WILL NEED TO BE MONITORED BY LATER SHIFTS. RIDGING AND ANTICYCLONIC FLOW LOOK TO BUILD IN QUICKLY BEHIND THE SYSTEM ON SATURDAY... WITH JUST SOME MORNING FLURRIES OVER THE EAST AND OTHERWISE DECREASING CLOUDS THROUGH THE DAY. HOWEVER... IT WON/T TAKE LONG FOR RETURN FLOW TO SET BACK UP... WITH WARM ADVECTION WORKING BACK IN BY SUNDAY AFTERNOON AND INCREASING MARKEDLY SUNDAY NIGHT AS THINGS SATURATE THROUGH THE COLUMN. WILL MAINTAIN THE IDEA OF INCREASING POPS FROM WEST TO EAST SUNDAY AFTERNOON AND SUNDAY NIGHT WITH HIGH CHANCE POPS. LATER FORECASTS WILL PROBABLY BE ABLE TO BUMP THE POPS UP FURTHER ONCE THE TIMING IS NAILED DOWN A BIT BETTER. THIS SHORTWAVE WILL SWING THROUGH ON MONDAY... DRIVING THE COLD FRONT THROUGH THE CWFA MONDAY AFTERNOON AND EVENING... WITH THE BOUNDARY LAYER FLOW QUICKLY BECOMING ANTICYCLONIC ONCE AGAIN WHICH SHOULD BRING A QUICK END TO PCPN MONDAY NIGHT. MADE NO ADJUSTMENTS TO THE GOING FORECAST BEYOND MONDAY. && .AVIATION.../06Z TAF ISSUANCE/ ...ACCUMULATING SNOW/IFR CONDS EXPECTED LATE AFTERNOON/EARLY EVENING FRIDAY... FAIRLY QUIET WEATHER IN THE NEAR TERM WITH HIGH PRESSURE SETTLING TO THE SOUTHWEST OF THE REGION. 2500 TO 4000FT CLOUDS CONTINUE TO FILL THE SKIES TONIGHT. LARGE BREAK IN THE CLOUDS NOW PASSING OVER CENTRAL MN AND WESTERN WI BUT SATELLITE IMAGERY SHOWS MORE 3000 TO 4000 FT CLOUDS UPSTREAM HEADED THIS WAY. OPTED FOR MOSTLY BROKEN SKIES INTO THE MORNING HOURS. WEST-NORTHWEST WINDS WILL BECOME SOUTHWESTERLY LATE TONIGHT AND THROUGH THE MORNING AHEAD OF AN ADVANCING ALBERTA CLIPPER. EXCEPT FOR A FEW BOUTS OF 2500 TO 3000 FT CIGS TONIGHT VFR CONDITIONS WILL PREVAIL INTO THE EARLY/MID AFTERNOON AT ALL SITES. MID CLOUDS WILL RAPIDLY INCREASE FROM MORNING ONWARD AHEAD OF THE CLIPPER. THIS CLIPPER LOOKS TO BE BETTER ORGANIZED/STRONGER THAN RECENT SYSTEMS THUS WIDESPREAD SNOWFALL LOOKS MORE LIKELY. EXPECT A 3 TO 5 HOUR WINDOW OF LOW CONDITIONS UNDER INTENSE SNOWFALL...ESPECIALLY AS THE SYSTEM ENTERS EAST CENTRAL MN AND WEST CENTRAL WI FRIDAY EVENING...WITH LARGER WINDOW OF MVFR CONDS WITH LIGHTER SNOW. CEILINGS WILL QUICKLY FALL AS THE SYSTEM APPROACHES WITH SNOW STARTING SOON AFTER. SNOW SHOULD BEGIN AT KAXN BY LATE AFTERNOON AND MOVE QUICKLY SOUTHEAST STARTING AT KSTC AND KRWF AFTER 23Z OR SO. KMSP AND KRNH WILL QUICKLY SEE DETERIORATING CONDITIONS AROUND/JUST AFTER 00-01Z WITH KEAU STARTING AROUND 02-03Z. WILL NEED TO WATCH THIS TIMING AS IT MAY NEED TO BE ADJUSTED AN HOUR OR SO IN EITHER DIRECTION. SNOW SHOULD ACCUMULATE QUICKLY WITH AN INCH OR 2 AT KAXN AND KRWF WITH 2 TO 3 AT KSTC/KRNH/KEAU. VISIBILITY IS EXPECTED TO DROP TO 1 TO 2 SM AT KAXN/KSTC/KRWF AND TO LESS THAN 1 SM AT KMSP/KRNH/KEAU. CIGS OF 500 TO 800 FEET ARE ALSO POSSIBLE AT THESE THREE SITES UNDER THE HEAVIEST SNOWFALL WITH CIGS PREDOMINATELY BETWEEN 1000 AND 2000 FT OUTSIDE OF THE HEAVIEST SNOW. WINDS WILL QUICKLY TURN WESTERLY TO NORTHWESTERLY AS THE SNOW WINDS DOWN AND BECOME GUSTY IN THE WEST CREATING SOME BLOWING SNOW CONCERNS. HAVE INDICATED MVFR VIS IN THE BLSN AT KAXN/KRWF/KSTC BUT WILL HAVE TO CONTINUE TO WATCH THIS THREAT. LIGHT SNOW/FLURRIES ALSO EXPECTED THROUGH MUCH OF THE NIGHT. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ TRH/MDB mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 1019 PM CST FRI DEC 5 2008 .UPDATE... CLOUD COVER AND MIXED BOUNDARY LAYER WILL KEEP LOW TEMPERATURES UP TONIGHT. VORT MAX HAS MOVED THROUGH WITH MID LEVEL FORCING AND MIXED LIGHT PRECIPITATION ENDING. HAVE REMOVED PRECIPITATION FOR THE REMAINDER OF THE NIGHT. && .PREV DISCUSSION... /ISSUED 256 PM CST FRI DEC 5 2008/ DISCUSSION... MID LEVEL COLD FRONT WILL DRAPE THROUGH NCNTL NEB THIS EVENING ACTING AS A FOCUS FOR VERY LIGHT SNOW...POSSIBLY MIXED WITH RAIN BEFORE NIGHTFALL. THIS FRONT WILL DRAPE ACROSS THE NERN PORTION OF THE FCST AREA SATURDAY PRODUCING WIDESPREAD CLOUDINESS AND PERHAPS SOME LIGHT SNOW. THE FRONT AND WARM AIR ADVECTION BEGIN OPERATING SATURDAY NIGHT AS BOTH THE NAM AND GFS INDICATE LIGHT SNOW DEVELOPING SATURDAY NIGHT FOR A TIME. LESS THAN AN INCH OF SNOW IS EXPECTED. FOR SUNDAY...THE WARM AIR WINS OUT AS THE WARM FRONT PUSHES EAST. ALL AREAS SHOULD CLEAR OUT AT THE LOWER LEVELS BUT PERSISTENT MID AND UPPER LEVEL MOISTURE WILL REMAIN ACROSS THE CENTRAL PLAINS. THE WARM AIR SHOULD BE SUFFICIENT FOR TEMPERATURES TO RISE INTO THE 40S ACROSS MOST OF THE AREA WITH 30S IN THE FAR ERN PTN OF THE FCST AREA. MONDAY...A COLD FRONT WILL DROP THROUGH THE FCST AREA. THE ECMWF IS VERY ACTIVE SUGGESTING A FAIRLY WIDESPREAD RAIN-SNOW EVENT MONDAY AND MONDAY NIGHT. THE GFS...NAM12...NOGAPS AND GEM INDICATE THE BEST FORCING WILL BE ACROSS WRN KS AND ERN COLO. THE ECMWF HAS NOT BEEN FULLY DISCOUNTED SO 20 TO 30 POPS BLANKET THE FCST AREA MONDAY AND MONDAY NIGHT. LATER FCSTS CAN RAISE OF LOWER THE POP AS THE MODELS COME INTO BETTER AGREEMENT. THE PROBLEM IS SOME FISHY UPPER LEVEL ENERGY ACROSS THE ERN PAC WHICH SOME MODELS PHASE FARTHER SOUTH VS THE ECMWF WHICH OPERATES FARTHER NORTH. IF THE ECMWF IS WRONG THEN ONLY SWRN NEB WILL GET PCPN FROM THIS SYSTEM. TUESDAY AND WEDNESDAY...TEMPERATURES MODERATE TO SEASONABLE LEVELS AS A WARM FRONT DEVELOPS AND PUSHES EAST ACROSS NEB. THE FCST IS DRY DURING THIS TIME. THURSDAY AND FRIDAY...A WEAK COLD FRONT WOBBLES THROUGH THE FCST AREA...PRESUMABLY ACTING AS A FOCUS FOR SNOW SHOWERS. OUR BEST GUESS IS 20S NORTH AND 30S SOUTH FOR HIGHS BUT THIS MAY BE TOO COLD. HPC SET TEMPERATURES IN THE 40S AND 50S THURSDAY WITH A COOL DOWN INTO THE 20S AND 30S FRIDAY. THESE GRIDS WERE DISCARDED FOR SOMETHING CLOSER TO CLIMO...ATLEAST ON THURSDAY WHEN IT WAS OBVIOUS A COLD FRONT WOULD DROP THROUGH. CLEARLY THE ECMWF AND GFS ARE WOBBLING THIS FAR OUT IN THE FCST. HOWEVER THE GFS ENSEMBLE SUPPORTS THE COOLER ECMWF. AVIATION... MID CLOUDS CONTINUING TO INCREASE ACROSS ESPECIALLY IN THE KVTN VCNTY THIS AFTERNOON...WITH CEILING HEIGHTS LOWERING WITH TIME. SOUNDING PROFILES INDICATE A SUBSTANTIAL DRY LAYER BELOW 6K FT OR SO THAT WILL NEED TO COOL/MOISTEN BEFORE PRECIP WILL BE REALIZED AT THE SFC. WOULD EXPECT THAT ANY SN WILL BE VERY LIGHT AT BEST AT KVTN...THEREFORE MAIN CONCERN WILL BE POTENTIAL FOR IFR CONDITIONS DUE TO CEILINGS. WITH BETTER FORCING INDICATED AT KVTN THAN KLBF...WET BULB EFFECT SHOULD ALLOW FOR A LOW CLOUD FORMATION BY LATE EVENING THROUGH THE OVERNIGHT HOURS. IN FACT RH TIME HEIGHTS AND SOUNDING PROFILES FROM RUC/NAM/LOCAL WRF ARW SHOULD THE LOWEST LAYER CONTINUING TO BE SATURATED THRU 18Z FOR KVTN. NO PRECIP MENTIONED FOR KVTN SINCE ANY SN WOULD BE VERY LIGHT...BETTER CHANCES FOR MORE FLURRIES FURTHER E. AS FOR KLBF...THOUGH CLOUD HEIGHTS WILL BE LOWERING...MOST SOUNDING PROFILES SHOW CLOUDS REMAINING ABOVE MVFR SO HAVE TRENDED TWD LOWER RANGE OF IFR FOR NOW. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ POWER ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTH PLATTE NE 256 PM CST FRI DEC 5 2008 .DISCUSSION... MID LEVEL COLD FRONT WILL DRAPE THROUGH NCNTL NEB THIS EVENING ACTING AS A FOCUS FOR VERY LIGHT SNOW...POSSIBLY MIXED WITH RAIN BEFORE NIGHTFALL. THIS FRONT WILL DRAPE ACROSS THE NERN PORTION OF THE FCST AREA SATURDAY PRODUCING WIDESPREAD CLOUDINESS AND PERHAPS SOME LIGHT SNOW. THE FRONT AND WARM AIR ADVECTION BEGIN OPERATING SATURDAY NIGHT AS BOTH THE NAM AND GFS INDICATE LIGHT SNOW DEVELOPING SATURDAY NIGHT FOR A TIME. LESS THAN AN INCH OF SNOW IS EXPECTED. FOR SUNDAY...THE WARM AIR WINS OUT AS THE WARM FRONT PUSHES EAST. ALL AREAS SHOULD CLEAR OUT AT THE LOWER LEVELS BUT PERSISTENT MID AND UPPER LEVEL MOISTURE WILL REMAIN ACROSS THE CENTRAL PLAINS. THE WARM AIR SHOULD BE SUFFICIENT FOR TEMPERATURES TO RISE INTO THE 40S ACROSS MOST OF THE AREA WITH 30S IN THE FAR ERN PTN OF THE FCST AREA. MONDAY...A COLD FRONT WILL DROP THROUGH THE FCST AREA. THE ECMWF IS VERY ACTIVE SUGGESTING A FAIRLY WIDESPREAD RAIN-SNOW EVENT MONDAY AND MONDAY NIGHT. THE GFS...NAM12...NOGAPS AND GEM INDICATE THE BEST FORCING WILL BE ACROSS WRN KS AND ERN COLO. THE ECMWF HAS NOT BEEN FULLY DISCOUNTED SO 20 TO 30 POPS BLANKET THE FCST AREA MONDAY AND MONDAY NIGHT. LATER FCSTS CAN RAISE OF LOWER THE POP AS THE MODELS COME INTO BETTER AGREEMENT. THE PROBLEM IS SOME FISHY UPPER LEVEL ENERGY ACROSS THE ERN PAC WHICH SOME MODELS PHASE FARTHER SOUTH VS THE ECMWF WHICH OPERATES FARTHER NORTH. IF THE ECMWF IS WRONG THEN ONLY SWRN NEB WILL GET PCPN FROM THIS SYSTEM. TUESDAY AND WEDNESDAY...TEMPERATURES MODERATE TO SEASONABLE LEVELS AS A WARM FRONT DEVELOPS AND PUSHES EAST ACROSS NEB. THE FCST IS DRY DURING THIS TIME. THURSDAY AND FRIDAY...A WEAK COLD FRONT WOBBLES THROUGH THE FCST AREA...PRESUMABLY ACTING AS A FOCUS FOR SNOW SHOWERS. OUR BEST GUESS IS 20S NORTH AND 30S SOUTH FOR HIGHS BUT THIS MAY BE TOO COLD. HPC SET TEMPERATURES IN THE 40S AND 50S THURSDAY WITH A COOL DOWN INTO THE 20S AND 30S FRIDAY. THESE GRIDS WERE DISCARDED FOR SOMETHING CLOSER TO CLIMO...ATLEAST ON THURSDAY WHEN IT WAS OBVIOUS A COLD FRONT WOULD DROP THROUGH. CLEARLY THE ECMWF AND GFS ARE WOBBLING THIS FAR OUT IN THE FCST. HOWEVER THE GFS ENSEMBLE SUPPORTS THE COOLER ECMWF. && .AVIATION... MID CLOUDS CONTINUING TO INCREASE ACROSS ESPECIALLY IN THE KVTN VCNTY THIS AFTERNOON...WITH CEILING HEIGHTS LOWERING WITH TIME. SOUNDING PROFILES INDICATE A SUBSTANTIAL DRY LAYER BELOW 6K FT OR SO THAT WILL NEED TO COOL/MOISTEN BEFORE PRECIP WILL BE REALIZED AT THE SFC. WOULD EXPECT THAT ANY SN WILL BE VERY LIGHT AT BEST AT KVTN...THEREFORE MAIN CONCERN WILL BE POTENTIAL FOR IFR CONDITIONS DUE TO CEILINGS. WITH BETTER FORCING INDICATED AT KVTN THAN KLBF...WET BULB EFFECT SHOULD ALLOW FOR A LOW CLOUD FORMATION BY LATE EVENING THROUGH THE OVERNIGHT HOURS. IN FACT RH TIME HEIGHTS AND SOUNDING PROFILES FROM RUC/NAM/LOCAL WRF ARW SHOULD THE LOWEST LAYER CONTINUING TO BE SATURATED THRU 18Z FOR KVTN. NO PRECIP MENTIONED FOR KVTN SINCE ANY SN WOULD BE VERY LIGHT...BETTER CHANCES FOR MORE FLURRIES FURTHER E. AS FOR KLBF...THOUGH CLOUD HEIGHTS WILL BE LOWERING...MOST SOUNDING PROFILES SHOW CLOUDS REMAINING ABOVE MVFR SO HAVE TRENDED TWD LOWER RANGE OF IFR FOR NOW. && .LBF WATCHES/WARNINGS/ADVISORIES...NONE. && $$ CDC/JWS ne AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 402 AM EST SAT DEC 6 2008 .SYNOPSIS...CHILLY HIGH PRESSURE WILL BUILD INTO NORTH CAROLINA FROM THE WEST OVERNIGHT...QUICKLY MOVING OFFSHORE DURING THE DAY ON SATURDAY. A STRONG UPPER LEVEL DISTURBANCE AND SURFACE COLD FRONT WILL SWING EAST THROUGH THE AREA SATURDAY EVENING...BRINGING A REINFORCING SHOT OF COLDER AND DRIER INTO THE REGION THROUGH MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 AM SATURDAY... HIGH PRESSURE BUILDING OVER THE AREA WILL RESULT IN SOME SUN THROUGH THE LATE MORNING. CLOUDINESS WILL INCREASE FROM THE NORTHWEST... AS A LOW PRESSURE CENTER OVER THE GREAT LAKES WITH ITS ASSOCIATED COLD FRONT APPROACHES THE REGION FROM THE NORTH THIS AFTERNOON AND SWEEPS ACROSS THE AREA TONIGHT. THERE ARE SOME DIFFERENCES IN THE MODELS... SOUNDING DATA DOES SHOW THE GFS HAS SOME LOW LEVEL MOISTURE DURING THE AFTERNOON AROUND 5 THOUSAND FEET... WHILE THE NAM IS SOMEWHAT DRY THROUGH THE COLUMN. THE CHANCE OF PRECIPITATION WILL REMAIN IN THE SLIGHT CHANCE CATEGORY... AND WILL KEEP THE SLIGHT CHANCE OF RAIN OR SNOW ACROSS THE NORTHERN PORTION SINCE PASSING THROUGH VERY DRY...COLD AIR AT THE SURFACE A FEW FLAKES MAY MAKE TO THE SURFACE. HIGHS WILL RANGE FROM THE MID 40S IN THE NORTHWEST TO THE LOWER 50S IN THE SOUTHEAST. LOWS TONIGHT WILL RANGE FROM THE MID 20S ACROSS THE NORTHWEST TO THE MID 30S OVER THE SOUTHEAST. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 310 AM SATURDAY... POLAR HIGH PRESSURE WILL BUILD OVER THE REGION FROM THE NORTHWEST ON SUNDAY. THIS SYSTEM COMBINED WITH STRONG UPPER LEVEL TROUGH TO THE NORTH/NORTHEAST WILL RESULT IN STRONG GUSTY WINDS. SUSTAINED SURFACE WINDS WILL BE AROUND 15 MPH WITH POSSIBLE GUSTS TO AT LEAST 25 MPH. WITH THE STRONG COLD AIR ADVECTION PREFER THE MET GUIDANCE... WITH HIGHS IN THE LOWER 40S NORTHWEST TO AROUND 50 IN THE SOUTHEAST. HIGH PRESSURE WILL SETTLE OVER THE AREA TONIGHT. LOWS WILL BE IN THE 20S. AS THE SURFACE FEATURE MOVES EAST AND WINDS SHIFT TO THE SOUTH... WE CAN EXPECT AN INCREASE IN TEMPERATURES. THERE WILL ALSO BE AN INCREASE IN MOISTURE AND CLOUDS DUE TO THE SOUTHERLY FLOW AT THE SURFACE... AND ALOFT AS WESTERLY FLOW ADVECTS MOISTURE EASTWARD FROM A DEVELOPING SYSTEM OVER TEXAS. HIGHS WILL RANGE FROM THE MID 40S TO LOWER 50S. CLOUDS COVER MONDAY NIGHT WILL HOLD TEMPERATURES IN THE 30S. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 400 AM... WHEELS QUICKLY FALL OFF THE WAGON AS SIGNIFICANT MODEL DIFFERENCES BEGIN TO APPEAR BEYOND 48 HOURS (MONDAY MORNING) AT 500 MILLIBARS. PLACEMENT AND STRENGTH OF SHORT WAVE ENERGY PROFOUNDLY AFFECT THE FORECAST AND CONFIDENCE PRETTY MUCH APPROACHES ZERO REGARDING THE LATER PERIODS (THURSDAY NIGHT AND FRIDAY). SURFACE HIGH PRESSURE WELL OFFSHORE TUESDAY MORNING WITH PRESSURE GRADIENTS TIGHTENING SURFACE AND ALOFT THROUGHOUT THE DAY. WITH TEMPERATURES WARMING ALOFT AND SOUTHWEST FLOW INCREASING... ISENTROPIC LIFT OVER THE SURFACE COOL POOL COULD PRODUCE RAIN. LIMITED MOISTURE SEEMS TO BE THE LIMITING FACTOR PREVENTING RAIN CHANCES FROM GOING TO LIKELY OR HIGHER IN THIS FORECAST FOR TUESDAY. COLD FRONT APPROACHES THE MOUNTAINS TUESDAY NIGHT. WINDS INCREASE TO 45 KNOTS OR HIGHER JUST OFF THE SURFACE WEDNESDAY AND GFS MODEL HELICITY QUITE LARGE AT 12Z WEDNESDAY (GREATER THAN 350). LCL LESS THAN 2500 FEET. THE HOPE IS THAT AN EARLY RAIN AND LOW CLOUDINESS PROVIDE ENOUGH SURFACE STABILITY TO MAKE THIS A NON SEVERE EVENT. THIS IS THE CURRENT THINKING BUT THE MARGIN FOR ERROR IS SLIM. THIS EVENT WILL HAVE TO BE CLOSELY WATCHED. TIMING WOULD BE FOR A DAYTIME EVENT WEDNESDAY. HAVE RAISED RAIN CHANCES TO HIGH LIKELY WEDNESDAY WITH THE THOUGHT CHANCES WILL GO CATEGORICAL IN FUTURE FORECASTS. RAINFALL AMOUNTS IN EXCESS OF ONE HALF INCH EXPECTED AT THIS TIME. ECMWF FORECASTS ANOTHER GULF LOW TO LIFT NORTHEAST FRIDAY PRODUCING ANOTHER RAIN EVENT THURSDAY NIGHT AND FRIDAY. ITS TRACK HAS THE LOW SOUTHEAST OF CENTRAL NORTH CAROLINA WHICH COULD BE PROBLEMATIC FOR THE END OF THE EVENT REGARDING PRECIPITATION TYPE. AS STATED EARLIER... CONFIDENCE IS LESS THAN LOW... AND WILL LEAVE SMALL RAIN CHANCES CURRENTLY FORECAST ALONE AT THIS TIME AS HAVE NO CONFIDENCE IN WHICH WAY TO SHIFT THEM. EXPECTING TEMPERATURES TO RISE OVERNIGHT TUESDAY NIGHT AHEAD OF THE FRONT WITH LOW TEMPERATURES OCCURRING WELL BEFORE MIDNIGHT. GFS IS TOO DEEP WITH THE APPROACHING LOW AND THEREFORE ADVECTS TOO MUCH WARMTH INTO NORTH CAROLINA. HOWEVER TEMPERATURES IN THE 50S SUNRISE WEDNESDAY LIKELY FOR MOST OF CENTRAL NORTH CAROLINA. AS FRONT SWEEPS THROUGH THE REGION... TEMPERATURES NOT LIKELY TO RISE MUCH AND THEN FALL DURING THE AFTERNOON... IF THE CURRENT TIMING HOLDS TRUE. WEDNESDAY HIGHS IN THE FIFTIES. MORNING LOWS FALL INTO THE MID TO UPPER 30S THURSDAY MORNING BEFORE DROPPING SIX TO EIGHT DEGREES FRIDAY MORNING. THURSDAY HIGHS IN THE 40S WITH LOW 50S FRIDAY. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... AS OF 130 AM... CIRRUS LEVEL MOISTURE EARLY THIS MORNING SHOULD PUSH EAST BY MID MORNING. LARGE PATCH OF STRATUS NEAR 6000 FEET OVER THE NORTHERN FOOTHILLS AND NORTHWEST PIEDMONT WITH ISOLATED CEILINGS AT THIS LEVEL AT TIMES WEST OF THE COASTAL PLAIN. ROCKY MOUNT WITH LOCALIZED LIFR CEILING AT TIMES UNTIL SHORTLY AFTER SUNRISE. RUC MODEL IS SHOWING STRATUS DISSIPATING TOWARD SUNRISE AS MID LEVEL WINDS BECOME PARALLEL TO THE MOUNTAINS AND THIS IS ACCEPTED. MODELS MOSTLY IN AGREEMENT IN DEVELOPING A LOW OFF THE CAROLINA COAST AS MOISTURE INCREASES ON SOUTHWEST WINDS ALOFT. FREEZING LEVELS DROPPING BELOW 10000 FEET IN THE NORTH TONIGHT WITH TINY PRECIPITATION CHANCES AFTER SUNSET... MAINLY NORTH OF HIGHWAY 64. VFR CONDITIONS EXPECTED SATURDAY NIGHT INTO MONDAY NIGHT. COMPUTER MODELS CONTINUE TO SHOW A DEVELOPING STORM SYSTEM WELL TO OUR SOUTHWEST TOWARD MID WEEK THAT MAY PRODUCE VARIOUS ADVERSE AVIATION CONDITIONS FROM TUESDAY THROUGH WEDNESDAY AND POSSIBLY BEYOND... SO AVIATION INTERESTS SHOULD STAY TUNED FOR LATER FORECASTS. && .FIRE WEATHER... MARGINALLY ADVERSE FIRE WEATHER CONDITIONS ARE POSSIBLE ON SUNDAY. THE COMBINATION OF DEEPENING LOW PRESSURE AND STRONG HIGH PRESSURE BUILDING IN FROM THE WEST WILL PRODUCE SUSTAINED WINDS AROUND 15 MPH AND GUSTS TO AROUND 25 MPH ON SUNDAY. IN ADDITION... AS VERY DRY LOW LEVEL AIR SPILLS INTO THE AREA... RELATIVE HUMIDITIES WILL BOTTOM OUT AT 21-26 PERCENT IN THE EARLY TO MID AFTERNOON. THOSE WITH FIRE WEATHER INTERESTS SHOULD KEEP A CLOSE EYE ON THE LATEST FORECASTS AND CONDITIONS THROUGH THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RHJ NEAR TERM...RHJ SHORT TERM...RHJ nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 310 AM EST SAT DEC 6 2008 .SYNOPSIS... CHILLY HIGH PRESSURE WILL BUILD OVER THE REGION FROM THE WEST... CONTINUE TO THE EAST TODAY... THEN MOVE OFFSHORE THIS EVENING. AN ALBERTA CLIPPER WITH ITS ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION THIS EVENING. COLD HIGH PRESSURE WILL ONCE AGAIN TAKE ITS GRIP ON CENTRAL NORTH CAROLINA ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 300 AM SATURDAY... HIGH PRESSURE BUILDING OVER THE AREA WILL RESULT IN SOME SUN THROUGH THE LATE MORNING. CLOUDINESS WILL INCREASE FROM THE NORTHWEST... AS A LOW PRESSURE CENTER OVER THE GREAT LAKES WITH ITS ASSOCIATED COLD FRONT APPROACHES THE REGION FROM THE NORTH THIS AFTERNOON AND SWEEPS ACROSS THE AREA TONIGHT. THERE ARE SOME DIFFERENCES IN THE MODELS... SOUNDING DATA DOES SHOW THE GFS HAS SOME LOW LEVEL MOISTURE DURING THE AFTERNOON AROUND 5 THOUSAND FEET... WHILE THE NAM IS SOMEWHAT DRY THROUGH THE COLUMN. THE CHANCE OF PRECIPITATION WILL REMAIN IN THE SLIGHT CHANCE CATEGORY... AND WILL KEEP THE SLIGHT CHANCE OF RAIN OR SNOW ACROSS THE NORTHERN PORTION SINCE PASSING THROUGH VERY DRY...COLD AIR AT THE SURFACE A FEW FLAKES MAY MAKE TO THE SURFACE. HIGHS WILL RANGE FROM THE MID 40S IN THE NORTHWEST TO THE LOWER 50S IN THE SOUTHEAST. LOWS TONIGHT WILL RANGE FROM THE MID 20S ACROSS THE NORTHWEST TO THE MID 30S OVER THE SOUTHEAST. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 310 AM SATURDAY... POLAR HIGH PRESSURE WILL BUILD OVER THE REGION FROM THE NORTHWEST ON SUNDAY. THIS SYSTEM COMBINED WITH STRONG UPPER LEVEL TROUGH TO THE NORTH/NORTHEAST WILL RESULT IN STRONG GUSTY WINDS. SUSTAINED SURFACE WINDS WILL BE AROUND 15 MPH WITH POSSIBLE GUSTS TO AT LEAST 25 MPH. WITH THE STRONG COLD AIR ADVECTION PREFER THE MET GUIDANCE... WITH HIGHS IN THE LOWER 40S NORTHWEST TO AROUND 50 IN THE SOUTHEAST. HIGH PRESSURE WILL SETTLE OVER THE AREA TONIGHT. LOWS WILL BE IN THE 20S. AS THE SURFACE FEATURE MOVES EAST AND WINDS SHIFT TO THE SOUTH... WE CAN EXPECT AN INCREASE IN TEMPERATURES. THERE WILL ALSO BE AN INCREASE IN MOISTURE AND CLOUDS DUE TO THE SOUTHERLY FLOW AT THE SURFACE... AND ALOFT AS WESTERLY FLOW ADVECTS MOISTURE EASTWARD FROM A DEVELOPING SYSTEM OVER TEXAS. HIGHS WILL RANGE FROM THE MID 40S TO LOWER 50S. CLOUDS COVER MONDAY NIGHT WILL HOLD TEMPERATURES IN THE 30S. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 PM FRIDAY... AN UNSETTLED WEATHER PATTERN IS STILL EXPECTED DURING THIS PORTION OF THE FORECAST. HOWEVER...SPECIFICS REMAIN DIFFICULT TO PIN DOWN DUE TO CONTINUED DIFFERENCES IN HOW THE LONG RANGE MODELS HANDLE NORTHERN/SOUTHERN STREAM PHASING. ON TUESDAY AN UPPER LEVEL WAVE IS EXPECTED TO DIG SOUTH THROUGH THE INTERMOUNTAIN WEST...INTO THE FAR WESTERN GOMEX BY WED. THIS WILL HELP PUSH A FRONTAL ZONE TOWARD THE AREA FROM THE WEST...IN ADDITION TO ALLOWING A MOIST SOUTHWEST FLOW ALOFT (FROM THE GOMEX) TO SETUP OVER THE SOUTHEAST STATES. AS OF THE LATEST 12Z MODEL RUNS...WED LOOKS LIKE A BETTER CHANCE FOR PRECIP THAN TUE...ALTHOUGH QUITE A BIT OF UNCERTAINTY REMAINS THROUGH MID/LATE WEEK. BOTH THE GFS/ECMWF SHOW THE UPPER LEVEL WAVE THAT DIGS INTO THE WESTERN GOMEX CLOSING OFF INTO AN UPPER LOW THURSDAY...WHICH SUBSEQUENTLY MOVES EAST ACROSS THE NORTHERN GOMEX AND THEN NORTHEAST THROUGH THE SOUTHEAST STATES...WITH A SFC LOW DEVELOPING IN THE GULF AND MOVING NORTHEAST ALONG THE SOUTHEAST COAST ON THU/FRI. ALTHOUGH THE GFS/ECMWF ARE NOW SHOWING A MORE SIMILAR PATTERN THROUGH MID/LATE NEXT WEEK...THERE ARE STILL TIMING DIFFERENCES...AND THERE IS ENOUGH UNCERTAINTY TO LEAVE THE EXTENDED FORECAST MORE OR LESS AS IS...WITH THE EXCEPTION OF SOME MINOR TWEAKING TO POPS AND TEMPS. WILL BASICALLY SHOW CHANCE POPS FROM TUE THROUGH FRI...WITH MOSTLY CLOUDY OR OVERCAST SKIES DURING THE ENTIRE PERIOD. TEMPERATURES REMAIN DIFFICULT TO FCST IN THIS PERIOD SINCE THEY WILL HIGHLY DEPEND ON THE TIMING OF FRONTAL PASSAGES... ONSET/DURATION OF PRECIP...AND THE TRACK OF ANY SFC LOW THAT MAY DEVELOP BY MID/LATE WEEK. AT THIS TIME WILL SHOW NEAR NORMAL TEMPS ON TUE/WED...WITH BELOW NORMAL TEMPS ON THU/FRI. -VINCENT && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 130 AM... CIRRUS LEVEL MOISTURE EARLY THIS MORNING SHOULD PUSH EAST BY MID MORNING. LARGE PATCH OF STRATUS NEAR 6000 FEET OVER THE NORTHERN FOOTHILLS AND NORTHWEST PIEDMONT WITH ISOLATED CEILINGS AT THIS LEVEL AT TIMES WEST OF THE COASTAL PLAIN. ROCKY MOUNT WITH LOCALIZED LIFR CEILING AT TIMES UNTIL SHORTLY AFTER SUNRISE. RUC MODEL IS SHOWING STRATUS DISSIPATING TOWARD SUNRISE AS MID LEVEL WINDS BECOME PARALLEL TO THE MOUNTAINS AND THIS IS ACCEPTED. MODELS MOSTLY IN AGREEMENT IN DEVELOPING A LOW OFF THE CAROLINA COAST AS MOISTURE INCREASES ON SOUTHWEST WINDS ALOFT. FREEZING LEVELS DROPPING BELOW 10000 FEET IN THE NORTH TONIGHT WITH TINY PRECIPITATION CHANCES AFTER SUNSET... MAINLY NORTH OF HIGHWAY 64. VFR CONDITIONS EXPECTED SATURDAY NIGHT INTO MONDAY NIGHT. COMPUTER MODELS CONTINUE TO SHOW A DEVELOPING STORM SYSTEM WELL TO OUR SOUTHWEST TOWARD MID WEEK THAT MAY PRODUCE VARIOUS ADVERSE AVIATION CONDITIONS FROM TUESDAY THROUGH WEDNESDAY AND POSSIBLY BEYOND... SO AVIATION INTERESTS SHOULD STAY TUNED FOR LATER FORECASTS. && .FIRE WEATHER... MARGINALLY ADVERSE FIRE WEATHER CONDITIONS ARE POSSIBLE ON SUNDAY. THE COMBINATION OF DEEPENING LOW PRESSURE AND STRONG HIGH PRESSURE BUILDING IN FROM THE WEST WILL PRODUCE SUSTAINED WINDS AROUND 15 MPH AND GUSTS TO AROUND 25 MPH ON SUNDAY. IN ADDITION... AS VERY DRY LOW LEVEL AIR SPILLS INTO THE AREA... RELATIVE HUMIDITIES WILL BOTTOM OUT AT 21-26 PERCENT IN THE EARLY TO MID AFTERNOON. THOSE WITH FIRE WEATHER INTERESTS SHOULD KEEP A CLOSE EYE ON THE LATEST FORECASTS AND CONDITIONS THROUGH THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...RHJ NEAR TERM...RHJ SHORT TERM...RHJ LONG TERM...VINCENT FIRE WEATHER...BADGETT nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 130 AM EST SAT DEC 6 2008 .SYNOPSIS... CHILLY HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE WEST. THIS HIGH WILL QUICKLY MOVE EAST AND OFFSHORE BY LATE SATURDAY... AND THEN AN ALBERTA CLIPPER AND ATTENDANT SURFACE COLD FRONT SWINGS THROUGH THE MID ATLANTIC REGION SATURDAY EVENING. COLD HIGH PRESSURE WILL AGAIN BUILD INTO THE AREA ON SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 915 PM FRIDAY... ONLY MINOR CHANGES TO GRIDDED DATABASE. OCCASIONAL SCATTERED HIGH CLOUDINESS...ASSOCIATED WITH THE RIGHT ENTRANCE DIVERGENCE REGION OF THE POLAR JET...WILL PRODUCE MOSTLY CLEAR TO FAIR SKIES OVERNIGHT. MANUAL SURFACE ANALYSIS COLD FRONT HAS PUSHED OFFSHORE...WITH A WEAKENING 1027 MB SURFACE HIGH BUILDING IN FROM THE TENNESSEE VALLEY. THERE REMAINS A PROMINENT DEWPOINT DISCONTINUITY ACROSS THE FORECAST AREA...WITH DEWPOINTS IN THE MID TO UPPER TEENS IN THE NW PIEDMONT...WITH DEWPOINT ACROSS THE CENTRAL PIEDMONT AND COASTAL PLAINS STAYING UP IN THE UPPER 20S TO LOWER 30S. WINDS ARE LIGHT OR CALM ACROSS CENTRAL NC....AND THIS WILL SET THE STAGE FOR GOOD RADIATIONAL COOLING...WITH A RATHER LARGE SPREAD DUE TO THE LARGE DEWPOINT GRADIENT. EXPECT LOWS OF IN THE MID 20S NW PIEDMONT...TO NEAR FREEZING SOUTHEAST. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 235 PM FRIDAY... FOR SATURDAY/SATURDAY NIGHT: SATURDAY SHOULD BEGIN WITH A GOOD BIT OF SUNSHINE BUT WITH INCREASING HIGH CLOUDS TOWARD MIDDAY. A CLIPPER SYSTEM IS STILL EXPECTED TO DROP THROUGH THE MIDWEST LATE FRIDAY NIGHT INTO SATURDAY MORNING... THEN PASS THROUGH NC AND OFF COAST SATURDAY NIGHT. THE NAM REMAINS MORE SUBDUED WITH THIS VORTICITY MAXIMUM AS COMPARED TO THE GFS... WEAKENING IT IN FAVOR OF A STRONGER MAXIMUM TO ITS NW... HOWEVER THERE HAS BEEN A GENERAL MODEL TREND TOWARD A STRONGER WAVE WITH MORE DYNAMIC LIFT AS IT APPROACHES. THE 12Z WRF-ARW IS GENERATING LIGHT PRECIP AMOUNTS ACROSS NORTH CENTRAL NC VERY LATE SATURDAY AFTERNOON THROUGH THE EVENING... AND THE 12Z GFS HAS TRENDED TOWARD GREATER QPF AS WELL... GENERATING SEVERAL HUNDREDTHS LIQUID ACROSS THE ENTIRE PIEDMONT. GIVEN THIS TREND... WILL SLIGHTLY EXPAND AREALLY THE SLIGHT CHANCE POPS SATURDAY AFTERNOON... SWEEPING THEM EAST AND RAISING THEM TO 20-30% SATURDAY EVENING. FORECAST WET BULB PROFILES ARE PRIMARILY BELOW FREEZING EXCEPT FOR THE LOWEST COUPLE THOUSAND FEET WHERE THE AIR IS ALSO MARKEDLY DRIER. BUT GFS FORECAST SOUNDINGS SHOW NEAR SATURATION UP TO -20C... SO A PRECIP TYPE OF LIGHT RAIN AT ONSET AND A MIXTURE OF LIGHT RAIN AND LIGHT SNOW IN THE EVENING NORTH OF HIGHWAY 64 WILL BE RETAINED. THE LOW LEVEL DRY AIR AND APPARENT LACK OF CONCENTRATED STRONG FORCING FOR ASCENT SHOULD LIMIT AMOUNTS SO AS TO BE INSIGNIFICANT... HOWEVER IF IT APPEARS THAT LIFT WILL BE BRIEFLY ENHANCED... WE MAY SEE A SHORT PERIOD OF MOSTLY SNOW MAINLY NEAR THE VA BORDER... BUT AGAIN THE BREVITY OF ANY SUCH OCCURRENCE SHOULD RENDER IT INSIGNIFICANT FOR TRAVELERS. THICKNESSES AND STATISTICAL GUIDANCE AGREE ON HIGHS OF 45-52. LOWS SATURDAY NIGHT 26-34 WITH INCREASING COLD ADVECTION BEHIND THE EXITING WAVE. FOR SUNDAY: THE MID LEVEL LONGWAVE TROUGH AXIS SHIFTS TO OUR NE SUNDAY MORNING AS THE POLAR HIGH BUILDS IN FROM THE NW... AND CONSIDERABLE SUNSHINE IS EXPECTED. WITH RAPIDLY DEEPENING SURFACE PRESSURES OVER THE NORTHEAST STATES... THE RESULTING TIGHTENING MSLP GRADIENT WILL PRODUCE BLUSTERY SURFACE WINDS AROUND 15 MPH WITH GUSTS TO AROUND 25 MPH POSSIBLE (SEE FIRE WEATHER DISCUSSION BELOW). WITH STRONG COLD ADVECTION AND CONSIDERING THE POLAR SOURCE OF THE INCOMING SURFACE HIGH... HAVE LOWERED HIGHS A BIT TO 41-48. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... AS OF 300 PM FRIDAY... MONDAY: THE LATEST 12Z MODEL RUNS CONTINUE TO SHOW SFC HIGH PRESSURE BUILDING ACROSS THE AREA FROM THE WEST ON SUNDAY NIGHT AND MONDAY...WITH UNIDIRECTIONAL FLOW ALOFT. CLEAR SKIES AND NEAR CALM WINDS WILL ALLOW EXCELLENT RADIATIONAL COOLING MON MORNING...AND EXPECT VERY CHILLY LOW TEMP READINGS IN THE LOWER/MID 20S. CLEAR SKIES WILL EVENTUALLY GIVE WAY TO INCREASING MID/UPPER LEVEL CLOUDS BY THE AFT/EVE AS UPPER LEVEL MOISTURE ADVECTS DOWNSTREAM OF AN AREA OF LOW PRESSURE EXPECTED TO DEVELOP ACROSS THE LOWER MIDWEST. FOR TEMPS...WENT WITH A BLEND OF MOS GUIDANCE AND THICKNESSES (1285- 1295M AT 12Z MON UP TO 1310-1325M BY 00Z TUE)...WHICH SUGGEST HIGHS RANGING FROM THE MID 40S TO LOWER 50S. TUESDAY THROUGH FRIDAY: AN UNSETTLED WEATHER PATTERN IS STILL EXPECTED DURING THIS PORTION OF THE FORECAST. HOWEVER...SPECIFICS REMAIN DIFFICULT TO PIN DOWN DUE TO CONTINUED DIFFERENCES IN HOW THE LONG RANGE MODELS HANDLE NORTHERN/SOUTHERN STREAM PHASING. ON TUESDAY AN UPPER LEVEL WAVE IS EXPECTED TO DIG SOUTH THROUGH THE INTERMOUNTAIN WEST...INTO THE FAR WESTERN GOMEX BY WED. THIS WILL HELP PUSH A FRONTAL ZONE TOWARD THE AREA FROM THE WEST...IN ADDITION TO ALLOWING A MOIST SOUTHWEST FLOW ALOFT (FROM THE GOMEX) TO SETUP OVER THE SOUTHEAST STATES. AS OF THE LATEST 12Z MODEL RUNS...WED LOOKS LIKE A BETTER CHANCE FOR PRECIP THAN TUE...ALTHOUGH QUITE A BIT OF UNCERTAINTY REMAINS THROUGH MID/LATE WEEK. BOTH THE GFS/ECMWF SHOW THE UPPER LEVEL WAVE THAT DIGS INTO THE WESTERN GOMEX CLOSING OFF INTO AN UPPER LOW THURSDAY...WHICH SUBSEQUENTLY MOVES EAST ACROSS THE NORTHERN GOMEX AND THEN NORTHEAST THROUGH THE SOUTHEAST STATES...WITH A SFC LOW DEVELOPING IN THE GULF AND MOVING NORTHEAST ALONG THE SOUTHEAST COAST ON THU/FRI. ALTHOUGH THE GFS/ECMWF ARE NOW SHOWING A MORE SIMILAR PATTERN THROUGH MID/LATE NEXT WEEK...THERE ARE STILL TIMING DIFFERENCES...AND THERE IS ENOUGH UNCERTAINTY TO LEAVE THE EXTENDED FORECAST MORE OR LESS AS IS...WITH THE EXCEPTION OF SOME MINOR TWEAKING TO POPS AND TEMPS. WILL BASICALLY SHOW CHANCE POPS FROM TUE THROUGH FRI...WITH MOSTLY CLOUDY OR OVERCAST SKIES DURING THE ENTIRE PERIOD. TEMPERATURES REMAIN DIFFICULT TO FCST IN THIS PERIOD SINCE THEY WILL HIGHLY DEPEND ON THE TIMING OF FRONTAL PASSAGES... ONSET/DURATION OF PRECIP...AND THE TRACK OF ANY SFC LOW THAT MAY DEVELOP BY MID/LATE WEEK. AT THIS TIME WILL SHOW NEAR NORMAL TEMPS ON TUE/WED...WITH BELOW NORMAL TEMPS ON THU/FRI. -VINCENT && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... AS OF 130 AM... CIRRUS LEVEL MOISTURE EARLY THIS MORNING SHOULD PUSH EAST BY MID MORNING. LARGE PATCH OF STRATUS NEAR 6000 FEET OVER THE NORTHERN FOOTHILLS AND NORTHWEST PIEDMONT WITH ISOLATED CEILINGS AT THIS LEVEL AT TIMES WEST OF THE COASTAL PLAIN. ROCKY MOUNT WITH LOCALIZED LIFR CEILING AT TIMES UNTIL SHORTLY AFTER SUNRISE. RUC MODEL IS SHOWING STRATUS DISSIPATING TOWARD SUNRISE AS MID LEVEL WINDS BECOME PARALLEL TO THE MOUNTAINS AND THIS IS ACCEPTED. MODELS MOSTLY IN AGREEMENT IN DEVELOPING A LOW OFF THE CAROLINA COAST AS MOISTURE INCREASES ON SOUTHWEST WINDS ALOFT. FREEZING LEVELS DROPPING BELOW 10000 FEET IN THE NORTH TONIGHT WITH TINY PRECIPITATION CHANCES AFTER SUNSET... MAINLY NORTH OF HIGHWAY 64. VFR CONDITIONS EXPECTED SATURDAY NIGHT INTO MONDAY NIGHT. COMPUTER MODELS CONTINUE TO SHOW A DEVELOPING STORM SYSTEM WELL TO OUR SOUTHWEST TOWARD MID WEEK THAT MAY PRODUCE VARIOUS ADVERSE AVIATION CONDITIONS FROM TUESDAY THROUGH WEDNESDAY AND POSSIBLY BEYOND... SO AVIATION INTERESTS SHOULD STAY TUNED FOR LATER FORECASTS. && .FIRE WEATHER... MARGINALLY ADVERSE FIRE WEATHER CONDITIONS ARE POSSIBLE ON SUNDAY. THE COMBINATION OF DEEPENING LOW PRESSURE AND STRONG HIGH PRESSURE BUILDING IN FROM THE WEST WILL PRODUCE SUSTAINED WINDS AROUND 15 MPH AND GUSTS TO AROUND 25 MPH ON SUNDAY. IN ADDITION... AS VERY DRY LOW LEVEL AIR SPILLS INTO THE AREA... RELATIVE HUMIDITIES WILL BOTTOM OUT AT 21-26 PERCENT IN THE EARLY TO MID AFTERNOON. THOSE WITH FIRE WEATHER INTERESTS SHOULD KEEP A CLOSE EYE ON THE LATEST FORECASTS AND CONDITIONS HEADING THROUGH THE WEEKEND. