AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 924 PM EST THU DEC 20 2007 .SYNOPSIS... HIGH PRESSURE OVER QUEBEC WILL BUILD SOUTH INTO NEW ENGLAND AND NEW YORK TONIGHT AND FRIDAY. SATURDAY IT WILL SLIDE OFFSHORE AND A SOUTHERLY FLOW OF MILDER AIR WILL BECOME ESTABLISHED OVER THE EASTERN SEABOARD. A STORM WILL ORGANIZE IN THE MID MISSISSIPPI VALLEY SATURDAY AFTERNOON AND INTENSIFY AS IT MOVES THROUGH THE GREAT LAKES REGION TO HUDSON`S BAY SUNDAY. AHEAD OF IT INCREASING MOISTURE WILL BRING A WINTRY MIX OF PRECIPITATION AT FIRST...BUT IT WILL WARM ENOUGH TO CHANGE THE PRECIPITATION TO RAIN...WHICH WILL BE HEAVY AT TIMES SUNDAY AFTERNOON. THE STORMS COLD FRONT WILL SWEEP TROUGH THE REGION SUNDAY NIGHT...AND IT WILL TURN MUCH COLDER. CHRISTMAS EVE AN UPPER LEVEL DISTURBANCE WILL PASS ACROSS THE REGION AND IN THE CHILLY NORTHWEST FLOW WILL TRIGGER SCATTERED SNOW SHOWERS. HIGH PRESSURE WILL BUILD INTO THE REGION FROM ONTARIO CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 AM FRIDAY/... IT SEEMS A NARROW YET PERSIST/INTERMITTENT BAND OF LIGHT SNOW CONTINUES TO IMPACT WESTERN NEW ENGLAND AND ATTEMPTING TO CROSS INTO EASTERN NEW YORK (NORTH OF THE MID HUDSON VALLEY). LATEST RUN OF THE RUC13 AND 00Z NAM/WRF INDICATE THIS IS RESPONSE TO LOW LEVEL CONVERGENCE AND DEFORMATION WHICH IS EXPECTED TO BE INTERMITTENT THROUGH TONIGHT. WILL UPDATE POPS ACCORDINGLY BUT KEEP IT IN THE SLIGHT CHANCE CATEGORY. WHERE IT HAS SNOWED...VISIBILITIES HAVE DROPPED BACK 1-3 MILES...MAINLY ACROSS THE HIGHER ELEVATIONS. THE OTHER CONCERN IS THE TEMPERATURES OVERNIGHT. WITH PERSISTENT CLOUD COVER AND LACK OF ADVECTION...WILL RAISE OVERNIGHT LOWS SEVERAL DEGREES WHICH CORRESPONDS WELL WITH THE 00Z RUN OF THE GFS LAMP. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... THE SURFACE HIGH WILL BE CENTERED TO OUR EAST AND WILL SHIFT OFF THE NEW ENGLAND COAST FRIDAY NIGHT. IT WILL KEEP US DRY WITH A DEVELOPING SOUTHEAST FLOW. LOW LEVEL CLOUDS WILL LIFT FRIDAY BUT HIGH LEVEL CLOUDS WELL IN ADVANCE OFF OF THE SYSTEM FOR THE WEEKEND WILL BE STREAMING IN...SO NOT MUCH SUN EXPECTED. TEMPERATURES WILL BE SEASONABLE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... HIGH PRESSURE SLIDES OFF THE ATLC COAST SATURDAY...AND SOUTHERNLY FLOW INCREASES THROUGH THE DAY. 500HPA RIDGE OVER THE EASTERN SEABOARD. CLOUDS WILL BE VARIABLE AS WAA PRODUCES MID AND HI CLOUDS. MEANWHILE THE LOW LEVEL SOUTHEAST FLOW WILL ALSO BRING MOISTURE INTO THE REGION AND CONSIDERABLE LOW LEVEL MOISTURE REMAINS THAT HAS LINGERED SINCE THURSDAY. SO ALOT OF CLOUDS AND BY SAT AFTN AND EVENING SPOTTY LIGHT DRIZZLE...FREEZING DRIZZLE AND FLURRIES. TEMPERATURES MAY FALL A BIT DURING THE EVENING...BUT INCREASING SOUTHERLY FLOW WILL RESULT IN STEADY OR SLOWLY RISING TEMPS OVERNIGHT. TEMPS WILL STILL BE