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...HARTFIELD LONG TERM...VINCENT FIRE WEATHER...BADGETT nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 904 PM CST SAT DEC 6 2008 .DISCUSSION... THE FCST IS ON TRACK...SO NO DRASTIC CHANGES ARE BEING MADE TO IT. SFC PRESSURE FALLS HAVE STARTED ALONG/WEST OF THE VALLEY NOW WITH THE RIDGE AXIS AT 03Z NEAR A KTVF-KBWP LINE. THE COLDEST TEMPS SO FAR HAVE BEEN NEAR CAVALIER /DOWN TO -12 F/ AND KFSE. THE LATTER IS NOT QUITE AS PORTRAYED IN THE FCST...AND SINCE NW MN WILL RADIATE LONGEST /PER SATELLITE IMAGERY AND 00Z RUC/NAM 700-300MB RH PROGS/ IT SEEMS PRUDENT TO LOWER MINS JUST A BIT MORE IN A FEW SPOTS. AGAIN THOUGH...TEMPS WILL STOP THEIR FREE-FALL AND THEN RISE AS CLOUDS INCREASE AND WAA TAKES OVER OFF THE SFC. WE WILL MODEL THE HOURLY TEMP GRIDS ON A MIX OF THE 21/00Z RUC AND 00Z NAM. THE 00Z NAM IS BASICALLY ON TRACK WITH THE SWATH OF -SN EXPECTED TO MOVE ACROSS THE AREA LATE TONIGHT/SUNDAY. MODERATE FRONTOGENSIS IN THE 850-700MB LAYER AND MODERATE 500-300MB Q-VECTOR CONVERGENCE /ALBEIT WEAKER ON THE 00Z RUN/ ARE BOTH NOTED. PERSISTENCE IN GUIDANCE AND UPSTREAM OBS BOTH SUPPORT THE IDEA OF LIKELY POPS WITH THIS BAND. BUT...THERE IS A SIGNAL IN THE 21Z SREF AND NOW THE 00Z NAM FOR A SLIGHTER FASTER PROGRESSION...WHICH IS NOT UNREASONABLE SINCE -SN IS ALREADY ON THE DOORSTEP OF KBIS. WE WILL INCREASE POPS ACCORDINGLY IN OUR WESTERN FA /INCLUDING KDVL/ IN THE 09-12Z TIME FRAME. && .AVIATION... VFR WILL APPLY MUCH OF THE NIGHT...BEFORE AN ALBERTA CLIPPER SPREADS A BAND OF -SN INTO THE KDVL AREA BY 12Z...THE RED RIVER VALLEY 15-18Z...AND THE KBJI AREA THEREAFTER. WE USED UPSTREAM TRENDS AND THE RAPID UPDATE CYCLE MODEL /AS WELL AS THE SIMILARITY TO FRIDAY/S EVENT/ AS A GUIDE IN BRINGING A PERIOD OF IFR VIS THROUGH MOST OF THE TAF SITES WITH THIS SYSTEM. MVFR /OR POSSIBLY LOWER/ CIGS WILL ALSO BE PRESENT WITH THIS SYSTEM ON SUNDAY. && .PREV DISCUSSION... /ISSUED 633 PM CST SAT DEC 6 2008/ DISCUSSION... THE SFC RIDGE AXIS AT 00Z IS SOMEWHERE ALONG A CYWG-KJMS-KABR LINE. WITH 1-2 INCHES OF FRESH SNOW ON THE GROUND IN MOST PLACES THIS IS AN IDEAL RADIATIONAL COOLING SCENARIO...AT LEAST FOR THE NEXT 3-6 HRS BEFORE MID/HIGH LVL CLOUDS AHEAD OF THE NEXT CLIPPER ADD EVEN MORE ISSUES INTO THE TEMP FCST. SFC TEMPS AT 00Z ARE ALREADY BLO 0 F IN MANY LOCALES...SO THE QUESTION BECOMES HOW LOW THEY WILL FALL. TOUGH QUESTION AS ALWAYS...BUT USING THE PRESENT SFC DEWPOINTS UNDER THE RIDGE /-5 TO -12 F/ AND THE 21Z RUC SFC TEMP FIELDS AS A PROXY GIVES AS REASONABLE OF A SOLUTION AS ANY. THE 21Z RUC IS THE ONLY SHORT TERM GUIDANCE EVEN CLOSE TO REALITY AT PRESENT. WE ALSO USED THIS MODEL AS A GUIDE IN BRINGING TEMPS BACK UP ALONG/WEST OF THE VALLEY 06-12Z WITH WAA RAMPING UP OFF THE DECK AND CLOUDS ON THE INCREASE. WE WILL MAKE A QUICK UPDATE TO THE FCST TO ADJUST THE HOURLY AND MINIMUM TEMPS...BUT LEAVE THE REMAINDER OF THE DATABASE UNCHANGED ATTM. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ SCHULTZ/RIDDLE nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 633 PM CST SAT DEC 6 2008 .DISCUSSION... THE SFC RIDGE AXIS AT 00Z IS SOMEWHERE ALONG A CYWG-KJMS-KABR LINE. WITH 1-2 INCHES OF FRESH SNOW ON THE GROUND IN MOST PLACES THIS IS AN IDEAL RADIATIONAL COOLING SCENARIO...AT LEAST FOR THE NEXT 3-6 HRS BEFORE MID/HIGH LVL CLOUDS AHEAD OF THE NEXT CLIPPER ADD EVEN MORE ISSUES INTO THE TEMP FCST. SFC TEMPS AT 00Z ARE ALREADY BLO 0 F IN MANY LOCALES...SO THE QUESTION BECOMES HOW LOW THEY WILL FALL. TOUGH QUESTION AS ALWAYS...BUT USING THE PRESENT SFC DEWPOINTS UNDER THE RIDGE /-5 TO -12 F/ AND THE 21Z RUC SFC TEMP FIELDS AS A PROXY GIVES AS REASONABLE OF A SOLUTION AS ANY. THE 21Z RUC IS THE ONLY SHORT TERM GUIDANCE EVEN CLOSE TO REALITY AT PRESENT. WE ALSO USED THIS MODEL AS A GUIDE IN BRINGING TEMPS BACK UP ALONG/WEST OF THE VALLEY 06-12Z WITH WAA RAMPING UP OFF THE DECK AND CLOUDS ON THE INCREASE. WE WILL MAKE A QUICK UPDATE TO THE FCST TO ADJUST THE HOURLY AND MINIMUM TEMPS...BUT LEAVE THE REMAINDER OF THE DATABASE UNCHANGED ATTM. && .AVIATION... VFR WILL APPLY MUCH OF THE NIGHT...BEFORE AN ALBERTA CLIPPER SPREADS A BAND OF -SN INTO THE KDVL AREA BY 12Z...THE RED RIVER VALLEY 15-18Z...AND THE KBJI AREA THEREAFTER. WE USED UPSTREAM TRENDS AND THE RAPID UPDATE CYCLE MODEL /AS WELL AS THE SIMILARITY TO FRIDAY/S EVENT/ AS A GUIDE IN BRINGING A PERIOD OF IFR VIS THROUGH MOST OF THE TAF SITES WITH THIS SYSTEM. MVFR /OR POSSIBLY LOWER/ CIGS WILL ALSO BE PRESENT WITH THIS SYSTEM ON SUNDAY. && .PREV DISCUSSION... /ISSUED 312 PM CST SAT DEC 6 2008/ SHORT TERM... MAIN FORECAST CHALLENGE IS PCPN. WHEN LOOKING AT THE LATEST SURFACE ANALYSIS...AN AREA OF HIGH PRESSURE EXTENDS THROUGH E ND INTO E SD. WHEN COMPARING THE MODELS...THE MODELS START OUT IN PRETTY GOOD AGREEMENT AND THEN DIVERGE ON SYSTEM TIMING...WITH NAM THE COMPROMISE SOLUTION. THUS...ENDED UP USING THE NAM FOR PCPN TIMING AS WELL AS TEMPS FOR EARLY ON AND THEN TRANSITIONED TO GFS FOR LATER PERIODS. THE HIGH PRESSURE RIDGE SHIFTS OFF TO THE SE TONIGHT AND ANOTHER ALBERTA CLIPPER APPROACHES. WITH GOOD WAA AND A S-SE RETURN FLOW AHEAD OF WARM FRONT OVERNIGHT...ANTICIPATE SNOW TO DEVELOP TOWARDS MORNING AND SPREAD THROUGH E ND AND NW AND WC MN ON SUN...WITH ONE TO TWO INCHES OF NEW SNOW ANTICIPATED. ANOTHER HIGH PRESSURE RIDGE BUILDS INTO THE N PLAINS FROM CANADA FOR MON INTO TUE...SO KEPT THE FORECAST BASICALLY DRY...BUT WILL NEED TO MONITOR CONDITIONS IN NW MN AS SOME MODEL SOUNDINGS INDICATE THE POTENTIAL FOR -ZL OR FLURRIES. THE NEXT CLIPPER APPROACHES ON TUE AFTERNOON...WITH ANOTHER POTENTIAL FOR -SN. LONG TERM... MODELS ARE IN RELATIVELY GOOD AGREEMENT IN THE WED-SAT TIME PERIOD WITH BROAD NW FLOW MAINTAINING A BELOW NORMAL TEMPERATURE REGIME. THE MAIN ISSUES REVOLVE AROUND THE TIMING AND PLACEMENT OF SYSTEMS...AND RESULTANT IMPACT ON THE SENSIBLE WEATHER. A REINFORCING SHOT OF ARCTIC AIR WILL PUSH ACROSS THE CWFA EARLY IN THE EXTENDED...SO HAVE MAINTAINED THE LOW POP WITH BOUNDARY AND UPPER SUPPORT. SHORT BREAK AFTER FROPA WED AS HIGH BUILD IN... GIVING COLD AIRMASS FLURRIES AND DECREASING THE CLOUD COVER. WITH FAST FLOW MOVING NEXT WAVE IN WED NIGHT INTO THU...THIS IS WHEN GFS/DGEX/ECMWF DIVERGE IN DETAILS. DGEX AND GFS HAVE NEXT WAVE MOVING ACROSS THE REGION THU. WELL DEFINED INVERTED TROUGH PROVIDES FOCUS FOR -SN MOVING W TO E ACROSS THE AREA. HIGH BUILDS IN THU NIGHT AND FRI. NEXT WAVE FRI-SAT TIME PERIOD MOVING FAR ENOUGH WEST OF CWFA TO REDUCE RISK OF -SN. DGEX MUCH FARTHER E AND DISCOUNTED. HAVE MODELED LOW POPS ACROSS THE S AS SYSTEM PUSHES LIMITED MOISTURE OVER COLD DOME. SAT DRY UNDER COLD HIGH. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ SCHULTZ/NG/EWENS nd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 935 PM CST SAT DEC 6 2008 .DISCUSSION... PRECIP FORECAST FOR TONIGHT SEEMS TO BE IN PRETTY GOOD SHAPE...WITH BAND OF SNOW DEVELOPING WARM ADVECTION/STRONG ISENTROPIC LIFT ZONE OVER WESTERN DAKOTAS AT THIS TIME. STRONGEST ISENTROPIC LIFT MOVES ACROSS THE CWA 06Z-18Z...WITH ONLY CONCERN FOR TIMING BEING HOW LONG IT WILL TAKE TO FULLY SATURATE BELOW 750-700MB IN THE WAKE OF THE DEPARTING SURFACE RIDGE. TIMING FROM PREVIOUS FORECAST LOOKS GOOD BASED ON LATEST RUNS OF RUC/NAM...AND HAVE MADE VERY FEW CHANGES TO PRECIP FORECAST. TEMPERATURES A LITTLE MORE TRICKY. AS EXPECTED...READINGS OVER CENTRAL AND EASTERN COUNTIES HAVE TANKED WITH MOSTLY CLEAR SKIES AND LIGHT WINDS WITHIN THE SURFACE RIDGE NOW MOVING ACROSS THE AREA. HAVE MADE ADJUSTMENTS TO HOURLY TEMPS TO COOL EASTERN AREAS... ESPECIALLY LOWER DRAINAGE LOCATIONS...DOWN 5-8 DEGREES FROM EARLIER FORECAST. STILL EXPECTING THESE AREAS TO RECOVER SOME THROUGH THE EARLY MORNING AS CLOUDS INCREASE. UPDATED GRIDS/PFM HAVE BEEN SENT AND WILL GET NEW ZFP OUT SHORTLY. && .AVIATION... VFR BCMG MVFR THEN IFR CIGS AND VSBYS IN BAND OF SNOW MOVG GRADUALLY EWD OVER CWA FM 07Z TO 17Z. PATCHY -FZRA OR -FZDZ PSBL NR AND WEST OF JAMES AND MISSOURI VALLEYS SUN MRNG. && .PREV DISCUSSION... COLD DRY SFC RIDGE MOVG EWD OVR CWA TNGT WITH RESULTANT DROP IN EVE TEMPS...FLWD BY INCRG SELY FLOW AND RISING TEMPS FM WEST TO EAST AFT MIDN. WENT HIGH END LIKELY POPS WITH EXPCD BAND OF SNOW DVLPG JAMES VALLEY WEST AFT MIDN...MOVG EWD OVER CWA SUN MRNG. STG CONVERGENCE AND LIFT AHEAD OF WARM FRONT IN THE LOW TO MID LVLS AND WITH EXPCD INFLUX OF PACIFIC MOISTURE FROM THE WEST...SHOULD BE SOME 1 TO 2 INCH SNOW AMOUNTS. A FEW 3 INCHERS PSBL IN SWRN MN SUN MRNG...IF BAND WAS NOT PROGRESSING EAST FAIRLY FAST. EVE SHIFT CAN THINK ABOUT UPPING THE POPS TO DEFINITE AFTER PINNING DOWN TIMING AND PLACEMENT OF BEST SNOW...BUT LOOKS LIKE I90 AND NORTH HAS BEST POTENTIAL. ANOTHER PROBLEM IS POTENTIAL FOR SOME -FZRA OR -FZDZ AS WARMER AIR ALOFT MOVES INTO MISSOURI VALLEY LATE TNGT AND SUN MRNG...BUT MAIN PRECIP SHOULD BE PULLING EAST WITH THE SNOW BAND. THE LGT SNOW AND ANY -FZDZ WILL CONT TO DCRS AND END THRU SUN AFTN. LOW AND SOME MID LVL MOISTR SHUD KEEP SKIES MOCLDY MON NGT INTO ERY TUE BTWN SYSTEMS. MODELS AND GUIDNCE ARE COMING TOGETEHR SURPRISINGLY WELL ON THE MON INTO TUE SYS WITH THE MAIN FOCUS MON NGT. AFTER YSTRDAYS WIDE SPLIT BTWN MODEL SOLUTIONS...THE ECMWF...WHICH YSTDY HAD SNOW BY BRINGING THE LOW ENTERING NRN BAJA UP TOO FAR N...IS NOW PRETTY CLOSE TO OTHER MODELS IN HAVING A ZONE OF DECENT DYNAMIC AND THERMAL SUPPORT AT LOW AND MID LVLS FOR A DECENT SNOW EVEN OVER FCST AREA...ESPLY SRN HALF...DESPITE MAIN UPEPR WAVE MOVG S OF AREA. SECONDARY WAVE BACKS FLOW ENUF TO TAKE ADVANTAGE OF THE TREMENDOUS THERMAL SUPPORT AND THIS SYS SHUD BE A VERY EFFICIENT PCPN PRODUCER FOR THIS TIME OF YEAR. FEEL NAM IS OVERDONE ON THE WARMING JUST AS GFS LIKELY A LTL TOO COOL. THIS ALL SHUD BE A MOOT POINT THO CONSIDERING LIKELY DYNAMIC NATUR OF ANY SIGNIFICANT PCPN WHICH WILL QUICKLY TAKE CARE OF ANY WARM AIR...AND HAVE ELECTED TO KEEP MENTN ALL SNOW EVEN AT THE START. DOESNT LOOK LIKE A WINTER STORM AT THIS POINT BUT WILL GO FOR SOME 4 INCH PLUS FCSTS AT THIS TIME FOR MON THRU TUE OVER THE SRN CWA. HPC GUIDNCE INCLUDING WWD GRAPHICS LOOK QUITE REASNBL XCP THE HIGHEST SNOWFALL POTENTIAL SEEMS TO EXITS JUST AS MUCH OVER THE SWRN CRNR OF FCST AREA AS MUCH AS EWD INTO NWRN IA...SO WILL GO FOR THAT SCENARIO WITH THE SWRN CRNR OF COURSE GETTING THE SNOW ERYR. THOSE TEMPS AFTER HOLDING RELTVLY MILD MON NGT WILL NOT SHOW TOO MUCH RISE TUE. WED THRU SAT EXTENDED PD KEEPS MOST OF TIS QSTNS FROM YSTDY XCP IN VRBL NWRLY FLOW ALOFT IT LOOKS LIKE ANY SNOW EVENTS SUCH AS WE HAVE FOR WED AND FRI WILL BE PRETTY MINOR. A LTL WARMING BY FRI THEN COOLING AGN FOR SAT AS PER GUIDNCE. THIS IS A WAITING PD AWAITING DIGGING OF MAJOR WCOAST TROF AS CONSISTENTLY SHOWN BY MODELS...WITH ANY BIG PCPN EVENTS AND TEMP CHANGES WAITING TILL AFTER THIS FCST PD. ERYR THOUGHTS OF AN IMPRTANT SYS FOR NEXT WEEKEND HAVE SLOWED SLGHTLY AS THE ECMWF WHICH WAS TRYING TO DO THIS ON 00Z RUN HAS SLOWED THE TROF PROGRESSION AND DVLPMNT WITH LATEST RUN AND HINTING AT NOTHING EXCITING...AT LEAST THRU NEXT SAT. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ RYRHOLM/WILLIAMS sd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD 855 PM CST FRI DEC 5 2008 .DISCUSSION... MIXING BEHIND SURFACE WARM FRONT/SWITCH TO MORE WESTERLY WINDS HAS ALLOWED TEMPERATURES OVER MUCH OF THE CWA TO CONTINUE RISING THIS EVENING...WITH MUCH OF THE WESTERN AND SOUTHERN CWA ABOVE FREEZING AS OF 02Z. COLDER AIR STILL POISED TO OUR NORTH...AND IS EXPECTED TO MAKE THE SOUTHWARD PUSH LATER TONIGHT SURFACE LOW IN NORTHERN MN MOVES INTO THE WESTERN GREAT LAKES...AND COLD FRONT IN FAR SOUTHEAST ND MOVES SOUTH THROUGH THE AREA. HAVE MADE QUITE A FEW ADJUSTMENTS TO HOURLY TEMPS TO SHOW NEARLY STEADY OR EVEN SLIGHTLY RISING TEMPS YET THROUGH THE BALANCE OF THE EVENING...WITH SHARPER DECLINE LATER IN THE NIGHT AS THE COLD FRONT PUSHES SOUTH. BUMPED UP OVERNIGHT LOWS 2-4 DEGREES OVERALL...WITH LOWS EXPECTED NEAR THE END OF THE VERIFICATION PERIOD TOWARD 14Z...THOUGH READINGS WILL LIKELY STILL FALL A LITTLE MORE THROUGH THE MIDDLE OF THE MORNING HOURS BEFORE A SUBTLE REBOUND IN THE AFTERNOON. AS FOR PRECIP...BATCH OF LIGHT SNOW WHICH PASSED THROUGH MAINLY THE NORTHEAST CWA WITH THE UPPER WAVE IS PUSHING OUT OF THE AREA...WITH BOTH THE 00Z NAM AND RUC MAINTAINING PUSH OF DRIER MID LEVEL AIR ACROSS THE CENTRAL AND NORTHEAST CWA THROUGH THE REMAINDER OF THE NIGHT. HAVE CUT BACK POPS AS A RESULT...HANGING ONTO A SLIGHT CHANCE IN THE FAR SOUTHWEST AFTER 06Z WHERE DEEPER MOISTURE PERSISTS SOUTHWEST OF THE COLD FRONT. UPDATED GRIDS/PFM/ZFP HAVE BEEN SENT. && .AVIATION... LIGHT SNOW IS LOOKING LESS LIKELY TONIGHT ACROSS THE AREA AS RADAR IMAGES SHOWING DRIER AIR WORKING INTO THE REGION. NORTHWESTERLY WINDS WILL INCREASE THROUGH THE NIGHT AS A COLD FRONT SLIDES THROUGH THE NORTHERN PLAINS. CEILINGS WILL VARY FROM VFR TO MVFR THROUGH THE LATE EVENING...THEN TREND TOWARD A MORE WIDESPREAD MVFR DECK AFTER 06Z AS MOISTURE POISED TO THE NORTH COMES SOUTHWARD. SOME DISCREPANCY AMONG MODEL GUIDANCE WITH RESPECT TO HOW QUICKLY MVFR CIGS BREAK UP ON SATURDAY MORNING...WITH SOME SUGGESTING THE LOW LEVEL MOISTURE HOLDING THROUGH 18Z. WITH THE UNCERTAINTY...PUT SCATTERED 2500 FT AT TAF SITES AFTER 15Z ON SATURDAY. && .PREV DISCUSSION... TEMPERATURES HAVE CLIMBED NICELY THIS AFTERNOON ON A MODERATELY STRONG SOUTHWEST WIND...WITH MOST LOCATIONS WELL INTO THE MID AND UPPER 20S...EVEN SOME LOW TO MID 30S FROM NORTHWEST IOWA WEST THROUGH THE MISSOURI VALLEY. THIS IS IN RESPONSE TO THE WAVE DIVING SOUTH INTO THE REGION TONIGHT. INITIALLY...THIS ENERGY WILL NEED TO OVERCOME A VERY DRY LAYER OF AIR FROM ABOUT 925-800MB. LOOKS LIKE WE WILL OVERCOME THIS FOR A BRIEF PERIOD...WITH THE BEST CHANCES FOR SNOW AROUND HON FROM ABOUT 22Z THROUGH 1Z...FSD FROM ABOUT 0Z-3Z AND SUX...WHICH SHOULD BE ON THE SOUTHERN EDGE...FROM ABOUT 2Z-5Z. WENT WITH SOME NON-DIURNAL FALLS FOR TEMPERATURES TONIGHT AS WINDS AND CLOUD COVER WILL LIKELY KEEP TEMPERATURES UP THROUGH THE EVENING AND EARLY OVERNIGHT HOURS...THEN MUCH COLDER AIR WILL START TO WORK INTO NORTHERN PARTS OF THE CWA BY ABOUT 10Z...WITH FALLING TEMPERATURES FOR MOST LOCATIONS THROUGH TOMORROW MORNING. LOWS THROUGH EARLY TOMORROW MORNING WILL LIKELY RANGE FROM NEAR 10 NORTH TO THE UPPER TEENS SOUTH. CLEARING MAY BE PRETTY STG ERN PART OF FCST AREA SAT DESPITE NAM TYPICALLY WANTING TO LINGER LO LV MOISTR OVER AREA. AS HIGH APPROACHES AND RIDGES INTO AREA SUBSDNCE SHOULD TAKE OVER. SOME CLOUDS SHOULD LINGER ERN PART OF FCST AREA ESPLY IN THE SW. MEANWHILE...TEMPERATURES WHICH WILL STILL BE FALLING IN ERY MRNG WILL NOT DO TOO MUCH RECOVERING AND HIGHS SOME AREAS MAY ACTUALLY BE IN ERY MRNG PREDAWN TIME WITH DAYTIME WARMING ONLY ALMOST COMPENSATING FOR CONTD MORNING FALL. WITH WINDS DROPPING OFF QUICKLY TEMPS WILL DROP WELL ERN FCST AREA SUN EVE AND EVEN A LTL THERE AFTER MIDNIGHT...AS TEMPS IN THE W LVL OFF SAT EVE AND BEGIN TO WARM SLWLY AFTER MIDNIGHT. STG LO LVL WARM ADVECTN PATTRN EXPECTED TO RESULT IN A BROAD BAND OF LGT SNOW WHICH SHOULD MOVE EWD/NEWD ACRS AREA LATE SAT NGT AND SUN MRNG. SOME OF THIS WILL STILL BE LEFT IN THE NORTHEAST FOR SUN AFTN BUT SHUD BE MOSTLY OUT BY LATE IN THE DAY. IN FACT...HAVE KEPT THE PCPN AS SNOW AS THINKING IS THAT PCPN WILL BE MOVING OUT BEFORE IT GETS WARM ENUF FOR FREEZING RAIN. NOT TOO EXCITED ABOUT ANY AMOUNTS AT THIS TIME WITH THERMAL SUPPORT AND LIFT NOT EXPECTED TO BE VERY DEEP...THAT IS WONT GO TOO FAR UP INTO MID LEVELS. SFC TEMPS WILL WARM INTO THE 20S MOST OF FCST AREA SUN AND IN THE LOW TO MID 30S SW. SUN NGT THRU TUE PERIOD PRESENTS INCRG PROBLEMS WITH DIFFERENCES IN MODEL SOLUTIONS. FOR NOW FAVOR GFS SOLUTION OF A GENERALLY DRY PD. ECMWF HINTS AT SIGNFCNT SNOW EVENT PSBL FOR SERN FCST AREA BY SOMEHOW BRINGING THE UPPER LOW COMING ACRS CA/BAJA BORDER AREA SUN NEWD FAR ENUF TO AFFECT FCST AREA. FOR NOW FAVOR GFS/NAM/CANADIAN SOLUTION OF THE DRY FCST BUT WILL HAVE IN A SLGT CHC FOR MON IN DEFERENCE TO THE ECMWF. NOGAPS MODEL IN A LTL DIFFERENT WAY TRIES TO BRING AN AREA OF LGT SNOW UP TO FCST AREA AS WELL. MON SHUD BE RELTVLY MILD ON TEMPS THEN COOLING FOR TUE. WED THRU FRI PERIOD PRESENTS EVEN MORE WIDELY DIFFERENT MODEL SOLUTIONS AND WILL CONT TO LEAN TO THE COLDER GFS WHICH IS IN LINE WITH WHAT WE HAVE BEEN GOING FOR ON TEMPS. AS FOR PCPN...MENTION OF LGT SNOW WITH LOW POPS AS PER HPC GUIDNCE SEEMS IN ORDER BOTH WITH MIDWEEK CDFNT AND IN COLD AIR BEHIND IT...AT LEAST FOR NOW AND TILL WE GET INDICATIONS OF DECENT SFC RIDGING IN COLD AIR WHICH WE DONT HAVE NOW. 00Z CANADIAN HAD A MOST INTERESTING SOLUTION OF WARMING IT UP ALREADY ON FRI THEN HITTING THE AREA WITH A PSBLY MAJOR SNOWSTORM FOR THAT FOLLOWING WEEKEND. THAT SEEMS A LTL GUNG HO BUT AT LEAST THE MODELS ARE STARTING TO SHOW A PATTERN STARTING ABOUT THEN WHICH WILL BE MUCH MORE ACTIVE THAN WE HAVE HAD SO FAR THIS COLD SEASON. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ JH/JM sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 1031 AM CST FRI DEC 5 2008 .UPDATE... MSAS SHOWS SFC TROF IS PROGRESSING SOUTHWARD AS FORECASTED...WITH NW WINDS PICKING UP BEHIND SYSTEM. RUC IS SHOWING FAIRLY IMPRESSIVE 85H THETA-E FORCING ASSOC WITH SFC TROF...COUPLED WITH INCREASE OMEGA IN THE 85H-7H AND 7H-5H LAYERS. LIGHT SNOW LOOKS TO BE A FAIRLY GOOD BET...AND HAVE UPPED POPS FOR MUCH OF THE NORTH AND EAST FOR THIS AFTERNOON. DOESN`T LOOK TO BE MUCH FOR ACCUMS AS DRY AS THE SYSTEM IS...BUT SHOULD BE EFFECIENT AT MAKING SNOW. CURRENT FCSTD HIGHS SEEM REASONABLE GIVEN STRENGTH OF LOW LEVEL WAA QUICKLY MOVING IN. UPDATED WORDED ZONES HAVE BEEN SENT. && .PREV DISCUSSION... .SHORT TERM...TODAY THROUGH SUNDAY PRECIPITATION CHANCES LATER THIS AFTERNOON IS THE MAIN FORECAST CHALLENGE IN THE SHORT TERM. CURRENTLY THERE IS A BAND OF HIGH CLOUDS MOVING ACROSS CENTRAL ND...AND INTO WESTERN SOUTH DAKOTA. THESE HIGHS CLOUDS ARE ERODING THE LOW CLOUDS WITH KABR REPORTING CLEAR SKIES AS OF 8Z. KATY HOWEVER IS STILL REPORTING OVERCAST SKIES. THE AREA OF LOW PRESSURE THAT WILL BRING SNOW BACK INTO THE CWA THIS AFTERNOON IS CURRENTLY SITUATED ALONG THE MONTANA...CANADIAN BORDER. MODELS AGREE WELL WITH BRINGING THIS LOW PRESSURE ACROSS NORTHERN NORTH DAKOTA THIS AFTERNOON...AND THEN OVER LAKE SUPERIOR TONIGHT. NOW COMES THE FORECAST CHALLENGE AS TO WHEN WILL IT SNOW TODAY? AS THE LOW TRACKS OVER NORTHERN NORTH DAKOTA TODAY...WINDS AT 850 MBS SHIFT TO THE WEST WITH MID LEVEL RH VALUES FALLING BELOW 30 PERCENT. MODEL SOUNDINGS OVER KMBG IS MOIST ENOUGH TO SEE SNOW BEGINNING AROUND 18Z. BUFKIT SHOWS THE BEST TIMING FOR SNOW TO BEGIN AROUND 21Z IN KABR AND KPIR. KATY IS MOIST ENOUGH FOR SNOW CLOSER TO 0Z. THIS WILL LIKELY BE ONE OF THOSE EVENTS WHERE WE HIGH POPS WITH LOW QPF AS THERE IS NOT MUCH IN THE WAY OF MID LEVEL FORCING. THERE IS SOME JET SUPPORT AT 300 MBS TONIGHT IN THE FORM OF 130 KT JET STREAK. SNOWFALL AMOUNTS FROM THIS SYSTEM WILL GENERALLY RANGE FROM AN INCH OR LESS...PER THE CARIBOU SNOWFALL AMOUNT TOOL. HIGH PRESSURE NOSES INTO THE NORTHERN PLAINS ON SATURDAY WITH DRIER AIR PUSHING IN AT THE MID LEVELS. UNFORTUNATELY THERE LOOKS TO BE MOISTURE TRAPPED IN THE LOWER LEVEL LEAVING ME TO BELIEVE WE WILL SEE AT LEAST PARTLY CLOUDY SKIES ACROSS THE CWA. WARM AIR IN THE MID LEVELS BEGIN TO PUSH INTO WESTERN SOUTH DAKOTA SATURDAY NIGHT WITH AN OVERRUNNING PRECIPITATION EVENT TAKING PLACE. MODELS HAVE BEEN CONSISTENT IN SHOWING THIS EVENT TAKING PLACE ON SATURDAY NIGHT AND INTO SUNDAY MORNING...FOR THE PAST FIVE MODEL RUNS. THE WARM AIR AT THE MID LEVELS BEGINS TO MIX DOWN TO THE SURFACE ON SUNDAY WITH TEMPS REACHING THE MID TO UPPER 30S IN WEST CENTRAL SOUTH DAKOTA. .LONG TERM...SUNDAY NIGHT THROUGH THURSDAY THE LONG RANGE MODELS...PARTICULARLY THE GFS AND ECMWF REMAIN QUITE SIMILAR IN THEIR DEPICTIONS OF THE LONG WAVE PATTERN THROUGH 180 HOURS. THAT PATTERN BASICALLY COMPRISED OF A MID LEVEL WEST COAST RIDGE AND DOWNSTREAM CENTRAL/EASTERN CONUS TROF. THIS OF COURSE PLACES THE ABR CWA IN A PESKY NORTHWEST FLOW SITUATION WITH A MEAN BAROCLINIC ZONE HANGING AROUND THE AREA. SO...NEEDLESS TO SAY TIMING OF PCPN AND COLD AIR INTRUSIONS ARE SOMEWHAT CHALLENGING. KEPT PCPN CHANCES FOR SUNDAY NIGHT INTO MONDAY WITH BOTH THE GFS AND ECMWF INDICATING SOME POTENTIAL FOR SNOW. THEN WENT DRY UNTIL LATER IN THE WEEK. AT THAT TIME ANOTHER STRONGISH LOOKING CLIPPER IS EXPECTED TO TRACK ACROSS THE NORTHERN PLAINS. AS FOR TEMPERATURES...NEAR TO SLIGHTLY BELOW NORMAL SHOULD SUFFICE FOR THE FIRST PART OF THE EXTENDED. BUT BY THURSDAY A MORE ROBUST CHUNK OF ARCTIC AIR SHOULD SLIDE DOWN INTO THE REGION...ESPECIALLY THE EASTERN CWA. LOOKING A BIT FURTHER OUT...BOTH THE ECMWF/GFS SHOW A PRETTY BIG CHANGE IN THE PATTERN...WITH A WEALTH OF COLD AIR BEGINNING TO WELL UP OVER WESTERN CANADA AS THE MID LEVEL PATTERN GOES THROUGH A RETROGRESSIVE PHASE. COULD THE MIDDLE OF THE MONTH BE COLD AND STORMY? && .AVIATION... A FEW LINGERING MVFR CIGS OVER EASTERN SOUTH DAKOTA SHOULD GRADUALLY BREAK UP THIS MORNING WITH THE REST OF THE MORNING AND EARLY AFTERNOON FEATURING CLOUDS MOSTLY AOA 10K FEET. HOWEVER...BY LATE AFTERNOON AND EARLY EVENING MVFR CIGS ARE EXPECTED TO ROLE SOUTH OVER THE REGION...AND SNOW SHOWERS COULD OCCASIONALLY CAUSE IFR/MVFR VSBYS AT ALL TERMINAL SITES. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...HINTZ SHORT TERM...SD LONG TERM...TDK AVIATION...TDK WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BROWNSVILLE TX 221 PM CST FRI DEC 5 2008 .DISCUSSION...THE LATEST KBRO RADAR REFLECTIVITY SHOWS THE PATCHY LIGHT DRIZZLE CONTINUING OVER THE EASTERN PORTIONS OF THE BRO CWA AND OFFSHORE OVER THE GULF WATERS. THIS PESKY ACTIVITY WILL PERSIST ALONG THE COASTAL AREAS INTO THIS EVENING AS THE CURRENT RUC GUIDANCE SHOWS WEAK SURFACE TROFFING CONTINUING INTO THE EARLY EVENING EVENTUALLY DISSIPATING LATE TONIGHT DIMINISHING THE LOW LEVEL CONVERGENCE. OVER THE NEXT SEVERAL DAYS...THE BROAD 500 MB TROFFING OVER THE EASTERN U.S. WILL WEAKEN ALLOWING A MORE ZONAL PATTERN TO RE-ESTABLISH OVER THE LOWER 48 STATES. THIS WILL ALLOW THE WAA TO STRENGTHEN AND THE DAYTIME HEATING TO INCREASE OVER THE REGION RESULTING IN WARMING TEMPS THROUGH MON. THE MAV AND MET FORECAST TEMPS AND POPS THROUGH MON MORNING ARE IN PRETTY GOOD AGREEMENT AND WILL NOT DEVIATE FROM THIS TREND TOO MUCH IN THE SHORT TERM. EARLY NEXT WEEK...A 500 MB CLOSED LOW CURRENTLY OVER THE SOUTHERN CA COASTLINE WILL OPEN UP AND PHASE WITH A SHORT WAVE DIGGING SOUTHEAST ACROSS THE PACIFIC NORTHWEST. THIS WILL RESULT IN INCREASED 500 MB TROFFING OVER THE SOUTH CENTRAL PLAINS STATES NEXT MON AND TUES AND THIS WILL PUSH THROUGH ANOTHER STRONG COLD FRONT THROUGH THE REGION NEXT TUES. SO FAR...BOTH THE ECMWF AND THE GFS SHOW DECENT AGREEMENT IN THE HANDLING OF THIS FEATURE WITH THE GFS SHOWING A LITTLE FASTER EASTWARD PROGRESSION OF THE 500 MB LOW/TROUGH VERSUS THE ECMWF. RUN TO RUN CONSISTENCY WITH THE GFS IS OK FOR TEMPS AND WORSE FOR POPS WITH THE LATEST GFS MEX TRYING TO HOLD ONTO THE SLGT CHC/CHC POPS INTO WED. DUE TO THE DECENT AGREEMENT SHOWN IN THE LONGER RANGE PERIOD...WILL STICK FAIRLY CLOSE TO THE CURRENT GFS MEX NUMBERS WITH THE EXCEPTION OF THE POPS FOR MON. THE INCREASE SHOWN IN THE POPS ON WED IN THE LATEST MEX RUN MAY LOWER IN THE NEXT RUN...SO MY CONFIDENCE IN POPS FOR NEXT WED IS PRETTY LOW. && .AVIATION...NORTHERLY WINDS AT THE SURFACE...AND SOUTHWESTERLY WINDS IN THE MIDDLE LAYERS OF THE ATMOSPHERE...WILL PRODUCE VFR/MVFR SKIES AND LIGHT TO MODERATE WINDS THROUGH TONIGHT. SKIES WILL THEN RAPIDLY CLEAR AROUND SUNRISE SATURDAY MORNING AS THE MID-LEVEL FLOW SHIFTS TO THE NORTHWEST. && .MARINE...BUOY 42020 REPORTED NORTHEAST WINDS AROUND 19 KNOTS GUSTING TO AROUND 23 KNOTS WITH SEAS SLIGHTLY UNDER 8 FEET WITH A 7 SECOND PERIOD AT 11 CST/17 UTC. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE GULF OF MEXICO WATERS EAST OF PADRE ISLAND UNTIL 6 PM CST THIS AFTERNOON DUE TO STRONG WINDS AND ROUGH SEAS OFFSHORE. HIGH PRESSURE BUILDING SOUTH INTO TEXAS WILL PRODUCE MODERATE WINDS AND SEAS ALONG THE LOWER TEXAS COAST TONIGHT THROUGH SATURDAY. MARINE CONDITIONS WILL BRIEFLY IMPROVE SATURDAY NIGHT AS HIGH PRESSURE MOVES OVER DEEP SOUTH TEXAS AND THEN FARTHER EAST...WITH WINDS AND SEAS INCREASING SUNDAY AND MONDAY AS IT INTERACTS WITH LOW PRESSURE OVER TEXAS. WINDS AND SEAS WILL CONTINUE TO INCREASE TUESDAY AS A COLD FRONT SWEEPS THROUGH. A SMALL CRAFT ADVISORY MAY BE NEEDED MONDAY THROUGH WEDNESDAY DUE TO STRONG WINDS AND ROUGH SEAS AHEAD OF...AND BEHIND...THE COLD FRONT. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 52 71 55 75 / 20 10 0 0 BROWNSVILLE 49 70 54 78 / 20 10 0 0 HARLINGEN 47 70 52 77 / 10 10 0 0 MCALLEN 48 73 53 77 / 10 10 0 0 RIO GRANDE CITY 48 71 53 76 / 10 10 0 0 SOUTH PADRE ISLAND 56 69 57 71 / 20 10 0 0 && .BRO WATCHES/WARNINGS/ADVISORIES...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS AFTERNOON FOR GMZ150-155-170-175. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE SYNOPTIC/GRIDS...60 MARINE/AVIATION...66 MESO/NOWCASTING...MARTINEZ tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 1126 AM CST FRI DEC 5 2008 .DISCUSSION... SEE AVIATION DISCUSSION BELOW. && .AVIATION... LIGHT SOUTHEAST WINDS ARE SWINGING AROUND TO THE SOUTH AND SOUTHWEST AT THE MOMENT...AND WILL CONTINUE TO VEER AROUND OVERNIGHT EVENTUALLY BECOMING NORTHWESTERLY TOMORROW AS A WEAK COLD FRONT MOVES THROUGH THE AREA. NO RAIN AND FEW CLOUDS ARE EXPECTED WITH THE FRONT AS ITS MAIN IMPACT WILL BE ON THE WIND DIRECTION. HENNIG && .PREV DISCUSSION... /ISSUED 938 AM CST FRI DEC 5 2008/ UPDATE... UPDATED THE FORECAST FOR THE EXPIRATION OF THE HIGH WIND WARNING. DISCUSSION... THE PRESSURE GRADIENT HAS BEEN DIMINISHING AND IT IS SHOWING IN THE GDP OBS. HAVE ALLOWED THE HIGH WIND WARNING TO EXPIRE...AND HAVE UPDATED ALL RELEVANT PRODUCTS. OTHERWISE THE ONGOING FORECAST LOOKS GOOD FOR NOW. HENNIG PREV DISCUSSION... /ISSUED 500 AM CST FRI DEC 5 2008/ DISCUSSION... EARLY MORNING SURFACE ANALYSIS CONTINUING TO DEPICT A WELL DEVELOPED SURFACE RIDGE EXTENDING INTO WEST TEXAS AND SOUTHEAST NM FROM A PARENT HIGH LOCATED ACROSS NORTH-CENTRAL OK. PRESSURE GRADIENT IN ASSOCIATION WITH FEATURE HAS KEPT A STEADY NORTHEASTERLY WIND THIS MORNING...ULTIMATELY CREATING HIGH WIND WARNING CONDITIONS ACROSS GUADALUPE PASS. LATEST OBS FROM KGDP INDICATE WINDS BLOWING JUST ABOVE WARNING CRITERIA AND BASED ON WIND FORECASTS FROM BOTH THE WRF AND RUC...FAVORABLE NORTHEASTERLY TRAJECTORY WILL CONTINUE THROUGH THE MID MORNING. BASED ON THIS...HAVE DECIDED TO EXTEND THE WARNING THROUGH 15Z...AFTER WHICH WINDS WILL QUICKLY DECEASE AS THE SURFACE FLOW BEGINS TO VEER MORE SOUTHEASTERLY. AFOREMENTIONED RIDGE AXIS REMAINING IN PLACE ACROSS THE REGION TODAY ENSURING ANOTHER DAY OF WELL BELOW NORMAL TEMPS. CURRENT CONDITIONS UPSTREAM SHOW LOW TO MID TEEMS ACROSS NORTHEASTERN KS THIS MORNING...AN INDICATION OF JUST HOW COOL THE AIRMASS IS. WITH THIS IN MIND...HAVE DECIDED TO KEEP TEMPS IN THE LOW TO MID 40S ACROSS MUCH OF THE PERMIAN BASIN TODAY...AS REINFORCED COLD AIR WILL CONTINUE TO SETTLE INTO THE AREA AS SIGNALED BY COOLER H85 TEMPS ALOFT. WITH HIGHS YESTERDAY ONLY CLIMBING INTO THE MID TO UPPER 40S ACROSS MUCH OF THE REGION...FEEL BASING THE CURRENT FORECAST ON PERSISTENCE IS THE WAY TO GO. ALOFT...A HIGHLY SHEARED POSITIVELY TILTED TROUGH WILL PASS OVERHEAD TODAY...YIELDING NOTHING MORE THAN ENHANCED CLOUDINESS ALOFT BEFORE GRADUALLY CLEARING LATE THIS AFTERNOON AND EVENING FROM NORTHWEST TO SOUTHEAST. OVERNIGHT TONIGHT...A SURFACE PRESSURE TROUGH ORIGINATING FROM THE SOUTHERN ROCKIES WILL BEGIN TO WORK ITS WAY EASTWARD...WITH CONTINUATION ACROSS THE REGION THROUGH TOMORROW AFTERNOON. BEHIND THE FEATURE...LOW-LEVEL FLOW WILL BECOME MORE NORTHWESTERLY AS THE AFTERNOON PROGRESSES...SUGGESTING SOME DOWNSLOPE COMPRESSIONAL WARMING POTENTIAL ACROSS PORTIONS OF THE AREA. THIS IN COMBINATION WITH WARMING TEMPS ALOFT WILL SUPPORT NEAR NORMAL TEMPS ACROSS MUCH OF THE REGION TOMORROW...WITH LOW TO MID 60S LIKELY RETURNING. PERIOD OF TRANSITION EXPECTED BY SUNDAY AS A STUBBORN UPPER LOW OFF THE CA COAST BEGINS TO WORK EAST INTO THE DESERT SW/NORTHERN MEX. NORTHWESTERLY MID-LEVEL FLOW WILL GRADUALLY BECOME MORE ZONAL WITH TIME IN ADVANCE OF THIS FEATURE...WITH EMBEDDED SHORTWAVES EXPECTED TO APPROACH WEST TX/SE NM BEGINNING SUN AFTERNOON. INCREASING WESTERLY FLOW ALOFT WILL LEAD TO ENHANCED LEESIDE TROUGHING...WITH TROUGH AXIS EXPECTED TO EXTEND SOUTHWARD ACROSS THE SOUTHEAST NM PLAINS AND WEST TX MOUNTAINS. STRONG WARM AIR ADVECTION EXPECTED ACROSS THE REGION WITH RISING H85 TEMPS THROUGH THE AFTERNOON. FAVORABLE MIXING ALSO ANTICIPATED AS LOW-LEVEL LAPSE RATES BECOME NEARLY DRY ADIABATIC. ONLY CAVEAT WITH INCREASING TEMPS SIGNIFICANTLY WITH THIS MORNING/S UPDATE IS THE EXPECTATIONS OF INCREASING MID AND HIGH LEVEL CLOUDS. IN ANY EVENT...FORECASTED H85 TEMPS SUPPORT LOW TO MID 70S ACROSS MUCH OF THE REGION...HOWEVER WITH CONCERNS REGARDING CLOUDS...HAVE ATTEMPTED TO PLAY IT SAFE AND ONLY RAISE TEMPS A FEW DEGREES FOR NOW PENDING LATER MODEL RUNS. UNSETTLED WEATHER CONTINUING INTO THE EARLY WORK WEEK AS LEESIDE TROUGH/SFC LOW EXITS THE SOUTHERN ROCKIES AND SETTLES INTO THE CENTRAL TX PANHANDLE BY 00Z TUE. ACROSS THE MID-LEVELS...AN UPPER TROUGH IS EXPECTED TO SWING INTO THE REGION AS WELL...WITH THE ECMWF BEING THE MOST BULLISH OF MID-RANGE GUIDANCE. MODELS IN RELATIVELY GOOD AGREEMENT THAT A WELL DEFINED DRYLINE WILL SUPERSEDE THE LOW...HOWEVER FEATURE IS EXPECTED TO GRADUALLY MOVE EASTWARD THROUGHOUT THE DAY AS THE LOW SINKS SOUTHWARD TRAPPING THE BEST RETURN FLOW MOISTURE WELL OFF TO THE EAST OF THE CWA. DESPITE THIS...MODELS DO DEVELOP PRECIP ACROSS THE REGION AS AN UPPER SPEED MAX MOVES ACROSS THE REGION ALONG WITH APPRECIABLE SHORTWAVE ENERGY. HAVE RAISED POPS TO JUST UNDER MENTIONABLE LIMITS FOR NOW BASED ON COLLABORATION WITH ADJACENT OFFICES WHILE AWAITING FOR RUN TO RUN MODEL MODEL CONTINUITY. STRONG COLD FRONT EXPECTED ACROSS THE AREA EARLY TUESDAY MORNING WITH CONTINUED ACCELERATION TO THE SOUTH THROUGH THE DAY. COLD HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL LEAD TO COOLER TEMPS HOWEVER TEMPS WILL LIKELY REBOUND ON WED BEFORE ANOTHER REINFORCING SHOT OF COLD AIR ARRIVES ON THU. GENERALLY USED A GFS/ECMWF BLEND FOR THE EXTENDED AS MINOR DIFFERENCES AT THE START OF THE PERIOD IRONED THEMSELVES OUT AS THE FORECAST PERIOD ADVANCED. && .MAF WATCHES/WARNINGS/ADVISORIES... NM...NONE. TX...NONE. && $$ 10 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 938 AM CST FRI DEC 5 2008 .UPDATE... UPDATED THE FORECAST FOR THE EXPIRATION OF THE HIGH WIND WARNING. && .DISCUSSION... THE PRESSURE GRADIENT HAS BEEN DIMINISHING AND IT IS SHOWING IN THE GDP OBS. HAVE ALLOWED THE HIGH WIND WARNING TO EXPIRE...AND HAVE UPDATED ALL RELEVANT PRODUCTS. OTHERWISE THE ONGOING FORECAST LOOKS GOOD FOR NOW. HENNIG && .PREV DISCUSSION... /ISSUED 550 AM CST FRI DEC 5 2008/ DISCUSSION... SEE 12Z AVIATION DISCUSSION BELOW. AVIATION... SURFACE HIGH PRESSURE IS WELL ESTABLISHED ACROSS ALL TERMINALS THIS MORNING. NORTHEAST WINDS WILL CONTINUE THROUGH THE MORNING HOURS WITH HIGH PRESSURE CENTERED EAST OF THE REGION. A TRANSITION TO SOUTH AND SOUTHWEST WINDS WILL TAKE PLACE THIS AFTERNOON AS A SURFACE TROUGH BECOMES ESTABLISHED OVER THE PLAINS OF EASTERN NEW MEXICO AND WEST TEXAS. MID AND HIGH LEVEL CLOUDS WILL ALSO CONTINUE THROUGH THE CURRENT TAF FORECAST PERIOD. PREV DISCUSSION... /ISSUED 500 AM CST FRI DEC 5 2008/ DISCUSSION... EARLY MORNING SURFACE ANALYSIS CONTINUING TO DEPICT A WELL DEVELOPED SURFACE RIDGE EXTENDING INTO WEST TEXAS AND SOUTHEAST NM FROM A PARENT HIGH LOCATED ACROSS NORTH-CENTRAL OK. PRESSURE GRADIENT IN ASSOCIATION WITH FEATURE HAS KEPT A STEADY NORTHEASTERLY WIND THIS MORNING...ULTIMATELY CREATING HIGH WIND WARNING CONDITIONS ACROSS GUADALUPE PASS. LATEST OBS FROM KGDP INDICATE WINDS BLOWING JUST ABOVE WARNING CRITERIA AND BASED ON WIND FORECASTS FROM BOTH THE WRF AND RUC...FAVORABLE NORTHEASTERLY TRAJECTORY WILL CONTINUE THROUGH THE MID MORNING. BASED ON THIS...HAVE DECIDED TO EXTEND THE WARNING THROUGH 15Z...AFTER WHICH WINDS WILL QUICKLY DECEASE AS THE SURFACE FLOW BEGINS TO VEER MORE SOUTHEASTERLY. AFOREMENTIONED RIDGE AXIS REMAINING IN PLACE ACROSS THE REGION TODAY ENSURING ANOTHER DAY OF WELL BELOW NORMAL TEMPS. CURRENT CONDITIONS UPSTREAM SHOW LOW TO MID TEEMS ACROSS NORTHEASTERN KS THIS MORNING...AN INDICATION OF JUST HOW COOL THE AIRMASS IS. WITH THIS IN MIND...HAVE DECIDED TO KEEP TEMPS IN THE LOW TO MID 40S ACROSS MUCH OF THE PERMIAN BASIN TODAY...AS REINFORCED COLD AIR WILL CONTINUE TO SETTLE INTO THE AREA AS SIGNALED BY COOLER H85 TEMPS ALOFT. WITH HIGHS YESTERDAY ONLY CLIMBING INTO THE MID TO UPPER 40S ACROSS MUCH OF THE REGION...FEEL BASING THE CURRENT FORECAST ON PERSISTENCE IS THE WAY TO GO. ALOFT...A HIGHLY SHEARED POSITIVELY TILTED TROUGH WILL PASS OVERHEAD TODAY...YIELDING NOTHING MORE THAN ENHANCED CLOUDINESS ALOFT BEFORE GRADUALLY CLEARING LATE THIS AFTERNOON AND EVENING FROM NORTHWEST TO SOUTHEAST. OVERNIGHT TONIGHT...A SURFACE PRESSURE TROUGH ORIGINATING FROM THE SOUTHERN ROCKIES WILL BEGIN TO WORK ITS WAY EASTWARD...WITH CONTINUATION ACROSS THE REGION THROUGH TOMORROW AFTERNOON. BEHIND THE FEATURE...LOW-LEVEL FLOW WILL BECOME MORE NORTHWESTERLY AS THE AFTERNOON PROGRESSES...SUGGESTING SOME DOWNSLOPE COMPRESSIONAL WARMING POTENTIAL ACROSS PORTIONS OF THE AREA. THIS IN COMBINATION WITH WARMING TEMPS ALOFT WILL SUPPORT NEAR NORMAL TEMPS ACROSS MUCH OF THE REGION TOMORROW...WITH LOW TO MID 60S LIKELY RETURNING. PERIOD OF TRANSITION EXPECTED BY SUNDAY AS A STUBBORN UPPER LOW OFF THE CA COAST BEGINS TO WORK EAST INTO THE DESERT SW/NORTHERN MEX. NORTHWESTERLY MID-LEVEL FLOW WILL GRADUALLY BECOME MORE ZONAL WITH TIME IN ADVANCE OF THIS FEATURE...WITH EMBEDDED SHORTWAVES EXPECTED TO APPROACH WEST TX/SE NM BEGINNING SUN AFTERNOON. INCREASING WESTERLY FLOW ALOFT WILL LEAD TO ENHANCED LEESIDE TROUGHING...WITH TROUGH AXIS EXPECTED TO EXTEND SOUTHWARD ACROSS THE SOUTHEAST NM PLAINS AND WEST TX MOUNTAINS. STRONG WARM AIR ADVECTION EXPECTED ACROSS THE REGION WITH RISING H85 TEMPS THROUGH THE AFTERNOON. FAVORABLE MIXING ALSO ANTICIPATED AS LOW-LEVEL LAPSE RATES BECOME NEARLY DRY ADIABATIC. ONLY CAVEAT WITH INCREASING TEMPS SIGNIFICANTLY WITH THIS MORNING/S UPDATE IS THE EXPECTATIONS OF INCREASING MID AND HIGH LEVEL CLOUDS. IN ANY EVENT...FORECASTED H85 TEMPS SUPPORT LOW TO MID 70S ACROSS MUCH OF THE REGION...HOWEVER WITH CONCERNS REGARDING CLOUDS...HAVE ATTEMPTED TO PLAY IT SAFE AND ONLY RAISE TEMPS A FEW DEGREES FOR NOW PENDING LATER MODEL RUNS. UNSETTLED WEATHER CONTINUING INTO THE EARLY WORK WEEK AS LEESIDE TROUGH/SFC LOW EXITS THE SOUTHERN ROCKIES AND SETTLES INTO THE CENTRAL TX PANHANDLE BY 00Z TUE. ACROSS THE MID-LEVELS...AN UPPER TROUGH IS EXPECTED TO SWING INTO THE REGION AS WELL...WITH THE ECMWF BEING THE MOST BULLISH OF MID-RANGE GUIDANCE. MODELS IN RELATIVELY GOOD AGREEMENT THAT A WELL DEFINED DRYLINE WILL SUPERSEDE THE LOW...HOWEVER FEATURE IS EXPECTED TO GRADUALLY MOVE EASTWARD THROUGHOUT THE DAY AS THE LOW SINKS SOUTHWARD TRAPPING THE BEST RETURN FLOW MOISTURE WELL OFF TO THE EAST OF THE CWA. DESPITE THIS...MODELS DO DEVELOP PRECIP ACROSS THE REGION AS AN UPPER SPEED MAX MOVES ACROSS THE REGION ALONG WITH APPRECIABLE SHORTWAVE ENERGY. HAVE RAISED POPS TO JUST UNDER MENTIONABLE LIMITS FOR NOW BASED ON COLLABORATION WITH ADJACENT OFFICES WHILE AWAITING FOR RUN TO RUN MODEL MODEL CONTINUITY. STRONG COLD FRONT EXPECTED ACROSS THE AREA EARLY TUESDAY MORNING WITH CONTINUED ACCELERATION TO THE SOUTH THROUGH THE DAY. COLD HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL LEAD TO COOLER TEMPS HOWEVER TEMPS WILL LIKELY REBOUND ON WED BEFORE ANOTHER REINFORCING SHOT OF COLD AIR ARRIVES ON THU. GENERALLY USED A GFS/ECMWF BLEND FOR THE EXTENDED AS MINOR DIFFERENCES AT THE START OF THE PERIOD IRONED THEMSELVES OUT AS THE FORECAST PERIOD ADVANCED. && .PRELIMINARY POINT TEMPS/POPS... BIG SPRING TX 44 29 61 34 / 0 0 0 0 CARLSBAD NM 49 31 67 33 / 0 0 0 0 DRYDEN TX 49 35 67 41 / 0 0 0 0 FORT STOCKTON TX 50 35 70 41 / 0 0 0 0 GUADALUPE PASS TX 47 34 60 39 / 0 0 0 0 HOBBS NM 47 30 65 33 / 0 0 0 0 MARFA TX 51 24 65 28 / 0 0 0 0 MIDLAND INTL AIRPORT TX 45 30 63 35 / 0 0 0 0 ODESSA TX 45 30 63 35 / 0 0 0 0 WINK TX 49 31 70 34 / 0 0 0 0 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...NONE. TX...NONE. && $$ 10/99 tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 550 AM CST FRI DEC 5 2008 .DISCUSSION... SEE 12Z AVIATION DISCUSSION BELOW. && .AVIATION... SURFACE HIGH PRESSURE IS WELL ESTABLISHED ACROSS ALL TERMINALS THIS MORNING. NORTHEAST WINDS WILL CONTINUE THROUGH THE MORNING HOURS WITH HIGH PRESSURE CENTERED EAST OF THE REGION. A TRANSITION TO SOUTH AND SOUTHWEST WINDS WILL TAKE PLACE THIS AFTERNOON AS A SURFACE TROUGH BECOMES ESTABLISHED OVER THE PLAINS OF EASTERN NEW MEXICO AND WEST TEXAS. MID AND HIGH LEVEL CLOUDS WILL ALSO CONTINUE THROUGH THE CURRENT TAF FORECAST PERIOD. && .PREV DISCUSSION... /ISSUED 500 AM CST FRI DEC 5 2008/ DISCUSSION... EARLY MORNING SURFACE ANALYSIS CONTINUING TO DEPICT A WELL DEVELOPED SURFACE RIDGE EXTENDING INTO WEST TEXAS AND SOUTHEAST NM FROM A PARENT HIGH LOCATED ACROSS NORTH-CENTRAL OK. PRESSURE GRADIENT IN ASSOCIATION WITH FEATURE HAS KEPT A STEADY NORTHEASTERLY WIND THIS MORNING...ULTIMATELY CREATING HIGH WIND WARNING CONDITIONS ACROSS GUADALUPE PASS. LATEST OBS FROM KGDP INDICATE WINDS BLOWING JUST ABOVE WARNING CRITERIA AND BASED ON WIND FORECASTS FROM BOTH THE WRF AND RUC...FAVORABLE NORTHEASTERLY TRAJECTORY WILL CONTINUE THROUGH THE MID MORNING. BASED ON THIS...HAVE DECIDED TO EXTEND THE WARNING THROUGH 15Z...AFTER WHICH WINDS WILL QUICKLY DECEASE AS THE SURFACE FLOW BEGINS TO VEER MORE SOUTHEASTERLY. AFOREMENTIONED RIDGE AXIS REMAINING IN PLACE ACROSS THE REGION TODAY ENSURING ANOTHER DAY OF WELL BELOW NORMAL TEMPS. CURRENT CONDITIONS UPSTREAM SHOW LOW TO MID TEEMS ACROSS NORTHEASTERN KS THIS MORNING...AN INDICATION OF JUST HOW COOL THE AIRMASS IS. WITH THIS IN MIND...HAVE DECIDED TO KEEP TEMPS IN THE LOW TO MID 40S ACROSS MUCH OF THE PERMIAN BASIN TODAY...AS REINFORCED COLD AIR WILL CONTINUE TO SETTLE INTO THE AREA AS SIGNALED BY COOLER H85 TEMPS ALOFT. WITH HIGHS YESTERDAY ONLY CLIMBING INTO THE MID TO UPPER 40S ACROSS MUCH OF THE REGION...FEEL BASING THE CURRENT FORECAST ON PERSISTENCE IS THE WAY TO GO. ALOFT...A HIGHLY SHEARED POSITIVELY TILTED TROUGH WILL PASS OVERHEAD TODAY...YIELDING NOTHING MORE THAN ENHANCED CLOUDINESS ALOFT BEFORE GRADUALLY CLEARING LATE THIS AFTERNOON AND EVENING FROM NORTHWEST TO SOUTHEAST. OVERNIGHT TONIGHT...A SURFACE PRESSURE TROUGH ORIGINATING FROM THE SOUTHERN ROCKIES WILL BEGIN TO WORK ITS WAY EASTWARD...WITH CONTINUATION ACROSS THE REGION THROUGH TOMORROW AFTERNOON. BEHIND THE FEATURE...LOW-LEVEL FLOW WILL BECOME MORE NORTHWESTERLY AS THE AFTERNOON PROGRESSES...SUGGESTING SOME DOWNSLOPE COMPRESSIONAL WARMING POTENTIAL ACROSS PORTIONS OF THE AREA. THIS IN COMBINATION WITH WARMING TEMPS ALOFT WILL SUPPORT NEAR NORMAL TEMPS ACROSS MUCH OF THE REGION TOMORROW...WITH LOW TO MID 60S LIKELY RETURNING. PERIOD OF TRANSITION EXPECTED BY SUNDAY AS A STUBBORN UPPER LOW OFF THE CA COAST BEGINS TO WORK EAST INTO THE DESERT SW/NORTHERN MEX. NORTHWESTERLY MID-LEVEL FLOW WILL GRADUALLY BECOME MORE ZONAL WITH TIME IN ADVANCE OF THIS FEATURE...WITH EMBEDDED SHORTWAVES EXPECTED TO APPROACH WEST TX/SE NM BEGINNING SUN AFTERNOON. INCREASING WESTERLY FLOW ALOFT WILL LEAD TO ENHANCED LEESIDE TROUGHING...WITH TROUGH AXIS EXPECTED TO EXTEND SOUTHWARD ACROSS THE SOUTHEAST NM PLAINS AND WEST TX MOUNTAINS. STRONG WARM AIR ADVECTION EXPECTED ACROSS THE REGION WITH RISING H85 TEMPS THROUGH THE AFTERNOON. FAVORABLE MIXING ALSO ANTICIPATED AS LOW-LEVEL LAPSE RATES BECOME NEARLY DRY ADIABATIC. ONLY CAVEAT WITH INCREASING TEMPS SIGNIFICANTLY WITH THIS MORNING/S UPDATE IS THE EXPECTATIONS OF INCREASING MID AND HIGH LEVEL CLOUDS. IN ANY EVENT...FORECASTED H85 TEMPS SUPPORT LOW TO MID 70S ACROSS MUCH OF THE REGION...HOWEVER WITH CONCERNS REGARDING CLOUDS...HAVE ATTEMPTED TO PLAY IT SAFE AND ONLY RAISE TEMPS A FEW DEGREES FOR NOW PENDING LATER MODEL RUNS. UNSETTLED WEATHER CONTINUING INTO THE EARLY WORK WEEK AS LEESIDE TROUGH/SFC LOW EXITS THE SOUTHERN ROCKIES AND SETTLES INTO THE CENTRAL TX PANHANDLE BY 00Z TUE. ACROSS THE MID-LEVELS...AN UPPER TROUGH IS EXPECTED TO SWING INTO THE REGION AS WELL...WITH THE ECMWF BEING THE MOST BULLISH OF MID-RANGE GUIDANCE. MODELS IN RELATIVELY GOOD AGREEMENT THAT A WELL DEFINED DRYLINE WILL SUPERSEDE THE LOW...HOWEVER FEATURE IS EXPECTED TO GRADUALLY MOVE EASTWARD THROUGHOUT THE DAY AS THE LOW SINKS SOUTHWARD TRAPPING THE BEST RETURN FLOW MOISTURE WELL OFF TO THE EAST OF THE CWA. DESPITE THIS...MODELS DO DEVELOP PRECIP ACROSS THE REGION AS AN UPPER SPEED MAX MOVES ACROSS THE REGION ALONG WITH APPRECIABLE SHORTWAVE ENERGY. HAVE RAISED POPS TO JUST UNDER MENTIONABLE LIMITS FOR NOW BASED ON COLLABORATION WITH ADJACENT OFFICES WHILE AWAITING FOR RUN TO RUN MODEL MODEL CONTINUITY. STRONG COLD FRONT EXPECTED ACROSS THE AREA EARLY TUESDAY MORNING WITH CONTINUED ACCELERATION TO THE SOUTH THROUGH THE DAY. COLD HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL LEAD TO COOLER TEMPS HOWEVER TEMPS WILL LIKELY REBOUND ON WED BEFORE ANOTHER REINFORCING SHOT OF COLD AIR ARRIVES ON THU. GENERALLY USED A GFS/ECMWF BLEND FOR THE EXTENDED AS MINOR DIFFERENCES AT THE START OF THE PERIOD IRONED THEMSELVES OUT AS THE FORECAST PERIOD ADVANCED. && .MAF WATCHES/WARNINGS/ADVISORIES... NM...NONE. TX...HIGH WIND WARNING UNTIL 8 AM MST THIS MORNING FOR THE FOLLOWING ZONES... GUADALUPE MOUNTAINS. && $$ 06 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 500 AM CST FRI DEC 5 2008 .DISCUSSION... EARLY MORNING SURFACE ANALYSIS CONTINUING TO DEPICT A WELL DEVELOPED SURFACE RIDGE EXTENDING INTO WEST TEXAS AND SOUTHEAST NM FROM A PARENT HIGH LOCATED ACROSS NORTH-CENTRAL OK. PRESSURE GRADIENT IN ASSOCIATION WITH FEATURE HAS KEPT A STEADY NORTHEASTERLY WIND THIS MORNING...ULTIMATELY CREATING HIGH WIND WARNING CONDITIONS ACROSS GUADALUPE PASS. LATEST OBS FROM KGDP INDICATE WINDS BLOWING JUST ABOVE WARNING CRITERIA AND BASED ON WIND FORECASTS FROM BOTH THE WRF AND RUC...FAVORABLE NORTHEASTERLY TRAJECTORY WILL CONTINUE THROUGH THE MID MORNING. BASED ON THIS...HAVE DECIDED TO EXTEND THE WARNING THROUGH 15Z...AFTER WHICH WINDS WILL QUICKLY DECEASE AS THE SURFACE FLOW BEGINS TO VEER MORE SOUTHEASTERLY. AFOREMENTIONED RIDGE AXIS REMAINING IN PLACE ACROSS THE REGION TODAY ENSURING ANOTHER DAY OF WELL BELOW NORMAL TEMPS. CURRENT CONDITIONS UPSTREAM SHOW LOW TO MID TEEMS ACROSS NORTHEASTERN KS THIS MORNING...AN INDICATION OF JUST HOW COOL THE AIRMASS IS. WITH THIS IN MIND...HAVE DECIDED TO KEEP TEMPS IN THE LOW TO MID 40S ACROSS MUCH OF THE PERMIAN BASIN TODAY...AS REINFORCED COLD AIR WILL CONTINUE TO SETTLE INTO THE AREA AS SIGNALED BY COOLER H85 TEMPS ALOFT. WITH HIGHS YESTERDAY ONLY CLIMBING INTO THE MID TO UPPER 40S ACROSS MUCH OF THE REGION...FEEL BASING THE CURRENT FORECAST ON PERSISTENCE IS THE WAY TO GO. ALOFT...A HIGHLY SHEARED POSITIVELY TILTED TROUGH WILL PASS OVERHEAD TODAY...YIELDING NOTHING MORE THAN ENHANCED CLOUDINESS ALOFT BEFORE GRADUALLY CLEARING LATE THIS AFTERNOON AND EVENING FROM NORTHWEST TO SOUTHEAST. OVERNIGHT TONIGHT...A SURFACE PRESSURE TROUGH ORIGINATING FROM THE SOUTHERN ROCKIES WILL BEGIN TO WORK ITS WAY EASTWARD...WITH CONTINUATION ACROSS THE REGION THROUGH TOMORROW AFTERNOON. BEHIND THE FEATURE...LOW-LEVEL FLOW WILL BECOME MORE NORTHWESTERLY AS THE AFTERNOON PROGRESSES...SUGGESTING SOME DOWNSLOPE COMPRESSIONAL WARMING POTENTIAL ACROSS PORTIONS OF THE AREA. THIS IN COMBINATION WITH WARMING TEMPS ALOFT WILL SUPPORT NEAR NORMAL TEMPS ACROSS MUCH OF THE REGION TOMORROW...WITH LOW TO MID 60S LIKELY RETURNING. PERIOD OF TRANSITION EXPECTED BY SUNDAY AS A STUBBORN UPPER LOW OFF THE CA COAST BEGINS TO WORK EAST INTO THE DESERT SW/NORTHERN MEX. NORTHWESTERLY MID-LEVEL FLOW WILL GRADUALLY BECOME MORE ZONAL WITH TIME IN ADVANCE OF THIS FEATURE...WITH EMBEDDED SHORTWAVES EXPECTED TO APPROACH WEST TX/SE NM BEGINNING SUN AFTERNOON. INCREASING WESTERLY FLOW ALOFT WILL LEAD TO ENHANCED LEESIDE TROUGHING...WITH TROUGH AXIS EXPECTED TO EXTEND SOUTHWARD ACROSS THE SOUTHEAST NM PLAINS AND WEST TX MOUNTAINS. STRONG WARM AIR ADVECTION EXPECTED ACROSS THE REGION WITH RISING H85 TEMPS THROUGH THE AFTERNOON. FAVORABLE MIXING ALSO ANTICIPATED AS LOW-LEVEL LAPSE RATES BECOME NEARLY DRY ADIABATIC. ONLY CAVEAT WITH INCREASING TEMPS SIGNIFICANTLY WITH THIS MORNING/S UDPATE IS THE EXPECTATIONS OF INCREASING MID AND HIGH LEVEL CLOUDS. IN ANY EVENT...FORECASTED H85 TEMPS SUPPORT LOW TO MID 70S ACROSS MUCH OF THE REGION...HOWEVER WITH CONCERNS REGARDING CLOUDS...HAVE ATTEMPTED TO PLAY IT SAFE AND ONLY RAISE TEMPS A FEW DEGREES FOR NOW PENDING LATER MODEL RUNS. UNSETTLED WEATHER CONTINUING INTO THE EARLY WORK WEEK AS LEESIDE TROUGH/SFC LOW EXITS THE SOUTHERN ROCKIES AND SETTLES INTO THE CENTRAL TX PANHANDLE BY 00Z TUE. ACROSS THE MID-LEVELS...AN UPPER TROUGH IS EXPECTED TO SWING INTO THE REGION AS WELL...WITH THE ECMWF BEING THE MOST BULLISH OF MID-RANGE GUIDANCE. MODELS IN RELATIVELY GOOD AGREEMENT THAT A WELL DEFINED DRYLINE WILL SUPERSEDE THE LOW...HOWEVER FEATURE IS EXPECTED TO GRADUALLY MOVE EASTWARD THROUGHOUT THE DAY AS THE LOW SINKS SOUTHWARD TRAPPING THE BEST RETURN FLOW MOISTURE WELL OFF TO THE EAST OF THE CWA. DESPITE THIS...MODELS DO DEVELOP PRECIP ACROSS THE REGION AS AN UPPER SPEED MAX MOVES ACROSS THE REGION ALONG WITH APPRECIABLE SHORTWAVE ENERGY. HAVE RAISED POPS TO JUST UNDER MENTIONABLE LIMITS FOR NOW BASED ON COLLABORATION WITH ADJACENT OFFICES WHILE AWAITING FOR RUN TO RUN MODEL MODEL CONTINUITY. STRONG COLD FRONT EXPECTED ACROSS THE AREA EARLY TUESDAY MORNING WITH CONTINUED ACCELERATION TO THE SOUTH THROUGH THE DAY. COLD HIGH PRESSURE BUILDING IN BEHIND THE FRONT WILL LEAD TO COOLER TEMPS HOWEVER TEMPS WILL LIKELY REBOUND ON WED BEFORE ANOTHER REINFORCING SHOT OF COLD AIR ARRIVES ON THU. GENERALLY USED A GFS/ECMWF BLEND FOR THE EXTENDED AS MINOR DIFFERENCES AT THE START OF THE PERIOD IRONED THEMSELVES OUT AS THE FORECAST PERIOD ADVANCED. && .PRELIMINARY POINT TEMPS/POPS... BIG SPRING TX 44 29 61 34 / 0 0 0 0 CARLSBAD NM 49 31 67 33 / 0 0 0 0 DRYDEN TX 49 35 67 41 / 0 0 0 0 FORT STOCKTON TX 50 35 70 41 / 0 0 0 0 GUADALUPE PASS TX 47 34 60 39 / 0 0 0 0 HOBBS NM 47 30 65 33 / 0 0 0 0 MARFA TX 51 24 65 28 / 0 0 0 0 MIDLAND INTL AIRPORT TX 45 30 63 35 / 0 0 0 0 ODESSA TX 45 30 63 35 / 0 0 0 0 WINK TX 49 31 70 34 / 0 0 0 0 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...NONE. TX...HIGH WIND WARNING UNTIL 8 AM MST THIS MORNING FOR THE FOLLOWING ZONES... GUADALUPE MOUNTAINS. && $$ 32 tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 252 AM EST SAT DEC 6 2008 .SYNOPSIS... COLD HIGH PRESSURE WILL BE CENTERED OVER THE MID ATLANTIC STATES TONIGHT. A FAST MOVING ALBERTA CLIPPER WILL MOVE ACROSS THE OHIO VALLEY SATURDAY PASSING NORTH OF THE AREA SATURDAY NIGHT. MOUNTAIN SNOW SHOWERS AND FLURRIES ARE LIKELY SATURDAY NIGHT INTO SUNDAY ALONG WITH BLUSTERY NORTHWEST WINDS. && .NEAR TERM /THROUGH TONIGHT/... THE LATEST 12KM NAM...AND TO AN EXTENT THE RUC13 IS DOING A GOOD JOB SHOWING THE CLOUDINESS OVER THE NC FOOTHILLS. NAM MODEL SOUNDINGS SUGGEST A SHALLOW LAYER OF THIS CLOUD DECK TO SHIFT NORTH AND EAST INTO THE OUR SRN CWA THROUGH DAWN. HAVE MADE ADJUSTMENTS TO THE GRIDS TO ACCOUNT FOR THIS. OTHERWISE...LOOKING AT EXCELLENT RADIATIONAL COOLING CONDITIONS TONIGHT AS HIGH PRESSURE SETTLES OVER THE AREA. MODELS DO SHOW SOME WARM AIR ADVECTING IN ALOFT AFTER MIDNIGHT. THIS MAY KEEP SOUTHWESTERN VIRGINIA RIDGES (BLF) WARMER THAN THE REST OF THE AREA OVERNIGHT. DESPITE CALLING THE RIDGES WARMER...STILL LOOKING AT A COLD NIGHT WITH TEMPERATURES 10-20F ACROSS THE MOUNTAINS TO LOWER 20S EAST AND ALONG SW VA WESTERN RIDGES. THE 12KM NAM IS DEPICTING WARM AIR ADVECTION CONTINUES INTO THE DAY SATURDAY...AHEAD OF A CLIPPER CROSSING OVER THE GREAT LAKES. MOISTURE TRANSPORT INCREASING THROUGH THE DAY ON SOUTHWESTERLY FLOW. THIS WILL BRING AN INCREASE IN CLOUDS ACROSS THE AREA THROUGH THE DAY. ATMOSPHERE REMAINING COLD WITH 850 MB TEMPERATURES -4C TO -7C. IF PRECIP DOES FALL SATURDAY AFTERNOON...IT WILL REMAIN AS SNOW...ALONG AND WEST OF THE BLUE RIDGE AS RELATIVELY WARM SURFACE LAYER WILL BE SHALLOW.. IF CLOUDS INCREASE DURING THE MORNING...INSOLATION WILL BE LIMITED AND A FEW FLAKES COULD BE OBSERVED IN THE PIEDMONT. OF COURSE...THAT IS IF PRECIP FALLS. 12Z NAM BEING ONE OF THE DRIEST MODELS TODAY ONLY HAS GREENBRIER AND BATH COUNTY WITH MEASURABLE PRECIP. ON THE OTHER HAND...12Z GFS/CANADIAN/EUROPEAN HAS PRECIP AS FAR EAST AS THE FOOTHILLS. I DO HAVE SOME CONCERNS ABOUT THE START TIME AND MEASURABLE AMOUNTS WITH PARENT LOW SO FAR NORTH AND OVER THE GREAT LAKES. WILL SLOW DOWN POPS JUST A TAD UNTIL THE MID TO LATE AFTERNOON WITH THESE CONCERNS AND THAT THE ATMOSPHERE WILL NEED TIME TO SATURATE AGAIN. WILL MAINTAIN CHANCE POPS ACROSS THE WEST WITH SLIGHT CHANCE IN THE EAST. NEVERTHELESS...ACCUMULATIONS WILL BE LIGHT DURING THE DAY. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... DRY AIR QUICKLY MOVES INTO EXTREME SW VA AND NE NC...SUCH THAT SNOW SHWS SHOULD SHUT OFF QUICK SUNDAY MORNING THERE. DESPITE LACK OF MOISTURE...-15C H85 TEMPS IN WESTERN GREENBRIER COULD CHURN OUT ANOTHER COUPLE INCHES...MAINLY THE FIRST PART OF SUNDAY. WINDS WILL BE GUSTY ALONG NW NC...WITH BUFKIT MOMENTUM TRANSFER SHOWING 50KT GUSTS BLO THE INVERSION. CONSIDERING THAT SOME SUN WILL POP OUT LATER SUNDAY...AND AT LEAST A WIND ADV WILL NEED TO BE CONSIDERED FOR THE NW NC HIGHLANDS. COLD HIGH PRESSURE WILL SETTLE OVER THE AREA SUNDAY NIGHT...1030 MB...PASSING OVERHEAD AROUND 06 UTC...THEN TO ALONG THE MID ATLANTIC COAST BY 18 UTC. CLEAR SKIES AND DIMINISHING WINDS SHOULD PROMOTE COLD SURFACE TEMPS SUNDAY NIGHT. THIS LOOKS LIKE THE COLDEST NIGHT THUS FAR THIS SEASON...AND WENT AT LEAST A FEW DEGREES BLO GUIDANCE EVERYWHERE. VALLEYS WILL LIKELY HIT THE SINGLE DIGITS. && .LONG TERM /MONDAY THROUGH FRIDAY/... GUIDANCE HAS COME INTO BETTER AGREEMENT ON MAINTAINING TWO SEPARATE SHORTWAVE TROUGHS AS A MEAN LONGWAVE TROUGH DEVELOPS OVER THE PLAINS AND SOUTHERN ROCKIES ON DAY 3...BEFORE PROGRESSING THROUGH THE REMAINDER OF THE CONUS BY DAYS 6/7. HIGH PRESSURE WILL BE OFFSHORE BY MONDAY NIGHT WITH STRONG WARM AIR ADVECTION DEVELOPING. BY TUESDAY NIGHT THE FORECAST AREA WILL BE WELL INTO THE WARM SECTOR SO THERE MAY NOT BE MUCH OF A DROP IN OVERNIGHT TEMPERATURES. HAVE SLOWED DOWN THE TIMING OF THE FRONT...BUT EVEN WITH FRONT NOT COMING THROUGH UNTIL LATER ON WEDNESDAY...TEMPERATURES MAY ONLY RISE A FEW DEGREES WITH ALL THE PRECIPITATION AND CLOUD COVER. NOT MUCH CHANGE TO HPC GUIDANCE FOR DAYS 6 AND 7 EXCEPT TO CONFINE SHOWERS TO THE MOUNTAINS. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE WILL SLOWLY MOVE OVER THE AREA THROUGH THE PERIOD...KEEPING VFR CONDITIONS IN PLACE. SATURDAY...CLOUDS INCREASE AHEAD OF ANOTHER CLIPPER. LOOK FOR CIGS TO REMAIN VFR AT ROA/LYH/DAN THIS PERIOD...WHILE SOME LIGHT SNOW...SNOW FLURRIES MOVE INTO BLF/LWB DURING THE AFTERNOON. CIGS WILL DROP TO MVFR WITH IT. THERE WILL BE A BRIEF PERIOD OF IMPROVEMENT TO VFR LATER IN THE AFTERNOON IN SE WV...B4 FLOW SHIFTS TO THE WEST/NW WITH SNOW SHOWERS ARRIVING TOWARD THE END OF THIS TAF PERIOD. AGAIN...CIGS WILL DROP TO MVFR...AND COULD FALL TO IFR AFTER 06Z SUNDAY. THIS WILL CONTINUE THROUGH SUNDAY MORNING WITH UPSLOPE SNOW SHOWERS AFTER THE CLIPPER PASSES BY. ROA...LYH AND DAN WILL BE VFR INTO SUNDAY...BUT WITH GUSTY NORTHWEST WINDS...ARRIVING LATE SAT NIGHT. VFR WEATHER IS EXPECTED SUNDAY NIGHT THROUGH MONDAY NIGHT AS ANOTHER COLD HIGH PRESSURE BUILDS INTO THE AREA. ANOTHER COLD FRONT WILL APPROACH THE REGION TUESDAY...BRINGING DETERIORATING CONDITIONS IN RAIN AND A GOOD CHC OF MVFR...POSSIBLY IFR CIGS AND VSBYS BY THE END OF THE DAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...RCS/WP SHORT TERM...KM/PM LONG TERM...AMS AVIATION...RCS/WP va AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 311 AM CST SAT DEC 6 2008 .SHORT TERM...THROUGH MONDAY MUCH OF THE CONCERN IN THE SHORT TERM LIES IN TWO AREAS....TODAY/S WINDS AND COLD WITH FLURRIES AND BLOWING SNOW...AND SUNDAY AFTN/NIGHT SNOW AMOUNTS. FORECAST CONFIDENCE THROUGH THE SHORT TERM REMAINS RELATIVELY HIGH THANKS TO SOLID SHORT TERM MODEL AGREEMENT BEFORE THINGS RAPIDLY DETERIORATE INTO MONDAY/MONDAY NIGHT. CURRENTLY...POTENT FAMILY OF SHORTWAVES MOVING THROUGH WI/MN IN LEFT EXIT REGION OF 160KT JETLET DIGGING DOWN THE BACKSIDE OF IMPRESSIVE WRN CONUS RIDGING. THIS HAS DRIVEN A LARGE AREA OF LGT/MOD SNOWS ACROSS THE AREA OVERNIGHT WITH WIDESPREAD 1-2 INCH AMOUNTS AND POSSIBLY A LITTLE MORE ALONG/EAST OF MS RIVER. IN WAKE OF DEEP LIFT/STEADY SNOW...SOME -FZDZ/SNOW GRAIN MIXTURE HAS DEVELOPED BETWEEN TC METRO AND KLSE WITH MANY OBS HAVING UNKNOWN PRECIP AND LOOK OUTSIDE THE OFFICE CONFIRMS A SKOSH OF FZDZ IN THE NARROW WARM SECTOR SOUTH/WEST OF THE LOW AS IT MOVES THROUGH WITH RUC SOUNDINGS SUGGESTING TOP OF LOW CLOUD DECK RIGHT AT -8C TO -10C...WHICH SUPPORTS THE MIX OF FZDZ/SNOW GRAINS. 1002MB SFC LOW NEAR KEAU ALSO HELPING TO FOCUS CONVERGENCE ACROSS THE MS RIVER INTO CNTL WISCONSIN. COLD TEMPS /AND GUARANTEED ICE ACTIVATION/ NOT TOO FAR ENOUGH WITH TEMPS PLUMMETING INTO THE LOW TEENS NOW IN CNTL MN WITH STRONG WINDS /25-30KTS/. NEXT SHORTWAVE OF CONCERN SEEN IN GOES WV LOOPS CRESTING WRN CONUS RIDGE OFF BC COAST. TODAY...COLD FRONT SWINGS THROUGH THE AREA AROUND SUNRISE OR A LITTLE EARLIER WHICH STARTS A TEMP FREEFALL AS 850MB TEMPS START DAY AT -10C AND END THE DAY AT -20C. SFC TEMPS WILL BE IN A STEADY FALL ALL DAY FROM THE MID/UPPER 20S AT DAYBREAK INTO THE LOW/MIDDLE TEENS BY SUNSET. WINDS A BIG CONCERN TODAY...AS LAPSE RATES REALLY STEEPEN IN THE STRONG COLD ADVECTION...SUPPORTING TRANSFER OF 30KT GUSTS TO THE SFC IN THE STRONG SUBSIDENCE/PRESSURE RISE BUBBLE ESPECIALLY THIS MORNING. WITH THE NEW 1-3 INCHES OF SNOW AREA-WIDE...AND THEN THE PERIOD OF TEMPS NEAR 30 AND FZDZ OVERNIGHT...THERE IS UNCERTAINTY HOW THE SNOW WILL BLOW AROUND TODAY. THINK WINDS WILL BE STRONG ENOUGH TO REALLY DRIFT IN OPEN AREAS...SO EXPANDED BLSN ACROSS ENTIRE AREA THROUGH EARLY AFTN WHEN WINDS BEGIN TO FALL BACK SOME. DON/T SEE VIS RESTRICTIONS FROM BLSN UPSTREAM...BUT ROADS MAY GET DICEY IN A FEW OPEN AREAS. PLENTY OF FLURRIES UPSTREAM IN THE THIN BKN-OVC STRATOCUMULUS FIELD...SO KEPT FLURRIES IN THE FORECAST...ALL AREAS SHOULD SEE FLAKES FLYING FROM TIME TO TIME. A LITTLE CONCERN GIVEN THE LAPSE RATES THAT A FEW MORE VIGOROUS SHSN MAY DEVELOP...AND THIS WILL NEED TO BE WATCHED. WIND CHILLS BY LATE AFTERNOON DIP BELOW ZERO...WILL BE QUITE UNCOMFORTABLE OUTDOORS TODAY. TONIGHT...RIDGING/HIGH PRESSURE BRINGS CLEARING SKIES FOR A BRIEF PERIOD BEFORE MID/HIGH CLOUDS AHEAD OF NEXT WAVE SPREAD IN FROM WEST TO EAST LATE IN THE NIGHT. SHOULD BE ENOUGH TIME GIVEN FRESH SNOW AND CLEAR SKIES AND RAPIDLY DECOUPLING BOUNDARY LAYER TO DROP TEMPS NEAR/BELOW ZERO MOST AREAS...AND KEPT PREVIOUS TEMPS INTACT. SUNDAY/SUNDAY NIGHT...STILL FEEL GOOD ABOUT LIGHT SNOW ACCUMULATION EVENT SPREADING IN FROM WEST TO EAST DURING SUN AFTN INTO SUN NIGHT. DRIVEN LARGELY BY DEEP LAYER ISENTROPIC ASCENT /WARM ADVECTION/ AND STRONG LOW/MID LEVEL QG WITH AN OVERALL WEAK PV STRUCTURE. WIND VECTORS ON THE THETA SFCS ALMOST PERFECTLY ORTHOGONAL TO THE PRESSURE SFCS SUGGESTING OPTIMUM UPGLIDE AND GOOD OMEGA..CONFIRMED IN CROSS SECTIONS AND BUFR SOUNDINGS THROUGH THE EVENT. WHILE OVERALL SYSTEM MUCH WEAKER THAN CURRENT...WILL MAKE UP FOR IT IN GOOD SNOWFALL RATIOS /AT START OF EVENT/ AND BETTER MOISTURE ON 280-290K LAYER /SPEC HUMIDITY/. ANOTHER 1-2 INCHES LOOKS LIKELY...WITH 3 INCHES PROBABLY AN OUTLIER BUT POSSIBLE ESPECIALLY WEST OF RIVER WITH LIFT WEAKENING AS IT MOVES EAST/SOUTHEAST ACROSS THE AREA. A MORE RECENT DEVELOPMENT HERE ON SUNDAY NIGHT AS RAPID EROSION OF ICE-BEARING CLOUD IN LATE EVENING/OVERNIGHT WITH BOTH DETERMINISTIC RUNS OF GFS/NAM BUFR SOUNDINGS SHOWING A VERY DEEP LOW LEVEL /SFC-2.5KM/ SATURATED LAYER UNDERNEATH THE DRY AIR ALOFT. STRONG WARM ADVECTION STILL OCCURRING IN THIS LAYER BUT OMEGA IS WEAK. HINTS OF CONVERGENCE AXIS /WARM FRONT/ MOVING THROUGH AT THIS TIME SO SNOW COULD DEFINITELY END AS A PERIOD OF FREEZING DRIZZLE SUNDAY NIGHT SO ADDED THIS POTENTIAL TO FORECAST. BOTH MODELS ALSO PAINTING TELL- TALE SPECKLES OF VERY LIGHT QPF /DRIZZLE SIGNAL/ ON THE FORECAST AREA AFTER MIDNIGHT SO THIS TOO NEEDS TO BE WATCHED. .LONG TERM...MONDAY NIGHT THROUGH FRIDAY CONFIDENCE STILL WELL BELOW AVG IN THIS TIME PERIOD. STILL SEEING HUGE DISCREPANCIES IN NUMEROUS AREAS...FIRST WITH HOW MON NIGHT/TUES WAVES PHASE /OR NOT PHASE/ AND THEN HOW MUCH ARCTIC AIR IS AROUND FOR WED/THUR/FRI. STILL SEEING VERY LARGE SPREAD IN BOTH LOW RESOLUTION ENSEMBLE MEMBERS...AND HIGHER RESOLUTION DETERMINISTIC RUNS WITH 850MB TEMPS ABOUT 15C TO 20C DIFFERENT FOR WED/THUR BETWEEN GFS AND ECMWF. NO WONDER CONFIDENCE PLOTS BASICALLY SUGGESTING ENSEMBLE DATA USELESS IN THIS DEGREE OF SPREAD/UNCERTAINTY. THE BIG FOCUS WILL BE ON MON NIGHT/TUES CNTL CONUS STORM WHICH HAS SHOWN A TREND IN ALL DETERMINISTIC RUNS TO SHIFT NORTHWARD GIVEN VARYING DEGREES OF PHASING OF THE NRN/SRN STREAMS ACROSS THE CNTL CONUS. THE NEW 06.00Z ECMWF /PROVEN SUPERIOR IN THIS TIME FRAME TO NCEP MODELS/ HAS TRENDED TOWARD A BONAFIDE HEAVY SNOW EVENT FOR MUCH OF IOWA INTO SRN WISCONSIN. THERE IS LESSER SUPPORT...BUT SUPPORT NONETHELESS FROM THE 06.00Z NAM-WRF AND CAN GEM...BUT 06.00Z GFS AND GEFS PROBABILITIES ARE WELL SOUTH. GIVEN THE UNCERTAINTY...TOOK BABY STEPS FOR THE TIME BEING AND BUMPED UP SNOW CHANCES ALL AREAS...ESP SOUTH TO 50S/60S WITH NOTION THESE MAY NEED TO GO SIGNIFICANTLY HIGHER WITH ONE MORE BATCH OF SUPPORTING RUNS FROM ECMWF/GEM/WRF. THERE/S EVEN A HINT AT A START OF RAIN/FZRA IN THE SOUTH MONDAY NIGHT...BUT NEED TO SEE MORE SUPPORT FOR THIS BEFORE PUTTING IN FORECAST. BOTTOM LINE...IF ECMWF TRENDS PROVE CORRECT...THIS STORM HAS CAPABILITY FOR SIGNIFICANT ACCUMULATIONS...AND WILL BEAR CLOSE WATCHING. FURTHER UNCERTAINTIES WITH THE SHORTWAVE /NRN STREAM/ SET TO RUN ACROSS THE NRN CONUS WED/WED NIGHT. MADE NO CHANGES HERE...AND THIS WAVE HAS HUGE IMPLICATIONS FOR TEMPERATURES /THUS THE HUGE SPREAD CURRENTLY SEEN IN ENSEMBLE/DETERMINISTIC RUNS/. PLENTY MORE ENERGY TO BE HAD IN THIS PATTERN TOWARD END OF WEEK INTO THE WEEKEND...CERTAINLY WILL BE ACTIVE/INTERESTING WITH BOATLOADS OF ARCTIC AIR CONTINUING TO BUILD IN CANADA AS LONGWAVE TROUGH SHIFTS TO WEST CONUS BY NEXT WEEKEND. && .AVIATION...TODAY INTO SUNDAY SHORTWAVE RESPONSIBLE FOR THE -SN AND PATCHY -FZDZ WILL EXIT QUICKLY EARLY THIS MORNING WITH THE PRECIP COMING TO AN END BEFORE 12Z. HOWEVER...AN EXPANSIVE MVFR STRATO-CU DECK EXTENDS UPSTREAM ACROSS MN/EASTERN DAKOTAS BEHIND IT. BRISK NORTHWEST WINDS BEHIND THIS SYSTEM WILL SPREAD ACROSS THE AREA FOR MUCH OF THE DAY...CREATING SOME BLOWING/DRIFTING OF THE NEW SNOW THRU THIS MORNING. THESE WINDS AND STRONG SUBSIDENCE IN THE WAKE OF THE LOW/FRONT AND SHORTWAVE CREATING SOME BREAKS IN THE MVFR CLOUD DECK ACROSS WESTERN MN. THESE BREAKS RATHER PATCHY AND TRANSITORY AND BKN/OVC MVFR CLOUDS EXPECTED TO DOMINATE THRU THE DAY. SFC TO 850MB RIDGE AXIS SLIDES ACROSS THE REGION FOR TONIGHT. LOWER LEVEL DIVERGENCE IN THE RIDGE AXIS AND SHALLOWER MOISTURE/DRIER AIR MOVING IN SHOULD ALLOW THE LOWER CLOUD DECK TO BREAK UP/SCATTER OUT FOR TONIGHT. VFR CONDITIONS EXPECTED THRU SUN MORNING WITH CLOUDS INCREASING AND -SN MOVING BACK INTO THE TAF SITES BY LATER SUN AFTERNOON. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ SHORT/LONG TERM...BINAU AVIATION...RRS wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI 357 AM CST FRI DEC 5 2008 .DISCUSSION...FORECAST FOCUS IS ON SNOW FOR TONIGHT INTO SATURDAY MORNING...THEN SYSTEM FOR SUNDAY NIGHT THROUGH MONDAY NIGHT. TODAY- COLD 850 MILLIBAR POCKET WILL GET WHISKED EAST AS WARM AIR ADVECTION GETS GOING. QUITE A BIT OF STRATOCU AROUND FROM WESTERN WI EXTENDING INTO IA AND MN WITH THE CIRRUS SHIELD SPREADING SEWD FROM CANADA. 925 MB TEMPERATURES SUPPORT THE LOWER 20S WE HAVE GOING IN THE GRIDS SO WONT CHANGE TOO MUCH THERE. SO EVEN THOUGH WAA KICKING IN...INCREASE IN CLOUDS...WINDS AND THE COLD START WILL PRETTY MUCH KEEP THE CHILL GOING ALL DAY. TONIGHT- RAPID ISENTROPIC MOISTENING ON THE 280-285K ISENTROPIC PLOTS THIS EVENING AS DECENT UPGLIDE LEADS TO SATURATION WITHIN THE WAA REGIME AHEAD OF APPROACHING TROUGH. THIS LOOKS TO BE A QUICK HITTER WITH 700-300MB Q VECTOR CONVERGENCE SHOWING A PEAK IN THE L-M20S AROUND 6Z WITH MUCH OF THE LIFT AND ISENTROPIC ADIABATIC OMEGA EXITING SHORTLY AFTER 12Z SATURDAY. NOT A REAL STRONG CROSS HAIRS SIGNATURE. MIXING RATIOS ARE AROUND 1.5 G/KG IN THE 700-725MB LAYER. RATIOS EXPECTED TO BE 15:1. GIVEN QPF AMOUNTS AROUND 0.15 THE GOING 2-3 INCH FORECAST LOOKS LIKE A TOUGH TWEEK. WILL MENTION SOME BLOWING SNOW IN THE HWO AS BUFKIT WINDS/PROGGD SFC GRADIENT SHOW PRETTY BRISK CONDITIONS DURING TIME OF PEAK SNOWFALL AND COMBINED WITH HIGHER RATIOS/LOWER WATER CONTENT SNOW...COULD BE SOME ISSUES WITH THAT. SATURDAY- SURFACE-850 FRONT WILL BE EXITING EARLY WITH MID LEVEL TROUGH AXIS ROTATING ACROSS MIDDAY. WILL HAVE HIGHEST POPS IN THE EAST. RETURN TO COLD AIR ADVECTION DURING THE DAY WITH 700 MILLIBAR DRYING AND SUBSIDENCE ESPECIALLY AFTER PASSAGE OF MID LEVEL TROUGH AXIS. FAIRLY STEEP LOW LEVEL LAPSE RATES MAY BE CONDUCIVE TO A FEW SNOW SHOWERS DURING THE AFTERNOON WITH WINDS CRANKING UP AS WELL. GFS/NAM AND CRAS SUGGESTING LIGHT QPF TIED TO THE MID LEVEL VORT. SUNDAY- QUIET AND CHILLY AS HIGH PRESSURE RIDGE SLIDES ACROSS THE STATE. SUNDAY NIGHT INTO MONDAY- SNOW EXPECTED TO REDEVELOP SUNDAY EVENING AS RENEWED ISENTROPIC FORCING INTERACTS WITH RIGHT REAR QUADRANT OF UPPER LEVEL JET STREAM. RAPID SATURATION AGAIN NOTED ON THE ISENTROPIC SURFACES WITH CRASHING CONDENSATION PRESSURE DEFICITS. 