AROUND OR BLO FREEZING IN MANY AREAS AND PTYPE LIKELY TO BE ZR...BUT AMOUNTS WILL BE LIGHT. RAPIDLY DEEPENING SURFACE LOW IN THE GREAT LAKES SUNDAY WILL PUSH A CDFNT INTO NYS SUN AFTERNOON...WHICH SWEEPS EAST ACROSS REGION BY EVENING. WITH RAPIDLY INCREASE SOUTHERNLY INFLOW AHEAD OF THE SYSTEM TEMPS WILL RISE INTO THE 40S...AND KATAFRONT TYPE DYNAMICS OF SHOWERY/SQUALLY RAINS WILL DEVELOP ALONG AND AHEAD OF CDFNT. ENSEMBLE QPF AMOUNTS FM PLUMES OF 1 TO 2 INCHES LIKELY IN 6 TO 9 HOUR PERIOD. SIGNIFICANT SNOWMELT AND RUNOFF LIKELY. SEE HYDRO SECTION FOR PARTICULARS. THE 500HPA CUTOFF...FOLLOWS ACROSS THE REGION SUNDAY NIGHT AS VERY STRONG CAA FLASH FREEZES ANY REMAINING LIQUID...AND MELTED SNOW. ALSO THE PASSAGE OF THE CUT OFF WILL BE ACCOMPANIED BY SECONDARY ARCTIC CDFNT CHRISTMAS EVE WITH SCT -SHSN IN CAA...WITH STRONG UPPER DYNAMICS...BUT NOT IDEAL SETUP FOR LAKE EFFECT IN FCA. FINALLY SURFACE HIGH AND 500HPA RIDGE BUILD ACROSS THE REGION CHRISTMAS DAY...AND SEASONABLE TEMPS AND MAINLY CLEAR SKIES THE RESULT. BEYOND THEN THE SURFACE HIGH PASSES OFFSHORE...AND THE MODELS DIVERGE ON A VARIETY OF PASSING WEATHER SYSTEMS. WITH CUT OFF LOW ORGANIZING OVER GRTLKS REGION..ONE SFC LOW PASSES WELL SOUTH OF REGION OR THROUGH REGION THURSDAY OR FRIDAY. FOR NOW WENT WITH GFS MOS GUIDANCE AND SCT -SHSN AND CHC SNOW AT END OF EFP. AFTER ALL THE 1.5 PVU ANOMALY THAT WILL ORGANIZE THIS SYSTEM IS CURRENTLY NEAR TOKYO JAPAN. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... RIDGING BUILDS...HOWEVER...LOW LEVELS ARE VERY MOIST AND HAVE LITTLE WIND FLOW (LIGHT NORTHEAST WIND). MVFR-VFR CONDITIONS WILL LOWER THIS EVENING BACK TO IFR CONDITIONS WHICH WILL PERSIST THROUGH FRIDAY MORNING. THERE COULD ALSO BE PERIOD OF LIFR AFTER 06Z WITH NOCTURNAL COOLING OF THE COLUMN AND SHRINKING DEWPOINT DEPRESSIONS. WITH TEMPERATURES BELOW FREEZING...FREEZING FOG IS CONCERN OVERNIGHT. CONDITIONS SLOWLY IMPROVE FRIDAY BUT LIKELY NOT MUCH BETTER THAN MVFR. OUTLOOK... SAT...VFR...NO SIGNIFICANT WEATHER EXPECTED. SUN...IFR MIXED PCPN...STRONG S-SE WINDS...POSSIBLE LLWS. MON...VFR...EXCEPT MVFR/IFR IN LAKE EFFECT SNOW SHOWERS DOWNWIND OF LAKE ONTARIO...WINDY WITH LLWS POTENTIAL. TUE...VFR...NO SIGNIFICANT WEATHER EXPECTED AT THIS TIME. && .HYDROLOGY... NO HYDRO PROBLEMS ARE ANTICIPATED THROUGH SATURDAY. A STRONG STORM SYSTEM WILL IMPACT THE REGION ON SUNDAY. STRONG SOUTHERLY WINDS ARE EXPECTED TO DEVELOP ACROSS THE AREA ON SUNDAY. THIS WILL BRING A WARM SURGE OVER A SNOW PACK THAT CONTAINS 1 TO 3 INCHES OF WATER EQUIVALENT FROM ALBANY SOUTH AND 2 TO 4 INCHES OF WATER EQUIVALENT OVER NORTHERN AREAS. A COLD FRONT WILL CROSS THE AREA SUNDAY EVENING. MODELS HAVE TRENDED WETTER BRINGING AROUND AN INCH OF RAIN TO ALL AREAS IN A 6 HOUR PERIOD SUNDAY AFTERNOON OR EVENING. THE UPPER MOHAWK...MOOSE...UPPER HUDSON AND VERMONT BASINS ARE EXPECTED TO SEE A 6 TO 12 HOUR WARM PERIOD LATE SUNDAY...WHICH WILL PROBABLY NOT BE ENOUGH TO RIPEN THE SNOW. NORTHERN SNOW COVER SHOULD ABSORB THE RAIN WITH MINIMAL RUNOFF BEFORE REFREEZING. HOWEVER...SOUTHERN AREAS MAY SEE 18 TO 24 HOURS OF ABOVE FREEZING TEMPERATURES. THE QUESTION IS HOW MUCH SNOW MELTS. LOCAL RIVER MODELS SHOW THAT STREAMS CAN HANDLE AS MUCH AS TWO INCHES OF COMBINED MELT AND RAIN WITH MINIMAL FLOODING. 3 INCHES OR MORE OF MELT AND RAIN WOULD CAUSE SIGNIFICANT FLOODING. THE GROUND HERE AT ALBANY IS FROZEN TO A DEPTH OF 5 INCHES. FROZEN GROUND ENHANCES THE CHANCES THAT FLOODING...AND POSSIBLY FLASH FLOODING...MAY OCCUR. RIVER ICE COVER IS NOT THICK ENOUGH TO CAUSE ICE JAM PROBLEMS. THE HIGHEST CONFIDENCE IS FOR TIDAL FLOODING LATE SUNDAY ALONG THE MID HUDSON RIVER NEAR KINGSTON AND POUGHKEEPSIE DUE TO STRONG SOUTHERLY WINDS. OTHER BASINS AT RISK FOR FLOODING INCLUDES THE SCHOHARIE...THE LOWER MOHAWK...THE ESOPUS...THE BATTEN KILL...THE HOOSIC...WAPPINGERS CREEK AND THE HOUSATONIC AND ITS TRIBUTARIES FROM FALLS VILLAGE DOWN STREAM. FREEZING TEMPERATURES ARE EXPECTED ACROSS THE ENTIRE AREA BY MONDAY MORNING WHICH WILL END THE RUNOFF. IF FLOODING WERE TO OCCUR IT WOULD MOST LIKELY BEGIN SUNDAY AFTERNOON AND LINGER INTO MONDAY. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ SYNOPSIS...SNYDER NEAR TERM...BGM SHORT TERM...IAA LONG TERM...SNYDER AVIATION...BGM HYDROLOGY...DIRIENZO WWW.WEATHER.GOV/ALBANY ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 654 AM EST THU DEC 20 2007 .SYNOPSIS... LOW PRESSURE WELL SOUTHEAST OF CAPE COD WILL MOVE EAST TODAY...AS THE UPPER LEVEL LOW ASSOCIATED WITH THE SYSTEM CONTINUES SCATTERED SNOW SHOWERS THROUGH THE AFTERNOON. HIGH PRESSURE WILL BUILD IN FROM EASTERN QUEBEC THURSDAY NIGHT INTO FRIDAY. THE HIGH WILL MOVE SOUTHWARD FRIDAY NIGHT TO NEAR THE GULF OF MAINE. A RETURN SOUTHERLY FLOW OF MILD AIR WILL OCCUR ON SATURDAY WITH TEMPERATURES ABOVE NORMAL FOR LATE DECEMBER. A COLD FRONT PROGRESSING SLOWLY EAST FROM THE MISSISSIPPI RIVER VALLEY ON SATURDAY...WILL BRING RAIN AND WINDY CONDITIONS FOR SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE LATEST RUC ANALYSIS COUPLED WITH NEIGHBORING RADARS THIS MORNING DEPICTS SECONDARY COASTAL REDEVELOPMENT OCCURRING WELL SOUTHEAST OF NANTUCKET WITH THE PRIMARY CLIPPER WEAKENING OVER CNTRL NY. A SHORT WAVE PIVOTING AROUND THE CLOSED 500 MB LOW IS MOVING ACROSS ERN NY...WHICH IS HELPING TO FOCUS SOME OF THE -SN ACTIVITY. MOST SNOWFALL REPORTS IN OUR FCST AREA WERE IN THE HALF AN INCH TO TWO INCH RANGE EARLY THIS MORNING. ADDITIONAL SNOW AMOUNTS OF A DUSTING TO AN INCH OR SO WILL BE POSSIBLE...EXCEPT A LITTLE MORE IS LIKELY OVER SRN VT. THE SHORT WAVE ENERGY ROUNDING THE BASE OF THE LONG