12Z AND 00Z ECMWF HAD QPF MAX TO OUR NORTH HOWEVER THEY HAVE TRENDED A BIT SOUTH MORE INTO THE OUR CWA. MEANWHILE GFS AND NAM HAVE A MORE SOUTHERN PLACEMENT OF QPF ACORSS NORTHERN ILLINOIS. BEST ROUTE FOR NOW IS TO GO WITH CHANCE POPS FOR THIS LEAD WAA EVENT. MONDAY NIGHT AND TUESDAY- 00Z ECMWF DEFINITELY PAINTING A GLOOMIER SCENARIO WITH A STRONGER SOUTHERN WAVE SCOOTING NEWD TOWARDS OHIO VALLEY WHILE GFS HAS MUCH MORE INFLUENCE OF THE NORTHERN STREAM AND A QUICKER MORE PROGRESSIVE LOOK TO THINGS. ECMWF CERTAINLY TAPS MORE MOISTURE AND BRINGS ALMOST 0.50 INCH LIQUID WITH IT/S ASSOCIATED ENERGY. && .AVIATION...LATEST IR IMAGES SHOWING WIDE SWATH OF LOW CLOUDS UPSTREAM OVER MN/IA CAUGHT UNDERNEATH SUBSIDENCE INVERSION. WITH THERMAL TROUGH LINGERING OVER WI THROUGH THE MORNING AND INCREASING WSW LOW LEVEL FLOW...WOULD EXPECT A PERIOD OF BKN-OVC CLOUDS THIS MORNING WITH CEILING HEIGHTS AROUND 3K FEET. LATEST RUC ALSO SHOWING SOME INCREASE IN LOW LEVEL RH THIS MORNING. WOULD EXPC CEILINGS TO INCREASE TO VFR THIS AFTN IN INCREASING LOW LEVEL FLOW AHEAD OF APPROACHING CLIPPER SYSTEM. PERIOD OF SNOW FROM 05Z THROUGH 14Z WILL RESULT IN IFR VSBYS AND MVFR CIGS TONIGHT. && .MARINE...WILL CONTINUE BORDERLINE SMALL CRAFT ADVISORY THIS MORNING AS RELATIVELY WARMER WATERS OF LAKE MICHIGAN WITH SURFACE TEMPS AROUND 4 DEGREES C ALLOWING WINDS TO GUST INTO THE LOWER TO MIDDLE 20S TOWARDS THE OPEN WATERS...AS VERIFIED BY HARRISON CRIB LAST FEW HOURS. TIGHTENING PRESSURE GRADIENT AHEAD OF CANADIAN CLIPPER WILL RESULT IN STRONG LOW LEVEL SOUTHWEST WINDS DEVELOPING OVER THE NEARSHORE WATERS THIS AFTERNOON AND EVENING. STEEP LOW LEVEL LAPSE RATES COULD RESULT IN A BRIEF PERIOD OF GALE FORCE GUSTS MIXING DOWN TO SURFACE THIS EVENING BUT ATTM THINKING THIS WILL BE BRIEF...SO WL CONTINUE SMALL CRAFT ADVISORY THROUGH TONIGHT AND SATURDAY MORNING LEADING UP TO WIND SHIFT ASSOCIATED WITH PASSING SYSTEM. STRONG LOW LEVEL COLD AIR ADVECTION DEVELOPS SATURDAY AFTERNOON WITH A BETTER CHANCE FOR A MORE PROLONGED PERIOD OF GALE FORCE WINDS AND/OR GUSTS DUE TO VERY STEEP LOW LEVEL LAPSE RATES. HENCE CONVERTED SMALL CRAFT ADVISORY THAT WAS IN EFFECT SAT AFTN TO GALE WATCH AND EXTENDED HEADLINE TO 06Z/SUN. && .MKX WATCHES/WARNINGS/ADVISORIES... WI...NONE. LM...GALE WATCH FROM SATURDAY AFTERNOON THROUGH SATURDAY EVENING FOR LMZ643>646. SMALL CRAFT ADVISORY UNTIL 12 PM CST SATURDAY FOR LMZ643>646. && $$ SHORT/LONG TERM...PAC AVIATION/MARINE...MBK wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1254 AM EST SUN DEC 7 2008 .AVIATION.../06Z TAFS/ PERIODS OF MVFR RESTRICTIONS ARE EXPECTED ACROSS PORTIONS OF THE REGION TODAY. LAKE EFFECT SNOW SHOWERS WILL CONTINUE ACROSS THE NORTHERN HALF OF THE FA WITH VISIBILITY RESTRICTIONS DOWN TO 1 MILE POSSIBLE IN SOME OF THE MORE INTENSE BANDS ACROSS SOUTHERN MI. OTHERWISE...DRY AIR ENTRAINMENT AND DIMINISHING INSTABILITY WILL SUPPORT A WANING TREND IN ACTIVITY THROUGH MORNING. IN ADDITION...WINDS WILL CONTINUE TO SUBSIDE AS HIGH PRESSURE BUILDS INTO THE REGION...BACKING IN THE PROCESS. VERY COLD AIR ALOFT COMBINED WITH SUNSHINE AND ADDED LL MOISTURE FROM THE LAKE MI WILL SUPPORT A PERIOD OF SCT TO BKN MVFR CIGS INTO EARLY AFTERNOON ACROSS THE EASTERN HALF OF THE FA...SHIFTING NORTH THROUGH THE DAY WITH DEVELOPING SOUTHERLY FLOW. A FEW FLURRIES ARE ALSO POSSIBLE. WEAK UPPER LEVEL IMPULSE WILL ADVANCE INTO THE GREAT LAKES BY EVENING...SUPPORTING AREAS OF LIGHT SNOW...ESPECIALLY ACROSS THE NORTH. DETAILS ON INTENSITY AND COVERAGE ARE STILL UNKNOWN. HENCE...WILL LEAVE OUT ANY RESTRICTIONS AND ONLY ADD WX MENTION TO TAF TO HIGHLIGHT POTENTIAL. && .PREV DISCUSSION... /ISSUED 616 PM EST SAT DEC 6 2008/ UPDATE... SFC CDFNT IN ASSOCN/W SW TROUGH CLIPPING THROUGH CNTRL LWR MI ATTM ABT TO CLR NW OH. STG CAA IN WAKE OF SFC BNDRY W/RAPID VEERING OF FLW ACRS LK MI AND RAMPING SNOW STREAMERS DVLPG IN ITS WAKE. UPSTREAM TEMPS CRASHING W/SINGLE DIGITS NOTED OVR MOST OF MN. INITIAL LL FLW TRAJECTORY AT 320 DEGREES BUT VEERS FURTHER UPSTREAM TO 300 AND SIMILAR TO 21Z RUC/12Z 4KM ARW PROGS. WHILE THIS SUGGESTS GOING WSW HIGHLIGHTS ON THE MARK...IT ALSO RAISES SOME FLAGS FURTHER INLAND ESP IN LIGHT OF STG LL MEAN FLW AND INLAND CREEP XPCD W/INTENSE MULTIPLE SNOW BANDS. HIRES ARW OUTPUT CONFIRMED BY 21Z RUC MAKE A CASE FOR E/SE EXPANSION OF ADVISORY OVERNIGHT AND POTENTIAL UPGRADE TO WARNING FOR ST JOE MI/ELKHART. HWVR GIVEN DIMINISHING RESIDUAL CYCLONIC MSTR AND DECREASING INVERSION HGTS LT TONIGHT...DURATION OF HEAVIER SNOW LIMITED. WILL CONT TO MONITOR UPSTREAM DVLPMNTS THROUGH 7PM GIVEN EXISTING ADVISORY TIL THEN. GENERALLY MVFR CONDS THROUGH THE PD XCP AT KSBN WHERE IFR RESTRICTIONS TO VSBY/CIG WILL CONT OVERNIGHT BFR IMPRVG SOMEWHAT AFT DAYBREAK SUN. SHORT TERM... LOW OVER NRN MI WITH CDFNT EXTENDING SW ACROSS NRN INDIANA THIS AFTN. MID LEVEL DRY SLOT ASSOCIATED WITH THIS SYSTEM WAS ALSO PUSHING EAST ACROSS THE CWA THIS AFTN. CONTINUING TO GET SOME REPORTS OF FREEZING DRIZZLE IN THE DRY SLOT AND NORTHEAST OF THERE SNOWFALL WAS IN THE 1-3" RANGE WITH GUSTY WINDS AND SNOW SHOWERS ALONG THE COLD FRONT CAUSING SOME SGFNT WINTER WX HAZARDS SO EXTENDED ADVISORY ISSUED THIS MORNING TIL 7PM. MULT BAND LAKE EFFECT SNOW SHOWERS DVLPG OVER NW PORTION OF CWA ATTM. SHRTWV SEEN ON WATER VAPOR MOVG SE ACROSS NRN LM/NE WI THIS AFTN WILL MOVE SE ACRS THE CWA THIS EVE...LIKELY ENHANCING THE SNOW SHOWER ACTIVITY. 925MB OMEGA FCSTS SUGGEST BEST POTENTIAL FOR DOMINANT BAND OVERNIGHT WILL BE ACROSS BERRIEN/CASS SEWD THROUGH ELKHART/ST. JOE INDIANA. INVERSION FCST TO LOWER TO UNDER 5KFT LATE TONIGHT. WOULD EXPECT THIS TO DIMINISH INTENSITY OF SNOW SHOWERS CONSIDERABLY BY MORNING... HWVR AS GRADIENT WINDS DECREASE OVERNIGHT... THERE WILL BE A TENDENCY FOR LAND BREEZE COMPONENT TO WIND TO DVLP ENHANCING CONVERGENCE ALONG ERN SHORE...LIKELY CAUSING OR SUSTAINING A DOMINANT BAND IN THAT AREA THROUGH SUNDAY MORNING. NAM12 SHOWING WK SFC TROF MOVG SSE DOWN THE LAKE LATE TONIGHT... LIKELY AS A RESULT OF THIS LAND/LAKE WIND/CONVERGENCE INTERACTION. GOING FCST OF UP TO 6" OVERNIGHT IN ERN BERRIEN/CASS WITH LESSER AMOUNTS TO THE SE SEEMS REASONABLE AND NO CHANGES TO AMOUNTS/HEADLINES MADE ATTM. ADDITIONAL SNOWFALL IN THE WARNING/ADVISORY AREA AROUND AN INCH EXPECTED SUNDAY BEFORE SNOW SHOWERS TAPER END. LITTLE CHANGE MADE TO HIGHS FOR SUNDAY WHICH ARE AOB ALL 12Z MOS...BUT SEEM REASONABLE IF NOT A TOUCH TOO WARM BASED ON FCST -15C H85 TEMPS AND RECENT MOS WARM BIAS IN SIMILAR SITUATION ON FRI. SHRTWV TOPPING RIDGE OVER PAC NW THIS AFTN IS EXPECTED TO DROP SE INTO BACKSIDE OF LONGWAVE TROF OVER ERN US. THIS SYSTEM EXPECTED TO APPROACH OUR AREA SUNDAY NIGHT COINCIDING WITH WAA ON BACKSIDE OF SFC RIDGE RESULTING IN DECENT MID LEVEL ISENT LIFT WITH 2G/KG MIXING RATIO ON 290K ISENT SFC AROUND 700MB. LOW LEVELS REMAIN RATHER DRY THROUGH THIS PD SO STILL SOME DOUBT IF THIS WAA SNOW WILL FALL THIS FAR SOUTH...BUT DID BUMP UP POPS OVER ALL BUT SRN PORTION OF THE CWA. ALTHOUGH SKIES SHOULD BE MOSTLY CLOUDY SUNDAY NIGHT... LIGHT WINDS IN THE EVE WITH FRESH SNOW COVER AND RATHER DRY LOW LEVELS...ALONG WITH PRECEEDING COOLER DAY THAN FCST BY MOS...ALL SUGGEST GOING LOWS IN TEENS AND BLO ALL 12Z MOS GUIDANCE ARE REASONABLE AND NO CHANGES MADE. LONG TERM...(MONDAY THROUGH SATURDAY)... EXTENDED PERIOD CONTINUES WITH AN ACTIVE BEGINNING AS MONDAY SEES WEAKENING CLIPPER WASH OUT AS IT APPROACHES THE AREA WITH ASSOCIATED AREA OF MOISTURE HEADING THROUGH THE GREAT LAKES. UPR LOW OVER SOUTHWEST OPENS AND PHASES WITH DEEPENING TROUGH OVER MOUNTAIN WEST AND SHIFTS EAST WITH SFC LOW EJECTING THROUGH THE OHIO VALLEY. WHILE DIFFERENCES EXITS IN SPEED AND INTENSITY OF THE LOW THE OPERATIONAL MODELS ARE TRENDING TOWARDS A BETTER CONSENSUS ON A WARMER SOLUTION WITH SFC LOW TRACKING ACROSS INDIANA. FOLLOWED A GFS/ECMWF BLEND FOR THIS SYSTEM WHILE NOTING THAT THE ENTIRE SUITE OF GFS ENSEMBLE MEMBERS IS SUBSTANTIALLY FURTHER SE WITH THIS SYSTEM PUTTING CWA IN A DECIDEDLY COLDER ENVIRONMENT. BASED ON A COMPROMISE BETWEEN OP GFS/ECMWF...THICKNESS FIELDS AND THERMAL PROFILES SUGGEST SNOW MONDAY NIGHT IN AN AREA OF WAA/ISENTROPIC LIFT INDICATED BY BRISK 40 KT FLOW ALONG MOIST 295K SFC. PROFILES DO NOT CURRENTLY SUGGEST A SUBSTANTIAL WINDOW FOR FREEZING RAIN BUT WILL NEED TO MONITOR WITH TIME AS SCENARIO OF WAA ALOFT OVER TRAPPED COLD AIR BELOW COULD YET PRODUCE A PERIOD WITH FZRA HAZARD. AS LOW DEEPENS AND MOVES NE ALONG BAROCLINIC ZONE COLUMN WARMS THROUGHOUT AND THERE IS CONSIDERABLE OPERATIONAL MODEL EVIDENCE TO SUGGEST CHANGING GRIDS OVER TO AN ALL RAIN TUESDAY. MODEL GUIDANCE NOW REACHING NEAR/ABV 40 FOR TUESDAY HIGHS AND BUFR SOUNDINGS SHOWING ABV FZ PROFILE THROUGH A SIGNIFICANT LAYER BY TUESDAY AFTERNOON. ALSO..GFS/EC NOW IN BASIC AGREEMENT WITH PTYPE SCENARIO...AND THE OP GFS HAS NUDGED FURTHER NORTH/WARMER WITH 3 SUCCESSIVE RUNS. HOWEVER..THE FACT THAT IT IS AN OUTLIER AMONG ITS OWN ENSEMBLE MEMBERS WARRANTS HOLDING ON TO CHC SNOW MENTION TUESDAY ALONG WITH LIKELY RAIN FOR THE TIME BEING. ECMWF IS FASTER/SHALLOWER WITH SFC LOW BUT HAS TRENDED TOWARDS GFS WITH 12Z RUN AND CURRENT WINDOW OF LIKELY POPS IS SLANTED TOWARDS SLOWER/DEEPER GFS. BEHIND SYSTEM COLDER AIR ONCE AGAIN FILTERS INTO THE CWA CHANGING EVERYONE BACK OVER TO A PD OF SNOW SHOWERS AS SFC LOW DEPARTS AND RETURNING TEMPS BACK BELOW NORMAL BY THE END OF THE WEEK. COLD H85 TEMPS AND NW FLOW ONCE AGAIN SIGNAL A CHANCE OF LAKE EFFECT AND HAVE CONSERVATIVELY ADDED CHC POPS IN BERRIEN COUNTY. MODELS THEN BRING IN ANOTHER WAVE AT THE END OF THE EXTENDED WITH SIGNIFICANT TIMING DIFFERENCES AND LARGE CONTRASTS IN DEPICTION OF UPPER LEVEL FLOW OVER NOAM. HAVE LEFT DAY 7 DRY FOR NOW TO LET THINGS SORT OUT WITH ANOTHER MODEL CYCLE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR INZ004>008-016-017. MI...WINTER STORM WARNING UNTIL 7 AM EST THIS MORNING FOR MIZ077-078. WINTER WEATHER ADVISORY UNTIL 7 AM EST THIS MORNING FOR MIZ079- 080. OH...NONE. LM...GALE WARNING UNTIL 3 AM EST EARLY THIS MORNING FOR LMZ043-046. && $$ SHORT TERM...TAYLOR LONG TERM...LUDINGTON UPDATE...HOLSTEN AVIATION...JC in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 348 AM CST SUN DEC 7 2008 .SHORT TERM /TODAY/... SFC RIDGE AXIS BEGINNING TO SHIFT EAST OF THE AREA...WITH HIGH CLOUDS SPREADING EASTWARD INTO THE CENTRAL CWA AHEAD OF THE WARM FRONT ASSOCIATED WITH THE NEXT WAVE DIVING SOUTHEAST FROM THE CANADIAN ROCKIES. BEST LIFT WITH THIS WAVE AS IT DIVES SOUTHEASTWARD THROUGH SRN MN/NRN IA THIS MORNING INTO THIS AFTERNOON WILL MAINLY BE NORTH OF HWY 20. GFS/NAM/RUC IN DISAGREEMENT REGARDING AMOUNT OF MOISTURE/QPF WITH THE NAM/RUC ADVERTISING ONLY A FEW HUNDREDTHS ACROSS THE NORTHERN CWA VERSUS JUST OVER A TENTH WITH THE GFS. SOUNDINGS INDICATING BRIEF SATURATION...WITH PROBABLY AROUND A FEW HOURS OF LIGHT SNOW AT MOST LOCATIONS NORTH OF I-80. OTHERWISE MAYBE ONLY A BRIEF SNOW SHOWER OR FLURRIES EXPECTED ACROSS THE SOUTHERN CWA. PREVIOUS FORECAST MORE IN LINE WITH THE GFS...BUT LOOKING AT TRENDS UPSTREAM FEEL THE GFS MAY BE A BIT OVERDONE. THEREFORE HAVE TRENDED GRIDS SLIGHTLY TOWARD THE NAM/RUC BY LOWERING POPS ACROSS THE SOUTHERN HALF OF THE CWA AND CUTTING THE QPF DOWN BY 30 TO 40 PERCENT. COULD STILL SEE AROUND AN INCH ACROSS THE NORTHERN TIER COUNTIES...TAPERING TO A FEW TENTHS AROUND HWY 30 TO AROUND A TRACE FURTHER SOUTH. BUFKIT SOUNDINGS DID SHOW A BRIEF PERIOD OF FZDZ AS THE SNOW TAPERED OFF AND SATURATION WAS LOST ALOFT. HOWEVER THIS WAS QUITE BRIEF ONLY AROUND AN HOUR OR SO...SO LEFT PRECIP TYPE ALL SNOW FOR NOW. .LONG TERM /TONIGHT-SATURDAY/... WILL HAVE ANOTHER WEAK SHORTWAVE TRANSLATING OVER SOUTHERN IOWA TONIGHT WITH BAND OF WARM ADVECTION AND MID LEVEL FRONTOGENETICAL FORCING. MODELS DIFFER ON AREA THAT RECIEVES LIGHT PRECIP...SO WENT WITH ONLY LOW CHANCES ACROSS THE SOUTHERN HALF OR SO. OTHERWISE MAIN CONCERN FOR THIS FORECAST PACKAGE IS SIGNIFICANT SYSTEM FOR MONDAY NIGHT AND TUESDAY. THE ECMWF/UKMET/CANADIAN SOLUTIONS ARE PREFERRED FOR THIS PERIOD GIVEN THEIR CONSISTENCY. UNFORTUNATELY THE NAM/SREF AND TO A CERTAIN EXTENT THE GFS/GEFS ARE NOT EXACTLY GOING THE SAME DIRECTION...SO CONFIDENCE IS NOT AS HIGH AS I`D LIKE. HOWEVER...SINCE OUR FORECAST IS LEANING STRONGLY TO THE FIRST SET OF MODELS MENTIONED ABOVE...WILL NEED TO ISSUE A WINTER STORM WATCH FOR A STRIP OF COUNTIES SW TO NE THROUGH CENTRAL IOWA. EVEN AFTER TAKING A BLEND OF THE GFS/HPC/ECMWF QPF FOR THIS PERIOD...STILL CAME OUT WITH 4 TO 8 INCHES OF SNOW FOR MUCH OF OUR AREA. THAT SEEMS A BIT MUCH FOR THE UNCERTAINTY THAT STILL EXISTS...BUT I AM IN COLLABORATION WITH NEIGHBORS. AS LOW PRESSURE ORGANIZES IN THE SOUTHERN PLAINS MONDAY...FRONTOGENETICAL FORCES AND ISENTROPIC LIFT BEGIN OVER IOWA...AND MAY YIELD LIGHT PRECIP. SOUTHERN IOWA SHOULD BE ABOVE FREEZING DURING THE DAY MONDAY INTO MONDAY NIGHT. SO AS THE SYSTEM APPROACHES...RAIN WILL BE THE DOMINATE P-TYPE ALONG AND SOUTH OF I-80. HOWEVER...AS THE LOW INTENSIFIES AND WRAPS IN THE COLDER AIR TO THE NORTH...ALONG WITH DYNAMIC PROCESSES IN THE TROWAL AND DEFORMATION ZONE TO THE NORTH OF SFC LOW TRACK...PRECIP SHOULD TRANSITION TO ALL SNOW MONDAY NIGHT NW TO SE. SOUNDINGS DON`T OFFER MUCH CHANCE FOR ANYTHING OTHER THAN RAIN OR SNOW. HOWEVER...THERE IS STILL A POSSIBILITY OF A LITTLE FREEZING RAIN IF COLDER SFC AIR WORKS ITS WAY IN BEFORE THE UPPER LEVELS COOL ENOUGH. AT THIS TIME THOUGH SOUNDINGS SUPPORT MORE OF A RAIN TO SNOW TRANSITION WHERE IT STARTS AS RAIN. AM USING SNOW RATIOS AT OR BELOW CLIMO FOR NOW...GIVEN UNCERTAINTIES OF WHERE ANY HEAVIER BANDED SNOW MAY SET UP. EVEN IF SNOWFALL AMOUNTS DO NOT REACH WARNING CRITERIA ALONE...THE WIND WILL BE INCREASING ENOUGH TO WARRANT A WINTER STORM WATCH. WINDS ARE EXPECTED TO BE SUSTAINED BETWEEN 20 AND 30 MPH WITH GUSTS POTENTIALLY CLOSE TO 35 OR 40 MPH AT TIMES. AND THIS BRINGS US DANGEROUSLY CLOSE TO BLIZZARD CONDITIONS. BUT...GIVEN SOME UNCERTAINTY THERE...WE WILL JUST MENTION THE WIND AND BLOWING SNOW POTENTIAL IN THE WINTER STORM WATCH. ALSO...BEING THE FIRST WINTER STORM THREAT OF THE SEASON...WE WILL LOWER OUR THRESHOLD A BIT. THE SNOW SHOULD END TUESDAY EVENING IF NOT BEFORE...BUT CONTINUE TO BLOW AROUND WELL INTO TUESDAY NIGHT. AN ACTIVE PATTERN DOES NOT SLOW DOWN...WITH A COUPLE OF CLIPPER SYSTEMS FOR LATE IN THE WEEK...EACH WITH RESPECTABLE CHANCES FOR LIGHT SNOW IN OUR AREA. TEMPS WERE ADJUSTED DOWNWARD FOR THE MIDDLE OF THE WEEK GIVEN TREND IN THE MEDIUM RANGE GUIDANCE. && .AVIATION...07/06Z WARM ADVECTION SETTING IN QUICKLY WEST WITH WINDS BECOMING SSE BY MORNING. ZONE OF STRONGER THETAE ADVECTION OVER THE CENTRAL DAKOTAS ALREADY LOWERING CIGS TO MVFR LEVELS AND WILL MOVE EAST OVERNIGHT. CLOUDS NOW ENTERING WESTERN IA WITH CEILINGS LOWERING. MODEST MID LEVEL LIFT WILL CAUSE A BAND OF LIGHT SNOW TO DEVELOP AND TRACK ACROSS THE NORTH CENTRAL WITH UP TO 1 TO 2 INCHES OF SNOW POSSIBLE SUNDAY. EXPECT MVFR CIGS MAINLY WITH VSBYS OF GENERAL 3-5SM CAT. SMALL CHANCE THAT IFR CIGS MAY BRIEFLY ACCOMPANY THE HEAVIER SNOWFALL RATES BETWEEN 15Z AND 19Z NORTH SECTIONS. CIGS GRADUALLY LIFTING TOWARD 00Z FROM WEST TO EAST. FARTHER SOUTH...IMPACT NOT AS GREAT WITH KOTM SEEING LEAST IMPACT FROM THE WARM FRONTAL PRECIP THAT WILL BE ENTERING THE WESTERN PORTION OF THE TAF FORECAST AREA BY 12Z SUNDAY. AFT 08/00Z WILL SEE LOW LEVELS DRY OUT A BIT AND ALLOW FOR VFR CIGS TO RETURN BRIEFLY BEFORE NEXT SYSTEM IMPACTS THE REGION. /REV && .DMX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ADAIR-ADAMS-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN- CARROLL-CASS-CERRO GORDO-CLARKE-DALLAS-FRANKLIN-GREENE-GRUNDY- GUTHRIE-HAMILTON-HARDIN-JASPER-MADISON-MARSHALL-POLK-POWESHIEK- RINGGOLD-STORY-TAMA-TAYLOR-UNION-WARREN-WEBSTER-WRIGHT. && $$ SHORT TERM...ALBRECHT LONG TERM...MOYER AVIATION...REV ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 246 AM MST SUN DEC 7 2008 .DISCUSSION...NORTHWEST FLOW WILL BECOME ZONAL TONIGHT AS SHORTWAVE ENERGY DIGS SOUTH ACROSS WESTERN UTAH. FLOW THEN BECOMES SOUTHWEST ON MONDAY AS THE TROUGH MOVES EAST OF THE ROCKIES. FLOW IS NORTHWEST ON TUESDAY. A SURFACE TROUGH OVER EASTERN COLORADO TODAY WILL MOVE INTO THE OKLAHOMA/TEXAS PANHANDLE REGION TONIGHT/MONDAY. HIGH PRESSURE WILL BUILD INTO NORTHWEST KANSAS MONDAY NIGHT THROUGH TUESDAY. THE MAIN FORECAST ISSUES ARE PRECIPITATION TYPE AND WIND. TIMING OF THE EVENT LOOKS ON TRACK WITH UPWARD VERTICAL VELOCITIES INDICATED MONDAY AFTERNOON...CONTINUING MONDAY NIGHT AND ENDING AROUND 12Z TUESDAY. THE CURRENT FORECAST KEEPS THE EVENT ABOUT 6 HOURS PAST THIS TIME. 1000-500MB THICKNESSES FROM THE GFS/NAM SUGGEST THAT PRECIPITATION SHOULD BE LIQUID THROUGH MOST OF MONDAY AFTERNOON EXCEPT IN THE NORTHWEST ZONES. BY MONDAY EVENING PRECIPITATION SHOULD BE ALL SNOW OVER THE NORTHWEST HALF OF THE FORECAST AREA WITH ONLY THE SOUTHEAST ZONES HAVING A MIX OF RAIN/SNOW. THE ENTIRE FORECAST AREA SHOULD HAVE ALL SNOW BY 06Z TUESDAY THROUGH THE END OF THE EVENT. THE NEXT ISSUE IS WIND WHICH THE RUC SHOWS TO BE A SIGNIFICANT CONCERN WITH THIS EVENT. BY 09Z TUESDAY SURFACE WIND IS PROGGED TO BE SUSTAINED AT GREATER THAN 30KTS AND WIND GUSTS GREATER THAN 40KTS. THIS WILL CAUSE SIGNIFICANT BLOWING AND DRIFTING OF ANY SNOW. MOST OF THE SNOW SHOULD END BY 12Z TUESDAY BUT THIS STRONG WIND SHOULD LAST WELL INTO TUESDAY AFTERNOON. CURRENT FORECAST ALREADY HAS AREAS OF BLOWING SNOW FOR THIS TIME PERIOD. A WINTER HIGHLIGHT MAY BE NEEDED IF MODELS CONTINUE TO SHOW THIS MUCH WIND. FOR NOW PLAN TO CONTINUE WORDING IN THE HWO FOR THIS POTENTIAL. SNOWFALL AMOUNTS STILL LOOK LIKE 1 TO 3 INCHES WITH HEAVIEST AMOUNTS OVER THE CENTRAL AND EAST ZONES. TEMPERATURES WILL STILL BE UNSEASONABLY WARM. GUIDANCE SHOWING READINGS ABOUT 20 DEGREES ABOVE NORMAL. FOLLOWED COOLER GUIDANCE BASED ON UNCERTAINTY WITH AMOUNT OF CLOUDS. COLD FRONT WILL COME THROUGH TONIGHT. MAX TEMPERATURES WILL REACH INTO THE LOWER 40S MONDAY AND IN THE UPPER 30S TUESDAY. MIN TEMPERATURES WILL FALL INTO THE MID 20S TONIGHT AND AROUND 20 MONDAY AND TUESDAY NIGHTS. FS && .AVIATION... 426 PM MST SAT DEC 6 2008 FOR SATURDAY EVENING THROUGH SUNDAY EVENING...VFR CONDITIONS WILL PREVAIL THROUGHOUT THE TAF PERIOD FOR BOTH KGLD AND KMCK. BY 05Z OR 06Z...LIGHT AND VARIABLE WINDS WILL SET UP FROM THE SOUTHWEST AT 8 TO 10 KTS UNDER SCT-BKN MID LEVEL CLOUDS. BY ABOUT 16Z...WINDS WILL BE FROM THE NORTHWEST AT AROUND 7 KTS UNDER SCT-BKN HIGH LEVEL CLOUDS WITH WINDS BECOMING MORE VARIABLE BY THE END OF THE TAF PERIOD. BLM && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ WFO GOODLAND ks AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE JACKSON KY 125 AM EST SUN DEC 7 2008 .SHORT TERM.../THE REST OF TONIGHT/ SCATTERED TO NUMEROUS LIGHT SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA. THESE ARE ALL OUT AHEAD OF THE APPROACHING COLD FRONT. MUCH OF THESE WILL BE WINDING DOWN OVER THE NEXT COUPLE OF HOURS. THE NEXT BATCH OF PRECIP THAT WILL BE AFFECTING OUR AREA IS OVER INDIANA. THIS IS POST FRONTAL...AND ASSOCIATED WITH A SUBTLE H5 VORT MAX...VISIBLE ON THE RUC13 AND WATER VAPOR IMAGERY. VISIBILITIES IN THIS PRECIP ARE ALL 3 TO 5 MILES ATTM...BUT AM CONCERNED THIS COULD BE ENHANCED JUST A LITTLE AS IT MOVES OVER THE HIGHER TERRAIN OF EASTERN KENTUCKY. FOR THIS REASON...INCREASED POPS TONIGHT AND MENTIONED NUMEROUS LIGHT SNOW SHOWERS AS OPPOSED TO FLURRIES FOR MUCH OF OUR AREA. TAPERED POPS DOWN RAPIDLY IN THE SOUTHWESTERN CWA...WHERE THEY REMAIN IN THE LEAST FAVORABLE MOISTURE FOR SIGNIFICANT SHSN COVERAGE. FROPA SHOULD OCCUR WITHIN A COUPLE HOURS OF MIDNIGHT ACROSS THE CWA. MEAN RH DECREASES...BUT LOW LEVEL MOISTURE LINGERS IN THE SNOW GROWTH REGION. STILL THINK ANY ACCUMULATIONS WILL BE LESS THAN A HALF INCH...WITH AROUND A HALF INCH POSSIBLE IN FAR SOUTHEAST KENTUCKY. BEST UPSLOPE FLOW WILL NOT LIKELY OCCUR UNTIL 08 OR 09Z AS WINDS SHIFT AROUND TO THE NORTHWEST. BY THEN...MOISTURE SHOULD BE BEGINNING TO DECREASE. LOW TEMPS LOOKED GOOD...SO NO MAJOR ADJUSTMENTS THERE. DID TWEAK THE HOURLY TEMPS...AS TEMPS RANGE FROM THE UPPER 20S TO THE MID 30S ACROSS OUR CWA JUST AHEAD OF THE FRONT. THESE WILL DROP OFF AFTER FROPA. STILL THE MAJOR TRAVEL CONCERN OVERNIGHT IS REFREEZING WATER ON ROADWAYS. WILL CONTINUE TO HIGHLIGHT THIS IN SPECIAL WEATHER STATEMENTS...WEB HEADLINES...AND IN THE HWO. UPDATED FORECAST PRODUCTS ARE ALREADY OUT. THE PREVIOUS SHORT TERM FORECAST DISCUSSION FOLLOWS... /TONIGHT THROUGH MONDAY NIGHT/ AN UPPER LEVEL TROUGH IS IN PLACE OVER MUCH OF THE EASTERN CONUS...WITH A RELATIVELY POTENT SW/V CURRENTLY WORKING THROUGH THE OH VALLEY. THE SFC AREA OF LOW PRESSURE IS WORKING INTO MI AND ONTARIO...WITH THE COLD FRONT TRAILING SOUTH INTO THE OH VALLEY. THE EARLIER BAND OF LIGHT SNOW HAS GENERALLY MOVED EAST OF THE AREA WITH SOME WARMER AND DRIER AIR ATTEMPTING TO ADVECT IN IN THE WARM SECTOR. A FEW ISOLATED SNOW SHOWERS WERE OVER INDIANA AND ILLINOIS IN ADVANCE OF THE FRONT. THE COLD FRONT WILL WORK ACROSS WESTERN AND INTO CENTRAL KY THIS EVENING AND THEN CROSS THE JKL CWA GENERALLY BETWEEN 0Z AND 4Z. IN ADDITION AS THE SW/V MOVES THROUGH THE OH VALLEY...THE LAPSE RATES WILL INCREASE AND THERE SHOULD BE REDEVELOPMENT OF SNOW SHOWERS DURING THE EVENING HOURS OVER THE NE PART OF THE CWA AND ALONG THE VA BORDER AREA THIS MORNING. WENT WITH SCATTERED POPS OVER MUCH OF THE CWA...WITH SLIGHT CHANCE IN THE SW AND LIKELY NEAR THE VA BORDER. ALTHOUGH QPF WILL BE VERY MINIMAL...A DUSTING TO ONE HALF OF AN INCH OF SNOW CANNOT BE RULED OUT FROM THIS EVENING INTO THE OVERNIGHT HOURS GIVEN HIGH SNOW TO LIQUID RATIOS. THE SUBSIDENCE INVERSION WILL LOWER AND THE BL IS EXPECTED TO DRY OUT TOWARD 12Z SUN...SO WE WENT WITH ONLY ISOLATED FLURRIES AND SNOW SHOWERS OVER THE SE ON SUN. AS FAR AS TEMPS...WITH A COLDER START THAN WAS EXPECTED EARLIER...OPTED TO LOWER MIN T TONIGHT. 8H TEMPS ARE EXPECTED TO REMAIN COLD FOR MUCH OF TOMORROW...EVEN AS HEIGHTS BEGIN TO INCREASE AND SFC HIGH PRESSURE BUILDS INTO THE TN AND OH VALLEYS. BY THE END OF THE DAY -4C IS FORECAST IN THE SW...WITH COLDER...-10 OR -11C IN THE EAST. WITH THAT IN MIND...OPTED TO LEAN TOWARD THE COLDER END OF MOS GUIDANCE. DEPENDING ON THE EXACT TIMING OUT OF THE EXPECTED CU AND SC...TEMPS COULD END UP EVEN COLDER THAN THAT...ESPECIALLY SINCE THERE SHOULD BE SOME CIRRUS FROM TIME TO TIME IN NW FLOW ALOFT. HOWEVER...MUCH OF THE AREA WILL STRUGGLE TO REACH THE FREEZING MARK. HIGH PRESSURE WILL BEGIN TO SHIFT EAST ACROSS THE APPALACHIANS AND REACH THE EAST COAST PIEDMONT REGION BY EARLY MON. MID AND HIGH CLOUDS LATE MAY LIMIT THE TEMP FALL...BUT WITH DRIER DEWPOINTS IN THE TEENS EXPECTED BY LATE ON SUN AND EXPECTED EARLY DECOUPLING DUE TO CLEARING SKIES...KEPT THE SLIGHTLY COOLER THAN GUIDANCE TEMPS FOR VALLEYS ON SUN NIGHT. SOUTHERLY FLOW ON THE RIDGES SHOULD LEAD TO A MODERATE RIDGE/VALLEY SPLIT. MON APPEARS TO BE A TRANSITION DAY AS WEAK UPPER RIDGING WORKS ACROSS THE AREA...WITH WARMER TEMPERATURES. GUIDANCE HAS TRENDED WARMER OVERALL AND UPPED MAX T FOR MON. HOWEVER...TWO SHORTWAVES...ONE OVER THE NORTHERN ROCKIES AND ANOTHER OVER THE SOUTHERN ROCKIES WILL BEGIN TO CARVE OUT A PLAINS TROUGH. LEE CYCLOGENESIS SHOULD TAKE PLACE LATER IN THE PERIOD...WITH AN INCREASING LOW LEVEL JET LATE ON TUE NIGHT AS WELL AS INCREASING PRESS GRADIENT. ISENTROPIC LIFT SHOULD PRODUCE CLOUDS AT THE VERY LEAST...WITH BETTER LIFT AND ASSOCIATED PRECIP LIKELY REMAINING WEST AND NORTH OF THE AREA. .LONG TERM.../TUESDAY THROUGH SATURDAY/ THE LONG RANGE MODELS ARE IN DECENT AGREEMENT WITH REGARDS TO NEXT WEEKS WEATHER. A FRONT WILL PUSH ACROSS THE OHIO VALLEY ON TUESDAY. PRECIPITATION AHEAD OF THE FRONT WILL LIKELY BE IN THE FORM OF RAIN...AS BOTH GFS MODELS SOUNDINGS AND TIME HEIGHT CROSS SECTIONS ARE KEEPING TEMPERATURES ABOVE FREEZING FOR THE ENTIRE DAY. IT APPEARS AT THIS TIME THAT THE SUB FREEZING AIR WILL NOT MAKES ITS WAY INTO THE REGION UNTIL AFTER THE FRONT PASSES BY AND WINDS SHIFT TO THE WEST AND NORTHWEST. WITH THAT IT MIND...IT LOOKS LIKE THERE WILL BE A PERIOD OF LIGHT SNOW SHOWERS BEGINNING AT 7Z WEDNESDAY AND LASTING THROUGH 15 OR 16Z ON WEDNESDAY. LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED. IT IS LOOKING MORE AND MORE LIKE NEXT WEEKS SYSTEM WILL BRING GOOD SOAKING RAINS TO THE FORECAST AREA. THE LATEST GFS MODEL HAS A 60-70KT LOW LEVEL JET MOVING ACROSS KENTUCKY TUESDAY AFTERNOON AND NIGHT...WHICH WILL ACT TO REALLY ENHANCE THE RAINFALL AHEAD OF THE FRONT. BY THE TIME ENOUGH COLD AIR MAKES IT INTO THE AREA FOR SNOW TO FORM...THE BEST JET DYNAMICS WILL BE WELL EAST OF THE AREA. TEMPERATURES WERE A MAJOR CHALLENGE FOR NEXT WEEK AS ALL OF THE MODEL DATA IS HAVING A VERY DIFFICULT TIME COMING INTO ANY SORT OF AGREEMENT WITH REGARD TO HOW WARM OR COLD IT IS GOING TO BE. MODEL SOUNDINGS ARE PAINTING A PICTURE OF VERY COLD DAYTIME HIGHS NEAR FREEZING ON THURSDAY AND FRIDAY...WHILE AT THE SAME TIME THE LATEST MEXMOS HAS HIGH TEMPERATURES AROUND 40 ON THU AND FRI...WITH HPC COMING IN WITH TEMPS IN THE UPPER 40S FOR THU AND AROUND 40 ON FRIDAY. WHAT I ULTIMATELY DECIDED TO DO WAS ADJUST TEMPERATURES DOWN A BIT ACROSS THE BOARD WITH THE EXCEPTION OF TUESDAY AFTERNOON...WHERE I ADJUSTED TEMPS UP A BIT MORE TOWARD THE VERY WARM MEXMOS AND HPC NUMBERS AND TO MATCH UP WITH SURROUNDING OFFICES BETTER. A FEW ADJUSTMENTS WERE ALSO MADE TO SKY COVER TO ACCOUNT FOR TIMING CHANGES MADE TO NEXT WEEKS FRONTAL PASSAGE. DEWPOINTS ARE ALSO OUT OF SORTS WITH SURROUNDING OFFICES FOR LATE NEXT WEEK...SO ADJUSTMENTS WERE NEEDED THERE AS WELL. && .AVIATION.../06Z TO 06Z/...UPDATED BANDS OF SNOW SHOWERS CONTINUE TO MOVE ACROSS THE AREA ACCOMPANYING A REINFORCING COLD FRONT. EXPECT PREDOMINANT VFR CONDITIONS THROUGH 10Z WITH SOME LIGHT SNOW AROUND AS DEPICTED BY THE VCSH IN THE TAFS. PUT A TEMPO INTO THE TAFS FROM 07 THROUGH 11Z FOR MVFR CONDITIONS... BOTH VIS AND CIG...WITH THE SNOW SHOWERS. THE LIGHT SNOW SHOWERS WILL DIMINISH TO JUST FLURRIES TOWARD DAWN WITH CIGS DISAPPEARING BY NOON. FOLLOWING THE FRONT...NOW EAST OF THE TAF SITES...THE WINDS HAVE SHIFTED TO THE NORTHWEST WITH AN ELEMENT OF GUSTINESS. EXPECT THESE NORTHWEST WINDS TO SETTLE DOWN TOWARD DAWN AND BECOME RATHER LIGHT DURING THE DAY SUNDAY. && .JKL WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JP/WJM LONG TERM....AR AVIATION...GREIF ky AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 420 AM EST SUN DEC 7 2008 .SYNOPSIS... COLD UPPER TROUGH WITH H85 TEMPS -15C TO -20C REMAINS IN PLACE FM HUDSON BAY INTO THE UPR GREAT LAKES. PRIMARY COLD FRONT IS MOVING INTO THE LWR GREAT LAKES AND DIVING INTO THE SOUTHERN PLAINS. NW FLOW AND THE COLD TEMPS BEHIND THE FRONT IS PRODUCING MOSTLY MULTIPLE LK EFFECT SNOW BANDS. IR SATELLITE AND RADAR INDICATES HEAVIEST SNOW SHOWERS INTO ALGER COUNTY AND NRN DELTA COUNTY. THIS BAND IS STRONGEST DUE TO PRECONDITIONED FLOW OFF LK NIPEGON AND ALSO SINCE THE TRAJECTORIES ARE CROSSING THE LONGEST AVIALIABLE FETCH ACROSS LK SUPERIOR. MEANWHILE...DRY AIR AND INVERSION BLO H9 ASSOCIATED WITH INCOMING SFC RIDGE AND AS SEEN ON 00Z INL/WPL SOUNDINGS...IS LIMITING EXTENT OF LK EFFECT OVR WRN CWA. && .DISCUSSION... ALTHOUGH WINDS HAVE DIMINISHED...LK EFFECT STILL AN ISSUE TODAY AS SFC-925MB WINDS STAY NW. EFFECTS OF THE DRY AIR/SUBSIDENCE SEEN UPSTREAM WILL BE OFFSET FOR SNOW SHOWERS EAST OF MARQUETTE AS LOW-LEVEL TRAJECTORIES CROSS LK SUPERIOR THE LONGEST. INVERSION HEIGHT BTWN 5-7KFT AND IDEAL TEMPS WITHIN CLOUD LAYER FOR DENDRETIC SNOW GROWTH ENSURES THAT LK EFFECT WILL BE SUFFICIENT AT PRODUCING ACCUMS DESPITE NEGATIVE LARGE SCALE FACTORS. BY FAR BEST SNOW WILL BE IN SNOWBAND PRECONDITIONED BY LK NIPEGON. MAJORITY OF HIGH RES GUIDANCE...NAM/REG CANADIAN/RUC13/LOCAL WRF POINT TO HEAVIEST SNOW TO REMAIN IN ALGER/NRN SCHOOLCRAFT AREAS. KEPT WINTER STORM WARNING FOR THESE TWO ZONES GIVEN THAT STRONG BAND IS STILL OUT THERE AND SNOWFALL RATES UP TO 1"/HR ARE STILL POSSIBLE. OTHERWISE...CANX REST OF THE GOING HEADLINES. 925MB WIND FIELD BECOMES DISORGANIZED AFT 21Z TODAY...AND BY THAT TIME SNOW SHOWERS SHOULD DIMINISH/LIFT OFFSHORE. ELSEWHERE...AS WINDS BACK WITH RIDGE THROUGH HERE...THERE COULD BE SOME SUNSHINE. TEMPS WILL REMAIN CHILLY THOUGH WITH MAINLY TEENS EXPECTED. SHEARED OUT UPPER WAVE WITH SWATH OF DEEP MOISTURE SWINGS ACROSS UPR LAKES. GFS/NAM/LOCAL WRF SIMILAR IN HANDLING THE SYSTEM. ISENTROPIC LIFT ON 280K SFC...ROUGHLY 800-700MB...SHOWS STRONGEST LIFT OCCURING ALONG SW BORDER INTO LK MICHIGAN. KEPT HIGHEST POPS CLOSER TO WI BORDER...WITH JUST CHANCE POPS CLOSER TO LK SUPERIOR AS SW LOW-LEVEL FLOW MAINLY DOWNSLOPES. UP TO AN INCH OF SNOW NEAR THE WI BORDER. MAIN ISSUE WILL BE IN SE CWA NEAR LK MICHIGAN. 925MB WINDS BECOME VERY FAVORABLE FOR LK EFFECT OFF LK MICHIGAN INTO SRN SCHOOLCRAFT INTO SRN PORTION OF LUCE COUNTY AFT MIDNIGHT AND INTO MONDAY. H85 TEMPS -13C WITH DEEP MOISTURE ADDED FM THE SYSTEM MOVING IN FM THE WEST YIELD MORE THAN SUFFICIENT OVER WATER INSTABILITY ALTHOUGH EXACT AREA OF HEAVIEST SNOW IS UNCERTAIN. SINCE THE HIGH PRESSURE RIDGE LINGERS OVR LWR MICHIGAN AND ONTARIO...INTERACTING LAND BREEZES ENHANCE LOW-LEVEL CONVERGENCE. HIGH RESOLUTION MODELS FCST A DOMINANT BAND OVR FAR SE CWA...BUT VARY ON EXACT PLACEMENT. WILL SAY THAT THE RUC13 SHOWING A STRONG LAND BREEZE EMERGING FM LWR MI...AND SETTING UP THE BAND AS FAR WEST AS DELTA COUNTY WAS NOT PREFERRED AS SWRLY 925MB WINDS SHOULD PIN THE LAND BREEZE CLOSER TO THE LWR MI SHORE. IN ANY EVENT...COULD SEE WARNING CRITERIA SNOWFALL OVR FAR SE CWA FM THIS BAND OF LK EFFECT SO ISSUED A LAKE EFFECT SNOW WATCH FOR LATE TONIGHT THROUGH MOST OF MONDAY FOR SOUTHERN SCHOOLCRAFT INTO LUCE. OUTSIDE OF LK EFFECT OFF LK MICHIGAN...MONDAY FEATURES LGT SNOW MAINLY AFFECTING THE WI BORDER AREAS DUE TO UPPER LEVEL JET FORCING AND PERSISTENT ISENTROPIC ASCENT ON 280K SFC. NW LOW-LEVEL WINDS AND H85 TEMPS BLO -10C COULD ALSO PRODUCE LGT LK EFFECT OVR NW UPR MI. NEXT ISSUE IS LOW PRESSURE EMERGING FM THE PLAINS LATER TUE. ECMWF WAS MOST EMPHATIC WITH THIS SYSTEM LAST COUPLE DAYS...AND OTHER GUIDANCE NOW LOOKS LIKE IT IS TRENDING THIS WAY. ECMWF IDEA WOULD BRUSH FAR SOUTH CENTRAL...BASICALLY SRN MNM COUNTY...WITH WIDESPREAD SNOW LATE MON NIGHT THROUGH TUE NIGHT. PRIMARY SYSTEM SNOW SHOULD STAY SOUTH OF CWA...BUT ADVY MAY BE NEEDED IN THE SCNTRL. NRLY FLOW OVR LK SUPERIOR WITH COOLING WILL LEAD TO LK EFFECT SNOW SHOWERS INCREASING IN THE TUE/WED PERIOD. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... MULTI-PARALLEL BAND LAKE EFFECT SNOW WINDING DOWN FROM THE WEST THIS EVENING. VERY DRY AIR UPSTREAM GREATLY DIMINISHING LES OVER WRN LAKE SUPERIOR THIS EVENING. HAVE DECIDED TO GO WITH VFR VBSY AT KCMX THROUGH THE PERIOD BUT WILL KEEP MVFR CIGS UNTIL WINDS BACK SW BY 20Z SUN. MVFR CIGS/VSBYS IN LIGHT SNOW SHOULD RETURN BY LATE SUN EVENING AHEAD OF THE NEXT SYSTEM MOVING IN FROM THE NRN PLAINS. WINDS BACKING NW AT KSAW WILL SHIFT SIGNIFICANT LES BANDS EAST OVERNIGHT WITH VFR VSBYS EXPECTED THROUGH MUCH OF THE PERIOD. WINDS BACKING W LATE TONIGHT WILL BREAK UP MVFR CIGS AND KEEP SKIES VFR INTO SUN EVENING. THERE IS ANOTHER CHANCE OF LIGHT SNOW LATE SUN EVENING WHICH COULD LOWER VBSYS/CIGS INTO THE MVFR CATEGORY. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS A LOW PRESSURE CENTER OVER SOUTHEAST CANADA CONTINUES TO THE EAST TODAY...A HIGH PRESSURE RIDGE WILL MIGRATE ACROSS THE UPPER GREAT LAKES BY THIS EVENING AND INTO NEW ENGLAND BY LATE MONDAY. STRONG N WINDS EARLY TODAY WILL DIMINISH QUICKLY AS THIS RIDGE APPROACHES. IN THE WAKE OF THE RIDGE...EXPECT A LOW PRESSURE TROUGH TO DRIFT OVER LAKE SUPERIOR ON MONDAY NIGHT. ONCE THIS TROUGH PUSHES TO THE EAST ON TUESDAY...A LOW PRESSURE SYSTEM OVER MISSOURI WILL MOVE NORTHEAST ACROSS THE LOWER GREAT LAKES AND TO THE ST LAWRENCE RIVER VALLEY BY EARLY WEDNESDAY. NORTH WINDS ON THE NORTHERN FLANK OF THIS LOW TRACK MAY REACH 30 KNOTS OVER CENTRAL AND EASTERN LAKE SUPERIOR ON TUESDAY AND TUESDAY NIGHT. A HIGH PRESSURE RIDGE WILL FOLLOW ACROSS THE UPPER GREAT LAKES ON WEDNESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM MOVES EAST FROM THE PLAINS TO NEAR UPPER MICHIGAN ON THURSDAY. RELATIVELY LIGHT WINDS WILL PREVAIL ON THESE TWO DAYS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... WINTER STORM WARNING UNTIL 11 AM EST THIS MORNING FOR MIZ006-085. LAKE EFFECT SNOW WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR MIZ007-014. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...JLA AVIATION...JV MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1218 AM EST SUN DEC 7 2008 UPDATE FOR 06Z AVIATION DISCUSSION .UPDATE... BIGGEST CHANGE ON UPDATE WAS TO DROP BLIZZARD WARNINGS FOR ALGER AND NRN SCHOOLCRAFT AND PUT UP WINTER STORM WARNINGS INTO SUNDAY MORNING AS STRONG NNW WINDS SHOWING SIGNS OF WEAKENING SOME WITH BUILDING RDG FROM THE WEST. STILL EXPECT ENHANCED LLVL CONV TO FOCUS HEAVIER LES BANDS INTO THESE COUNTIES OVERNIGHT INTO SUNDAY AND WIND GUSTS TO 30 MPH AT TIMES WILL ALSO CONTRIBUTE TO BLOWING/DRIFTING AND OCCASIONAL WHITEOUT CONDITIONS. ALSO DROPPED LES ADVISORY FOR BARAGA AS DRIER AIR HAS REALLY DIMINISHED LES BANDS OVER WRN LAKE SUPERIOR. REST OF FCST STILL OF TRACK SO DIDN`T MAKE ANY OTHER BIG CHANGES. && .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED RIDGING OVER THE WESTERN U.S. AND A TROUGH EXTENDING FROM HUDSON BAY SOUTHWARD INTO THE TENNESSEE VALLEY. UPPER MI SITS IN THE MIDDLE OF THE TROUGH AXIS...AND RIGHT UNDERNEATH A SHRTWV AT 500MB. DPVA FORCING WITH THE SHRTWV COMBINED WITH LAKE EFFECT AND A COLD FRONT TO GENERATE A BAND OF HEAVY SNOWFALL THAT MOVED THROUGH UPPER MI EARLY THIS AFTN. THE COLD FRONT IS ASSOCIATED WITH A 1001 MB LOW...LOCATED NOW NEAR DRUMMOND ISLAND. WITH THE SHRTWV OVER UPPER MI...THE CWA IS BEGINNING TO SEE DNVA AND LOWERING INVERSIONS...AS NOTED BY 12Z SOUNDINGS FROM INL AND CWPL. NUMEROUS LAKE EFFECT MULTI-PARALLEL BANDS HAVE DEVELOPED WITH COLD AIR FLOWING IN UNDERNEATH THE INVERSION...MOST INTENSE OVER THE NORTH CENTRAL AND EAST WITH THE LONGER FETCH OF NW WINDS. 850MB TEMPS PER RUC ANALYSIS RANGED FROM -20C WEST TO -15C EAST. DESPITE THE COLD AIRMASS...LAKE EFFECT IS DIMINISHING OVER WESTERN LAKE SUPERIOR THANKS TO DRIER AIR ADVECTING IN OUT OF MN. THIS DRIER AIR IS NOTED BY THE 12Z INL AND CWPL SOUNDINGS HAVING PRECIPITABLE WATER VALUES LESS THAN 0.10 OF AN INCH AND SFC DEWPOINTS BELOW ZERO F. THE DRIER AIR IS ALSO ASSOCIATED WITH A HIGH PRESSURE RIDGE THAT COVERS MANITOBA AND NORTH DAKOTA. FARTHER TO THE WEST...MID AND HIGH CLOUDS ARE MOVING ACROSS THE WESTERN DAKOTAS AND EASTERN MONTANA...ASSOCIATED WITH WARM ADVECTION AHEAD OF A SHRTWV MOVING THROUGH CENTRAL BRITISH COLUMBIA AND ALBERTA. FOR LATEST SNOWFALL REPORTS AND BLOWING SNOW IMPACTS...SEE ARBLSRMQT. && .SHORT TERM (TONIGHT AND SUN)... UPPER LEVEL HEIGHTS ARE PROGGED TO RISE DURING THE NEXT 24 HOURS AS THE TROUGH AXIS PUSHES OFF TO THE EAST. THEREFORE...INVERSIONS WILL CONTINUE TO LOWER ACROSS THE CWA WHILE DRIER AIR ADVECTS IN FROM THE WEST. THE COMBINATION OF BOTH FACTORS SHOULD ALLOW SNOW SHOWERS TO BECOME SCATTERED OVER WESTERN UPPER MI TONIGHT WITH MUCH LESS ACCUMULATION. GOING END TIMES FOR THE WARNINGS FOR WESTERN UPPER MICHIGAN AT 7 PM EST THIS EVENING LOOK GOOD. FOR NORTH CENTRAL AND EASTERN UPPER MICHIGAN...THE LONGER FETCH OF NW WINDS COMBINED WITH LAND BREEZES COMING OUT OF WESTERN UPPER MI SHOULD KEEP THE LAKE EFFECT GOING LONGER. IN ADDITION...UPSTREAM MOISTENING OFF LAKE NIPIGON IS EXPECTED...AS IS OCCURRING ATTM. IN FACT...LAST FEW RUC RUNS AND OUR LOCAL WRF-ARW RUNS SUGGEST A SINGLE BAND FROM LAKE NIPIGON...OFF THE TIP OF THE KEWEENAW AND INTO THE ALGER/DELTA/MARQUETTE COUNTY LINES. THIS SEEMS REASONABLE AS THE LAND BREEZE DEVELOPS AND CONVERGES ON THE GENERAL NNW TO NW FLOW BEHIND THE DEPARTING SFC LOW. SHOULD THE BAND STAY IN PLACE... SOUNDINGS AND MODEL DERIVED QPF AMOUNTS SUGGEST THAT 1 INCH PER HOUR RATES ARE REASONABLE. THEREFORE...WILL CONTINUE WARNINGS FOR ALGER...DELTA AND MARQUETTE COUNTIES. SCHOOLCRAFT AND LUCE COUNTIES ARE A LITTLE MORE TROUBLESOME...AND WAS TEMPTED TO DROP THE WARNINGS AS ONLY THE MULTI-PARALLEL BANDS ARE EXPECTED THERE. HOWEVER...WITH THE WIND BLOWING THE SNOW THIS EVENING AND THE WARNING ONLY BEING UP FOR ABOUT 3 TO 4 HOURS SO FAR...HAVE DECIDED TO LEAVE IT UP FOR NOW. LAKE EFFECT OVER THE NORTH CENTRAL AND EAST SHOULD GRADUALLY DIMINISH ON SUNDAY AS THE DRIER AIR OVER WESTERN UPPER MI BUILDS IN THERE. STILL MAINTAINED LIKELY POPS SUNDAY AFTN FOR NORTHERN SCHOOLCRAFT/LUCE AS IT LOOKS LIKE THE LAKE NIPIGON ENHANCED BAND WILL SHIFT IN THERE. BESIDES THE LAKE EFFECT...ANOTHER POSSIBLE PCPN IMPACT IS SOME WARM ADVECTION -SN MOVING IN SUNDAY AFTN. THIS WARM ADVECTION PCPN IS ASSOCIATED WITH THE MID/HIGH CLOUD IN THE WESTERN DAKOTAS AND EASTERN MONTANA. THE CANADIAN MODEL WAS VERY AGGRESSIVE BRINGING THIS PCPN INTO UPPER MI...MAKING ITS WAY INTO THE CENTRAL U.P.. HOWEVER...IT IS AN OUTLIER AND PROBABLY TOO FAST GIVEN THAT SOUNDINGS SHOW PLENTY OF DRY AIR. INSTEAD...FOLLOWED THE GFS/LOCAL WRF-ARW RUNS WHICH ONLY BRING A HUNDREDTH OF QPF INTO FAR WESTERN UPPER MI. ANOTHER ISSUE FOR THE FORECAST IS TEMPS TONIGHT. IT APPEARS SOME OF THE WI BORDER AREAS COULD CLEAR OUT. GIVEN FRESH SNOW AND THE DRY AIRMASS MOVING IN...TEMPS WOULD PLUMMET ASSUMING WINDS BECOME CALM. LOWERED MINS ALONG THE WI BORDER OF GOGEBIC AND IRON COUNTIES TO 0 TO 5 BELOW ZERO...BUT MAY NOT BE LOW ENOUGH IF CLOUDS CLEAR SOONER. FOR SUNDAY...WITH THE HIGH CLOUDS MOVING IN DURING THE AFTERNOON AND A COLD AIRMASS IN PLACE (850MB TEMPS ONLY REACHING -16C AT 18Z)...FOLLOWED SIMILARLY TO THE MIDNIGHT SHIFT OF STAYING WITH THE COLDER MAV GUIDANCE READINGS FOR HIGHS. .LONG TERM (SUN NIGHT THROUGH NEXT SATURDAY)... UPPER FLOW CONTINUES TO BE FROM THE NW THROUGH THE PERIOD WITH TROUGHING IN THE AREA WITH MORE TROUGHING DIGGING TOWARDS THE AREA FOR TUE. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE AND MOISTURE MOVING THROUGH THE AREA SUN NIGHT INTO MON MORNING BEFORE BOTH MOVE OUT BY MON AFTERNOON. NAM SHOWING ISENTROPIC LIFT ON I280K-I295K SURFACES WITH SOME MOISTURE MOVING ACROSS THE CWA SUN NIGHT WITH THE MOISTURE MOVING OUT MON MORNING EXCEPT IN THE LOWEST LEVELS ON I280K SURFACE WHICH LINGERS. GFS SHOWS SOME ISENTROPIC LIFT ON I280K SURFACE WITH MOISTURE AS WELL SUN NIGHT AND THE MOISTURE MOVES OUT ON MON. BASICALLY...LOOKS LIKE RIGHT NOW...THIS SYSTEM FOR SUN NIGHT GOES MOSTLY TO THE SOUTH OF CWA AND DOES NOT LOOK LIKE HEADLINES WILL BE NEEDED. ONLY EXCEPTION AND WILL NEED TO BE WATCHED IS LUCE AND SCHOOLCRAFT COUNTIES WHERE THERE COULD BE A LAKE MICHIGAN BAND THAT FORMS FROM THE SOUTH WINDS THAT OCCUR AND THIS COULD POSSIBLY BE ACROSS THE EASTERN PORTIONS OF THOSE TWO COUNTIES. IT IS COLD ENOUGH FOR LAKE EFFECT TO FORM AND WITH WINDS CONVERGING ACROSS EASTERN LAKE MICHIGAN...A LONG FETCH WOULD FORM. ONLY THING IS THERE COULD BE ENOUGH OF A LAND BREEZE TO PUSH THIS BAND A BIT FURTHER EAST AND KEEP OUT OF THOSE TWO COUNTIES AS WELL. THE LAND BREEZE COULD ALSO DISRUPT THE BAND AS WELL. WILL MENTION THIS IN THE HWO PRODUCT FOR NOW AND NOT HIGHLIGHT...BUT THIS POSSIBILITY OF A HEAVY LAKE EFFECT BAND WILL HAVE TO BE WATCHED. CHANGE FOR THIS FORECAST WAS ALSO TO GO LIKELY POPS LATE SUNDAY NIGHT FOR ALL OF CWA WITH DEEP MOISTURE. FOR TUESDAY...SIGNIFICANT TROUGH DIGGING CAUSES A SYSTEM TO COME UP FROM THE SW. SOUTHERN CWA IS ON THE NORTHERN END OF THIS SYSTEM WITH LAKE EFFECT ACROSS THE REST OF THE CWA. SIGNIFICANT SYSTEM SNOW WOULD BE ACROSS THE SOUTHERN CWA AND BUMPED POPS UP TO LIKELY FOR THIS AREA. IF THIS SYSTEM COMES A BIT FURTHER NORTH...THEN WILL HAVE TO BE WATCHED AS WELL. SUBSEQUENT MODEL RUNS WILL HELP TO DETERMINE IF THIS SYSTEM WILL AFFECT US MORE WITH HEAVIER SNOW OR NOT. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A 500 MB TROUGH ACROSS THE CENTRAL U.S. WITH RIDGING IN THE WESTERN U.S. 00Z WED. MORE TROUGHING COMES IN FOR 00Z THU AND REMAINS THROUGH 00Z SUN. LOOKS PRETTY ACTIVE IN THE EXTENDED AND LOOKS LIKE REPEAT LAKE EFFECT EVENT EPISODES WITH ALBERTA CLIPPER TYPE SYSTEMS MOVING THROUGH EVERY SO OFTEN. BROADBRUSHED THE EXTENDED AND KEPT SOME POPS IN NEAR LAKE SUPERIOR EVERY DAY WITH COLD ENOUGH AIR AROUND AND SOME SHORTWAVES NEAR THE AREA AS WELL. TEMPERATURES LOOK TO STAY BELOW NORMAL.USED THE ECMWF AS GUIDANCE FOR THIS EXTENDED FORECAST AND DID NOT STRAY TOO MUCH FROM IT. CLIPPER SYSTEM MOVES THROUGH WED NIGHT AND THIS LOOKS TO BE THE BEST CHANCE FOR WIDEPSREAD SNOW THEN. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... MULTI-PARALLEL BAND LAKE EFFECT SNOW WINDING DOWN FROM THE WEST THIS EVENING. VERY DRY AIR UPSTREAM GREATLY DIMINISHING LES OVER WRN LAKE SUPERIOR THIS EVENING. HAVE DECIDED TO GO WITH VFR VBSY AT KCMX THROUGH THE PERIOD BUT WILL KEEP MVFR CIGS UNTIL WINDS BACK SW BY 20Z SUN. MVFR CIGS/VSBYS IN LIGHT SNOW SHOULD RETURN BY LATE SUN EVENING AHEAD OF THE NEXT SYSTEM MOVING IN FROM THE NRN PLAINS. WINDS BACKING NW AT KSAW WILL SHIFT SIGNIFICANT LES BANDS EAST OVERNIGHT WITH VFR VSBYS EXPECTED THROUGH MUCH OF THE PERIOD. WINDS BACKING W LATE TONIGHT WILL BREAK UP MVFR CIGS AND KEEP SKIES VFR INTO SUN EVENING. THERE IS ANOTHER CHANCE OF LIGHT SNOW LATE SUN EVENING WHICH COULD LOWER VBSYS/CIGS INTO THE MVFR CATEGORY. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... NORTH GALES OF UP TO 45 KNOTS...STRONGEST ON EASTERN SUPERIOR...WILL DIMINISH BELOW 30 KT AFTER MIDNIGHT AS A RIDGE OF HIGH PRESSURE BUILDS IN FROM THE DAKOTAS. EXPECT WINDS TO GENERALLY REMAIN AT OR BELOW 30 KNOTS THEN THROUGH MONDAY NIGHT. ON TUESDAY...AN AREA OF LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS IS EXPECTED TO MOVE NORTHEAST...REACHING THE EASTERN GREAT LAKES ON WEDNESDAY. A PERIOD OF NORTH GALES TO 35 KNOTS ARE POSSIBLE BEHIND THE LOW OVER EASTERN LAKE SUPERIOR TUESDAY NIGHT...THEN WINDS WILL DROP BACK DOWN BELOW 30 KNOTS FOR WEDNESDAY AND THURSDAY. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... WINTER STORM WARNING UNTIL 11 AM EST SUNDAY FOR MIZ006-085. WINTER STORM WARNING UNTIL 10 AM EST SUNDAY FOR MIZ007. WINTER STORM WARNING UNTIL 7 AM EST SUNDAY FOR MIZ005-013-014. LAKE SUPERIOR... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LSZ248>251-265>267. GALE WARNING UNTIL 10 PM EST THIS EVENING FOR LSZ263-264. GALE WARNING UNTIL MIDNIGHT EST TONIGHT FOR LSZ242>245. LAKE MICHIGAN... GALE WARNING UNTIL 3 AM EST SUNDAY FOR LMZ221-250. && $$ UPDATE...VOSS SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...JV MARINE...AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 353 AM CST SUN DEC 7 2008 .DISCUSSION... BAND OF SNOW SETTING UP IN STRONG ISENTROPIC LIFT ZONE ACROSS EASTERN DAKOTAS...WHICH WILL BE MOVING ACROSS CWA TODAY. DPROG/DT ON BOTH NAM AND GFS SHOWING A FASTER MOVEMENT ACROSS THE AREA...AND LATEST RUC13 TRENDS SHOWING A FASTER TREND AS WELL. WILL SPEED UP ENDING ACROSS THE AREA. HIGH PRECIPITABLE WATER VALUES LAST EVENING OVER EASTERN MT AND SOME OF THIS GETS ENTRAINED IN THE LIFT ZONE. 3 TO 4 GT/KG ON THE 290 SURFACE SHOWS UP THIS AFTERNOON JUST TO OUR WEST AS WELL. BETTER LAYER THETA E ADVECTION SEEMS TO DEVELOP OVER SE MN THIS AFTERNOON BUT MORE INSTABILITY IN THE MID LEVELS INDICATED OVER N MN. WILL BE HARD TO PIN DOWN BETTER SNOW AMOUNTS...SO WILL KEEP THE IDEA OF THE CHANCE OF A BROAD AREA OF AN 1 TO 2 INCHES ACROSS MAINLY EASTERN AREAS. PATTERN MOVING ALONG AT A GOOD CLIP SO THIS WILL HOLD DOWN AMOUNTS DESPITE THE GOOD MOISTURE EVENTUALLY BECOMING INVOLVED. FORECAST SOUNDINGS SUGGEST THE POTENTIAL OF FZDZ AFTER THE WAVE MOVES THROUGH THIS EVENING WITH SOME WEAK LIFT HANGING AROUND. WILL KEEP THIS CHANCE MAINLY SOUTH CENTRAL MN WHERE MINOR SREF POPS OF ZR SHOW UP. FORECAST A LITTLE TRICKY FOR LATER MONDAY INTO TUESDAY. ECMWF HAS BEEN SHOWING SOME CONSISTENCY WITH A FARTHER NORTH BIAS TO STRONGER FORCING DEVELOPING OVER THE PLAINS. EVEN GFS AND NAM SHOW A RIGHT ENTRANCE REGION OF THE UPPER JET FAVORING SOUTHERN MN FOR A TIME MONDAY AFTERNOON INTO EARLY TUESDAY. WILL UP POPS A LITTLE OVER A WIDER AREA BEGINNING MONDAY AFTERNOON BUT STILL KEEP THE BETS POTENTIAL OVER THE FAR SOUTH. PATTERN LOOKING MORE ACTIVE IN THE LONGER RANGE WITH MORE UPPER RIDGING DEVELOPING OVER AK ALLOWING FOR WSW OVERRUNNING OVER THE DEEPENING ARCTIC AIR OVER THE UPPER MIDWEST. THIS CAUSING TIMING AND INTENSITY DIFFERENCES IN THE MODELS. REALLY SHOWS UP IN THE ENSEMBLE UNCERTAINTY WITH HUGE VALUES THIS WEEKEND. && .AVIATION.../06Z TAF ISSUANCE/ VFR CONDITIONS WILL PREVAIL THROUGH 600 AM SUNDAY MORNING...THEN CLOUDS WILL BEGIN TO LOWER AS WARM AND MOIST AIR OVERRUNS THE COLDER AIR THAT IN PLACE OVER THE UPPER MIDWEST. IN THE MEANTIME...HIGH CLOUDS WILL SPREAD OVER THE TAF SITES GENLY ABV 10K AGL OVERNIGHT. ANOTHER IN THE SERIES OF ALBERTA CLIPPERS THAT HAVE ADVANCED OVER THE UPPER MIDWEST DURING THE PAST FEW DAYS WILL MOVE SOUTHEAST AS WEAKEN AS MOVES OVER THE DAKOTAS SUNDAY NIGHT. WEATHER CONDITIONS WILL LOWER IN SNOW OVER THE WESTERN SECTION OF MN BY NOON AND OVER THE WESTERN WISCONSIN BY LATE AFTERNOON/SUNDAY EVENING. VISIBILITY LOWERING BETWEEN 1-3 MILES AND CEILINGS 1000-2000 FT AGL. CEILINGS EXPECTED TO LOWER TO IFR CONDS BY MONDAY MORNING OVER MOST TAF SITES. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ JPR/JVM mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 411 AM CST SUN DEC 7 2008 .SHORT TERM...THROUGH TUESDAY NIGHT PLENTY OF HEADACHES IN THE SHORT TERM WITH WEAK SYSTEM/LIGHT SNOW EVENT TODAY...POTENTIAL FOR FREEZING DRIZZLE TONIGHT...AND THEN WINTER STORM POTENTIAL BEGINNING MONDAY NIGHT AND CONTINUING INTO TUESDAY. CURRENTLY...SFC HIGH SITS RIGHT ON TOP OF MS RIVER WITH WIDESPREAD SUBZERO TEMPS IN THE FRESH SNOWPACK/CLEAR SKIES/CALM WIND AREA OVER THE FORECAST AREA. HIGH CLOUDS SO FAR DOING LITTLE TO HOLD BACK THE RADIATIONAL COOLING. -13F AT SPARTA AS OF 09Z. GOES WATER VAPOR SHOWS WEAK/SHEARED PV ANOMALY OVER SASKATCHEWAN SHIFTING QUICKLY SOUTHEAST IN NORTHWEST FLOW ALOFT. BROAD WARM ADVECTION WING OF LIGHT SNOW OVER DAKOTAS WITH 1-3SM VSBYS CROSSING INTO MN SOON. 07.06Z RUC ANALYSIS HAD -14 TO -16C AIR OVER ARX FORECAST AREA /NWLY FLOW/ WITH +1C AT KUNR /RAPID CITY/ ON SWLY FLOW. REGARDING MODEL AGREEMENT/CONFIDENCE...ENOUGH HAS COME INTO LINE REGARDING MON NIGHT/TUES SYSTEM TO ISSUE WINTER STORM WATCH FOR SRN/SERN SIDE OF FORECAST AREA. 07.00Z GFS/GEM CONTINUE TO SHIFT NORTH TOWARD PVS RUNS OF ECMWF AND NOW SPORT SIGNIFICANT QPF ACROSS IOWA INTO INTO SRN WISCONSIN FROM MONDAY NIGHT INTO TUESDAY. EVEN LOCALLY RUN WRF /ARW-WRF INITIALIZED WITH GFS BOUNDARY CONDITIONS/ HAS COME INTO LINE WITH A VERY NICE DOWNSCALED RENDITION OF THE 07.00Z GFS...SHOWING POTENTIAL FOR SIGNIFICANT SNOW ACCUMULATIONS ACROSS NERN IA INTO SWRN WISCONSIN. WFO COLLABORATION SUPPORTED CURRENT WATCH ALIGNMENT WITH MAIN FOCUS ON MONDAY NIGHT INTO TUESDAY AFTERNOON. MORE ON THIS SYSTEM BELOW. FIRST WITH TODAY/TONIGHT WEATHER SYSTEM...THE TREND HERE IS TOWARD A LITTLE WEAKER SYSTEM...QUICKER...WITH A SHORTER DURATION EVENT. EXPECT STRONG BURST OF ISENTROPIC ASCENT /285K-295K/ AND MID LEVEL Q/G SIGNAL TO WORK MODEST MOISTURE IN PLACE TO CONTINUE TO MIGRATE BAND OF SNOW INTO THE AREA EITHER VERY LATE THIS MORNING BUT FOR SURE BY THIS AFTERNOON INTO AND ACROSS THE FORECAST AREA. WHILE WE BUMPED THE SNOW CHANCES HIGHER...THE QUICKER/MORE TRANSIENT NATURE OF THE FORCING ALLOWED FOR A LITTLE LIGHTER QPF/SNOW AMOUNT. THINKING NOW IS FOR WIDESPREAD 1 INCH AMOUNTS...WITH A FEW LOCALLY UP TO 2 INCHES...MAINLY WEST OF MS RIVER. PV ALOFT IS AWFULLY WEAK/SHEARED OUT...SO THIS SUPPORTS A WEAKER REFLECTION BELOW...AND AN EVENT DRIVEN LARGELY BY MODEST THERMODYNAMICS. WITH WARMER AIR STREAMING IN ALOFT...THE DENDRITIC GROWTH POTENTIAL WANES QUICKLY WITH RATIOS DECREASING BY THE HOUR. TONIGHT...EXPECT BAND OF SNOW TO BE MAINLY EAST OF MS RIVER AND WEAKENING. STILL SEEING A WINDOW /3-5HR/ RIGHT AS THE SNOW ENDS FOR ICE-BEARING CLOUD TO DEPART BUT HAVE SFC-2KM DEEP MOISTURE FIELD STILL FEELING SOME SYNOPTIC SCALE LIFT/LOW LEVEL WARM ADVECTION TO PRODUCE SOME FREEZING DRIZZLE. WHILE SOME NAM/GFS RUNS OVER THE PAST DAYS HAVE BROUGHT A NICE SFC REFLECTION OF THE UPPER LEVEL WAVE INTO THE AREA TO HELP INCREASE CONVERGENCE/LIFT...THE LATTER RUNS ARE NOT HITTING THIS SO HARD...HENCE WE MAY BE LACKING OMEGA IN AN OTHERWISE VERY NICE SETUP FOR FREEZING DRIZZLE. HENCE...WILL KEEP IT PATCHY WORDING FOR NOW...AND IF IT LOOKS LIKE WE CAN SET UP A GOOD ENOUGH CONVERGENCE AXIS IN THE LOWEST 1-2KM...COVERAGE CAN BE UPGRADED. WITH TIME OVERNIGHT...THE MOISTURE SHALLOWS OUT BELOW 1KM SO THREAT WILL BE DIMINISHING WITH TIME. HAVE SEEN /ESPECIALLY THE HIGHER RESOLUTION SPC-WRF/NCAR-WRF/LOCALLY RUN WRF/ THE TRADEMARK SPECKLES OF QPF INDICATING DRIZZLE HERE AND THERE...SO THINK IT/S STILL QUITE POSSIBLE. MONDAY...TRICKY DAY. LARGE SCALE FORCING /MID AND UPPER LEVEL Q/G AND FRONTOGENESIS/ SLOWLY STARTS TO INCREASE AS NRN/SRN STREAM ENERGY ADVANCES ACROSS THE ROCKIES INDUCING A BACKING OF THE MID LEVEL FLOW. QPF IN THE MODELS HAS BEEN HERE AND THERE...BUT THERE HAS BEEN SOME TRENDS TOWARD A BAND OF LIGHT SNOW /WHICH MAY BRIEFLY MIX WITH FREEZING RAIN OR SLEET/ GIVEN MARGINAL THERMAL STRUCTURES IN WARM ADVECTION TO DEVELOP ACROSS THE AREA DURING THE AFTERNOON. VERY LIGHT IN AMOUNTS...BUT ENOUGH TO REINTRODUCE SNOW CHANCES BACK TO THE FORECAST. A WARMER DAY WITH HIGHS NEAR 30. MONDAY NIGHT THROUGH TUESDAY NIGHT...DESPITE 07.00Z AND 07.06Z NAM-WRF BACKING WAY OFF OF PREVIOUS SHIFT TOWARD ECMWF SOLN AND MANY NAM SREF MEMBERS IN THIS NAM-WRF CAMP...THERE WAS SIGNIFICANT MOVEMENT IN NON-NAM SOLUTIONS TOWARD A WINTER STORM OVER IOWA/SRN WISCONSIN THIS TIME PERIOD. 07.00Z GEM/GFS/ECMWF ALL AGREE /IN MOST PART/ THAT SRN STREAM ENERGY WILL COME OUT OF THE SRN ROCKIES AND BECOME DOMINANT INDUCING 995MB ELONGATED LOW PRESSURE OVER TX/OK BORDER REGION ON MONDAY EVENING. INFLUX OF DEEPER MOISTURE ON THETA-SFC AND ISENTROPIC LIFT REALLY TAKE OFF MONDAY NIGHT AS SFC LOW MOVES INTO CNTL/SRN MO. SFC LOW NEVER REALLY DEEPENS...AND EVENTUALLY BECOMES MORE ELONGATED WITH THE MAIN CENTER INTO ERN ILL BY 00Z WED. INITIAL PV/SHORTWAVE OVER TX PANHANDLE MON EVENING EJECTS NORTHEAST AHEAD OF STRONGER WAVE OVER COLORADO...WHICH DIGS AND EJECTS INTO IA/MO ON TUESDAY AFTERNOON. RESULT IS LONGER DURATION SNOW EVENT WITH EPISODES OF HEAVIER QPF THROUGH THE LONG EVENT TIED TO THESE SHORTWAVES...AND SOME ENERGY IN THE NRN STREAM AS WELL. TROUGH AXIS/PV EAST OF AREA BY TUESDAY NIGHT SUPPORTING RAPID END OF SNOW. MATURE BAND OF DEEP MOISTURE FROM KS/NEB THROUGH IA/SRN WISCONSIN IN PLACE AS WAVES ARRIVE TO ASSIST IN PCPN PRODUCTION. MID LEVEL /700-500MB/ FRONTOGENESIS AXIS...WHILE NOT OVERLY STRONG...REMAINS IN PLACE ACROSS NRN IA INTO NRN WIS THROUGH THE PERIOD TO AUGMENT LARGER SCALE LIFT IN RIGHT ENTRANCE REGION OF 150-170KT JET ACROSS ERN CANADA...WITH COUPLING OF JETS NOTED AS 120KT JET EJECTS OUT OF SRN STREAM INTO CNTL CONUS ON TUES. PLENTY OF FORCING HERE. ACCORDING TO 07.00Z GFS CROSS SECTIONS NORMAL TO THE THICKNESS PATTERN...BEST DEEP LAYERED OMEGA/AGEOSTROPHIC RESPONSE COMES IN 06Z TUES-18Z TUES TIME FRAME ACROSS NERN IA/SWRN WI. AFOREMENTIONED MODELS ALL PRODUCING 0.5 TO 0.8 INCHES OF LIQUID ACROSS NERN IA/SWRN WISCONSIN...WHICH SEEMS ENOUGH FOR WATCH GIVEN CONSIDERATION TO STRONGER WINDS WHICH MAY DEVELOP ACROSS NERN IA ON TUES WHICH MAY ADD SOME BLOWING SNOW. ECMWF WOULD ARGUE FOR ADDING ANOTHER TIER OF COUNTIES ON THE NORTH SIDE OF CURRENT WATCH...BUT IS ALONE IN THIS DEPICTION RIGHT NOW. 07.00Z GEM IS VERY MUCH LIKE THE ECMWF WITH QPF FOR THE EVENT TOWARD 1 INCH ACROSS SWRN WISCONSIN...BUT RIGHT NOW FORCING DOESN/T SEEM TO SUPPORT THIS AMOUNT OF QPF WITH LACK OF MID LEVEL INSTABILITY /-EPV/ OR A STRONGER FGEN SIGNAL. ONE OTHER CAVEAT...INITIAL WARM AIR ALOFT /USING MAX WET BULB TEMP/ CLOSE ENOUGH THAT PERIOD OF SLEET/FREEZING RAIN MAY BEGIN THE EVENT BEFORE LIFT/COOLING TURNS IT TO SNOW. RIGHT NOW THAT/S NOT IN ARX FORECAST AREA...BUT CLOSE ENOUGH THAT IT MAY BECOME A PLAYER. BOTTOM LINE...CURRENT THINKING IS A 5-8 INCH BAND OF SNOW ACROSS MUCH OF NERN IA INTO SWRN WISCONSIN...WITH MAIN EMPHASIS ON LATER MONDAY NIGHT INTO TUESDAY MORNING. .LONG TERM...WEDNESDAY THROUGH SATURDAY NOT MUCH TIME SPENT IN THIS PERIOD THANKS TO WEATHER SYSTEMS IN THE SHORT TERM OCCUPYING MUCH OF THE TIME THIS MORNING. THE BOTTOM LINE HASN/T CHANGED...THERE/S STILL TREMENDOUS SPREAD BETWEEN THE DETERMINISTIC AND ENSEMBLE MEMBERS WITH REGARDS TO THE LARGE POOL OF ARCTIC AIR WITH THE POLAR VORTEX OVER CANADA...AND HOW/IF/WHEN SOME OF THAT BITTER AIR SPILLS SOUTH. THERE/S ENOUGH AGREEMENT THAT WED WILL BE DRY/COLD IN THERMAL TROUGH IN WAKE OF MONDAY/TUESDAY STORM. AFTER THAT...CONFIDENCE RAPIDLY DETERIORATES. STILL SEEING CONFIDENCE PLOTS SPELL OUT AN EXTREME DEGREE OF VOLATILITY IN THE 21 MEMBER GEFS...THAT AN ENSEMBLE APPROACH IS BASICALLY USELESS WITH FORECAST ENSEMBLE SPREAD EXCEEDING THE 25 YEAR REANALYSIS OBSERVED CLIMATOLOGICAL SPREAD...WHICH IS RARE. VIEWED GRAPHICALLY...THE GEFS MEMBER PLUMES SHOWING 850MB TEMP RANGE FROM 0C TO -30C...WITH THIS DEGREE OF SPREAD FROM DEC11 INTO DEC15. ACTUALLY FIND SOME SEMBLANCE OF AGREEMENT AFTER FRIDAY IN THE 07.00Z ECMWF/GFS DETERMINISTIC RUNS WHICH ARE HIGHER RESOLUTION...BUT THURSDAY/FRIDAY HAVE A HUGE SPREAD ON TEMPERATURES WITH GFS SAYING ARCTIC PLUNGE AND ECMWF MUCH MORE MODIFIED. CHOSE TO CHANGE VERY LITTLE HERE UNTIL A MORE CLEAR SIGNAL IS SEEN. WEAK WAVES IN THE NORTHWEST FLOW UNDERNEATH THE POLAR VORTEX WILL KEEP PESKY LIGHT SNOW CHANCES INTO THE END OF THE WEEK. HEADING INTO NEXT WEEKEND/EARLY NEXT WEEK...THERE SEEMS TO BE GROWING CONSENSUS OF AN EXTREMELY ACTIVE PERIOD DEVELOPING AS WRN TROUGHING/VERY COLD AIRMASS SETTLES SOUTH INTO NRN ROCKIES SETTING UP VERY TIGHT BAROCLINIC ZONE FROM SW-NE ACROSS THE HEART OF THE CONUS. MASSIVE 1040-1045MB HIGH PRESSURE IN WRN CANADA/NRN CONUS FUNNELS ARCTIC AIR SOUTH...WITH BAROCLINIC ZONE SERVING FOCUS FOR SNOW EPISODES ON AND OFF. WHERE THE FRONT SETS UP WILL BE THE MAJOR QUESTION. THERE/S NO DOUBT...WINTER IS IN FULL SWING. && .AVIATION... ZONE OF STRONG 850-700MB WARM ADVECTION/ISENTROPIC LIFT WILL MOVE ACROSS THE AREA CENTERED ON THIS AFTERNOON. A MODEST AMOUNT OF MOISTURE ACCOMPANIES THIS LIFT...WITH CLOUDS THICKENING/LOWERING THRU THE MORNING AS THE LIFT APPROACHES. STRONGEST LIFT/DEEPEST MOISTURE/SATURATION MOVE ACROSS THE TAF SITES DURING THE AFTERNOON...BUT WITH THE MODEST MOISTURE AT BEST...APPEARS CIG/VSBY RESTRICTIONS WILL MAINLY BE MVFR AS THE BAND OF -SN MOVES ACROSS THE AREA. OF GREATER CONCERN IS LOSS OF DEEPER MOISTURE FOR THE LATE AFTERNOON EVENING HOURS WHILE SOME FORCING/LIFT/MOISTURE REMAIN IN THE LOWEST 2KM TO 3KM OF THE ATMOSPHERE...WHICH IS A FREEZING DRIZZLE SIGNAL. THIS SIGNAL MOST PRONOUNCED DURING THE EARLY EVENING AND WILL ADD A MENTION OF THE -FZDZ WITH NEXT TAF ISSUANCE. IFR/MVFR CIGS EXPECTED TONIGHT WITH THE WEAK LIFT AND SOUTH/SOUTHEAST WINDS CONTINUING TO PULL LOWER LEVEL MOISTURE NORTHWARD INTO THE AREA. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR WIZ043-WIZ044-WIZ053-WIZ054-WIZ055-WIZ061. MN...NONE. IA...WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030. && $$ SHORT/LONG TERM...BINAU AVIATION...RRS wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 316 AM MST SUN DEC 7 2008 .SHORT TERM...TODAY THROUGH MONDAY NIGHT... WEAK RETURNS ON THE KCYS 88D CONTINUE EARLY THIS MORNING OVER THE WEST PART OF THE CWA. MOST OF THE MOISTURE REMAINS ABOVE 700 MB AND WITH CURRENT FAIRLY LARGE SURFACE TEMPERATURE AND DEW POINT SPREADS VERY LITTLE PRECIPITATION SHOULD REACH THE GROUND. THE RUC DEPICTS SOME LIGHT QPF OVER THE WEST PART OF THE CWA THROUGH 15Z. WILL PLACE LOW POPS OVER THAT AREA FIRST THING THIS MORNING. OTHERWISE FOR TODAY...FAST NORTHWEST WIND FLOW ALOFT WILL PERSIST ACROSS THE REGION. THE SURFACE BOUNDARY CURRENTLY OVER THE FAR EAST PART OF WYOMING WILL BE ERODED FROM WEST TO EAST. BEHIND THE BOUNDAY ARE VERY MILD TEMPERATURES...WITH 20S CURRENTLY OVER PARTS OF THE WESTERN PANHANDLE. THE 700 MB TEMPERATURES WILL BE ABOVE ZERO TODAY AND WITH THE WEST WINDS...HIGHS SHOULD AGAIN BE ABOVE NORMAL. LOW LEVEL HEIGHT DIFFERENCES ARE NOT AS LARGE AS THE PAST FEW DAYS OVER THE REGION AND SUGGEST THAT WINDS WILL NOT BE AS AS STRONG TODAY. THE FLOW ALOFT BACKS TONIGHT AND MUCH OF MONDAY IN ADVANCE OF A SHORTWAVE TROUGH APPROACHING FROM THE PACIFIC NORTHWEST. THE CURRENT UPPER LOW JUST OFF THE CALIFORNIA COAST WILL BE CAUGHT UP IN THE FLOW ALOFT AND FILL AS IT MOVES ACROSS NEW MEXICO AND SOUTHERN COLORADO TONIGHT. THAT WILL START SURFACE CYCLOGENESIS OVER EXTREME SOUTHEAST COLORADO. A PACIFIC FRONT ASSOCIATED WITH THE PACIFIC NORTHWEST SHORTWAVE TROUGH WILL ALSO MOVE ACROSS THE CWA TONIGHT. BOUNDARY LAYER UPSLOPE WIND FLOW WILL START LATER TONIGHT AND MONDAY MORNING AND MOISTURE WILL BE INCREASING IN THE MID AND UPPER LEVELS AHEAD OF THE SHORTWAVE TROUGH. SNOW WILL DEVELOP FROM THE NORTHWEST PART OF THE CWA TO THE SOUTHEAST DURING THE DAY MONDAY. THE SREF AND GFS SPREAD THE SNOW MORE QUICKLY SOUTHEAST THAN DOES THE NAM. AT THIS TIME IT LOOKS LIKE THE MORE SIGNIFICANT SNOWFALL WILL BE MONDAY AFTERNOON AND EARLY MONDAY NIGHT. THAT IS THE TIME FRAME WHERE THE MOISTURE IS DEEPEST AND THE BEST DYNAMICS AND SURFACE FORCING WILL BE OVER THE CWA. HAVE INCREASED POPS AND SNOWFALL AMOUNTS DURING THAT TIME WITH 2 TO 4 INCHES OVER MOST OF THE LOWER ELEVATIONS BY 12Z TUESDAY AND 5 TO 9 INCHES IN THE MOUNTAINS. THOSE AMOUNTS GENERALLY FIT THE HPC GUIDANCE FOR THE CWA. AT THIS TIME...WILL HOLD OFF ON THE ISSUANCE OF ANY HIGHLIGHTS FOR THIS QUICK SNOW EVENT. THE SNOWFALL WILL TAPER OFF FROM NORTH TO SOUTH AFTER 06Z TUESDAY AS THE SHORTWAVE TROUGH MOVES EAST OF THE CWA AND THE SURFACE UPSLOPE WEAKENS. THE TEMPERATURES WILL BE MUCH COOLER MONDAY AND MONDAY NIGHT THAN THOSE OF TODAY AND TONIGHT. && .LONG TERM...NW FLOW WILL BE ALOFT OVER THE FORECAST AREA FROM TUES THROUGH THURSDAY AS A HIGH AMPLITUDE UPPER RIDGE REMAINS ON THE WEST COAST. VERY WINDY CONDITIONS WILL OCCUR ACROSS THE AREA ON WED AND THUR. MAINLY DRY CONDITIONS WILL OCCUR EAST OF THE LARAMIE RANGE DURING THIS TIME PERIOD...WITH A SLIGHT CHANCE OF SNOW WEST OF THE LARAMIE RANGE. WITH A BETTER CHANCE OF SNOW IN THE MOUNTAINS. A SERIES OF DISTURBANCES WILL MOVE ACROSS THE CWA FRIDAY AS CYCLONIC FLOW OCCURS ALOFT DUE TO A BROAD UPPER TROUGH OVER MUCH OF THE U.S. A COLD FRONT WILL MOVE INTO THE NORTHERN PORTION OF THE CWA IN THE MORNING AND WILL MOVE ACROSS THE FORECAST AREA BY EVENING. THIS WILL RESULT IN A SLIGHT CHANCE OF SNOW FOR MUCH OF THE AREA. A STRONGER COLD FRONT WILL MOVE SOUTH ACROSS THE CWA ON SAT AND DEEP...MOIST UPSLOPE FLOW WILL OCCUR ACROSS THE FORECAST AREA...RESULTING IN A CHANCE OF SNOW FOR THE CWA. THE ECMWF IS FARTHER WEST WITH THE UPPER TROUGH AND IS SLOWER TO BRING IT EAST...WHICH WOULD RESULT IN LATER TIMING OF THE SYSTEM. HIGH TEMPERATURES WILL BE FROM 5 TO 8 DEGREES BELOW NORMAL FOR TUES...5 TO 8 DEGREES ABOVE NORMAL FOR WED AND THU...AND AROUND NORMAL FOR FRI AND SAT. && .AVIATION...VFR CONDITIONS WILL BE OVER THE CWA THROUGH TONIGHT. WEST WINDS WILL GUST TO BETWEEN 25 AND 35 KNOTS ALONG AND WEST OF THE LARAMIE RANGE TODAY WITH WEAK MOUNTAIN WAVE ACTIVITY. MVFR AND IFR CONDITIONS IN SNOW AND MOUNTAIN OBSCURATION WILL SPREAD FROM NORTHWEST TO SOUTHEAST OVER THE CWA ON MONDAY AND CONTINUE FOR MOST OF MONDAY NIGHT. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ WEILAND/KMD wy AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 330 AM MST SUN DEC 7 2008 .SHORT TERM...IN THE PAST SEVERAL HOURS...BAROMETRICALLY DRIVEN CHINOOK WINDS IN AND NEAR THE BASE OF THE FRONT RANGE FOOTHILLS HAVE CONTINUED TO GUST TO AS HIGH AS 45 MPH...CENTERED JUST SOUTHWEST OF BOULDER. HAVE SEEN ONLY A SLIGHT DECREASE IN THE CROSS MTN PRESSURE GRADIENT SINCE 07Z. RUC AND NAM CROSS SECTIONS INDICATE THE PRESENCE OF A WELL DVLPD LEE SIDE MTN WAVE...NOW MARKED BY A GROWING ACSL CLOUD...FOR AT LEAST THE NEXT 3-6 HOURS. WOULD EXPECT TO SEE A CONTINUATION OF THESE GUSTY AND ERRATIC DOWNSLOPE WINDS PRETTY MUCH IN THE SAME AREA THROUGH MID-MORNING. BY LATE MORNING...MODELS SHOW THE CROSS MTN P.G. WEAKENING AND THE AMPLITUDE THE MTN WAVE DECREASING AS IT MOVES AWAY FROM THE FRONT RANGE TAKING WITH IT A PRETTY THICK WAVE CLOUD. THEREFORE SHOULD SEE CLEARING ALONG THE FRONT RANGE LATER THIS MORNING WHILE SKIES REMAIN MOSTLY CLOUDY FARTHER EAST. THIS SHOULD PRODUCE A SHARP TEMPERATURE GRADIENT FROM WEST TO EAST ACROSS THE PLAINS...WITH WARMEST READINGS IN THE DENVER AREA AND COLDEST TEMPS ONCE AGAIN IN LOW LYING AREAS ALONG THE SOUTH PLATTE...CENTERED ALONG A GREELEY TO FORT MORGAN AXIS. COULD SEE AS MUCH AS A 25 DEG F DIFFERENCE IN MAX TEMPS BETWEEN THE TWO LOCALES. PREVIOUS FORECAST DEPICTED A SIMILAR ARRANGEMENT. IN THE HIGH COUNTRY...SHOULD SEE INTERMITTENT CLOUD COVER AS POCKETS OF MID- LEVEL MOISTURE MOVED ALONG BY 45-60KT KT WLY FLOW ALOFT PASS OVER THE AREA. MAY SEE A FEW -SHSN UP ALONG THE CONTINENTAL DIVIDE... BUT LITTLE IF ANY NEW ACCUMULATION AS MTN TOP STATIC STABILITY ONLY INCREASES THRU THE DAY. BY TONIGHT...MODELS SHOW MID/HIGH-LEVEL SUBTROPICAL MOISTURE FLOWING UP FROM THE DESERT SOUTHWEST AHEAD OF A SHORTWAVE LOW TRACKING EWRD ACROSS ARIZONA. SOME OF THIS MOISTURE IS PROGGED TO REACH SWRN PORTIONS OF THE FORECAST AREA SOMETIME AFTER 06Z/MON. EVEN THOUGH MOST OF THIS MOISTURE WILL RESIDE ABOVE MTN TOP LEVEL HAVE INTRODUCED A SLIGHT CHANCE OF -SN TO THE HIGH MTN ZONES LATE TONIGHT. ON THE PLAINS...THINGS REMAIN DRY OVERNIGHT. ALTHOUGH THE NAM SHOWS A SHALLOW SURGE OF MOISTURE WITH THE ONSET OF WEAK ANTICYCLONIC UPSLOPE FLOW AFTER MIDNIGHT. THIS COULD RESULT IN AREAS OF STRATUS AND PSBLY SOME PATCHY FOG TO THE NORTH AND EAST OF DENVER TOWARDS DAWN. .LONG TERM....THE NEXT STORM SYSTEM IS GENERALLY ON TRACK TO EFFECT BOU CWA MONDAY AFTERNOON AND NIGHT BEFORE MOVING OUT OF THE REGION QUICKLY TUESDAY MORNING. THERE CONTINUE TO SOME TIMING DIFFERENCES BETWEEN THE GFS AND NAM...THOUGH EVEN THE LATEST GFS IS A BIT FASTER AND FAIRLY CLOSE TO THE NAM SOLUTION. INITIAL FRONTAL SURGE EXPECTED MIDDAY MONDAY AS SFC WINDS SHIFT AROUND NORTHEAST WHILE THE SURFACE LOW BEGINS TO STRENGTHEN ACROSS THE TEXAS PANHANDLE. PRECIP WILL BE DEVELOPING MON AFTN AND THERE MAY STILL BE A BRIEF TIME OF RAIN/SNOW MIX DURING THE AFTN BEFORE THE BIGGER PUSH OF COLD AIR MOVES IN. SECONDARY SURGE WITH THE COLDER AIR EXPECTED MONDAY EVENING AS SFC WINDS STRENGTHEN FROM THE NORTHEAST. UPSLOPE DEEPENS MON EVENING TO AROUND 600MB WITH MODEST ASCENT FROM VERTICAL VELOCITY FIELDS. BEST ASCENT WILL BE TO THE WEST AND SOUTH OF OUR AREA. SO AS CONFIDENCE CONTINUES TO RISE...WILL CONTINUE TO EDGE POPS UPWARDS INTO HIGH LIKELY CATEGORY AS EARLY AS MONDAY AFTN AS THE TIMING AS QUICKENED A BIT SINCE EARLIER RUNS. EVENTUAL ADVISORY HILITES MAY BE NEEDED WITH THIS SYSTEM...AND THE MAIN AREA OF CONCERN WILL HAVE TO WATCH WILL BE THE SOUTHERN FRONT RANGE FOOTHILLS AND ADJ PALMER DIVIDE. LOCAL SNOW MODEL YIELDED ADVISORY TYPE SNOW AMOUNTS FOR THE FOOTHILLS. NO HILITES AT THIS TIME. THERE IS MORE POTENTIAL FOR SNOW LATER IN THE WEEK AND THRU NEXT WEEKEND AS A STRONG JET ALOFT MOVES INTO THE REGION. THIS IS ALREADY HANDLED IN THE GRIDS SO NO CHANGES IN THE OUT PERIODS. $$ .AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH SUNDAY NIGHT AT DENVER AREA AIRPORTS. GUSTY WEST WINDS IN AND NEAR THE FOOTHILLS THIS MORNING COULD REACH DENVER INTERNATIONAL AIRPORT FROM TIME TO TIME. OTHERWISE EXPECT CLEARING LATER TODAY WITH UNSEASONABLY WARM TEMPERATURES. TONIGHT DRAINAGE WINDS IN THE EVENING EXPECTED TO REVERSE TO A LIGHT NORTH-NORTHEAST FLOW WITH ARRIVAL OF A WEAK FRONTAL SURGE AROUND 09Z/MONDAY. MAY SEE SOME LOW CLOUD WITH THIS SUBTLE WIND SHIFT. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE. $$ BAKER/ENTREKIN co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 600 AM CST SUN DEC 7 2008 .UPDATED FOR THE 12Z AVIATION DISCUSSION... .SHORT TERM /TODAY/... SFC RIDGE AXIS BEGINNING TO SHIFT EAST OF THE AREA...WITH HIGH CLOUDS SPREADING EASTWARD INTO THE CENTRAL CWA AHEAD OF THE WARM FRONT ASSOCIATED WITH THE NEXT WAVE DIVING SOUTHEAST FROM THE CANADIAN ROCKIES. BEST LIFT WITH THIS WAVE AS IT DIVES SOUTHEASTWARD THROUGH SRN MN/NRN IA THIS MORNING INTO THIS AFTERNOON WILL MAINLY BE NORTH OF HWY 20. GFS/NAM/RUC IN DISAGREEMENT REGARDING AMOUNT OF MOISTURE/QPF WITH THE NAM/RUC ADVERTISING ONLY A FEW HUNDREDTHS ACROSS THE NORTHERN CWA VERSUS JUST OVER A TENTH WITH THE GFS. SOUNDINGS INDICATING BRIEF SATURATION...WITH PROBABLY AROUND A FEW HOURS OF LIGHT SNOW AT MOST LOCATIONS NORTH OF I-80. OTHERWISE MAYBE ONLY A BRIEF SNOW SHOWER OR FLURRIES EXPECTED ACROSS THE SOUTHERN CWA. PREVIOUS FORECAST MORE IN LINE WITH THE GFS...BUT LOOKING AT TRENDS UPSTREAM FEEL THE GFS MAY BE A BIT OVERDONE. THEREFORE HAVE TRENDED GRIDS SLIGHTLY TOWARD THE NAM/RUC BY LOWERING POPS ACROSS THE SOUTHERN HALF OF THE CWA AND CUTTING THE QPF DOWN BY 30 TO 40 PERCENT. COULD STILL SEE AROUND AN INCH ACROSS THE NORTHERN TIER COUNTIES...TAPERING TO A FEW TENTHS AROUND HWY 30 TO AROUND A TRACE FURTHER SOUTH. BUFKIT SOUNDINGS DID SHOW A BRIEF PERIOD OF FZDZ AS THE SNOW TAPERED OFF AND SATURATION WAS LOST ALOFT. HOWEVER THIS WAS QUITE BRIEF ONLY AROUND AN HOUR OR SO...SO LEFT PRECIP TYPE ALL SNOW FOR NOW. .LONG TERM /TONIGHT-SATURDAY/... WILL HAVE ANOTHER WEAK SHORTWAVE TRANSLATING OVER SOUTHERN IOWA TONIGHT WITH BAND OF WARM ADVECTION AND MID LEVEL FRONTOGENETICAL FORCING. MODELS DIFFER ON AREA THAT RECEIVES LIGHT PRECIP...SO WENT WITH ONLY LOW CHANCES ACROSS THE SOUTHERN HALF OR SO. OTHERWISE MAIN CONCERN FOR THIS FORECAST PACKAGE IS SIGNIFICANT SYSTEM FOR MONDAY NIGHT AND TUESDAY. THE ECMWF/UKMET/CANADIAN SOLUTIONS ARE PREFERRED FOR THIS PERIOD GIVEN THEIR CONSISTENCY. UNFORTUNATELY THE NAM/SREF AND TO A CERTAIN EXTENT THE GFS/GEFS ARE NOT EXACTLY GOING THE SAME DIRECTION...SO CONFIDENCE IS NOT AS HIGH AS I`D LIKE. HOWEVER...SINCE OUR FORECAST IS LEANING STRONGLY TO THE FIRST SET OF MODELS MENTIONED ABOVE...WILL NEED TO ISSUE A WINTER STORM WATCH FOR A STRIP OF COUNTIES SW TO NE THROUGH CENTRAL IOWA. EVEN AFTER TAKING A BLEND OF THE GFS/HPC/ECMWF QPF FOR THIS PERIOD...STILL CAME OUT WITH 4 TO 8 INCHES OF SNOW FOR MUCH OF OUR AREA. THAT SEEMS A BIT MUCH FOR THE UNCERTAINTY THAT STILL EXISTS...BUT I AM IN COLLABORATION WITH NEIGHBORS. AS LOW PRESSURE ORGANIZES IN THE SOUTHERN PLAINS MONDAY...FRONTOGENETICAL FORCES AND ISENTROPIC LIFT BEGIN OVER IOWA...AND MAY YIELD LIGHT PRECIP. SOUTHERN IOWA SHOULD BE ABOVE FREEZING DURING THE DAY MONDAY INTO MONDAY NIGHT. SO AS THE SYSTEM APPROACHES...RAIN WILL BE THE DOMINATE P-TYPE ALONG AND SOUTH OF I-80. HOWEVER...AS THE LOW INTENSIFIES AND WRAPS IN THE COLDER AIR TO THE NORTH...ALONG WITH DYNAMIC PROCESSES IN THE TROWAL AND DEFORMATION ZONE TO THE NORTH OF SFC LOW TRACK...PRECIP SHOULD TRANSITION TO ALL SNOW MONDAY NIGHT NW TO SE. SOUNDINGS DON`T OFFER MUCH CHANCE FOR ANYTHING OTHER THAN RAIN OR SNOW. HOWEVER...THERE IS STILL A POSSIBILITY OF A LITTLE FREEZING RAIN IF COLDER SFC AIR WORKS ITS WAY IN BEFORE THE UPPER LEVELS COOL ENOUGH. AT THIS TIME THOUGH SOUNDINGS SUPPORT MORE OF A RAIN TO SNOW TRANSITION WHERE IT STARTS AS RAIN. AM USING SNOW RATIOS AT OR BELOW CLIMO FOR NOW...GIVEN UNCERTAINTIES OF WHERE ANY HEAVIER BANDED SNOW MAY SET UP. EVEN IF SNOWFALL AMOUNTS DO NOT REACH WARNING CRITERIA ALONE...THE WIND WILL BE INCREASING ENOUGH TO WARRANT A WINTER STORM WATCH. WINDS ARE EXPECTED TO BE SUSTAINED BETWEEN 20 AND 30 MPH WITH GUSTS POTENTIALLY CLOSE TO 35 OR 40 MPH AT TIMES. AND THIS BRINGS US DANGEROUSLY CLOSE TO BLIZZARD CONDITIONS. BUT...GIVEN SOME UNCERTAINTY THERE...WE WILL JUST MENTION THE WIND AND BLOWING SNOW POTENTIAL IN THE WINTER STORM WATCH. ALSO...BEING THE FIRST WINTER STORM THREAT OF THE SEASON...WE WILL LOWER OUR THRESHOLD A BIT. THE SNOW SHOULD END TUESDAY EVENING IF NOT BEFORE...BUT CONTINUE TO BLOW AROUND WELL INTO TUESDAY NIGHT. AN ACTIVE PATTERN DOES NOT SLOW DOWN...WITH A COUPLE OF CLIPPER SYSTEMS FOR LATE IN THE WEEK...EACH WITH RESPECTABLE CHANCES FOR LIGHT SNOW IN OUR AREA. TEMPS WERE ADJUSTED DOWNWARD FOR THE MIDDLE OF THE WEEK GIVEN TREND IN THE MEDIUM RANGE GUIDANCE. && .AVIATION...07/12Z VFR CIGS...WILL GRADUALLY LOWER THIS MORNING AS BANDS OF LIGHT SNOW MOVE THROUGH THE CWA ASSOCIATED WITH AN UPPER WAVE DROPPING SOUTHEAST THROUGH THE NORTHERN PLAINS/MINNESOTA. VSBYS REDUCTIONS FROM LIGHT SNOW SHOULD MAINLY IMPACT THE NORTHERN 3 TAF SITES WHERE MVFR/MARGINAL IFR VSBYS ARE EXPECTED FOR A FEW HOURS IN HEAVIER BANDS. CIGS SHOULD STAY IN THE IFR/LOW MVFR RANGE WITHIN THE BANDS OF SNOW AS WELL. EXPECT LOW CLOUDS TO CLEAR OUT BEHIND THE SYSTEM WITH SOME HIGH CLOUDS MOVING BACK IN TONIGHT FROM THE SOUTH. MODELS INDICATING POSSIBILITY OF SOME LOW CLOUDS STICKING AROUND...BUT ATTM HAVE ONLY HIGHLIGHTED WITH A SCT DECK. ALSO A WEAK DISTURBANCE TRAVELING ACROSS SRN IA LATE TONIGHT...MAY BRING SOME LOW CLOUDS AND PATCHY FZDZ TO KOTM. UNCERTAINTY QUITE HIGH WITH THIS...SO HAVE LEFT OUT OF THE TAF ATTM. && .DMX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ADAIR-ADAMS-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN- CARROLL-CASS-CERRO GORDO-CLARKE-DALLAS-FRANKLIN-GREENE-GRUNDY- GUTHRIE-HAMILTON-HARDIN-JASPER-MADISON-MARSHALL-POLK-POWESHIEK- RINGGOLD-STORY-TAMA-TAYLOR-UNION-WARREN-WEBSTER-WRIGHT. && $$ SHORT TERM/AVIATION...ALBRECHT LONG TERM...MOYER ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 441 AM MST SUN DEC 7 2008 .DISCUSSION... 246 AM MST SUN DEC 7 2008 NORTHWEST FLOW WILL BECOME ZONAL TONIGHT AS SHORTWAVE ENERGY DIGS SOUTH ACROSS WESTERN UTAH. FLOW THEN BECOMES SOUTHWEST ON MONDAY AS THE TROUGH MOVES EAST OF THE ROCKIES. FLOW IS NORTHWEST ON TUESDAY. A SURFACE TROUGH OVER EASTERN COLORADO TODAY WILL MOVE INTO THE OKLAHOMA/TEXAS PANHANDLE REGION TONIGHT/MONDAY. HIGH PRESSURE WILL BUILD INTO NORTHWEST KANSAS MONDAY NIGHT THROUGH TUESDAY. THE MAIN FORECAST ISSUES ARE PRECIPITATION TYPE AND WIND. TIMING OF THE EVENT LOOKS ON TRACK WITH UPWARD VERTICAL VELOCITIES INDICATED MONDAY AFTERNOON...CONTINUING MONDAY NIGHT AND ENDING AROUND 12Z TUESDAY. THE CURRENT FORECAST KEEPS THE EVENT ABOUT 6 HOURS PAST THIS TIME. 1000-500MB THICKNESSES FROM THE GFS/NAM SUGGEST THAT PRECIPITATION SHOULD BE LIQUID THROUGH MOST OF MONDAY AFTERNOON EXCEPT IN THE NORTHWEST ZONES. BY MONDAY EVENING PRECIPITATION SHOULD BE ALL SNOW OVER THE NORTHWEST HALF OF THE FORECAST AREA WITH ONLY THE SOUTHEAST ZONES HAVING A MIX OF RAIN/SNOW. THE ENTIRE FORECAST AREA SHOULD HAVE ALL SNOW BY 06Z TUESDAY THROUGH THE END OF THE EVENT. THE NEXT ISSUE IS WIND WHICH THE RUC SHOWS TO BE A SIGNIFICANT CONCERN WITH THIS EVENT. BY 09Z TUESDAY SURFACE WIND IS PROGGED TO BE SUSTAINED AT GREATER THAN 30KTS AND WIND GUSTS GREATER THAN 40KTS. THIS WILL CAUSE SIGNIFICANT BLOWING AND DRIFTING OF ANY SNOW. MOST OF THE SNOW SHOULD END BY 12Z TUESDAY BUT THIS STRONG WIND SHOULD LAST WELL INTO TUESDAY AFTERNOON. CURRENT FORECAST ALREADY HAS AREAS OF BLOWING SNOW FOR THIS TIME PERIOD. A WINTER HIGHLIGHT MAY BE NEEDED IF MODELS CONTINUE TO SHOW THIS MUCH WIND. FOR NOW PLAN TO CONTINUE WORDING IN THE HWO FOR THIS POTENTIAL. SNOWFALL AMOUNTS STILL LOOK LIKE 1 TO 3 INCHES WITH HEAVIEST AMOUNTS OVER THE CENTRAL AND EAST ZONES. TEMPERATURES WILL STILL BE UNSEASONABLY WARM. GUIDANCE SHOWING READINGS ABOUT 20 DEGREES ABOVE NORMAL. FOLLOWED COOLER GUIDANCE BASED ON UNCERTAINTY WITH AMOUNT OF CLOUDS. COLD FRONT WILL COME THROUGH TONIGHT. MAX TEMPERATURES WILL REACH INTO THE LOWER 40S MONDAY AND IN THE UPPER 30S TUESDAY. MIN TEMPERATURES WILL FALL INTO THE MID 20S TONIGHT AND AROUND 20 MONDAY AND TUESDAY NIGHTS. FS && .AVIATION... 437 AM MST SUN DEC 7 2008 FOR THE 12Z TAF...EXPECT VFR CONDITIONS OVER THE NEXT 24 HOURS AT BOTH KGLD AND KMCK WITH LIGHT AND VARIABLE WINDS. WILL SEE A GENERALLY BROKEN MID LEVEL CLOUD DECK CENTERED AROUND 20-25K FT AGL THROUGH THE TAF CYCLE. FOLTZ && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CARIBOU ME 1052 AM EST SUN DEC 7 2008 .SYNOPSIS... LOW PRESSURE OFF THE MID ATLANTIC COAST WILL TRACK NORTH ACROSS NOVA SCOTIA AND INTENSIFY TODAY. THE LOW WILL CONTINUE TOWARD LABRADOR TONIGHT. HIGH PRESSURE WILL BUILD IN FROM THE WEST ON MONDAY AND SLIDE SOUTH OF THE REGION MONDAY NIGHT. INTENSIFYING LOW PRESSURE LIFTING THROUGH THE GREAT LAKES WILL PULL A WARM FRONT TOWARD THE AREA ON TUESDAY AND NORTH ACROSS THE STATE TUESDAY NIGHT INTO WEDNESDAY. A STRONG COLD FRONT WILL FOLLOW WEDNESDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... PRIMARY CONCERN IS ADDITIONAL BANDING SNOW OVER WASHINGTON COUNTY. WILL FOCUS ON RUC13 AND CARWRF WHICH ARE BEST SUITED TO HANDLE THIS TYPE OF EVENT. OBSERVATIONS THIS MORNING SHOW LOCAL REPORTS UP TO 10 INCHES OVER PORTIONS OF WASHINGTON COUNTY. PRIMARY CONCERN IS RUC13 SUGGESTING ADDITIONAL BANDING SNOW OVER SAME PORTION OF THE FORECAST AREA. RUC13 BUFKIT ALSO INDICATING STRONG OMEGA. WITH SUBSTANTIAL AMOUNTS ALREADY ON GROUND AND MORE BANDING INDICATED HAVE OPTED TO ISSUE WINTER STORM WARNING FOR SOUTHEAST PORTIONS OF FORECAST AREA BASED ON 24 HOUR TOTALS. HAVE INITIALIZED QPF WITH 12Z/RUC13 WITH SOME MANUAL ADJUSTMENTS. SNOW GRIDS GENERATED ON QPF GRIDS BASED ON 10:1 RATIO. WINDS ARE EXPECTED TO INCREASE TO 15-25 MPH LATER THIS AFTERNOON AND CONTINUE INTO TONIGHT. GUSTS OF UP 35 MPH IN SOME LOCATIONS WILL LEAD TO BLOWING AND DRIFTING SNOW. DAYCREW WILL NEED TO MONITOR THINGS AND DECIDED WHETHER TO EXTEND OR NOT. THE SNOW WILL GRADUALLY WIND DOWN OVERNIGHT W/THE FAR NORTHERN AREAS HANGING ONTO SOME LINGERING SNOW W/THE COLD NW FLOW COMING OFF THE ST. LAWRENCE. WINDS AND CLOUDS WILL KEEP TEMPS FROM DROPPING TOO FAR. USED THE GMOS NUMBERS AND RAISED THEM UP A FEW DEGS DUE TO THE CLOUDS AND WIND. && .SHORT TERM /MONDAY THROUGH TUESDAY/... INTENSE LOW PRESSURE OVER EASTERN CANADA WILL BRING STRONG GUSTY COLD WINDS MONDAY MORNING. BLOWING SNOW WILL CONTINUE ACROSS AREAS THAT HAD SIGNIFICANT SNOWFALL. WINDS WILL DIMINISH LATE MONDAY INTO MONDAY NIGHT AS HIGH PRESSURE BUILDS SOUTH OF THE REGION. COLD AIR IN PLACE AND LIGHT WINDS MONDAY NIGHT WILL ALLOW TEMPS TO DROP INTO THE SINGLE DIGITS IN MANY AREAS. HIGH PRESSURE SLIDING SOUTHEAST OF THE AREA COMBINED WITH LOW PRESSURE LIFTING THROUGH THE MIDWEST WILL PULL A WARM FRONT TOWARD THE AREA ON TUESDAY SPREADING SNOW FROM SOUTH TO NORTH OVER THE REGION. SNOW SHOULD CHANGE TO RAIN ALONG THE DOWNEAST COAST LATE TUESDAY AS WARMER AIR BEGINS SURGING IN FROM THE OCEAN. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... SNOW SHOULD CHANGE TO RAIN DOWNEAST LATE TUESDAY AND ACROSS THE REST OF THE AREA TUESDAY NIGHT AS MUCH WARMER AIR SURGES NORTH. THE LOW LIFTING TO OUR WEST ON WEDNESDAY SHOULD THEN BRING STRONG SOUTH WINDS...RAIN AND TEMPS RISING INTO THE 50S DOWNEAST AND 40S OVER THE NORTH. A WIND ADVISORY AND POSSIBLY WARNING MAY BE NEEDED FOR DOWNEAST AREAS. A POWERFUL COLD FRONT WILL FOLLOW TUESDAY NIGHT BRINGING A RETURN TO COLDER CONDITIONS. THE GFS AND ECMWF ARE THEN INDICATING THAT A SECONDARY WAVE SWINGING UP FROM THE SOUTHEAST MAY TRACK ALONG THE FRONTAL BOUNDARY AS THE FRONT STALLS TO OUR EAST...AND POSSIBLY BRING SNOW ON THURSDAY TO EASTERN AREAS. FOR NOW ONLY GOING CHANCE SNOW NORTH AND LIKELY DOWNEAST ON THURSDAY WITH CONSIDERABLE UNCERTAINTY ABOUT THIS SCENARIO. THE END OF THE WEEK SHOULD THEN BE DRY AND COOL. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... MVFR FOR DOWNEAST AND THE COAST AT TIMES TODAY W/IMPROVING CONDITIONS TONIGHT. IFR/MVFR ACROSS THE NORTH TODAY INTO THIS EVENING. VFR CONDITIONS ARE EXPECTED MONDAY INTO MONDAY NIGHT. THIS WILL BE FOLLOWED BY IFR CONDITIONS TUESDAY THROUGH THURSDAY AS A SERIES OF LOW PRESSURE SYSTEMS AFFECTS THE AREA. && .MARINE... NEAR TERM: AS MENTIONED BELOW A GALE WARNING IS UP. EXPECT THE WINDS TO COME ON THE BACKSIDE OF THE LOW LATER THIS AFTERNOON AND THEN KICK TO GALE FORCE THIS EVENING INTO TONIGHT. BLENDED THE NAM12 AND GFS W/SOME ADJUSTMENTS TO THE EASTERN SECTIONS THIS MORNING AS WINDS WERE A BIT STRONGER THAN THE GUIDANCE AT INITIALIZATION. DECIDED ON GUSTS HITTING 40 KT TONIGHT AS COLD NW FLOW COMES OVER THE WATERS. USED THE GFSSWAN TO START THE SEAS OUT AS THEY WERE UP TO 6-7 FT AND THEN BLENDED THE WNAWAVE4 WHICH SHOWS SEAS FALL BACK THIS MORNING AND THEN BUILD AGAIN LATER THIS AFTERNOON INTO TONIGHT. SHORT TERM: A GALE WARNING WILL BE IN EFFECT SUNDAY NIGHT THROUGH MONDAY FOR STRONG GUSTY NORTHWEST WINDS BEHIND THE LOW MOVING NORTH THROUGH THE MARITIMES. WINDS WILL RAPIDLY DIMINISH MONDAY EVENING. WINDS WILL THEN INCREASE TUESDAY INTO TUESDAY NIGHT LIKELY REACHING A STRONG GALE ON WEDNESDAY AND AN EXTENSIVE SOUTH FETCH WILL BUILD SEAS TO NEAR 20 FT BY LATE WEDNESDAY NIGHT INTO THURSDAY. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MEZ002- 005-006-011-016-029. WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MEZ017- 030-032. MARINE...GALE WARNING FROM 7 PM THIS EVENING TO 7 PM EST MONDAY FOR ANZ050>052. && $$ NEAR TERM...HEWITT/MIGNONE SHORT TERM...BLOOMER LONG TERM...BLOOMER AVIATION...HEWITT/MIGNONE MARINE...HEWITT/MIGNONE/BLOOMER me AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 952 AM EST SUN DEC 7 2008 .UPDATE... LAKE EFFECT SNOW SHOWERS OVER EASTERN LAKE SUPERIOR HAVE BROKEN UP QUITE A BIT OVER THE PAST TWO HOURS...DUE TO A COMBINATION OF WIND SHEAR IN THE MIXED LAYER SEEN ON THE KMQT VAD WIND PROFILE AND DRY AIR FLOWING ACROSS. THEREFORE...WENT AHEAD AND CANCELLED THE WARNING FOR ALGER AND NORTHERN SCHOOLCRAFT COUNTIES EARLY. REST OF THE FORECAST FOR TODAY IS IN GOOD SHAPE. MAIN CONCERN THIS AFTERNOON WILL BE TO WATCH THE POSITION OF THE FORECAST LAKE EFFECT BAND OFF LAKE MICHIGAN. 06Z RUNS SUGGESTED THAT THE BAND MAY IMPACT MOSTLY MACKINAC COUNTY TONIGHT...THEN SHIFT WESTWARD ON MONDAY AS THE FLOW BACKS MORE SOUTHERLY. IF THIS OCCURS...THEN THE WATCH MAY OR MAY NOT PAN OUT...ESPECIALLY IF THE BAND KEEPS MOVING AS SUGGESTED BY THE 06Z NAM. && .SYNOPSIS... COLD UPPER TROUGH WITH H85 TEMPS -15C TO -20C REMAINS IN PLACE FM HUDSON BAY INTO THE UPR GREAT LAKES. PRIMARY COLD FRONT IS MOVING INTO THE LWR GREAT LAKES AND DIVING INTO THE SOUTHERN PLAINS. NW FLOW AND THE COLD TEMPS BEHIND THE FRONT IS PRODUCING MOSTLY MULTIPLE LK EFFECT SNOW BANDS. IR SATELLITE AND RADAR INDICATES HEAVIEST SNOW SHOWERS INTO ALGER COUNTY AND NRN DELTA COUNTY. THIS BAND IS STRONGEST DUE TO PRECONDITIONED FLOW OFF LK NIPIGON AND ALSO SINCE THE TRAJECTORIES ARE CROSSING THE LONGEST AVAILABLE FETCH ACROSS LK SUPERIOR. MEANWHILE...DRY AIR AND INVERSION BLO H9 ASSOCIATED WITH INCOMING SFC RIDGE AND AS SEEN ON 00Z INL/WPL SOUNDINGS...IS LIMITING EXTENT OF LK EFFECT OVR WRN CWA. && .DISCUSSION... ALTHOUGH WINDS HAVE DIMINISHED...LK EFFECT STILL AN ISSUE TODAY AS SFC-925MB WINDS STAY NW. EFFECTS OF THE DRY AIR/SUBSIDENCE SEEN UPSTREAM WILL BE OFFSET FOR SNOW SHOWERS EAST OF MARQUETTE AS LOW-LEVEL TRAJECTORIES CROSS LK SUPERIOR THE LONGEST. INVERSION HEIGHT BTWN 5-7KFT AND IDEAL TEMPS WITHIN CLOUD LAYER FOR DENDRITIC SNOW GROWTH ENSURES THAT LK EFFECT WILL BE SUFFICIENT AT PRODUCING ACCUMS DESPITE NEGATIVE LARGE SCALE FACTORS. BY FAR BEST SNOW WILL BE IN SNOWBAND PRECONDITIONED BY LK NIPIGON. MAJORITY OF HIGH RES GUIDANCE...NAM/REG CANADIAN/RUC13/LOCAL WRF POINT TO HEAVIEST SNOW TO REMAIN IN ALGER/NRN SCHOOLCRAFT AREAS. KEPT WINTER STORM WARNING FOR THESE TWO ZONES GIVEN THAT STRONG BAND IS STILL OUT THERE AND SNOWFALL RATES UP TO 1"/HR ARE STILL POSSIBLE. OTHERWISE...CANX REST OF THE GOING HEADLINES. 925MB WIND FIELD BECOMES DISORGANIZED AFT 21Z TODAY...AND BY THAT TIME SNOW SHOWERS SHOULD DIMINISH/LIFT OFFSHORE. ELSEWHERE...AS WINDS BACK WITH RIDGE THROUGH HERE...THERE COULD BE SOME SUNSHINE. TEMPS WILL REMAIN CHILLY THOUGH WITH MAINLY TEENS EXPECTED. SHEARED OUT UPPER WAVE WITH SWATH OF DEEP MOISTURE SWINGS ACROSS UPR LAKES. GFS/NAM/LOCAL WRF SIMILAR IN HANDLING THE SYSTEM. ISENTROPIC LIFT ON 280K SFC...ROUGHLY 800-700MB...SHOWS STRONGEST LIFT OCCURRING ALONG SW BORDER INTO LK MICHIGAN. KEPT HIGHEST POPS CLOSER TO WI BORDER...WITH JUST CHANCE POPS CLOSER TO LK SUPERIOR AS SW LOW-LEVEL FLOW MAINLY DOWNSLOPES. UP TO AN INCH OF SNOW NEAR THE WI BORDER. MAIN ISSUE WILL BE IN SE CWA NEAR LK MICHIGAN. 925MB WINDS BECOME VERY FAVORABLE FOR LK EFFECT OFF LK MICHIGAN INTO SRN SCHOOLCRAFT INTO SRN PORTION OF LUCE COUNTY AFT MIDNIGHT AND INTO MONDAY. H85 TEMPS -13C WITH DEEP MOISTURE ADDED FM THE SYSTEM MOVING IN FM THE WEST YIELD MORE THAN SUFFICIENT OVER WATER INSTABILITY ALTHOUGH EXACT AREA OF HEAVIEST SNOW IS UNCERTAIN. SINCE THE HIGH PRESSURE RIDGE LINGERS OVR LWR MICHIGAN AND ONTARIO...INTERACTING LAND BREEZES ENHANCE LOW-LEVEL CONVERGENCE. HIGH RESOLUTION MODELS FCST A DOMINANT BAND OVR FAR SE CWA...BUT VARY ON EXACT PLACEMENT. WILL SAY THAT THE RUC13 SHOWING A STRONG LAND BREEZE EMERGING FM LWR MI...AND SETTING UP THE BAND AS FAR WEST AS DELTA COUNTY WAS NOT PREFERRED AS SWRLY 925MB WINDS SHOULD PIN THE LAND BREEZE CLOSER TO THE LWR MI SHORE. IN ANY EVENT...COULD SEE WARNING CRITERIA SNOWFALL OVR FAR SE CWA FM THIS BAND OF LK EFFECT SO ISSUED A LAKE EFFECT SNOW WATCH FOR LATE TONIGHT THROUGH MOST OF MONDAY FOR SOUTHERN SCHOOLCRAFT INTO LUCE. OUTSIDE OF LK EFFECT OFF LK MICHIGAN...MONDAY FEATURES LGT SNOW MAINLY AFFECTING THE WI BORDER AREAS DUE TO UPPER LEVEL JET FORCING AND PERSISTENT ISENTROPIC ASCENT ON 280K SFC. NW LOW-LEVEL WINDS AND H85 TEMPS BLO -10C COULD ALSO PRODUCE LGT LK EFFECT OVR NW UPR MI. NEXT ISSUE IS LOW PRESSURE EMERGING FM THE PLAINS LATER TUE. ECMWF WAS MOST EMPHATIC WITH THIS SYSTEM LAST COUPLE DAYS...AND OTHER GUIDANCE NOW LOOKS LIKE IT IS TRENDING THIS WAY. ECMWF IDEA WOULD BRUSH FAR SOUTH CENTRAL...BASICALLY SRN MNM COUNTY...WITH WIDESPREAD SNOW LATE MON NIGHT THROUGH TUE NIGHT. PRIMARY SYSTEM SNOW SHOULD STAY SOUTH OF CWA...BUT ADVY MAY BE NEEDED IN THE SCNTRL. NRLY FLOW OVR LK SUPERIOR WITH COOLING WILL LEAD TO LK EFFECT SNOW SHOWERS INCREASING IN THE TUE/WED PERIOD. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... EXPECT SC CIGS TO GRDLY ERODE THIS AFTN WITH ARRIVAL OF HI PRES RDG/ DRY AIRMASS FM THE W THAT IS SHOWN ON 00Z INL RAOB. MVFR CIGS WL PERSIST THE LONGEST AT CMX WITH FVRBL UPSLOPE WLY WIND COMPONENT. CLDS WL THICKEN WITH CIGS FALLING TO HI END MVFR RANGE WITH APRCH OF WEAK LO PRES TROF TNGT. SINCE THE BEST DYNAMICS LOOK TO PASS TO THE S...SUSPECT THE ANTECEDENT DRY AIRMASS WL NOT SATURATE SUFFICIENTLY FOR ANY SGNFT SN/VSBY RESTRICTION AT EITHER SAW OR CMX. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS A LOW PRESSURE CENTER OVER SOUTHEAST CANADA CONTINUES TO THE EAST TODAY...A HIGH PRESSURE RIDGE WILL MIGRATE ACROSS THE UPPER GREAT LAKES BY THIS EVENING AND INTO NEW ENGLAND BY LATE MONDAY. STRONG N WINDS EARLY TODAY WILL DIMINISH QUICKLY AS THIS RIDGE APPROACHES. IN THE WAKE OF THE RIDGE...EXPECT A LOW PRESSURE TROUGH TO DRIFT OVER LAKE SUPERIOR ON MONDAY NIGHT. ONCE THIS TROUGH PUSHES TO THE EAST ON TUESDAY...A LOW PRESSURE SYSTEM OVER MISSOURI WILL MOVE NORTHEAST ACROSS THE LOWER GREAT LAKES AND TO THE ST LAWRENCE RIVER VALLEY BY EARLY WEDNESDAY. NORTH WINDS ON THE NORTHERN FLANK OF THIS LOW TRACK MAY REACH 30 KNOTS OVER CENTRAL AND EASTERN LAKE SUPERIOR ON TUESDAY AND TUESDAY NIGHT. A HIGH PRESSURE RIDGE WILL FOLLOW ACROSS THE UPPER GREAT LAKES ON WEDNESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM MOVES EAST FROM THE PLAINS TO NEAR UPPER MICHIGAN ON THURSDAY. RELATIVELY LIGHT WINDS WILL PREVAIL ON THESE TWO DAYS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR MIZ007-014. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ UPDATE...AJ SYNOPSIS/DISCUSSION...JLA AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 625 AM EST SUN DEC 7 2008 UPDATED FOR 12Z TAF ISSUANCE .SYNOPSIS... COLD UPPER TROUGH WITH H85 TEMPS -15C TO -20C REMAINS IN PLACE FM HUDSON BAY INTO THE UPR GREAT LAKES. PRIMARY COLD FRONT IS MOVING INTO THE LWR GREAT LAKES AND DIVING INTO THE SOUTHERN PLAINS. NW FLOW AND THE COLD TEMPS BEHIND THE FRONT IS PRODUCING MOSTLY MULTIPLE LK EFFECT SNOW BANDS. IR SATELLITE AND RADAR INDICATES HEAVIEST SNOW SHOWERS INTO ALGER COUNTY AND NRN DELTA COUNTY. THIS BAND IS STRONGEST DUE TO PRECONDITIONED FLOW OFF LK NIPEGON AND ALSO SINCE THE TRAJECTORIES ARE CROSSING THE LONGEST AVIALIABLE FETCH ACROSS LK SUPERIOR. MEANWHILE...DRY AIR AND INVERSION BLO H9 ASSOCIATED WITH INCOMING SFC RIDGE AND AS SEEN ON 00Z INL/WPL SOUNDINGS...IS LIMITING EXTENT OF LK EFFECT OVR WRN CWA. && .DISCUSSION... ALTHOUGH WINDS HAVE DIMINISHED...LK EFFECT STILL AN ISSUE TODAY AS SFC-925MB WINDS STAY NW. EFFECTS OF THE DRY AIR/SUBSIDENCE SEEN UPSTREAM WILL BE OFFSET FOR SNOW SHOWERS EAST OF MARQUETTE AS LOW-LEVEL TRAJECTORIES CROSS LK SUPERIOR THE LONGEST. INVERSION HEIGHT BTWN 5-7KFT AND IDEAL TEMPS WITHIN CLOUD LAYER FOR DENDRETIC SNOW GROWTH ENSURES THAT LK EFFECT WILL BE SUFFICIENT AT PRODUCING ACCUMS DESPITE NEGATIVE LARGE SCALE FACTORS. BY FAR BEST SNOW WILL BE IN SNOWBAND PRECONDITIONED BY LK NIPEGON. MAJORITY OF HIGH RES GUIDANCE...NAM/REG CANADIAN/RUC13/LOCAL WRF POINT TO HEAVIEST SNOW TO REMAIN IN ALGER/NRN SCHOOLCRAFT AREAS. KEPT WINTER STORM WARNING FOR THESE TWO ZONES GIVEN THAT STRONG BAND IS STILL OUT THERE AND SNOWFALL RATES UP TO 1"/HR ARE STILL POSSIBLE. OTHERWISE...CANX REST OF THE GOING HEADLINES. 925MB WIND FIELD BECOMES DISORGANIZED AFT 21Z TODAY...AND BY THAT TIME SNOW SHOWERS SHOULD DIMINISH/LIFT OFFSHORE. ELSEWHERE...AS WINDS BACK WITH RIDGE THROUGH HERE...THERE COULD BE SOME SUNSHINE. TEMPS WILL REMAIN CHILLY THOUGH WITH MAINLY TEENS EXPECTED. SHEARED OUT UPPER WAVE WITH SWATH OF DEEP MOISTURE SWINGS ACROSS UPR LAKES. GFS/NAM/LOCAL WRF SIMILAR IN HANDLING THE SYSTEM. ISENTROPIC LIFT ON 280K SFC...ROUGHLY 800-700MB...SHOWS STRONGEST LIFT OCCURING ALONG SW BORDER INTO LK MICHIGAN. KEPT HIGHEST POPS CLOSER TO WI BORDER...WITH JUST CHANCE POPS CLOSER TO LK SUPERIOR AS SW LOW-LEVEL FLOW MAINLY DOWNSLOPES. UP TO AN INCH OF SNOW NEAR THE WI BORDER. MAIN ISSUE WILL BE IN SE CWA NEAR LK MICHIGAN. 925MB WINDS BECOME VERY FAVORABLE FOR LK EFFECT OFF LK MICHIGAN INTO SRN SCHOOLCRAFT INTO SRN PORTION OF LUCE COUNTY AFT MIDNIGHT AND INTO MONDAY. H85 TEMPS -13C WITH DEEP MOISTURE ADDED FM THE SYSTEM MOVING IN FM THE WEST YIELD MORE THAN SUFFICIENT OVER WATER INSTABILITY ALTHOUGH EXACT AREA OF HEAVIEST SNOW IS UNCERTAIN. SINCE THE HIGH PRESSURE RIDGE LINGERS OVR LWR MICHIGAN AND ONTARIO...INTERACTING LAND BREEZES ENHANCE LOW-LEVEL CONVERGENCE. HIGH RESOLUTION MODELS FCST A DOMINANT BAND OVR FAR SE CWA...BUT VARY ON EXACT PLACEMENT. WILL SAY THAT THE RUC13 SHOWING A STRONG LAND BREEZE EMERGING FM LWR MI...AND SETTING UP THE BAND AS FAR WEST AS DELTA COUNTY WAS NOT PREFERRED AS SWRLY 925MB WINDS SHOULD PIN THE LAND BREEZE CLOSER TO THE LWR MI SHORE. IN ANY EVENT...COULD SEE WARNING CRITERIA SNOWFALL OVR FAR SE CWA FM THIS BAND OF LK EFFECT SO ISSUED A LAKE EFFECT SNOW WATCH FOR LATE TONIGHT THROUGH MOST OF MONDAY FOR SOUTHERN SCHOOLCRAFT INTO LUCE. OUTSIDE OF LK EFFECT OFF LK MICHIGAN...MONDAY FEATURES LGT SNOW MAINLY AFFECTING THE WI BORDER AREAS DUE TO UPPER LEVEL JET FORCING AND PERSISTENT ISENTROPIC ASCENT ON 280K SFC. NW LOW-LEVEL WINDS AND H85 TEMPS BLO -10C COULD ALSO PRODUCE LGT LK EFFECT OVR NW UPR MI. NEXT ISSUE IS LOW PRESSURE EMERGING FM THE PLAINS LATER TUE. ECMWF WAS MOST EMPHATIC WITH THIS SYSTEM LAST COUPLE DAYS...AND OTHER GUIDANCE NOW LOOKS LIKE IT IS TRENDING THIS WAY. ECMWF IDEA WOULD BRUSH FAR SOUTH CENTRAL...BASICALLY SRN MNM COUNTY...WITH WIDESPREAD SNOW LATE MON NIGHT THROUGH TUE NIGHT. PRIMARY SYSTEM SNOW SHOULD STAY SOUTH OF CWA...BUT ADVY MAY BE NEEDED IN THE SCNTRL. NRLY FLOW OVR LK SUPERIOR WITH COOLING WILL LEAD TO LK EFFECT SNOW SHOWERS INCREASING IN THE TUE/WED PERIOD. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... EXPECT SC CIGS TO GRDLY ERODE THIS AFTN WITH ARRIVAL OF HI PRES RDG/ DRY AIRMASS FM THE W THAT IS SHOWN ON 00Z INL RAOB. MVFR CIGS WL PERSIST THE LONGEST AT CMX WITH FVRBL UPSLOPE WLY WIND COMPONENT. CLDS WL THICKEN WITH CIGS FALLING TO HI END MVFR RANGE WITH APRCH OF WEAK LO PRES TROF TNGT. SINCE THE BEST DYNAMICS LOOK TO PASS TO THE S...SUSPECT THE ANTECEDENT DRY AIRMASS WL NOT SATURATE SUFFICIENTLY FOR ANY SGNFT SN/VSBY RESTRICTION AT EITHER SAW OR CMX. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS A LOW PRESSURE CENTER OVER SOUTHEAST CANADA CONTINUES TO THE EAST TODAY...A HIGH PRESSURE RIDGE WILL MIGRATE ACROSS THE UPPER GREAT LAKES BY THIS EVENING AND INTO NEW ENGLAND BY LATE MONDAY. STRONG N WINDS EARLY TODAY WILL DIMINISH QUICKLY AS THIS RIDGE APPROACHES. IN THE WAKE OF THE RIDGE...EXPECT A LOW PRESSURE TROUGH TO DRIFT OVER LAKE SUPERIOR ON MONDAY NIGHT. ONCE THIS TROUGH PUSHES TO THE EAST ON TUESDAY...A LOW PRESSURE SYSTEM OVER MISSOURI WILL MOVE NORTHEAST ACROSS THE LOWER GREAT LAKES AND TO THE ST LAWRENCE RIVER VALLEY BY EARLY WEDNESDAY. NORTH WINDS ON THE NORTHERN FLANK OF THIS LOW TRACK MAY REACH 30 KNOTS OVER CENTRAL AND EASTERN LAKE SUPERIOR ON TUESDAY AND TUESDAY NIGHT. A HIGH PRESSURE RIDGE WILL FOLLOW ACROSS THE UPPER GREAT LAKES ON WEDNESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM MOVES EAST FROM THE PLAINS TO NEAR UPPER MICHIGAN ON THURSDAY. RELATIVELY LIGHT WINDS WILL PREVAIL ON THESE TWO DAYS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... WINTER STORM WARNING UNTIL 11 AM EST THIS MORNING FOR MIZ006-085. LAKE EFFECT SNOW WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR MIZ007-014. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/DISCUSSION...JLA AVIATION...KC MARINE...