WAVE TROUGH SHOULD ALLOW THE COASTAL WAVE TO CONTINUE TO DEEPEN AND INTENSIFY...HOWEVER...THE AMOUNT OF MOISTURE/QPF DRAWN BACK UPSTREAM INTO OUR FCST AREA WILL BE LIMITED. SOUTHEASTERN VT /WINDHAM COUNTY/ MAY RECEIVE ANOTHER 1-4" OF SNOW TODAY...AS THE 850 MB CLOSED CIRCULATION IS JUST EAST OF CAPE COD 12Z-18Z. THE 850-700 MB DEFORMATION ZONE WITH WEAK TO MODERATE MID LEVEL FRONTOGENESIS EXTENDS TO THE W/NW ENOUGH FOR PERIODS OF LIGHT TO POSSIBLY MODERATE SNOW NORTHEAST OF THE CAPITAL REGION. FOR THE REST OF THE FORECAST AREA...STEEP LOW TO MID LEVEL LAPSE RATES...LOTS OF LOW LEVEL MOISTURE...AND CYCLONIC VORTICITY ADVECTION WILL KEEP SCT SNOW SHOWERS/FLURRIES AROUND THROUGH MOST OF THE DAY. ENOUGH WARMING IN THE BOUNDARY LAYER MAY EVEN ALLOW ONLY RAIN SHOWERS OR SPRINKLES IN THE MID HUDSON VALLEY. 850 MB TEMPS OF ABOUT -6C TO -8C SHOULD ALLOW HIGHS IN THE L30S TO U30S IN THE VALLEYS...AND M20S TO L30S IN THE HILLS AND MTNS. WE LEANED CLOSE TO THE GFSMOS MAX TEMP VALUES. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... THURSDAY NIGHT...THE UPPER LEVEL LOW MIGRATES DOWNSTREAM WITH ANY LEFTOVER SNOW SHOWERS/FLURRIES ENDING AROUND MIDNIGHT. WEAK 850 MB COLD AIR ADVECTION OCCURS WITH A 1037 HPA SFC ANTICYCLONE BUILDING SOUTH/SOUTHEAST FROM ERN QUEBEC/THE GULF OF ST LAWRENCE. THIS IS NOT AN ARCTIC AIR MASS. IT WILL MORE OF THE POLAR VARIETY WITH SEASONABLY COLD AIR AT BEST. IT WILL TAKE SOME TIME TO SCOUR OUT ALL THE LOW LEVEL MOISTURE WITH THE UPPER LEVEL LOW. THE BUFKIT PROFILES FROM KALB/KGFL/KPOU FROM THE GFS/NAM-WRF SHOW A FAIR AMOUNT OF MOISTURE LINGERING BELOW 5 KFT...SO CLOUDY/MOSTLY CLOUDY CONDITIONS SHOULD DO IT HERE. FRIDAY-SATURDAY...A FAIRLY QUIET STRETCH OF WEATHER WITH HIGH PRESSURE BUILDING OVER NY AND NEW ENGLAND. WE SHOULD SEE A FEW BREAKS OF SUNSHINE BY FRIDAY AFTERNOON. 925 HPA TEMPS OVER THE CAPITAL REGION WILL BE AROUND -5C...SO SEASONABLE HIGH TEMPS IN THE 30S IN THE VALLEYS LOOK FINE. HEIGHTS WILL CONTINUE TO RISE ALOFT AS A TROUGH FORMS UPSTREAM OVER THE 4 CORNERS AND EAST OF THE ROCKY MTN REGION. THE 500 MB RIDGE AXIS BEGINS TO MOVE OVER THE NORTHEAST BY 12Z SAT. FRIDAY NIGHT IS TRICKY IN TERMS OF TEMPS. LIGHT TO CALM WINDS AND CLEARING SKIES MAY ALLOW SOME RADIATIONAL COOLING. THE NAM/GFS GUIDANCE WANTS TO INCREASE MID AND HIGH CLOUDS WITH THE H850-700 WARM AIR ADVECTION. WE WENT COLDER THAN THE MOS GUIDANCE AND LEANED TOWARD THE POSSIBILITY OF RADIATIONAL COOLING AND COLD TEMPS...ESPECIALLY NORTH OF THE CAPITAL REGION. SATURDAY SHOULD BE MAINLY DRY...BUT WITH SOME INCREASING MID AND HIGH CLOUDS. WE MAY SEE A SPRINKLE/FLURRY WEST OF THE HUDSON RIVER VALLEY LATE IN THE DAY. WE LIKED THE DRY SCENARIO DEPICTED BY THE NAM/CAN GGEM. 850 MB TEMPS RISING CLOSE TO 0C SHOULD ALLOW TEMPS TO GET ABOVE NORMAL IN THE U30S TO L40S IN THE VALLEYS. THE ETAMOS GUIDANCE LOOKED WAY TOO COLD WITH THE SFC HIGH SOUTH OF PRINCE EDWARD ISLAND SAT MORNING. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... A STRONG SOUTHERLY FLOW IS EXPECTED TO DEVELOP ACROSS FA LATE SATURDAY NIGHT AHEAD OF NEXT SHORT WAVE WHICH IS EXPECTED TO DEEPEN RAPIDLY AS IT LIFTS NORTHEAST THROUGH UPPER GREAT LAKES REGION SUNDAY AND DRAGS A COLD FRONT THROUGH OUR REGION SUNDAY EVENING. AT THIS POINT IT LOOKS AS THOUGH TEMPS WILL BE STEADY OR SLOWLY RISING ON SATURDAY NIGHT WHICH WILL LIKELY RESULT IN SOME MIXED PCPN MAINLY IN THE FORM OF FREEZING RAIN AND SLEET SATURDAY NIGHT BASED ON PARTIAL THICKNESS VALUES WITH A TRANSITION TO RAIN ACROSS THE ENTIRE FA BY SUNDAY MORNING. THE PCPN SATURDAY NIGHT LOOKS TO BE FAIRLY LIGHT WITH THE POTENTIAL FOR AT LEAST A HALF INCH TO AN INCH OF QPF ON SUNDAY WHICH WILL RESULT IN SOME HYDRO CONCERNS...SEE HYDROLOGY DISCUSSION. 00Z MREF PLUME DIAGRAM WOULD GIVE KALB 0.2 TO 2.0 INCHES WITH VERY LITTLE CLUSTERING RESULTING IN A LARGE SPREAD AMONGST ENSEMBLE MEMBERS. QUITE A FEW ENSEMBLE MEMBERS ALSO INDICATE A BRIEF PERIOD OF FREEZING RAIN ON SATURDAY NIGHT BEFORE A QUICK CHANGEOVER TO RAIN AND MOSTLY RAIN UNTIL PCPN TAPERS OFF AS A LIGHT SNOW ACCUMULATION SUNDAY NIGHT. 00Z MREFS ALSO HAS THE LOW PRESSURE CENTER DEEPEN RAPIDLY AS IT TRACKS NORTH OF UPPER GREAT LAKES INTO CANADA ENDING UP 2-3 SD BELOW NORMAL AT 06Z MON WHILE H8 V COMPONENT WINDS NOW 3-4 SD ABOVE NORMAL IMPLYING STRONG SOUTHERLY COMPONENT AT 18Z SUNDAY THIS EVENT WILL NEED TO BE MONITORED CLOSELY FOR BOTH WIND CONCERNS AND HYDRO CONCERNS. AREAS PRONE TO STRONG SOUTHERLY WINDS SUCH AS TACONICS AND SOUTHERN VERMONT AND NORTHERN BERKSHIRES WOULD BE MOST AT RISK OF STRONGEST GUSTS WHICH COULD EASILY TOP 50 MPH IN SOME OF THE MOST PRONE LOCATIONS SUNDAY. IN WAKE OF FRONT SUNDAY NIGHT WINDS EXPECTED TO SHIFT TO THE WEST WITH GUSTS STILL STRONG ACROSS HIGHER TERRAIN OF ADIRONDACKS. GFS 0-30 MB AGL WINDS INDICATE POTENTIAL FOR 50+ KNOT GUSTS FROM THE SOUTH SUNDAY AND FROM THE WEST SUNDAY NIGHT. THE WINDS ARE EXPECTED TO BE AMPLIFIED AS PRESSURE GRADIENT TIGHTENS ACROSS FA BETWEEN DEPARTING 1035 MB HIGH PRESSURE OFF NEW ENGLAND COAST AND LOW PRESSURE MOVING FROM UPPER GREAT LAKES INTO SOUTHERN CANADA AND DEEPENING TO BELOW 990 MB. THIS STRONG PRESSURE GRADIENT IS ALSO SUPPORTED BY ECMWF AND GEM GLOBAL WITH SOME DIFFERENCES IN EXACT LOCATION OF MAIN FEATURES. QPF AMOUNTS OF AT LEAST 0.50 TO 1 INCH EXPECTED AND HYDRO CONCERNS ARE ADDRESSED IN HYDROLOGIC DISCUSSION. EVEN THOUGH THIS SYSTEM IS STILL 3-4 DAYS OUT WILL INCLUDE MENTION OF POTENTIAL FOR FREEZING RAIN...HIGH WINDS AND POSSIBLE FLOODING IN THE HWO. LATE SUNDAY NIGHT AND MONDAY EXPECT SOME LAKE EFFECT SNOW ACROSS THE WESTERN ADIRONDACKS WHICH IS LIKELY TO BE ENHANCED BY A STRONG VORT AXIS ACROSS THIS REGION ON MONDAY. DRY WEATHER IS THEN EXPECTED TO RETURN ON CHRISTMAS EVE AND CHRISTMAS DAY. ALTHOUGH A COASTAL SYSTEM LOOKS TO PASS FAR ENOUGH SOUTHEAST OF THE SOUTHERN NEW ENGLAND COAST ON TUESDAY NIGHT TO SPARE FA SNOW...BUT DUE TO IT BEING A CLOSE CALL BASED ON THE ECMWF AND GFS WILL LEAVE SLIGHT CHANCE TO CHANCE POPS IN FORECAST FOR NOW. BOTH MODELS INDICATE THAT A STRENGTHENING RIDGE OF HIGH PRESSURE ACROSS FA IS EXPECTED TO DEFLECT COASTAL LOW OUT TO SEA. THIS WILL NEED TO BE MONITORED FOR FURTHER MODEL RUN CONTINUITY AS THIS IS MUCH FARTHER SOUTH AND EAST THAN TRACK WAS INDICATED YESTERDAY. IF THIS SYSTEM MISSES OUR FA THEN DRY WEATHER WILL CONTINUE THROUGH WEDNESDAY WITH NEXT SHORT WAVE NOT EXPECTED BEFORE THURSDAY. OVERALL LONG TERM BEYOND MONDAY LOOKS COLD AND DRY AT THIS POINT IN TIME. && .AVIATION /12Z THURSDAY THROUGH MONDAY/... VERY MOIST LOW LEVELS WITH TEMPS HOVERING AROUND THE FREEZING MARK ALONG WITH LITTLE AIR CIRCULATION AND STILL SOME LIGHT SNOW FALLING WILL KEEP LIFR/IFR CONDITIONS IN PLACE FOR MOST IF NOT ALL OF THE MORNING...ALTHOUGH THE SNOW WILL GRADUALLY DIMINISH IN COVERAGE AND INTENSITY DURING THE NEXT COUPLE OF HOURS. THE BIG QUESTION CONTINUES TO BE HOW QUICKLY CIGS AND VSBYS WILL RISE LATER THIS MORNING OR EARLY THIS AFTERNOON. BASED ON BUFKIT MODEL SOUNDINGS CLOUD AND INVERSION HEIGHTS REMAIN IN IFR RANGE THROUGH AT LEAST 15Z AT KGFL AND KPOU...BUT KALB MAY HAVE MOST DIFFICULTY BREAKING OUT OF LIFR/IFR RANGE AS SNOW SHOWER AND FLURRY ACTIVITY MAY END LAST IN CAPITAL DISTRICT. THERE IS ALSO SOME UNCERTAINTY HEADING INTO THIS EVENING...BUT WITH LOW LEVELS STILL MOIST AND LIGHT WINDS EXPECT AT LEAST A RETURN TO MVFR CONDITIONS AFTER 00Z. WINDS GENERALLY LIGHT AND VARIABLE THROUGH 12Z FRIDAY. OUTLOOK... FRI-SAT...VFR. SUN...IFR MIXED PCPN...STRONG S-SE WINDS. MON...VFR...EXCEPT MVFR/IFR IN LAKE EFFECT -SHSN DOWNWIND OF LK ONT. && .HYDROLOGY... NO HYDRO PROBLEMS ARE ANTICIPATED THROUGH SATURDAY. WE HAVE ANNOTATED BOTH THE RVDALY TEXT PRODUCT AND THE AHPS PAGES WHERE ICE IS CAUSING UNREPRESENTATIVE RIVER STAGE AND FLOW READINGS. SOME PERIODS OF LIGHT SNOW EXPECTED TODAY. A STRONGER STORM SYSTEM MAY IMPACT THE REGION ON SUNDAY. THE STORM IS EXPECTED TO MOVE NORTH OF THE GREAT LAKES AND DRAG A COLD FRONT ACROSS OUR REGION LATE SUNDAY. AHEAD OF THE FRONT...TEMPERATURES ARE EXPECTED TO RISE ABOVE FREEZING WITH THE WARMEST TEMPERATURES OVER ULSTER...DUTCHESS AND LITCHFIELD COUNTIES. SOME RUNOFF IS EXPECTED ON SUNDAY SOUTH OF I-90 FROM A COMBINATION OF SNOW MELT AND RAINFALL. 