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 944 AM CST SUN DEC 7 2008 .UPDATE...MOVED START TIME FOR WWA TO 18Z. LES PLUME HAS DEVELOPED WITH VIS LOWERING TO 1-2SM FROM TWM TO BFW. LATEST RUC13/NAM12 SUPPORTS CONTINUED DEVELOPMENT ALONG NORTH SHORE. && .PREV DISCUSSION... /ISSUED 844 AM CST SUN DEC 7 2008/ UPDATE...LATEST DLH 88D INDICATES A MID LAKE CONVERGENCE ZONE ..THAT INITIALLY DEVELOPED OVERNIGHT...HAS PUSHED ONSHORE NEAR FRENCH RIVER TO TWM VICINITY. HAVE INCREASED POPS/QPF/SNOW/SKY GRIDS TO ACCOUNT FOR THE LES PLUME. USING NAM12 SFC/925H WINDS/MSTR FCST... AREA SHOULD EXPAND AND ENCOMPASS MOST OF NORTH SHORE BY 18Z. LATEST RUC13 925/85H WIND FCST SHOWS MINIMAL SHEAR SHOULD ALLOW INCREASE ORGANIZATION OF BAND AND ADDITIONAL BANDS BY LATE MORNING. RUC13 QPF IS MINIMAL IN RESPECT TO LOW LVL DRY AIR HOWEVER IT SEEMS ACTIVITY ALREADY STARTED AND RUC MAY BE PLAYING CATCHUP. MAY NEED TO PUSH ADVISORY TIME AHEAD. PREV DISCUSSION... /ISSUED 530 AM CST SUN DEC 7 2008/ DISCUSSION... SHORT TERM FOCUS REVOLVES AROUND APPROACHING CLIPPER SYSTEM AND LAKE EFFECT SNOW POTENTIAL ALONG THE NORTH SHORE. CURRENT SURFACE ANALYSIS SHOWS A RIDGE AXIS EXTENDING ACROSS MUCH OF WESTERN LAKE SUPERIOR...WITH A SHORTWAVE OVER THE DAKOTAS. TEMPERATURES HAVE DROPPED TO 20 BELOW AND COLDER IN A FEW SPOTS THIS MORNING...UNDER CLEAR SKIES AND CALM WINDS. DEPARTING RIDGE HAS EFFECTIVELY ERODED MUCH OF THE HIGH CLOUDS FROM THE APPROACHING CLIPPER FROM MAKING INROADS INTO OUR CWA. HOWEVER...WITH INCREASING WAA AND ISENTROPIC LIFT...CLOUDS SHOULD INCREASE FAIRLY STEADILY FROM WEST TO EAST THIS MORNING...WITH THE CHANCE FOR SNOW BEGINNING AS EARLY AS 13Z-15Z IN OUR FAR SOUTHWEST...BEFORE GRADUALLY OVERSPREADING THE REST OF THE AREA DURING THE DAY. AM A BIT CONCERNED THAT THE RIDGE PASSING OFF THE EAST MAY HELP KEEP DRY AIR LOCKED IN PLACE ACROSS AT LEAST OUR NE ZONES THROUGH MUCH OF THE DAY...SO INCREASED POPS MORE SLOWLY IN THIS AREA. ADDITIONALLY...THIS SYSTEM WILL BE WEAKENING...WITH THE BEST LIFT AND FORCING PASSING JUST SOUTH OF OUR AREA. NOT EXPECTING SNOW ACCUMULATIONS GREATER THAN 1 OR 2 INCHES...WITH THE HIGHEST AMOUNTS IN THE BRAINERD LAKES VICINITY. SNOW CHANCES WILL BEGIN TO DIMINISH LATE TONIGHT...ESPECIALLY IN THE WEST. WILL BE ISSUING A WINTER WEATHER ADVISORY FOR THE NORTH SHORE...WHERE THE SYNOPTIC SYSTEM COMBINED WITH LAKE EFFECT SNOW MAY DROP 3 TO 6 INCHES OF SNOW FROM MID AFTERNOON TODAY THROUGH EARLY MONDAY MORNING. SFC-85H RH REMAINS QUITE LOW THROUGH 21Z TODAY...BEFORE INCREASING RATHER RAPIDLY...WHILE WINDS IN THIS LAYER TURN SOUTHERLY...AND 85H TEMPS HOVER AROUND -16C...THROUGH AT LEAST EARLY MONDAY. HOWEVER...INVERSION HEIGHTS ARE SOMEWHAT MARGINAL FOR MUCH OF THIS PERIOD...AND GENERALLY REMAIN AROUND 5000 FT. STILL...THE POTENTIAL FOR SEVERAL INCHES OF SNOW IS CERTAINLY POSSIBLE...ESPECIALLY IN THE HIGHER TERRAIN. ANOTHER SHORTWAVE WILL PUSH SOUTH AND EAST OF THE AREA ON MONDAY. BOTH THE GFS AND NAM SHOW THAT OUR SOUTHERN ZONES MAY BE BRUSHED WITH SOME LIGHT SNOW FROM THIS SYSTEM...BUT HAVE OPTED TO MAKE ONLY VERY SLIGHT INCREASES IN POPS FOR NOW. FORECAST SOUNDINGS ALSO SUGGEST THE POSSIBILITY OF FREEZING DRIZZLE ACROSS MUCH OF THE AREA...PARTICULARLY THROUGH THE MIDDAY HOURS. .EXTENDED...MONDAY NIGHT THROUGH NEXT SATURDAY... MODELS HAVE BEEN DIFFERING WITH EACH OTHER AND WITH THEMSELVES DURING SUCCEEDING RUNS. THE EUROPEAN AND NAM SEEM TO BE IN AGREEMENT...HOWEVER THE SLOWER...DRIER AND COLDER GFS SEEMS TO BE CLOSEST BUT TO HOW THINGS HAVE BEEN HAPPENING HERE...AT LEAST AT LOW LEVELS. THE GFS NEEDS TO BE CORRECTED SIGNIFICANTLY...THOUGH. WITH A WAVY NORTHWEST FLOW ALOFT OVER OUR AREA...A STORM TRACK OF REALLY IMPRESSIVE STORMS HAD MAINTAINED ITSELF WELL TO OUR SOUTH AND EAST. THE OTHER MODELS TRY TO BRING CLIPPERS THROUGH OUR AREA...ONE EXCEPTION DID GO THROUGH HERE A COUPLE OF DAYS AGO ONLY BECAUSE OF VERY STRONG DYNAMICS. THE WEAKER CLIPPERS WILL CONTINUE TO SINK THROUGH THE WESTERN DAKOTAS WHILE A SERIES OF HIGHS TRACKS JUST WEST AND SOUTH OF US. THE CLIPPERS ADD THEIR STRENGTH TO THE SOUTHERN STORM SERIES. THE HIGHS HAVE A TENDENCY TO BOTH BUILD TEMPORARY RIDGES JUST NORTH OF LAKE SUPERIOR WHEN THEY ARE TO OUR WEST...THEN PUT A PERSISTENT RIDGE TO THE NORTH AND OVER OUR AREA. THE GFS...TO A LESSER EXTENT THAN THE OTHER MODELS...TAKE THAT NORTH-POKING RIDGE OUT MUCH TOO FAST AND ALSO...TO A LESSER EXTENT THAN THE OTHER MODELS...CARRY TOO MUCH MID AND HIGH CLOUDS OVER ANY UPPER RIDGE TO OUR WEST. WHAT HAS BEEN HAPPENING...AND WILL CONTINUE TO HAPPEN DURING THE COMING WEEK...IS WHEN WE HAVE THE RIDGING NORTHWARD OVER OUR AREA...THE MODELS ARE ABOUT 5C TOO WARM WITH DAILY HIGHS AND AS MUCH AS 15C TOO WARM WITH OVERNIGHT LOWS. THESE LOW TEMPERATURES SEEM TO BE OVER US...EVEN MORE THAN OVER CANADA AND MUCH MORE THAN OVER ADJACENT FORECAST AREAS. THE LOW TEMPERATURES...AOB -30C IN MANY PLACES THIS MORNING FOR EXAMPLE...ANCHOR THE RIDGE IN PLACE RESULTING IN FIRST...UPSTREAM CLOUDS REMAINING OUT OF OUR AREA FOR AS MUCH AS 24 HOURS LATER THAN THE MODELS SUGGEST. AND...MOST IMPORTANTLY...THE RIDGE...ANCHORED OVER THE BITTERLY COLD IRON RANGE AND RAINY RIVER VALLEY...MAINTAINS A NORTH GRADIENT OVER THE STILL OPEN LAKE SUPERIOR. SO...SNOW SHOWERS ALONG THE SHORE COUNTIES OF NORTHWEST WISCONSIN HAVE BEEN VERY HEAVY...PERSISTED LONGER THAN EXPECTED...RESULTING IN HEAVY SNOW. AGAIN...WE ANCPT THESE TRENDS TO CONTINUE. WE LIKE THE GFS LOWER THICKNESSES AND FURTHER INTRUSION OF ARCTIC AIR...AT LEAST ON THIS 07/00Z RUN. THOUGH THE GFS...AS USUAL...HAS TOO MUCH MOISTURE OVER US...ITS CLIPPER TRACK HAS BEEN REASONABLE. SO...WE ARE GOING COLD AND DRY...AND ANCPT SERIOUS SNOW SQUALLS ANYTIME AN ONSHORE FLOW BECOMES ESTABLISHED. AVIATION... PRIND CLDNS WL RMN W OF AREA AND SNW SQLS WL RMN OVER LK SUPR DURG THE MRNG. MID/HI CLDNS WL INCRS FM W TO E DURG AFTN... WITH CONDS DTRTG TO MVFR AND PSBLY IFR IN LGT SNW FM W TO E LT THIS AFTN THRUT THIS EVE. AN ONSHR FLO TO THE N SHR WL RESULT IN MLIFR IN LCLY INTS SNW SHWRS AND SNW SQLS BGNG LT AFTN AND CONTG THRUT TNGT WHEN WNDS WL VEER. SNW SHWRS WL BCM ISOLD...BUT WITH A PSBLTY OF PTCHY FRZG DRZL MON. && POINT TEMPS/POPS... DLH 12 6 19 2 / 70 70 20 20 INL 11 1 16 -6 / 60 50 10 10 BRD 13 7 22 5 / 80 50 20 10 HYR 14 6 24 5 / 70 80 20 20 ASX 14 6 24 9 / 40 70 30 30 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...WINTER WEATHER ADVISORY UNTIL 6 AM CST MONDAY FOR NORTHERN COOK/NORTHERN LAKE-SOUTHERN COOK/LAKESHORE-SOUTHERN LAKE/LAKESHORE. WI...NONE. LS...NONE. $$ CANNON mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 844 AM CST SUN DEC 7 2008 .UPDATE...LATEST DLH 88D INDICATES A MID LAKE CONVERGENCE ZONE ...THAT INITIALLY DEVELOPED OVERNIGHT...HAS PUSHED ONSHORE NEAR FRENCH RIVER TO TWM VICINITY. HAVE INCREASED POPS/QPF/SNOW/SKY GRIDS TO ACCOUNT FOR THE LES PLUME. USING NAM12 SFC/925H WINDS/MSTR FCST... AREA SHOULD EXPAND AND ENCOMPASS MOST OF NORTH SHORE BY 18Z. LATEST RUC13 925/85H WIND FCST SHOWS MINIMAL SHEAR SHOULD ALLOW INCREASE ORGANIZATION OF BAND AND ADDITIONAL BANDS BY LATE MORNING. RUC13 QPF IS MINIMAL IN RESPECT TO LOW LVL DRY AIR HOWEVER IT SEEMS ACTIVITY ALREADY STARTED AND RUC MAY BE PLAYING CATCHUP. MAY NEED TO PUSH ADVISORY TIME AHEAD. && .PREV DISCUSSION... /ISSUED 530 AM CST SUN DEC 7 2008/ DISCUSSION... SHORT TERM FOCUS REVOLVES AROUND APPROACHING CLIPPER SYSTEM AND LAKE EFFECT SNOW POTENTIAL ALONG THE NORTH SHORE. CURRENT SURFACE ANALYSIS SHOWS A RIDGE AXIS EXTENDING ACROSS MUCH OF WESTERN LAKE SUPERIOR...WITH A SHORTWAVE OVER THE DAKOTAS. TEMPERATURES HAVE DROPPED TO 20 BELOW AND COLDER IN A FEW SPOTS THIS MORNING...UNDER CLEAR SKIES AND CALM WINDS. DEPARTING RIDGE HAS EFFECTIVELY ERODED MUCH OF THE HIGH CLOUDS FROM THE APPROACHING CLIPPER FROM MAKING INROADS INTO OUR CWA. HOWEVER...WITH INCREASING WAA AND ISENTROPIC LIFT...CLOUDS SHOULD INCREASE FAIRLY STEADILY FROM WEST TO EAST THIS MORNING...WITH THE CHANCE FOR SNOW BEGINNING AS EARLY AS 13Z-15Z IN OUR FAR SOUTHWEST...BEFORE GRADUALLY OVERSPREADING THE REST OF THE AREA DURING THE DAY. AM A BIT CONCERNED THAT THE RIDGE PASSING OFF THE EAST MAY HELP KEEP DRY AIR LOCKED IN PLACE ACROSS AT LEAST OUR NE ZONES THROUGH MUCH OF THE DAY...SO INCREASED POPS MORE SLOWLY IN THIS AREA. ADDITIONALLY...THIS SYSTEM WILL BE WEAKENING...WITH THE BEST LIFT AND FORCING PASSING JUST SOUTH OF OUR AREA. NOT EXPECTING SNOW ACCUMULATIONS GREATER THAN 1 OR 2 INCHES...WITH THE HIGHEST AMOUNTS IN THE BRAINERD LAKES VICINITY. SNOW CHANCES WILL BEGIN TO DIMINISH LATE TONIGHT...ESPECIALLY IN THE WEST. WILL BE ISSUING A WINTER WEATHER ADVISORY FOR THE NORTH SHORE...WHERE THE SYNOPTIC SYSTEM COMBINED WITH LAKE EFFECT SNOW MAY DROP 3 TO 6 INCHES OF SNOW FROM MID AFTERNOON TODAY THROUGH EARLY MONDAY MORNING. SFC-85H RH REMAINS QUITE LOW THROUGH 21Z TODAY...BEFORE INCREASING RATHER RAPIDLY...WHILE WINDS IN THIS LAYER TURN SOUTHERLY...AND 85H TEMPS HOVER AROUND -16C...THROUGH AT LEAST EARLY MONDAY. HOWEVER...INVERSION HEIGHTS ARE SOMEWHAT MARGINAL FOR MUCH OF THIS PERIOD...AND GENERALLY REMAIN AROUND 5000 FT. STILL...THE POTENTIAL FOR SEVERAL INCHES OF SNOW IS CERTAINLY POSSIBLE...ESPECIALLY IN THE HIGHER TERRAIN. ANOTHER SHORTWAVE WILL PUSH SOUTH AND EAST OF THE AREA ON MONDAY. BOTH THE GFS AND NAM SHOW THAT OUR SOUTHERN ZONES MAY BE BRUSHED WITH SOME LIGHT SNOW FROM THIS SYSTEM...BUT HAVE OPTED TO MAKE ONLY VERY SLIGHT INCREASES IN POPS FOR NOW. FORECAST SOUNDINGS ALSO SUGGEST THE POSSIBILITY OF FREEZING DRIZZLE ACROSS MUCH OF THE AREA...PARTICULARLY THROUGH THE MIDDAY HOURS. ..EXTENDED...MONDAY NIGHT THROUGH NEXT SATURDAY... MODELS HAVE BEEN DIFFERING WITH EACH OTHER AND WITH THEMSELVES DURING SUCCEEDING RUNS. THE EUROPEAN AND NAM SEEM TO BE IN AGREEMENT...HOWEVER THE SLOWER...DRIER AND COLDER GFS SEEMS TO BE CLOSEST BUT TO HOW THINGS HAVE BEEN HAPPENING HERE...AT LEAST AT LOW LEVELS. THE GFS NEEDS TO BE CORRECTED SIGNIFICANTLY...THOUGH. WITH A WAVY NORTHWEST FLOW ALOFT OVER OUR AREA...A STORM TRACK OF REALLY IMPRESSIVE STORMS HAD MAINTAINED ITSELF WELL TO OUR SOUTH AND EAST. THE OTHER MODELS TRY TO BRING CLIPPERS THROUGH OUR AREA...ONE EXCEPTION DID GO THROUGH HERE A COUPLE OF DAYS AGO ONLY BECAUSE OF VERY STRONG DYNAMICS. THE WEAKER CLIPPERS WILL CONTINUE TO SINK THROUGH THE WESTERN DAKOTAS WHILE A SERIES OF HIGHS TRACKS JUST WEST AND SOUTH OF US. THE CLIPPERS ADD THEIR STRENGTH TO THE SOUTHERN STORM SERIES. THE HIGHS HAVE A TENDENCY TO BOTH BUILD TEMPORARY RIDGES JUST NORTH OF LAKE SUPERIOR WHEN THEY ARE TO OUR WEST...THEN PUT A PERSISTENT RIDGE TO THE NORTH AND OVER OUR AREA. THE GFS...TO A LESSER EXTENT THAN THE OTHER MODELS...TAKE THAT NORTH-POKING RIDGE OUT MUCH TOO FAST AND ALSO...TO A LESSER EXTENT THAN THE OTHER MODELS...CARRY TOO MUCH MID AND HIGH CLOUDS OVER ANY UPPER RIDGE TO OUR WEST. WHAT HAS BEEN HAPPENING...AND WILL CONTINUE TO HAPPEN DURING THE COMING WEEK...IS WHEN WE HAVE THE RIDGING NORTHWARD OVER OUR AREA...THE MODELS ARE ABOUT 5C TOO WARM WITH DAILY HIGHS AND AS MUCH AS 15C TOO WARM WITH OVERNIGHT LOWS. THESE LOW TEMPERATURES SEEM TO BE OVER US...EVEN MORE THAN OVER CANADA AND MUCH MORE THAN OVER ADJACENT FORECAST AREAS. THE LOW TEMPERATURES...AOB -30C IN MANY PLACES THIS MORNING FOR EXAMPLE...ANCHOR THE RIDGE IN PLACE RESULTING IN FIRST...UPSTREAM CLOUDS REMAINING OUT OF OUR AREA FOR AS MUCH AS 24 HOURS LATER THAN THE MODELS SUGGEST. AND...MOST IMPORTANTLY...THE RIDGE...ANCHORED OVER THE BITTERLY COLD IRON RANGE AND RAINY RIVER VALLEY...MAINTAINS A NORTH GRADIENT OVER THE STILL OPEN LAKE SUPERIOR. SO...SNOW SHOWERS ALONG THE SHORE COUNTIES OF NORTHWEST WISCONSIN HAVE BEEN VERY HEAVY...PERSISTED LONGER THAN EXPECTED...RESULTING IN HEAVY SNOW. AGAIN...WE ANCPT THESE TRENDS TO CONTINUE. WE LIKE THE GFS LOWER THICKNESSES AND FURTHER INTRUSION OF ARCTIC AIR...AT LEAST ON THIS 07/00Z RUN. THOUGH THE GFS...AS USUAL...HAS TOO MUCH MOISTURE OVER US...ITS CLIPPER TRACK HAS BEEN REASONABLE. SO...WE ARE GOING COLD AND DRY...AND ANCPT SERIOUS SNOW SQUALLS ANYTIME AN ONSHORE FLOW BECOMES ESTABLISHED. AVIATION... PRIND CLDNS WL RMN W OF AREA AND SNW SQLS WL RMN OVER LK SUPR DURG THE MRNG. MID/HI CLDNS WL INCRS FM W TO E DURG AFTN... WITH CONDS DTRTG TO MVFR AND PSBLY IFR IN LGT SNW FM W TO E LT THIS AFTN THRUT THIS EVE. AN ONSHR FLO TO THE N SHR WL RESULT IN MLIFR IN LCLY INTS SNW SHWRS AND SNW SQLS BGNG LT AFTN AND CONTG THRUT TNGT WHEN WNDS WL VEER. SNW SHWRS WL BCM ISOLD...BUT WITH A PSBLTY OF PTCHY FRZG DRZL MON. && POINT TEMPS/POPS... DLH 12 6 19 2 / 70 70 20 20 INL 11 1 16 -6 / 60 50 10 10 BRD 13 7 22 5 / 80 50 20 10 HYR 14 6 24 5 / 70 80 20 20 ASX 14 6 24 9 / 40 70 30 30 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM CST MONDAY FOR NORTHERN COOK/NORTHERN LAKE-SOUTHERN COOK/LAKESHORE-SOUTHERN LAKE/LAKESHORE. WI...NONE. LS...NONE. $$ CANNON mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1216 PM CST SUN DEC 7 2008 .UPDATED FOR THE 18Z AVIATION DISCUSSION... .SHORT TERM /TODAY/... SFC RIDGE AXIS BEGINNING TO SHIFT EAST OF THE AREA...WITH HIGH CLOUDS SPREADING EASTWARD INTO THE CENTRAL CWA AHEAD OF THE WARM FRONT ASSOCIATED WITH THE NEXT WAVE DIVING SOUTHEAST FROM THE CANADIAN ROCKIES. BEST LIFT WITH THIS WAVE AS IT DIVES SOUTHEASTWARD THROUGH SRN MN/NRN IA THIS MORNING INTO THIS AFTERNOON WILL MAINLY BE NORTH OF HWY 20. GFS/NAM/RUC IN DISAGREEMENT REGARDING AMOUNT OF MOISTURE/QPF WITH THE NAM/RUC ADVERTISING ONLY A FEW HUNDREDTHS ACROSS THE NORTHERN CWA VERSUS JUST OVER A TENTH WITH THE GFS. SOUNDINGS INDICATING BRIEF SATURATION...WITH PROBABLY AROUND A FEW HOURS OF LIGHT SNOW AT MOST LOCATIONS NORTH OF I-80. OTHERWISE MAYBE ONLY A BRIEF SNOW SHOWER OR FLURRIES EXPECTED ACROSS THE SOUTHERN CWA. PREVIOUS FORECAST MORE IN LINE WITH THE GFS...BUT LOOKING AT TRENDS UPSTREAM FEEL THE GFS MAY BE A BIT OVERDONE. THEREFORE HAVE TRENDED GRIDS SLIGHTLY TOWARD THE NAM/RUC BY LOWERING POPS ACROSS THE SOUTHERN HALF OF THE CWA AND CUTTING THE QPF DOWN BY 30 TO 40 PERCENT. COULD STILL SEE AROUND AN INCH ACROSS THE NORTHERN TIER COUNTIES...TAPERING TO A FEW TENTHS AROUND HWY 30 TO AROUND A TRACE FURTHER SOUTH. BUFKIT SOUNDINGS DID SHOW A BRIEF PERIOD OF FZDZ AS THE SNOW TAPERED OFF AND SATURATION WAS LOST ALOFT. HOWEVER THIS WAS QUITE BRIEF ONLY AROUND AN HOUR OR SO...SO LEFT PRECIP TYPE ALL SNOW FOR NOW. .LONG TERM /TONIGHT-SATURDAY/... WILL HAVE ANOTHER WEAK SHORTWAVE TRANSLATING OVER SOUTHERN IOWA TONIGHT WITH BAND OF WARM ADVECTION AND MID LEVEL FRONTOGENETICAL FORCING. MODELS DIFFER ON AREA THAT RECEIVES LIGHT PRECIP...SO WENT WITH ONLY LOW CHANCES ACROSS THE SOUTHERN HALF OR SO. OTHERWISE MAIN CONCERN FOR THIS FORECAST PACKAGE IS SIGNIFICANT SYSTEM FOR MONDAY NIGHT AND TUESDAY. THE ECMWF/UKMET/CANADIAN SOLUTIONS ARE PREFERRED FOR THIS PERIOD GIVEN THEIR CONSISTENCY. UNFORTUNATELY THE NAM/SREF AND TO A CERTAIN EXTENT THE GFS/GEFS ARE NOT EXACTLY GOING THE SAME DIRECTION...SO CONFIDENCE IS NOT AS HIGH AS I`D LIKE. HOWEVER...SINCE OUR FORECAST IS LEANING STRONGLY TO THE FIRST SET OF MODELS MENTIONED ABOVE...WILL NEED TO ISSUE A WINTER STORM WATCH FOR A STRIP OF COUNTIES SW TO NE THROUGH CENTRAL IOWA. EVEN AFTER TAKING A BLEND OF THE GFS/HPC/ECMWF QPF FOR THIS PERIOD...STILL CAME OUT WITH 4 TO 8 INCHES OF SNOW FOR MUCH OF OUR AREA. THAT SEEMS A BIT MUCH FOR THE UNCERTAINTY THAT STILL EXISTS...BUT I AM IN COLLABORATION WITH NEIGHBORS. AS LOW PRESSURE ORGANIZES IN THE SOUTHERN PLAINS MONDAY...FRONTOGENETICAL FORCES AND ISENTROPIC LIFT BEGIN OVER IOWA...AND MAY YIELD LIGHT PRECIP. SOUTHERN IOWA SHOULD BE ABOVE FREEZING DURING THE DAY MONDAY INTO MONDAY NIGHT. SO AS THE SYSTEM APPROACHES...RAIN WILL BE THE DOMINATE P-TYPE ALONG AND SOUTH OF I-80. HOWEVER...AS THE LOW INTENSIFIES AND WRAPS IN THE COLDER AIR TO THE NORTH...ALONG WITH DYNAMIC PROCESSES IN THE TROWAL AND DEFORMATION ZONE TO THE NORTH OF SFC LOW TRACK...PRECIP SHOULD TRANSITION TO ALL SNOW MONDAY NIGHT NW TO SE. SOUNDINGS DON`T OFFER MUCH CHANCE FOR ANYTHING OTHER THAN RAIN OR SNOW. HOWEVER...THERE IS STILL A POSSIBILITY OF A LITTLE FREEZING RAIN IF COLDER SFC AIR WORKS ITS WAY IN BEFORE THE UPPER LEVELS COOL ENOUGH. AT THIS TIME THOUGH SOUNDINGS SUPPORT MORE OF A RAIN TO SNOW TRANSITION WHERE IT STARTS AS RAIN. AM USING SNOW RATIOS AT OR BELOW CLIMO FOR NOW...GIVEN UNCERTAINTIES OF WHERE ANY HEAVIER BANDED SNOW MAY SET UP. EVEN IF SNOWFALL AMOUNTS DO NOT REACH WARNING CRITERIA ALONE...THE WIND WILL BE INCREASING ENOUGH TO WARRANT A WINTER STORM WATCH. WINDS ARE EXPECTED TO BE SUSTAINED BETWEEN 20 AND 30 MPH WITH GUSTS POTENTIALLY CLOSE TO 35 OR 40 MPH AT TIMES. AND THIS BRINGS US DANGEROUSLY CLOSE TO BLIZZARD CONDITIONS. BUT...GIVEN SOME UNCERTAINTY THERE...WE WILL JUST MENTION THE WIND AND BLOWING SNOW POTENTIAL IN THE WINTER STORM WATCH. ALSO...BEING THE FIRST WINTER STORM THREAT OF THE SEASON...WE WILL LOWER OUR THRESHOLD A BIT. THE SNOW SHOULD END TUESDAY EVENING IF NOT BEFORE...BUT CONTINUE TO BLOW AROUND WELL INTO TUESDAY NIGHT. AN ACTIVE PATTERN DOES NOT SLOW DOWN...WITH A COUPLE OF CLIPPER SYSTEMS FOR LATE IN THE WEEK...EACH WITH RESPECTABLE CHANCES FOR LIGHT SNOW IN OUR AREA. TEMPS WERE ADJUSTED DOWNWARD FOR THE MIDDLE OF THE WEEK GIVEN TREND IN THE MEDIUM RANGE GUIDANCE. && .AVIATION...07/18Z LIGHT SNOW WILL END NEAR MCW AND ALO BY AROUND 20Z THEN WILL HAVE A RETURN OF MAINLY VFR CONDITIONS ALL LOCATIONS THAT WILL LAST INTO A PORTION OF THE OVERNIGHT PERIOD. MVFR CLOUD COVER MAY AGAIN REDEVELOP LATE TONIGHT MAINLY EAST OF INTERSTATE 35. SOME FREEZING RAIN IS POSSIBLE NEAR OTM/ALO LATE TONIGHT AND MONDAY MORNING. POSSIBLE THIS PRECIPITATION MAY EXTEND WESTWARD INTO THE DSM AREA. && .DMX WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON FOR ADAIR-ADAMS-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN- CARROLL-CASS-CERRO GORDO-CLARKE-DALLAS-FRANKLIN-GREENE-GRUNDY- GUTHRIE-HAMILTON-HARDIN-JASPER-MADISON-MARSHALL-POLK-POWESHIEK- RINGGOLD-STORY-TAMA-TAYLOR-UNION-WARREN-WEBSTER-WRIGHT. && $$ SHORT TERM/AVIATION...ALBRECHT LONG TERM...MOYER ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DODGE CITY KS 351 PM CST SUN DEC 7 2008 .DISCUSSION... DAYS 1-2... THE MAIN FOCUS OF THE CURRENT FORECAST CONTINUES TO KEY ON A LIKELY PRECIPITATION EVENT MONDAY NIGHT AND EARLY TUESDAY. THIS MORNINGS UPPER AIR ANALYSIS INDICATED A FLATTENING OF THE UPPER FLOW OVER THE LAST 24 HOURS, WITH THE UPPER LOW OFF THE CALIFORNIA COAST PHASING INTO THE WEAKENING RIDGE, DROPPING THE MEAN HEIGHT FIELD OVER THE WESTERN UNITED STATES. A NARROW THERMAL AXIS WAS LOCATED FROM WEST TEXAS INTO WESTERN NEBRASKA AT SFC-700 MB. DOWNSLOPE FLOW WILL ALLOW TEMPERATURES LATE THIS AFTERNOON TO TOP OUT IN SOME LOCATIONS APPROACHING 70 DEGREES ACROSS WESTERN SECTIONS OF THE FAR EASTERN CWA, WHILE CLOUDS AND LOWER 850 TEMPERATURES WILL WILL HAVE TEMPERED HIGHS OVER THE NORTHEAST. FOR TONIGHT, CYCLOGENESIS SHOULD BEGIN TO DEVELOP ACROSS EASTERN COLORADO IN RESPONSE TO WIDESPREAD HEIGHT FALLS CONTINUING ACROSS THE WESTERN HALF OF THE CONUS. WE EXPECT TEMPERATURES TO BE SLIGHTLY MORE MILD THAN SATURDAY NIGHT AND HAVE FORECAST MID 30S NORTH TO NEAR 40 IN THE SOUTH WEST. INCREASING CLOUDS MAY EVEN KEEP TEMPERATURES FROM DROPPING THIS LOW OVER THE NORTH. REASONABLY WARM BOUNDARY LAYER AIR WILL STILL BE ACROSS THE FORECAST AREA ON MONDAY. WITH LESS DOWNSLOPE COMPONENT AND INCREASED CLOUD COVER WILL EXPECT TEMPERATURES TO NOT REACH QUITE AS WARM FOR MAXIMUM TEMPERATURES. THOUGH THE DAY ON MONDAY CHANCES FOR PRECIPITATION WILL INCREASE ALTHOUGH THE BEST CHANCES ARE NOT LIKELY UNTIL LATER IN THE DAY. THERE ARE SIGNIFICANT MODEL DIFFERENCES WITH THE UPCOMING EVENT. ECMWF/NAM ARE SIMILAR WITH THE STRENGTH OF THE SYSTEM WHILE THE GFS IS A MUCH MORE AGGRESSIVE SOLUTION WITH A DEEPER LOW CENTER AND RESULTING STRONGER FRONTOGENETICAL FORCING...SO MUCH SO THAT THE SNOW OUTPUT TOTAL IS IN EXCESS OF 6 INCHES ACROSS ALL OF SW KANSAS BY EARLY TUESDAY. GFS OUTPUTS A SIGNIFICANTLY HIGHER QPF TOTAL THAN THE OTHER MODELS...MOST OF WHICH IS BEING CONVERTED TO SNOW. IN CONTRAST, THE NAM IS LESS AGGRESSIVE, DEVELOPING 1-3 INCH AMOUNTS, AND LITTLE IF ANY IN THE FAR SOUTHEASTERN SECTIONS. THE ECMWF AND NAM SEEM TO BE THE MORE REASONABLE SOLUTIONS AT THIS POINT, ESPECIALLY GIVEN THE VERY DRY DEWPOINTS ACROSS OK/TX AND IT WOULD SEEM TREMENDOUS MOISTURE TRANSPORT WOULD BEE NEEDED TO PRODUCE THIS KIND OF A SYSTEM. WILL FORECAST 1 TO 3 INCHES PRIMARILY FROM NORTHEAST TO SOUTHWEST. WHAT IS MOST LIKELY IS THE FAR SOUTHEAST WOULD RECEIVE THE LEAST AMOUNT OF SNOWFALL. VERY LITTLE IF ANY RAINFALL WOULD BE EXPECTED MONDAY DURING THE MORNING WITH THE WARM ADVECTION/THETA-A E ADVECTION WAVE AHEAD OF THE SURFACE CYCLOGENESIS, WITH HIGH PROBABILITY BUT LOW QPF RAIN IN ADVANCE OF THE CHANGEOVER. LATER MONDAY EVENING, CHANCES WILL INCREASE AND THE 950-700 MB TEMPERATURE GRADIENT LAYER BEGINS TO UNDERGO STRETCHING ACROSS WESTERN KANSAS. 850 TEMPERATURES SHOULD BE WARM ENOUGH FOR A PERIOD OF RAINFALL BEFORE A RAIN SNOW MIX DEVELOPS MONDAY EVENING, CHANGING TO ALL SNOW BY LATE MONDAY EVENING. POST FRONTAL WINDS WILL BE SUFFICIENT FOR SIGNIFICANTLY REDUCED VISIBILITIES IN BLOWING SNOW HOWEVER REDUCED VISIBILITIES TO A QUARTER MILE REMAINS UNCERTAIN DESPITE WIND SPEEDS AROUND 25+ MPH AS DEV-RUC 13KM MAINTAINING VSBYS ABOVE 1/2 MILE DURING THE STRONGER PUSH OF COLD AIR ON MONDAY NIGHT. DAYS 3-7... AFTER THE SNOW MELTS WEDNESDAY AFTERNOON AND EARLY THURSDAY, IT APPEARS THAT TEMPERATURES COULD WARM SIGNIFICANTLY INTO THE 50S BY FRIDAY AND SATURDAY AS STRONG WSW MID LEVEL FLOW INDUCES A LEE TROUGH. TEMPERATURES WERE ADJUSTED ACCORDINGLY. AS A LARGE UPPER TROUGH DIGS ALONG THE WEST COAST, AN ARCTIC HIGH SHOULD MOVE DOWN THE PLAINS BY SUNDAY. TODAY`S SUITE OF MODELS HAVE CONTINUED TO SLOW DOWN THE ARCTIC OUTBREAK FOR NEXT WEEKEND, BUT ONLY BY ABOUT 12 HOURS. IT APPEARS THAT THE STRONG COLD SURGE MAY HOLD OFF UNTIL A STRONG SHORTWAVE TROUGH PASSES ACROSS THE CENTRAL AND NORTHERN PLAINS. ANY PRECIP WILL PROBABLY NOT OCCUR UNTIL MONDAY OR TUESDAY. AFTER THE COLD AIR ARRIVES, A STORM SYSTEM COULD DEVELOP AND PASS ACROSS THE SOUTHERN PLAINS PER ECMWF. IT IS VERY DIFFICULT TO GET PRECIP IN THE WARM SECTOR IN DEC/JAN IN SOUTHWEST KANSAS SINCE THE WARM CONVEYOR BELT TENDS TO BE TO OUR EAST. && .AVIATION... VFR CONDITIONS WILL CONTINUE THROUGHOUT THE PERIOD. && .PRELIMINARY POINT TEMPS/POPS... DDC 66 35 53 27 / 0 10 40 80 GCK 67 36 56 25 / 0 10 50 80 EHA 68 38 56 26 / 0 10 40 80 LBL 65 37 56 28 / 0 10 40 80 HYS 55 33 49 25 / 0 10 50 90 P28 64 35 58 32 / 0 10 40 80 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ FN33/24 ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 1116 AM MST SUN DEC 7 2008 .UPDATE... 1112 AM MST SUN DEC 7 2008 TEMPS HAVE WARMED RAPIDLY ON PERIPHERY OF CLOUD SHIELD...AND SFC WINDS AND TDS ALSO SUGGEST WEAK WARM FRONT MOVING EAST ACROSS THE AREA. SEVERAL LOCATIONS ALREADY NEARING FORECAST HIGHS...AND LATEST GUIDANCE AND 12Z RAOBS WOULD SUPPORT HIGHS IN THE 60S ACROSS MANY LOCATIONS. CLOUD COVER MAY RESULT IN A NORTH SOUTH GRADIENT ALONG WITH THE EXPECTED EAST-WEST GRADIENT...BUT BASED ON LATEST SFC OBS UNDER CLOUD COVER NOT SURE THAT IMPACT WILL BE THAT GREAT. BY 18Z TEMPS HAVE CONTINUED TO WARM RAPIDLY WITH GLD AREA BEING THE HOT SPOT. HAVE UPPED TEMPS INTO THE LOWER 70S ACROSS MUCH OF THE SOUTHWEST...AS CURRENT TEMP TRENDS ARE EXPECTED TO STABILIZE AS ATMOSPHERE BECOMING MORE MIXED. JRM && .DISCUSSION... 246 AM MST SUN DEC 7 2008 NORTHWEST FLOW WILL BECOME ZONAL TONIGHT AS SHORTWAVE ENERGY DIGS SOUTH ACROSS WESTERN UTAH. FLOW THEN BECOMES SOUTHWEST ON MONDAY AS THE TROUGH MOVES EAST OF THE ROCKIES. FLOW IS NORTHWEST ON TUESDAY. A SURFACE TROUGH OVER EASTERN COLORADO TODAY WILL MOVE INTO THE OKLAHOMA/TEXAS PANHANDLE REGION TONIGHT/MONDAY. HIGH PRESSURE WILL BUILD INTO NORTHWEST KANSAS MONDAY NIGHT THROUGH TUESDAY. THE MAIN FORECAST ISSUES ARE PRECIPITATION TYPE AND WIND. TIMING OF THE EVENT LOOKS ON TRACK WITH UPWARD VERTICAL VELOCITIES INDICATED MONDAY AFTERNOON...CONTINUING MONDAY NIGHT AND ENDING AROUND 12Z TUESDAY. THE CURRENT FORECAST KEEPS THE EVENT ABOUT 6 HOURS PAST THIS TIME. 1000-500MB THICKNESSES FROM THE GFS/NAM SUGGEST THAT PRECIPITATION SHOULD BE LIQUID THROUGH MOST OF MONDAY AFTERNOON EXCEPT IN THE NORTHWEST ZONES. BY MONDAY EVENING PRECIPITATION SHOULD BE ALL SNOW OVER THE NORTHWEST HALF OF THE FORECAST AREA WITH ONLY THE SOUTHEAST ZONES HAVING A MIX OF RAIN/SNOW. THE ENTIRE FORECAST AREA SHOULD HAVE ALL SNOW BY 06Z TUESDAY THROUGH THE END OF THE EVENT. THE NEXT ISSUE IS WIND WHICH THE RUC SHOWS TO BE A SIGNIFICANT CONCERN WITH THIS EVENT. BY 09Z TUESDAY SURFACE WIND IS PROGGED TO BE SUSTAINED AT GREATER THAN 30KTS AND WIND GUSTS GREATER THAN 40KTS. THIS WILL CAUSE SIGNIFICANT BLOWING AND DRIFTING OF ANY SNOW. MOST OF THE SNOW SHOULD END BY 12Z TUESDAY BUT THIS STRONG WIND SHOULD LAST WELL INTO TUESDAY AFTERNOON. CURRENT FORECAST ALREADY HAS AREAS OF BLOWING SNOW FOR THIS TIME PERIOD. A WINTER HIGHLIGHT MAY BE NEEDED IF MODELS CONTINUE TO SHOW THIS MUCH WIND. FOR NOW PLAN TO CONTINUE WORDING IN THE HWO FOR THIS POTENTIAL. SNOWFALL AMOUNTS STILL LOOK LIKE 1 TO 3 INCHES WITH HEAVIEST AMOUNTS OVER THE CENTRAL AND EAST ZONES. TEMPERATURES WILL STILL BE UNSEASONABLY WARM. GUIDANCE SHOWING READINGS ABOUT 20 DEGREES ABOVE NORMAL. FOLLOWED COOLER GUIDANCE BASED ON UNCERTAINTY WITH AMOUNT OF CLOUDS. COLD FRONT WILL COME THROUGH TONIGHT. MAX TEMPERATURES WILL REACH INTO THE LOWER 40S MONDAY AND IN THE UPPER 30S TUESDAY. MIN TEMPERATURES WILL FALL INTO THE MID 20S TONIGHT AND AROUND 20 MONDAY AND TUESDAY NIGHTS. FS && .AVIATION... 1112 AM MST SUN DEC 7 2008 FOR 18Z TAFS...VFR CONDITIONS EXPECTED THROUGH THE PERIOD WITH WINDS GENERALLY LIGHT AND VARIABLE UNTIL 15Z WHEN WINDS SHIFT TO THE NORTH AROUND 12 KTS. JRM && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 941 AM MST SUN DEC 7 2008 .UPDATE... 937 AM MST SUN DEC 7 2008 TEMPS HAVE WARMED RAPIDLY ON PERIPHERY OF CLOUD SHIELD...AND SFC WINDS AND TDS ALSO SUGGEST WEAK WARM FRONT MOVING EAST ACROSS THE AREA. SEVERAL LOCATIONS ALREADY NEARING FORECAST HIGHS...AND LATEST GUIDANCE AND 12Z RAOBS WOULD SUPPORT HIGHS IN THE 60S ACROSS MANY LOCATIONS. CLOUD COVER MAY RESULT IN A NORTH SOUTH GRADIENT ALONG WITH THE EXPECTED EAST-WEST GRADIENT...BUT BASED ON LATEST SFC OBS UNDER CLOUD COVER NOT SURE THAT IMPACT WILL BE THAT GREAT. JRM && .DISCUSSION... 246 AM MST SUN DEC 7 2008 NORTHWEST FLOW WILL BECOME ZONAL TONIGHT AS SHORTWAVE ENERGY DIGS SOUTH ACROSS WESTERN UTAH. FLOW THEN BECOMES SOUTHWEST ON MONDAY AS THE TROUGH MOVES EAST OF THE ROCKIES. FLOW IS NORTHWEST ON TUESDAY. A SURFACE TROUGH OVER EASTERN COLORADO TODAY WILL MOVE INTO THE OKLAHOMA/TEXAS PANHANDLE REGION TONIGHT/MONDAY. HIGH PRESSURE WILL BUILD INTO NORTHWEST KANSAS MONDAY NIGHT THROUGH TUESDAY. THE MAIN FORECAST ISSUES ARE PRECIPITATION TYPE AND WIND. TIMING OF THE EVENT LOOKS ON TRACK WITH UPWARD VERTICAL VELOCITIES INDICATED MONDAY AFTERNOON...CONTINUING MONDAY NIGHT AND ENDING AROUND 12Z TUESDAY. THE CURRENT FORECAST KEEPS THE EVENT ABOUT 6 HOURS PAST THIS TIME. 1000-500MB THICKNESSES FROM THE GFS/NAM SUGGEST THAT PRECIPITATION SHOULD BE LIQUID THROUGH MOST OF MONDAY AFTERNOON EXCEPT IN THE NORTHWEST ZONES. BY MONDAY EVENING PRECIPITATION SHOULD BE ALL SNOW OVER THE NORTHWEST HALF OF THE FORECAST AREA WITH ONLY THE SOUTHEAST ZONES HAVING A MIX OF RAIN/SNOW. THE ENTIRE FORECAST AREA SHOULD HAVE ALL SNOW BY 06Z TUESDAY THROUGH THE END OF THE EVENT. THE NEXT ISSUE IS WIND WHICH THE RUC SHOWS TO BE A SIGNIFICANT CONCERN WITH THIS EVENT. BY 09Z TUESDAY SURFACE WIND IS PROGGED TO BE SUSTAINED AT GREATER THAN 30KTS AND WIND GUSTS GREATER THAN 40KTS. THIS WILL CAUSE SIGNIFICANT BLOWING AND DRIFTING OF ANY SNOW. MOST OF THE SNOW SHOULD END BY 12Z TUESDAY BUT THIS STRONG WIND SHOULD LAST WELL INTO TUESDAY AFTERNOON. CURRENT FORECAST ALREADY HAS AREAS OF BLOWING SNOW FOR THIS TIME PERIOD. A WINTER HIGHLIGHT MAY BE NEEDED IF MODELS CONTINUE TO SHOW THIS MUCH WIND. FOR NOW PLAN TO CONTINUE WORDING IN THE HWO FOR THIS POTENTIAL. SNOWFALL AMOUNTS STILL LOOK LIKE 1 TO 3 INCHES WITH HEAVIEST AMOUNTS OVER THE CENTRAL AND EAST ZONES. TEMPERATURES WILL STILL BE UNSEASONABLY WARM. GUIDANCE SHOWING READINGS ABOUT 20 DEGREES ABOVE NORMAL. FOLLOWED COOLER GUIDANCE BASED ON UNCERTAINTY WITH AMOUNT OF CLOUDS. COLD FRONT WILL COME THROUGH TONIGHT. MAX TEMPERATURES WILL REACH INTO THE LOWER 40S MONDAY AND IN THE UPPER 30S TUESDAY. MIN TEMPERATURES WILL FALL INTO THE MID 20S TONIGHT AND AROUND 20 MONDAY AND TUESDAY NIGHTS. FS && .AVIATION... 437 AM MST SUN DEC 7 2008 FOR THE 12Z TAF...EXPECT VFR CONDITIONS OVER THE NEXT 24 HOURS AT BOTH KGLD AND KMCK WITH LIGHT AND VARIABLE WINDS. WILL SEE A GENERALLY BROKEN MID LEVEL CLOUD DECK CENTERED AROUND 20-25K FT AGL THROUGH THE TAF CYCLE. FOLTZ && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. NE...NONE. CO...NONE. && $$ ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CARIBOU ME 352 PM EST SUN DEC 7 2008 .SYNOPSIS... LOW PRESSURE WILL MOVE INTO THE MARITIMES TONIGHT. SNOW WILL END ACROSS THE STATE AS THE LOW MOVES TO THE NORTH. WIND WILL INCREASE LATER TONIGHT AND THIS WILL RESULT IN BLOWING SNOW LATE TONIGHT AND MONDAY. && .NEAR TERM /THROUGH MONDAY/... RAPIDLY INTENSIFYING LOW PRESSURE IS TRACKING EAST OF THE GULF OF MAINE INTO THE NORTH/CENTRAL PORTION OF NOVA SCOTIA. THE INTENSE SYSTEM WILL CONTINUE TO MOVE NORTHWARD INTO THE MARITIMES TONIGHT. PRIMARY SYNOPTIC SCALE PRECIPITATION WITH THIS SYSTEM WILL PASS JUST TO THE EAST OF THE FORECAST AREA. PRIMARY CONCERN FOR OUR AREA IS BANDING PRECIPITATION...THE HEAVIEST OF THIS IS CURRENTLY MOVING ACROSS WASHINGTON COUNTY. SITUATION IS FURTHER COMPLICATED WITH INTRUSION OF WARMER MARITIME AIR OVER EXTREME SOUTHEAST WASHINGTON COUNTY WHICH TEMPORARILY CHANGED SNOW TO RAIN. BANDING APPEARS TO BE CONNECTED WITH COASTAL FRONTOGENSIS INDUCED BY WARM SEA SURFACE TEMPERATURES. STRATEGY WILL BE TO USE RUC13...WHICH IS MOST SUITED FOR BANDING EVENT AND CURRENTLY CORRELATES BEST TO RADAR. WILL THEN TRANSITION TO NAM12 AFTER 03Z THIS EVENING. WILL USE NAM12 TEMPERATURES AND WIND INTO THIS EVENING THEN TRANSITION TO GMOS NUMBERS. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... SURFACE HIGH PRESSURE WILL CREST ACROSS OUR FORECAST AREA (FA) MONDAY NIGHT. A VERY QUICK FALL IN TEMPERATURE ARE EXPECTED EARLY MONDAY EVENING WITH CLEAR SKIES. IN FACT... SUBZERO READINGS ARE LIKELY IN THE NORTH AND SINGLE DIGITS ABOVE ZERO SOUTH...BEFORE TEMPS LEVEL OUT LATER AT NIGHT WITH OVERALL PRESSURE FALL PATTERN DEVELOPING...AND SOME CLOUDS ENTERING THE PICTURE IN WEAK WARM AIR ADVECTION (WWA). WE WILL TRY TO USE A SENSIBLE WEATHER APPROACH TO A VERY COMPLEX PATTERN SHAPING UP FOR TUESDAY INTO WEDNESDAY. FIRST AN INCREASING ISENTROPIC LIFTING REGIME WILL QUICKLY SATURATE THE AIRMASS TUESDAY...WITH PCPN BREAKING OUT FROM SOUTH TO NORTH. PCPN SHOULD START AS SNOW...THEN MIX WITH OR CHANGE TO RAIN OVER THE SOUTH AS OVERALL THERMAL STRUCTURE WARMS. SIGNIFICANT OVERRUNNING/WAA/ISENTROPIC LIFT WILL CONTINUE TUESDAY NIGHT...WHILE OUR AREA COMES UNDER THE RIGHT ENTRANCE REGION OF AN INTENSIFYING ANTICYCLONIC JET ALOFT. TREMENDOUS LIFTING POTENTIAL WILL YIELD PCPN OVER OUR FA. RAIN WILL CONTINUE SOUTH ..WHILE PCPN STRUCTURE SHIFTS FROM SNOW TO RAIN CENTRAL...AND PCPN GRADUALLY BECOMES A MIXTURE SNOW AND RAIN IN THE NORTH LATE. IF MODEL TRENDS HOLD WE SHOULD BE IN THE WARM SECTOR WEDNESDAY... WITH ALL PCPN BUSTING OVER TO RAIN. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... THE LONG TERM STARTS WITH THE MODELS A BIT AT ODDS...BUT THE ECMWF HAS BEEN TRENDING BACK TOWARD THE GFS SOLUTION. THE GFS INDICATES A 987MB LOW CENTERED NEAR QUEBEC CITY WITH A FRONTAL SYSTEM EXTENDING SOUTH ALONG THE APPALACHIANS. THE ECMWF HAS A 992MB LOW CENTER OVER THE GULF OF ST. LAWRENCE...WITH A COLD FRONT EXTENDING SW ALONG THE DOWNEAST COAST DOWN THE EASTERN SEABOARD. THOUGH THE DIFFERENCE DOESN`T SOUND DRASTIC...IT IS A MAJOR DIFFERENCE FOR THE COASTAL WATERS AND THE DOWNEAST COAST AND INLAND DOWNEAST. THE INCREASED GRADIENT WILL PRODUCT SIGNIFICANTLY HIGHER WINDS WITH THE GFS SOLUTION. THE DIFFERENCES CONTINUE THROUGH 12Z SATURDAY WHEN THE MODELS ARE BACK INTO AGREEMENT AND REMAIN IN GOOD AGREEMENT THROUGH THE END OF THE PERIOD. LOADED THE GMOS FOR THE EXTENDED PERIOD. IT FOLLOWS THE GFS SOLUTION. THE GFS HAS HELD ITS TREND THE LAST COUPLE OF RUNS WITH THE OTHER MODELS TRENDING TOWARD IT. THERE IS STILL SOME UNCERTAINTY WITH HOW THIS NEXT SYSTEM WILL PLAY OUT BUT...IF THIS TREND CONTINUES AS FORECASTED IT WILL RESULT IN AT LEAST ADVISORY STRENGTH WINDS FOR THE DOWNEAST COAST AND INTERIOR DOWNEAST FROM WED EVENING THROUGH THUR AFTERNOON. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... SHORT TERM...VFR CONDITIONS MONDAY NIGHT WILL TRANSITION TO IFR CONDITIONS ACROSS OUR ENTIRE FORECAST AREA TUESDAY INTO WEDNESDAY... AS THE NEXT STORM APPROACHES. UNSETTLED WEATHER CONDITIONS TO PERSIST BEYOND MIDWEEK. && .MARINE... NEAR TERM: ALL MODEL GUIDANCE IS INCREASING WIND SPEED TO QUICKLY DURING THE AFTERNOON. WILL MANUALLY ADJUST CURRENT WIND SPEEDS THEN TRANSITION TO NAM12 WINDS. HAVE INITIALIZED WINDS TONIGHT AND MONDAY WITH NAM12...THEN WILL INCREASE MODEL SPEEDS AROUND 3 KNOTS TO ELIMINATE LOW BIAS. FOR WAVES: HAVE USED WNA/4 WHICH LOOKS REASONABLE. WILL LEAVE TIMING OF GALE WARNING AS IS...DO NOT EXPECT SUSTAINED WINDS TO REACH GALE UNTIL LATER TONIGHT BUT GUSTS SHOULD JUSTIFY CURRENT TIMING. SHORT TERM. A CONSIDERABLE INCREASE IN WINDS AND WAVES ARE EXPECTED TUESDAY INTO WEDNESDAY. WAVES IN EXCESS OF 10 FEET AND GALES WILL BE LIKELY. LONG TERM: A STRONG GALE WARNING MAY BE REQUIRED WED AFTERNOON THROUGH THUR AFTERNOON AS A DEEP LOW AND ASSOCIATED FRONTAL SYSTEM WORK THEIR WAY THROUGH THE AREA. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...WINTER WEATHER ADVISORY UNTIL 5 AM EST MONDAY FOR MEZ001-002- 005-006. WINTER WEATHER ADVISORY UNTIL 7 PM EST THIS EVENING FOR MEZ011- 016-029. WINTER STORM WARNING UNTIL 7 PM EST THIS EVENING FOR MEZ017- 030-032. MARINE...GALE WARNING FROM 7 PM THIS EVENING TO 7 PM EST MONDAY FOR ANZ050>052. && $$ NEAR TERM...MIGNONE SHORT TERM...STUREY LONG TERM...NORTON AVIATION...MIGNONE MARINE...MIGNONE/STUREY/NORTON me AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 417 PM EST SUN DEC 7 2008 .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED A GENERAL WNW FLOW ACROSS NORTH AMERICA...WITH THE MAIN WESTERLIES JET TRACKING FROM WASHINGTON STATE INTO THE CAROLINAS. ALSO TO NOTE IS AN UPPER LOW COMING INTO SOUTHERN CALIFORNIA. WITHIN THE FLOW...A TROUGH IS NOTED NEAR VANCOUVER ISLAND AND A FEW SHRTWVS WERE MOVING THROUGH ERN ND AND SRN MN. OVER UPPER MI...DESPITE THE WNW FLOW...500MB HEIGHTS HAVE BEEN RISING AS THE UPPER TROUGH THAT WAS OVER THE CWA HAS MOVED OFF INTO NEW ENGLAND. THESE HEIGHT RISES HAVE RESULTED IN SUBSIDENCE...PRODUCING HIGH PRESSURE AT THE SFC. THIS HIGH PRESSURE RIDGE COVERS MUCH OF MI...LAKE SUPERIOR AND LAKE MI. DRY AIR AND THE SUBSIDENCE...AS SEEN ON 12Z SOUNDINGS FROM GRB AND INL (PRECIPITABLE WATER VALUES OF LESS THAN 0.10 OF AN INCH)...HAVE HELPED TO DIMINISH LAKE EFFECT ON BOTH LAKES SUPERIOR AND MI. TEMPERATURES ALOFT STILL REMAIN COLD ENOUGH FOR LAKE EFFECT... THOUGH...WITH 850MB READINGS OF -15C AT GRB...-20C AT CWPL AND AT APX. OUTSIDE OF THE LAKE EFFECT...HIGH CLOUDS HAVE BEEN INCREASING ACROSS THE CWA FROM THE WEST...ASSOCIATED WITH WARM ADVECTION OCCURRING OVER THE UPPER MISSISSIPPI VALLEY AND DPVA FROM THE SHRTWVS CROSSING ND/MN. CLOUDS THICKEN UP THE FARTHER WEST YOU GO...WITH THE REGIONAL RADAR LOOP AND SFC OBS SHOWING -N FROM NW MN INTO WRN WI. RADAR LOOP ALSO SHOWS RETURNS FARTHER TO THE NE INTO FAR WRN UPPER MI...BUT DRY AIR EVIDENT ON THE 12Z MPX SOUNDING THAT HAS MOVED INTO UPPER MI HAS KEPT MUCH OF THIS SNOW FROM REACHING THE GROUND. THE WARM ADVECTION GRADIENT WAS ACTUALLY QUITE TIGHT BACK AT 12Z...WITH BIS AND ABR SHOWING -6C TEMP/0C DEWPOINT DEPRESSION AT 850MB COMPARED TO THE -13C TEMP/21C DEWPOINT DEPRESSION AT MPX. && .SHORT TERM (TONIGHT AND MONDAY)... TROUGH OVER VANCOUVER ISLAND IS PROGGED TO DEEPEN AS IT DIVES DOWN INTO THE WESTERN U.S....WHICH ALLOWS IT TO PICK UP THE UPPER LOW NEAR SOUTHERN CALIFORNIA. BY 00Z TUE...THE UPPER TROUGH IS EXPECTED TO BE OVER UTAH AND CO WHILE THE UPPER LOW HEADS EAST INTO WEST TEXAS. DOWNSLOPE MID LEVEL FLOW AND DPVA AHEAD OF THE TROUGH AND LOW WILL RESULT IN THE FORMATION OF A LOW PRESSURE SYSTEM IN THE OKLAHOMA PANHANDLE...A FEATURE TO WATCH IN THE LONG TERM PORTION OF THE FORECAST. FOR THE SHORT TERM...THE DIGGING UPPER TROUGH ALLOWS THE MID LEVEL FLOW OVER THE WESTERN GREAT LAKES TO TURN MORE ZONAL. HOWEVER...THE FLOW CHANGE WILL HOLD OFF UNTIL THE SHRTWVS IN ND/MN MOVE TO THE ESE INTO THE TROUGH OVER NEW ENGLAND. TONIGHT...SOME -SN IS POSSIBLE WITH THE WARM ADVECTION AND DPVA FORCING FROM THE SHRTWVS...MOSTLY BEFORE 06Z SINCE THAT IS WHEN THE STRONGEST 700-300MB Q-VECTOR CONVERGENCE IS PRESENT. A FEW TENTHS OF ACCUMULATION AT BEST IS EXPECTED...THANKS TO THE PRESENCE OF THE LOW LEVEL DRY AIR AND LACK OF SIGNIFICANT VERTICAL MOTION. AFTER 06Z...DNVA IS INDICATED TO CROSS UPPER MI IN THE WAKE OF THE SHRTWVS. SOME MORE WARM ADVECTION SNOW MAY BEGIN TO FORM AFTER 06Z AS WELL...STRETCHING FROM ND...ACROSS CENTRAL MN AND INTO CENTRAL WI. THIS SNOW IS ALSO EXPECTED TO BE AIDED BY UPPER LEVEL DIVERGENCE IN THE RIGHT ENTRANCE REGION OF A 130 KT JET AT 250MB PROGGED OVER UPPER MI AT 12Z MON. AS THE FLOW TURNS ZONAL ON MONDAY...THE UPPER JET WILL LIFT NORTHWARD...PLACING UPPER MI IN THE RIGHT ENTRANCE REGION AND INTO THE WARM ADVECTION. IN FACT...850MB TEMPS ARE SHOWN TO WARM FROM -14 TO -16C AT 06Z MON TO -8 TO -10C AT 00Z TUE. THEREFORE...THE -SN THAT DEVELOPS JUST TO OUR SOUTH LATER TONIGHT WILL MOVE NORTH INTO THE CWA DURING THE DAY. PCPN AMOUNTS AGAIN DO NOT LOOK THAT IMPRESSIVE AS THE VERTICAL MOTION IS NOT THAT STRONG...BUT SOME AREAS IN THE FAR SOUTH CENTRAL COULD PICK UP AN INCH. HAVE RAISED POPS ON MONDAY...ESPECIALLY IN THE SOUTH CENTRAL. THE OTHER ISSUE TO DEAL WITH IN THE SHORT TERM FORECAST IS THE EXPECTED LAKE MICHIGAN BAND. THE CURRENT SFC RIDGE THAT IS OVER THE CWA WILL BE SHIFTING EAST DURING THE PERIOD...RESULTING IN SOUTHERLY FLOW. SINCE 850MB TEMPS REMAIN COLD TONIGHT AND LAND BREEZES WILL DEVELOP OFF LOWER MI THAT CONVERGE ON THE SOUTHERLY FLOW...A SINGLE BAND OFF LAKE MICHIGAN IS LIKELY. TRENDS FROM 06Z RUNS AND NOW INTO THE 12Z RUNS FROM THE NAM...GFS...LOCAL WRF-ARW AND RUC 13 SUGGEST THE BAND MOSTLY IMPACTS MACKINAC COUNTY TONIGHT...SINCE THE LOW LEVEL FLOW IS MAINLY SW. WINDS BACK SOUTH ON MONDAY...WHICH MEANS THE LAKE EFFECT BAND WILL BE PUSHING WESTWARD WITH TIME...BUT LIKELY NOT MAKING IT FARTHER WEST THAN FAR EASTERN DELTA AND NW SCHOOLCRAFT COUNTIES. HOWEVER...THERE IS SOME SUGGESTION BY THE NAM AND REGIONAL CANADIAN THAT THE BAND COULD FALL APART. NOT READY TO JUMP ON THIS IDEA YET...AND STAY WITH THE GFS/LOCAL WRF-ARW RUN/RUC 13 THAT KEEP IT TOGETHER. NONETHELESS...SINCE MORE OF THE BAND IS EXPECTED TO STAY OVER MACKINAC COUNTY TONIGHT...THIS LOWERS THE AMOUNT OF SNOW THAT COULD HAVE FELL IN OUR CWA. IN FACT...PROGGED QPF AMOUNTS OUT OF THE BAND DURING THE DAY MONDAY ARE ONLY UP TO 0.20 OF AN INCH...WHICH WITH SOUNDINGS THAT SUGGEST SNOW TO WATER RATIOS ON AVERAGE AROUND 15 TO 1 MEANS THAT SNOWFALL AMOUNTS WILL REACH MAYBE 4 INCHES. AGAIN..THIS ASSUMES THE BAND CAN STAY IN ONE SPOT. HAVE DECIDED TO DROP THE WATCH AND NOT PUT UP ANY ADVISORY...GIVEN THE UNCERTAINTY PRESENT OF THE BAND HOLDING TOGETHER OR STAYING IN ONE SPOT. TEMPERATURES SHOULD NOT FALL TOO MUCH TONIGHT...WITH FIRST MID/HIGH CLOUDS OVERHEAD THIS EVENING WITH -SN TRANSITIONING TO A LOWER STRATUS DECK. RAISED LOWS UP CLOSER TO THE WARMER MAV GUIDANCE. ON MONDAY...PLENTY OF CLOUD COVER WILL CONTINUE TO EXIST DUE TO THE WARM ADVECTION/UPPER DIVERGENCE FORCING. HOWEVER...THE SOUTHERLY FLOW BRINGING WARMER AIR INTO THE CWA SHOULD ALLOW HIGHS TO CLIMB INTO THE 20S. WARMEST READINGS EXPECTED IN THE EASTERN CWA WITH HEAT FLUX OFF LAKE MICHIGAN. LONGER TERM 00Z TUE ONWARD... NAM SHOWS A 500 MB RIDGING OFF THE WEST COAST AND ALSO ACROSS THE SE WITH TROUGHING ACROSS THE ROCKIES AND CENTRAL U.S. 00Z TUE. THERE IS A SHORTWAVE OVER THE NORTHERN PLAINS WILL HEAD EAST AND AFFECT THE UPPER GREAT LAKES MON NIGHT AND TUE WITH A 500 MB TROUGH REMAINING OVER THE FORECAST AREA THROUGH WED. NAM SHOWING 850-500 MB Q-VECTOR CONVERGENCE AND MOISTURE MON NIGHT WITH THE CONVERGENCE MOVING OUT BY 12Z TUE WITH DEEP MOISTURE MOVING OUT ON TUE. SOUTHERN CWA IS ON NORTHERN SIDE OF THIS NEXT SYSTEM WITH THE MAJORITY OF THE SYSTEM PASSING BY TO THE SOUTH OF CWA. NAM THEN SHOWS SOME 850-500 MB Q-VECTOR CONVERGENCE RETURNING ON WED WITH SOME DEEPER MOISTURE AGAIN. NAM SHOWING ISENTROPIC LIFT AND MOISTURE ON I280K-I295K SURFACES 00Z TUE WITH THE LIFT MOVING OUT BY 06Z TUE. SOUTHERN CWA STILL LOOKS LIKE IT MIGHT NEED AN ADVISORY OR SOMETHING OUT FOR MON NIGHT AND TUE WITH MENOMINEE SEEING ABOUT 6.5 INCHES OF SYSTEM SNOW AT THAT TIME. FURTHER NORTH...AIR IS COLD ENOUGH AT 850 MB FOR LAKE EFFECT AND WILL HAVE TWO DIFFERENT MECHANISMS BRINGING SNOW TO THE AREA...LAKE EFFECT ACROSS THE NORTH AND SYSTEM SNOW TO THE SOUTH. EVEN DELTA AND SOUTHERN SCHOOLCRAFT MIGHT NEED ADVISORIES FOR COMBO OF LAKE EFFECT AND SYSTEM SNOW. DO NOT THINK LAKE EFFECT WILL GET OUT OF HAND EVEN WITH THE NORTH WIND FLOW THAT DEVELOPS EVEN THOUGH IT IS COLD ENOUGH. MAIN FACTOR IS DRY AIR TO THE NORTH FROM A COLD HIGH PRESSURE SYSTEM AND THIS DRY AIR WOULD CUT DOWN ACCUMULATIONS AND COVERAGE. LIFT AND MOISTURE THEN RETURNS ON WED AGAIN ON THE I280K-I295K SURFACES ACCORDING TO THE NAM. NAM IS THE ONLY MODEL BRINGING IN THIS CLIPPER SYSTEM AS FAST AS IT DOES ON WED...AND WILL NOT USE THIS MODEL AFTER WED. WILL USE THE 00Z ECMWF FOR THIS FORECAST. BOTH GFS AND ECMWF ARE SLOWER WITH THIS CLIPPER BRINGING IT INTO THE AREA WED NIGHT AND THU INSTEAD AND THEY ARE SIMILAR IN THIS REGARD AND WILL USE THE ECMWF AND BRING THE SYSTEM IN WED NIGHT AND THU INSTEAD. IN THE EXTENDED...GFS...ECMWF AND CANADIAN SHOW A 500 MB TROUGH OVER THE UPPER GREAT LAKES 00Z THU WHICH LINGERS THROUGH SUN. THINGS WILL NOT CHANGE MUCH AS AN ALBERTA CLIPPER MOVES THROUGH AND PUSHES A COLD FRONT THROUGH WHICH GETS HUNG UP IN LOWER MICHIGAN WITH MORE WAVES MOVING ALONG THE FRONT. DID NOT MAKE MANY CHANGES TO THE GOING FORECAST EXCEPT TO KEEP CHANCE POPS IN FOR EVERYWHERE WITH EITHER CLIPPER TYPE SYSTEMS...LAKE EFFECT...OR COMBO OF THEM BOTH BRINGING MOISTURE THROUGH THE AREA. DID NOT SEE ANY REAL SHOT AT A DRY PERIOD IN THE EXTENDED FOR NOW. ALSO KEPT TEMPERATURES THE SAME WHICH WERE NEAR ENSEMBLE FORECASTS. TEMPERATURES LOOKED TO STAY AT OR BELOW NORMAL FOR THE EXTENDED PERIOD. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... LAKE EFFECT MVFR CLOUDS ARE CLOSE TO EXITING BOTH TAF SITES...AND SHOULD DO SO IN THE NEXT 1 TO 3 HRS AS FLOW CONTINUES BACKING TO THE SW. TO THE WEST...HIGH AND MID CLOUDS ARE APPROACHING FROM MN AND WI. FURTHER INTO MN IS SOME -SN ALONG WITH MVFR STRATUS. BOTH THE MVFR CLOUDS AND -SN WILL MOVE INTO BOTH TAF SITES THIS EVENING... BUT LACK OF SIGNIFICANT FORCING AND INITIAL DRY AIR SHOULD KEEP VSBYS VFR. MVFR STRATUS DECK LOOKS TO HANG AROUND INTO MONDAY. IN FACT...IT SHOULD BE ENFORCED LATER MONDAY MORNING AS WARM AIR MOVING IN PRODUCES SOME -SN...ADDING EXTRA MOISTURE. -SN EXPECTED TO MOSTLY IMPACT SAW...THOUGH. HAVE LEFT VSBYS AT VFR FOR NOW...BUT COULD SEE SOME MVFR VSBYS HAPPENING. UNCERTAINTY AND THE LATE TIME THAT THE SNOW OCCURS IN THE FORECAST PRECLUDES ANY MVFR MENTION TO THE VSBYS AT THIS TIME. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... A RIDGE OF HIGH PRESSURE OVER LAKE SUPERIOR WILL HEAD EAST TONIGHT...ALLOWING FOR SOUTHERLY WINDS OF 15 TO 25 KNOTS TO DEVELOP. THESE WINDS WILL DIMINISH ON MONDAY AS A TROUGH OF LOW PRESSURE MOVES ACROSS. FROM MONDAY NIGHT INTO WEDNESDAY...A LOW PRESSURE SYSTEM OVER THE CENTRAL PLAINS IS EXPECTED TO LIFT NORTHEAST ACROSS THE EASTERN GREAT LAKES. WINDS WILL SHIFT TO THE NORTH AND INCREASE TO 30 KT MON NIGHT INTO TUE...THEN DIMINISH TUE NIGHT AND WED AS THE SYSTEM MOVES AWAY. ANOTHER HIGH PRESSURE RIDGE WILL MOVE ACROSS LAKE SUPERIOR ON WED. LOOK FOR SOUTHERLY WINDS TO INCREASE UP TO 30 KT ON WED NIGHT INTO THU AS A LOW PRESSURE AREA MOVES OUT OF CANADA INTO WESTERN LAKE SUPERIOR. WINDS WILL SHIFT TO THE NW AND DIMINISH BELOW 25 KT THU NIGHT INTO FRI AS THE LOW HEADS EAST INTO EASTERN ONTARIO. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GM AVIATION...AJ MARINE...AJ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1236 PM EST SUN DEC 7 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE .UPDATE... (ISSUED AT 952 AM) LAKE EFFECT SNOW SHOWERS OVER EASTERN LAKE SUPERIOR HAVE BROKEN UP QUITE A BIT OVER THE PAST TWO HOURS...DUE TO A COMBINATION OF WIND SHEAR IN THE MIXED LAYER SEEN ON THE KMQT VAD WIND PROFILE AND DRY AIR FLOWING ACROSS. THEREFORE...WENT AHEAD AND CANCELLED THE WARNING FOR ALGER AND NORTHERN SCHOOLCRAFT COUNTIES EARLY. REST OF THE FORECAST FOR TODAY IS IN GOOD SHAPE. MAIN CONCERN THIS AFTERNOON WILL BE TO WATCH THE POSITION OF THE FORECAST LAKE EFFECT BAND OFF LAKE MICHIGAN. 06Z RUNS SUGGESTED THAT THE BAND MAY IMPACT MOSTLY MACKINAC COUNTY TONIGHT...THEN SHIFT WESTWARD ON MONDAY AS THE FLOW BACKS MORE SOUTHERLY. IF THIS OCCURS...THEN THE WATCH MAY OR MAY NOT PAN OUT...ESPECIALLY IF THE BAND KEEPS MOVING AS SUGGESTED BY THE 06Z NAM. && .SYNOPSIS... COLD UPPER TROUGH WITH H85 TEMPS -15C TO -20C REMAINS IN PLACE FM HUDSON BAY INTO THE UPR GREAT LAKES. PRIMARY COLD FRONT IS MOVING INTO THE LWR GREAT LAKES AND DIVING INTO THE SOUTHERN PLAINS. NW FLOW AND THE COLD TEMPS BEHIND THE FRONT IS PRODUCING MOSTLY MULTIPLE LK EFFECT SNOW BANDS. IR SATELLITE AND RADAR INDICATES HEAVIEST SNOW SHOWERS INTO ALGER COUNTY AND NRN DELTA COUNTY. THIS BAND IS STRONGEST DUE TO PRECONDITIONED FLOW OFF LK NIPIGON AND ALSO SINCE THE TRAJECTORIES ARE CROSSING THE LONGEST AVAILABLE FETCH ACROSS LK SUPERIOR. MEANWHILE...DRY AIR AND INVERSION BLO H9 ASSOCIATED WITH INCOMING SFC RIDGE AND AS SEEN ON 00Z INL/WPL SOUNDINGS...IS LIMITING EXTENT OF LK EFFECT OVR WRN CWA. && .DISCUSSION... ALTHOUGH WINDS HAVE DIMINISHED...LK EFFECT STILL AN ISSUE TODAY AS SFC-925MB WINDS STAY NW. EFFECTS OF THE DRY AIR/SUBSIDENCE SEEN UPSTREAM WILL BE OFFSET FOR SNOW SHOWERS EAST OF MARQUETTE AS LOW-LEVEL TRAJECTORIES CROSS LK SUPERIOR THE LONGEST. INVERSION HEIGHT BTWN 5-7KFT AND IDEAL TEMPS WITHIN CLOUD LAYER FOR DENDRITIC SNOW GROWTH ENSURES THAT LK EFFECT WILL BE SUFFICIENT AT PRODUCING ACCUMS DESPITE NEGATIVE LARGE SCALE FACTORS. BY FAR BEST SNOW WILL BE IN SNOWBAND PRECONDITIONED BY LK NIPIGON. MAJORITY OF HIGH RES GUIDANCE...NAM/REG CANADIAN/RUC13/LOCAL WRF POINT TO HEAVIEST SNOW TO REMAIN IN ALGER/NRN SCHOOLCRAFT AREAS. KEPT WINTER STORM WARNING FOR THESE TWO ZONES GIVEN THAT STRONG BAND IS STILL OUT THERE AND SNOWFALL RATES UP TO 1"/HR ARE STILL POSSIBLE. OTHERWISE...CANX REST OF THE GOING HEADLINES. 925MB WIND FIELD BECOMES DISORGANIZED AFT 21Z TODAY...AND BY THAT TIME SNOW SHOWERS SHOULD DIMINISH/LIFT OFFSHORE. ELSEWHERE...AS WINDS BACK WITH RIDGE THROUGH HERE...THERE COULD BE SOME SUNSHINE. TEMPS WILL REMAIN CHILLY THOUGH WITH MAINLY TEENS EXPECTED. SHEARED OUT UPPER WAVE WITH SWATH OF DEEP MOISTURE SWINGS ACROSS UPR LAKES. GFS/NAM/LOCAL WRF SIMILAR IN HANDLING THE SYSTEM. ISENTROPIC LIFT ON 280K SFC...ROUGHLY 800-700MB...SHOWS STRONGEST LIFT OCCURRING ALONG SW BORDER INTO LK MICHIGAN. KEPT HIGHEST POPS CLOSER TO WI BORDER...WITH JUST CHANCE POPS CLOSER TO LK SUPERIOR AS SW LOW-LEVEL FLOW MAINLY DOWNSLOPES. UP TO AN INCH OF SNOW NEAR THE WI BORDER. MAIN ISSUE WILL BE IN SE CWA NEAR LK MICHIGAN. 925MB WINDS BECOME VERY FAVORABLE FOR LK EFFECT OFF LK MICHIGAN INTO SRN SCHOOLCRAFT INTO SRN PORTION OF LUCE COUNTY AFT MIDNIGHT AND INTO MONDAY. H85 TEMPS -13C WITH DEEP MOISTURE ADDED FM THE SYSTEM MOVING IN FM THE WEST YIELD MORE THAN SUFFICIENT OVER WATER INSTABILITY ALTHOUGH EXACT AREA OF HEAVIEST SNOW IS UNCERTAIN. SINCE THE HIGH PRESSURE RIDGE LINGERS OVR LWR MICHIGAN AND ONTARIO...INTERACTING LAND BREEZES ENHANCE LOW-LEVEL CONVERGENCE. HIGH RESOLUTION MODELS FCST A DOMINANT BAND OVR FAR SE CWA...BUT VARY ON EXACT PLACEMENT. WILL SAY THAT THE RUC13 SHOWING A STRONG LAND BREEZE EMERGING FM LWR MI...AND SETTING UP THE BAND AS FAR WEST AS DELTA COUNTY WAS NOT PREFERRED AS SWRLY 925MB WINDS SHOULD PIN THE LAND BREEZE CLOSER TO THE LWR MI SHORE. IN ANY EVENT...COULD SEE WARNING CRITERIA SNOWFALL OVR FAR SE CWA FM THIS BAND OF LK EFFECT SO ISSUED A LAKE EFFECT SNOW WATCH FOR LATE TONIGHT THROUGH MOST OF MONDAY FOR SOUTHERN SCHOOLCRAFT INTO LUCE. OUTSIDE OF LK EFFECT OFF LK MICHIGAN...MONDAY FEATURES LGT SNOW MAINLY AFFECTING THE WI BORDER AREAS DUE TO UPPER LEVEL JET FORCING AND PERSISTENT ISENTROPIC ASCENT ON 280K SFC. NW LOW-LEVEL WINDS AND H85 TEMPS BLO -10C COULD ALSO PRODUCE LGT LK EFFECT OVR NW UPR MI. NEXT ISSUE IS LOW PRESSURE EMERGING FM THE PLAINS LATER TUE. ECMWF WAS MOST EMPHATIC WITH THIS SYSTEM LAST COUPLE DAYS...AND OTHER GUIDANCE NOW LOOKS LIKE IT IS TRENDING THIS WAY. ECMWF IDEA WOULD BRUSH FAR SOUTH CENTRAL...BASICALLY SRN MNM COUNTY...WITH WIDESPREAD SNOW LATE MON NIGHT THROUGH TUE NIGHT. PRIMARY SYSTEM SNOW SHOULD STAY SOUTH OF CWA...BUT ADVY MAY BE NEEDED IN THE SCNTRL. NRLY FLOW OVR LK SUPERIOR WITH COOLING WILL LEAD TO LK EFFECT SNOW SHOWERS INCREASING IN THE TUE/WED PERIOD. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... LAKE EFFECT MVFR CLOUDS ARE CLOSE TO EXITING BOTH TAF SITES...AND SHOULD DO SO IN THE NEXT 1 TO 3 HRS AS FLOW CONTINUES BACKING TO THE SW. TO THE WEST...HIGH AND MID CLOUDS ARE APPROACHING FROM MN AND WI. FURTHER INTO MN IS SOME -SN ALONG WITH MVFR STRATUS. BOTH THE MVFR CLOUDS AND -SN WILL MOVE INTO BOTH TAF SITES THIS EVENING... BUT LACK OF SIGNIFICANT FORCING AND INITIAL DRY AIR SHOULD KEEP VSBYS VFR. MVFR STRATUS DECK LOOKS TO HANG AROUND INTO MONDAY. IN FACT...IT SHOULD BE ENFORCED LATER MONDAY MORNING AS WARM AIR MOVING IN PRODUCES SOME -SN...ADDING EXTRA MOISTURE. -SN EXPECTED TO MOSTLY IMPACT SAW...THOUGH. HAVE LEFT VSBYS AT VFR FOR NOW...BUT COULD SEE SOME MVFR VSBYS HAPPENING. UNCERTAINTY AND THE LATE TIME THAT THE SNOW OCCURS IN THE FORECAST PRECLUDES ANY MVFR MENTION TO THE VSBYS AT THIS TIME. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... AS A LOW PRESSURE CENTER OVER SOUTHEAST CANADA CONTINUES TO THE EAST TODAY...A HIGH PRESSURE RIDGE WILL MIGRATE ACROSS THE UPPER GREAT LAKES BY THIS EVENING AND INTO NEW ENGLAND BY LATE MONDAY. STRONG N WINDS EARLY TODAY WILL DIMINISH QUICKLY AS THIS RIDGE APPROACHES. IN THE WAKE OF THE RIDGE...EXPECT A LOW PRESSURE TROUGH TO DRIFT OVER LAKE SUPERIOR ON MONDAY NIGHT. ONCE THIS TROUGH PUSHES TO THE EAST ON TUESDAY...A LOW PRESSURE SYSTEM OVER MISSOURI WILL MOVE NORTHEAST ACROSS THE LOWER GREAT LAKES AND TO THE ST LAWRENCE RIVER VALLEY BY EARLY WEDNESDAY. NORTH WINDS ON THE NORTHERN FLANK OF THIS LOW TRACK MAY REACH 30 KNOTS OVER CENTRAL AND EASTERN LAKE SUPERIOR ON TUESDAY AND TUESDAY NIGHT. A HIGH PRESSURE RIDGE WILL FOLLOW ACROSS THE UPPER GREAT LAKES ON WEDNESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM MOVES EAST FROM THE PLAINS TO NEAR UPPER MICHIGAN ON THURSDAY. RELATIVELY LIGHT WINDS WILL PREVAIL ON THESE TWO DAYS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN... LAKE EFFECT SNOW WATCH FROM LATE TONIGHT THROUGH MONDAY AFTERNOON FOR MIZ007-014. LAKE SUPERIOR...NONE. LAKE MICHIGAN...NONE. && $$ UPDATE...AJ SYNOPSIS/DISCUSSION...JLA AVIATION...AJ MARINE...KC mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 102 PM CST SUN DEC 7 2008 .DISCUSSION... RH VALUES CONTINUE TO FALL WITH READINGS NEAR OR BELOW 20 PERCENT IN PORTIONS OF SOUTH CENTRAL AND CENTRAL OKLAHOMA EARLY THIS AFTERNOON. RUC CONTINUES TO KEEP AN AXIS OF HIGHER DEWPOINTS ACROSS SOUTHWEST TO NORTH CENTRAL SECTIONS... AND WHILE DEWPOINTS ARE A FEW DEGREES HIGHER IN THIS AREA PER MESONET AND ASOSES... THE 00HR ANALYSIS SHOWING 18Z DEWPOINTS IN THE LOWER 30S IN NORTH CENTRAL OKLAHOMA SUGGEST THAT SOME OF THE HIGH AWOS DEWPOINTS ARE GETTING INTO THE ANALYSIS AND FORECAST. BUT THESE FEW DEGREES IN QUESTION ARE ENOUGH TO WARRANT PUTTING THE ENTIRE AREA UNDER THE RED FLAG WARNING. WIND CRITERIA MAY BE MARGINAL IN THE SOUTHEAST... BUT WILL NOT TRY TO BE TOO CUTE AND THE RED FLAG WARNING IS BEING EXPANDED TO THE ENTIRE AREA. RFW IS ALREADY OUT... AND WILL BE UPDATING GRIDS TO GET THE REMAINDER OF THE PACKAGE UPDATED SOON. THIS UPDATE WILL INCLUDE RAISING MAX TEMPERATURES FURTHER AS SOME LOCATIONS ARE ALREADY APPROACHING THE MAXES FROM THIS MORNINGS UPDATE. && .PREV DISCUSSION... /ISSUED 1040 AM CST SUN DEC 7 2008/ DISCUSSION... HAVE UPGRADED FIRE WEATHER WATCH TO RED FLAG WARNING FOR MOST OF THE WATCH AREA... AND ADDED HARPER COUNTY AS WELL. RUC SEEMS TO BE DOING THE BEST WITH CURRENT DEWPOINT TRENDS AND IT BRINGS AFTERNOON RH READINGS DOWN TO SUB-20 PERCENT IN THE WESTERN PORTION OF THE AREA... DESPITE CURRENTLY BEING ABOUT 5 DEGREES COOL ON SURFACE TEMPERATURES AT 16Z AND AFTERNOON TEMPERATURES BELOW OUR FORECAST. WOODWARD MESONET IS ALREADY DOWN TO 22 PERCENT RELATIVE HUMIDITY AT 16Z WITH A FEW OTHER SITES IN NORTHWEST OKLAHOMA BELOW 30 PERCENT ALREADY. DID NOT INCLUDE DEWEY/CUSTER/WASHITA COUNTIES IN THE UPGRADE AS RH VALUES ARE EXPECTED TO BE SOMEWHAT HIGHER... BUT IT MAY BE CLOSE TO RED FLAG CRITERIA BRIEFLY IN PORTIONS OF THESE COUNTIES AND THE FIRE WEATHER CONCERNS ARE STILL QUITE ELEVATED HERE. AS FAR AS THE GRIDS GO... HAVE REPOPULATED THE DEWPOINTS WITH THE RUC GIVEN ITS BETTER CURRENT TRENDS IN THIS FIELD. HAVE RAISED MAX TEMPERATURES JUST A TOUCH AS WELL AREAWIDE. PREV DISCUSSION... /ISSUED 443 AM CST SUN DEC 7 2008/ DISCUSSION...SOUTHERLY WINDS WILL INCREASE TODAY..ESP IN WESTERN OK. THIS COMBINED WITH WARM TEMPS AND LOW RH WILL INCREASE FIRE WX CONCERNS. CONDITIONS LOOK MARGINAL FOR RE FLAG THIS AFTERNOON SO WILL LEAVE FIRE WX WATCH IN PLACE. ACTIVE WEATHER EXPECTED ACROSS THE FORECAST AREA MONDAY THROUGH TUESDAY. LEAD WAVE EXPECTED TO EJECT INTO THE SOUTHERN PLAINS ON MONDAY/MONDAY NIGHT. STRONG SOUTHERLY LOW LEVEL FLOW WILL CONTINUE WITH INCREASED MOISTURE WORKING NORTHWARD INTO THE FA AHEAD OF THE APCHG S/W TROUGH. SUFFICIENT ELEVATED INSTABILITY WILL BE IN PLACE FOR SOME THUNDERSTORMS MAINLY OVER CENTRAL AND EASTERN SECTIONS. MAIN SYSTEM DROPS FROM CENTRAL ROCKIES INTO NM THEN EASTWARD ACROSS SOUTHERN PLAINS. COLD FRONT EXPECTED TO PUSH INTO NWRN OK LATE MONDAY THEN PUSH SEWD ACROSS MUCH OF THE FA BY TUESDAY MORNING. STEADY OR FALLING TEMPS EXPECTED ON TUESDAY AS COLDER AIR SURGES ON BRISK NORTH WINDS. EXPECT PRECIP TO CHANGEOVER TO SNOW IN THE NW LATE MONDAY NIGHT WITH RAIN BECOMING MIXED WITH OR CHANGING TO SNOW ACROSS MUCH OF THE AREA ON TUESDAY. ATTM IT LOOKS LIKE THE HEAVIEST WINTRY PRECIPITATION MAY FALL NORTH OF THE FA BUT SOME ACCUMULATING SNOWS ARE POSSIBLE...MAINLY OVER NORTHERN OK. SOME LIGHT PRECIP MAY LINGER INTO TUESDAY EVENING IN ERN SECS. DRY WEATHER EXPECTED THE REMAINDER OF THE FORECAST PD. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 64 44 63 40 / 0 0 30 60 HOBART OK 66 45 64 38 / 0 0 10 40 WICHITA FALLS TX 69 47 69 46 / 0 0 10 40 GAGE OK 67 37 60 31 / 0 0 30 40 PONCA CITY OK 62 45 59 37 / 0 0 30 70 DURANT OK 64 47 62 57 / 0 0 30 70 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...RED FLAG WARNING UNTIL 6 PM CST THIS AFTERNOON FOR OKZ004>048- 050>052. TX...RED FLAG WARNING UNTIL 6 PM CST THIS AFTERNOON FOR TXZ083>090. && $$ 01/01 ok AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 1040 AM CST SUN DEC 7 2008 .DISCUSSION... HAVE UPGRADED FIRE WEATHER WATCH TO RED FLAG WARNING FOR MOST OF THE WATCH AREA... AND ADDED HARPER COUNTY AS WELL. RUC SEEMS TO BE DOING THE BEST WITH CURRENT DEWPOINT TRENDS AND IT BRINGS AFTERNOON RH READINGS DOWN TO SUB-20 PERCENT IN THE WESTERN PORTION OF THE AREA... DESPITE CURRENTLY BEING ABOUT 5 DEGREES COOL ON SURFACE TEMPERATURES AT 16Z AND AFTERNOON TEMPERATURES BELOW OUR FORECAST. WOODWARD MESONET IS ALREADY DOWN TO 22 PERCENT RELATIVE HUMIDITY AT 16Z WITH A FEW OTHER SITES IN NORTHWEST OKLAHOMA BELOW 30 PERCENT ALREADY. DID NOT INCLUDE DEWEY/CUSTER/WASHITA COUNTIES IN THE UPGRADE AS RH VALUES ARE EXPECTED TO BE SOMEWHAT HIGHER... BUT IT MAY BE CLOSE TO RED FLAG CRITERIA BRIEFLY IN PORTIONS OF THESE COUNTIES AND THE FIRE WEATHER CONCERNS ARE STILL QUITE ELEVATED HERE. AS FAR AS THE GRIDS GO... HAVE REPOPULATED THE DEWPOINTS WITH THE RUC GIVEN ITS BETTER CURRENT TRENDS IN THIS FIELD. HAVE RAISED MAX TEMPERATURES JUST A TOUCH AS WELL AREAWIDE. && .PREV DISCUSSION... /ISSUED 443 AM CST SUN DEC 7 2008/ DISCUSSION...SOUTHERLY WINDS WILL INCREASE TODAY..ESP IN WESTERN OK. THIS COMBINED WITH WARM TEMPS AND LOW RH WILL INCREASE FIRE WX CONCERNS. CONDITIONS LOOK MARGINAL FOR RE FLAG THIS AFTERNOON SO WILL LEAVE FIRE WX WATCH IN PLACE. ACTIVE WEATHER EXPECTED ACROSS THE FORECAST AREA MONDAY THROUGH TUESDAY. LEAD WAVE EXPECTED TO EJECT INTO THE SOUTHERN PLAINS ON MONDAY/MONDAY NIGHT. STRONG SOUTHERLY LOW LEVEL FLOW WILL CONTINUE WITH INCREASED MOISTURE WORKING NORTHWARD INTO THE FA AHEAD OF THE APCHG S/W TROUGH. SUFFICIENT ELEVATED INSTABILITY WILL BE IN PLACE FOR SOME THUNDERSTORMS MAINLY OVER CENTRAL AND EASTERN SECTIONS. MAIN SYSTEM DROPS FROM CENTRAL ROCKIES INTO NM THEN EASTWARD ACROSS SOUTHERN PLAINS. COLD FRONT EXPECTED TO PUSH INTO NWRN OK LATE MONDAY THEN PUSH SEWD ACROSS MUCH OF THE FA BY TUESDAY MORNING. STEADY OR FALLING TEMPS EXPECTED ON TUESDAY AS COLDER AIR SURGES ON BRISK NORTH WINDS. EXPECT PRECIP TO CHANGEOVER TO SNOW IN THE NW LATE MONDAY NIGHT WITH RAIN BECOMING MIXED WITH OR CHANGING TO SNOW ACROSS MUCH OF THE AREA ON TUESDAY. ATTM IT LOOKS LIKE THE HEAVIEST WINTRY PRECIPITATION MAY FALL NORTH OF THE FA BUT SOME ACCUMULATING SNOWS ARE POSSIBLE...MAINLY OVER NORTHERN OK. SOME LIGHT PRECIP MAY LINGER INTO TUESDAY EVENING IN ERN SECS. DRY WEATHER EXPECTED THE REMAINDER OF THE FORECAST PD. && .PRELIMINARY POINT TEMPS/POPS... OKLAHOMA CITY OK 64 44 63 40 / 0 0 30 60 HOBART OK 66 45 64 38 / 0 0 10 40 WICHITA FALLS TX 69 47 69 46 / 0 0 10 40 GAGE OK 67 37 60 31 / 0 0 30 40 PONCA CITY OK 62 45 59 37 / 0 0 30 70 DURANT OK 64 47 62 57 / 0 0 30 70 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...RED FLAG WARNING UNTIL 6 PM CST THIS AFTERNOON FOR OKZ004-009- 010-014-021-033>037. TX...RED FLAG WARNING UNTIL 6 PM CST THIS AFTERNOON FOR TXZ083>089. && $$ ok AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHEYENNE WY 932 AM MST SUN DEC 7 2008 .UPDATE...SMALL BAND OF VERY LIGHT SHOWERS/SPRINKLES PERSISTS THIS MORNING FROM N OF KLAR TO S OF KBFF TO W OF KSNY. SO...HAVE EXTENDED THESE THROUGH 18Z ALTHOUGH THEY SHOULD BE GONE AFTER THAT. ALSO...UPDATED TEMP GRIDS FOR WARMER CURRENT NUMBERS. JLH && .PREV DISCUSSION... /ISSUED 316 AM MST SUN DEC 7 2008/ SHORT TERM...TODAY THROUGH MONDAY NIGHT... WEAK RETURNS ON THE KCYS 88D CONTINUE EARLY THIS MORNING OVER THE WEST PART OF THE CWA. MOST OF THE MOISTURE REMAINS ABOVE 700 MB AND WITH CURRENT FAIRLY LARGE SURFACE TEMPERATURE AND DEW POINT SPREADS VERY LITTLE PRECIPITATION SHOULD REACH THE GROUND. THE RUC DEPICTS SOME LIGHT QPF OVER THE WEST PART OF THE CWA THROUGH 15Z. WILL PLACE LOW POPS OVER THAT AREA FIRST THING THIS MORNING. OTHERWISE FOR TODAY...FAST NORTHWEST WIND FLOW ALOFT WILL PERSIST ACROSS THE REGION. THE SURFACE BOUNDARY CURRENTLY OVER THE FAR EAST PART OF WYOMING WILL BE ERODED FROM WEST TO EAST. BEHIND THE BOUNDARY ARE VERY MILD TEMPERATURES...WITH 20S CURRENTLY OVER PARTS OF THE WESTERN PANHANDLE. THE 700 MB TEMPERATURES WILL BE ABOVE ZERO TODAY AND WITH THE WEST WINDS...HIGHS SHOULD AGAIN BE ABOVE NORMAL. LOW LEVEL HEIGHT DIFFERENCES ARE NOT AS LARGE AS THE PAST FEW DAYS OVER THE REGION AND SUGGEST THAT WINDS WILL NOT BE AS AS STRONG TODAY. THE FLOW ALOFT BACKS TONIGHT AND MUCH OF MONDAY IN ADVANCE OF A SHORTWAVE TROUGH APPROACHING FROM THE PACIFIC NORTHWEST. THE CURRENT UPPER LOW JUST OFF THE CALIFORNIA COAST WILL BE CAUGHT UP IN THE FLOW ALOFT AND FILL AS IT MOVES ACROSS NEW MEXICO AND SOUTHERN COLORADO TONIGHT. THAT WILL START SURFACE CYCLOGENESIS OVER EXTREME SOUTHEAST COLORADO. A PACIFIC FRONT ASSOCIATED WITH THE PACIFIC NORTHWEST SHORTWAVE TROUGH WILL ALSO MOVE ACROSS THE CWA TONIGHT. BOUNDARY LAYER UPSLOPE WIND FLOW WILL START LATER TONIGHT AND MONDAY MORNING AND MOISTURE WILL BE INCREASING IN THE MID AND UPPER LEVELS AHEAD OF THE SHORTWAVE TROUGH. SNOW WILL DEVELOP FROM THE NORTHWEST PART OF THE CWA TO THE SOUTHEAST DURING THE DAY MONDAY. THE SREF AND GFS SPREAD THE SNOW MORE QUICKLY SOUTHEAST THAN DOES THE NAM. AT THIS TIME IT LOOKS LIKE THE MORE SIGNIFICANT SNOWFALL WILL BE MONDAY AFTERNOON AND EARLY MONDAY NIGHT. THAT IS THE TIME FRAME WHERE THE MOISTURE IS DEEPEST AND THE BEST DYNAMICS AND SURFACE FORCING WILL BE OVER THE CWA. HAVE INCREASED POPS AND SNOWFALL AMOUNTS DURING THAT TIME WITH 2 TO 4 INCHES OVER MOST OF THE LOWER ELEVATIONS BY 12Z TUESDAY AND 5 TO 9 INCHES IN THE MOUNTAINS. THOSE AMOUNTS GENERALLY FIT THE HPC GUIDANCE FOR THE CWA. AT THIS TIME...WILL HOLD OFF ON THE ISSUANCE OF ANY HIGHLIGHTS FOR THIS QUICK SNOW EVENT. THE SNOWFALL WILL TAPER OFF FROM NORTH TO SOUTH AFTER 06Z TUESDAY AS THE SHORTWAVE TROUGH MOVES EAST OF THE CWA AND THE SURFACE UPSLOPE WEAKENS. THE TEMPERATURES WILL BE MUCH COOLER MONDAY AND MONDAY NIGHT THAN THOSE OF TODAY AND TONIGHT. LONG TERM...NW FLOW WILL BE ALOFT OVER THE FORECAST AREA FROM TUES THROUGH THURSDAY AS A HIGH AMPLITUDE UPPER RIDGE REMAINS ON THE WEST COAST. VERY WINDY CONDITIONS WILL OCCUR ACROSS THE AREA ON WED AND THUR. MAINLY DRY CONDITIONS WILL OCCUR EAST OF THE LARAMIE RANGE DURING THIS TIME PERIOD...WITH A SLIGHT CHANCE OF SNOW WEST OF THE LARAMIE RANGE. WITH A BETTER CHANCE OF SNOW IN THE MOUNTAINS. A SERIES OF DISTURBANCES WILL MOVE ACROSS THE CWA FRIDAY AS CYCLONIC FLOW OCCURS ALOFT DUE TO A BROAD UPPER TROUGH OVER MUCH OF THE U.S. A COLD FRONT WILL MOVE INTO THE NORTHERN PORTION OF THE CWA IN THE MORNING AND WILL MOVE ACROSS THE FORECAST AREA BY EVENING. THIS WILL RESULT IN A SLIGHT CHANCE OF SNOW FOR MUCH OF THE AREA. A STRONGER COLD FRONT WILL MOVE SOUTH ACROSS THE CWA ON SAT AND DEEP...MOIST UPSLOPE FLOW WILL OCCUR ACROSS THE FORECAST AREA...RESULTING IN A CHANCE OF SNOW FOR THE CWA. THE ECMWF IS FARTHER WEST WITH THE UPPER TROUGH AND IS SLOWER TO BRING IT EAST...WHICH WOULD RESULT IN LATER TIMING OF THE SYSTEM. HIGH TEMPERATURES WILL BE FROM 5 TO 8 DEGREES BELOW NORMAL FOR TUES...5 TO 8 DEGREES ABOVE NORMAL FOR WED AND THU...AND AROUND NORMAL FOR FRI AND SAT. AVIATION...VFR CONDITIONS WILL BE OVER THE CWA THROUGH TONIGHT. WEST WINDS WILL GUST TO BETWEEN 25 AND 35 KNOTS ALONG AND WEST OF THE LARAMIE RANGE TODAY WITH WEAK MOUNTAIN WAVE ACTIVITY. MVFR AND IFR CONDITIONS IN SNOW AND MOUNTAIN OBSCURATION WILL SPREAD FROM NORTHWEST TO SOUTHEAST OVER THE CWA ON MONDAY AND CONTINUE FOR MOST OF MONDAY NIGHT. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...NONE. NE...NONE. && $$ SHORT TERM/AVIATION...WEILAND LONG TERM...KMD wy