00Z MREFS SHOW A 75 PERCENT CHANCE OF A HALF INCH OF RAIN...AND 30 TO 50 PERCENT CHANCE OF OVER ONE INCH OF RAIN. AT THIS TIME RIVER FLOODING IS NOT EXPECTED BUT THERE IS A THREAT THAT FLOODING COULD DEVELOP... ESPECIALLY OVER SOUTHERN COUNTIES...IF TEMPERATURES TURN OUT WARMER AND RAINFALL IS HEAVIER. LOCALIZED FLOODING IS POSSIBLE IN SOUTHERN URBAN AREAS WHERE STORM DRAINS ARE BLOCKED BY SNOW. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ SYNOPSIS...WASULA NEAR TERM...WASULA SHORT TERM...WASULA LONG TERM...11 AVIATION...11 HYDROLOGY...11 ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1257 AM EST THU DEC 20 2007 .SYNOPSIS... A CLIPPER LOW PRESSURE SYSTEM WILL DISSIPATE IN IN THE EASTERN GREAT LAKES REGION THIS EVENING...WITH A SECONDARY LOW FORMING OFF CAPE COD OVERNIGHT. THESE LOWS WILL BRING PERIODS OF LIGHT SNOW TO THE REGION INTO THURSDAY. HIGH PRESSURE WILL BUILD BACK IN THURSDAY NIGHT INTO FRIDAY AND SLIDE OFFSHORE SATURDAY. SATURDAY NIGHT AND SUNDAY A COLD FRONT WILL PUSH THROUGH THE REGION...WARMER AIR WILL STREAM INTO THE REGION AHEAD OF THE FRONT...RESULTING IN THE THREAT OF MIXED PRECIPITATION CHANGING TO RAIN SUNDAY. HIGH PRESSURE WILL BUILD FROM THE GREAT LAKES INTO QUEBEC MONDAY AND TUESDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... SHORT WAVE WAS PROGRESSING ACROSS UPSTATE NEW YORK WITH A WIDESPREAD AREA OF LIGHT SNOW IMPACTING MOST OF THE CWA (MAINLY THE EASTERN HALF). IT SEEMS A LOCAL HUDSON VALLEY CONVERGENCE ZONE HAS EVOLVED COMBINING WITH FAVORABLE UPSLOPE CONDITIONS FOR A BAND OF LIGHT-MODERATE SNOW. 18Z WRF/NAM AND LATEST RUC13 ALSO SHOW SOME HINTS IN THE LOW LEVEL CONVERGENCE FIELDS ALONG WITH INCREASING DEFORMATION/TROWAL AXIS ACROSS WESTERN NEW ENGLAND INTO PORTIONS OF LAKE GEORGE AND SARATOGA REGION. THESE REGIONS WILL LIKELY REMAIN WITHIN A FAVORABLE SNOWFALL REGION WHILE AREAS TO THE WEST...WE ARE LOSING ICE NUCLEI AS MID AND HIGHER LEVEL DRIER AIR ADVECTS INTO THE REGION. WILL NEED TO MONITOR FZDZ BUT NOTHING REPORTED THUS FAR UPSTREAM. TEMPERATURES ARE NOW AT OR BELOW THE FREEZING MARK WHICH SHOULD SIGNIFY SOME ACCUMULATIONS. MADE SOME MODIFICATIONS TO THE FORECAST/GRIDS BASED ON THOSE AFOREMENTIONED TRENDS AND CURRENT GUIDANCE. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 AM FRIDAY/... BY 12Z/THURSDAY COASTAL LOW IS THE DOMINATE LOW WITH BAGGINESS IN THE PRESSURE FIELDS ACROSS THE FORECAST AREA. IN ADDITION...A SHORT WAVE WILL ROTATE THROUGH THE UPPER LEVEL TROUGH OVER THE REGION THURSDAY. LIGHT SNOW SHOULD LINGER OVER SOUTHERN VERMONT WITH SOME SNOW SHOWERS ACROSS THE REST OF THE FORECAST AREA. CHANCES FOR PRECIPITATION WILL DECREASE AS THE DAY WEARS ON DAY. HIGH PRESSURE TO THE NORTH OVER EASTERN CANADA WILL BUILD SOUTH THURSDAY NIGHT. && .LONG TERM /FRIDAY THROUGH THURSDAY/... FIRST PART OF PERIOD FRIDAY AND SATURDAY FAIRLY QUIET AS SFC HIGH PRESSURE BUILDS ACROSS GREAT LAKES INTO QUEBEC. SATURDAY NIGHT IT SLIDES OFF SHORE AS 500HPA RIDGE BUILDS ALONG EASTERN SEABOARD. CDFNT PUSHES THROUGH GRTLKS SAT NIGHT AND ACROSS NY AND NEW ENG SUNDAY. MAJOR DYNAMICS WITH SYSTEM ARE WELL NORTH OF REGION IN QUEBEC WITH MAIN IMPACT BEING THE CDFNT. WITH PERIOD OF SOUTHERLY WINDS TEMPS WILL HOLD OR RISE SAT NIGHT...BUT WILL START SUFFICIENTLY COLD TO RESULT IN MIXED PCPN TYPES INTO SUN MRNG. PCPN WILL BE SPOTTY IN THE MOISTURE INFLOW AND BULK OF IT WILL BE ASSOCIATED WITH CFP. TEMPS WILL RISE ENOUGH TO TURN THE MIX TO RAIN IN MOST OF FCA PRIOR TO CFP. IN GENERAL ENSEMBLES CENTERED AROUND 0.75 INCH OF QPF WITH THIS EVENT..SOME PORTION OF WHICH WILL BE FROZEN. TREND HAS BEEN TWRD LOWER QPF. THIS IS COVERED IN MORE DETAIL IN HYDRO SECTION. THIS IS A SYSTEM THAT THE MAIN LOW IS WELL TO THE NORTH...ESSENTIALLY A CLIPPER...HAS LIMITED PERIOD OF MOISTURE INFLOW FROM THE ATLC. CDFNT SWEEPS QUICKLY OFFSHORE SUNDAY NIGHT AS HIGH PRESSURE BUILDS EAST FROM THE GRTLKS...FOLLOWED BY A SECONDARY ARCTIC FRONT ON MONDAY. MONDAY AND TUESDAY WILL BE MAINLY DRY EXCEPT FOR -SHSN ASSOCIATED WITH SECONDARY FRONT AND FLOW INTERACTIONS WITH TRRN. TUESDAY INTO WEDNESDAY THERE IS QUITE A BIT OF DIVERGENCE BETWEEN THE GFSMOS...EUROPEAN AND HPC. WITH THE GFS TAKING A LARGE LOW THROUGH THE TENNESSEE VALLEY AND THEN A SECONDARY FORMING OVER DELMARVA AS EARLY AS CHRISTMAS DAY. THE OTHERS DEVELOP THIS SYSTEM ALONG THE SE US COAST...AND TAKE IT UP THE SEABOARD EITHER AS SOME SORT OF SNOW EVENT...OR TOO FAR EAST TO AMOUNT TO ANYTHING. FOR NOW CHC OF SNOW WILL SUFFICE...WE ARE TALKING ABOUT DAYS 7/8. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... VERY MOIST LOW LEVELS WITH TEMPS HOVERING AROUND THE FREEZING MARK ALONG WITH LITTLE AIR CIRCULATION AND STILL SOME LIGHT SNOW FALLING WILL KEEP LIFR/IFR CONDITIONS IN PLACE FOR MOST IF NOT ALL OF THE REMAINDER OF THE OVERNIGHT PERIOD. THE BIG QUESTION AT THIS POINT WILL BE HOW QUICKLY CIGS AND VSBYS WILL RISE AFTER SUNRISE AND EXPECT THAT AT KGFL IT MAY TAKE UNTIL AFTERNOON AS LITTLE WIND FLOW EXPECTED. KALB AND KPOU HAVE A BETTER CHANCE TO MIX AND ALSO EXPECT LESS IN THE WAY OF SNOW SHOWER ACTIVITY AS CLIPPER TYPE SYSTEM PULLS AWAY FROM FA. EVEN AT KALB AND KPOU IT MAY TAKE MUCH OF THE MORNING BEFORE MVFR CONDITIONS GIVE WAY TO VFR. THERE IS SOME UNCERTAINTY HEADING INTO THIS EVENING...BUT WITH LOW LEVELS STILL MOIST AND LIGHT WINDS EXPECT AT LEAST A RETURN TO MVFR CONDITIONS AFTER 00Z. WINDS GENERALLY LIGHT AND VARIABLE THROUGH 06Z FRIDAY...EXCEPT NORTHWEST AT 5-8 KTS AT KALB BETWEEN 12Z AND 00Z. OUTLOOK... FRI-SAT...VFR. SUN...IFR MIXED PCPN...STRONG S-SE WINDS. MON...VFR...EXCEPT MVFR/IFR IN LAKE EFFECT -SHSN DOWNWIND OF LK ONT. && .HYDROLOGY... NO HYDRO PROBLEMS ARE ANTICIPATED THROUGH SATURDAY. WE HAVE ANNOTATED BOTH THE RVDALY TEXT PRODUCT AND THE AHPS PAGES WHERE ICE IS CAUSING UNREPRESENTATIVE RIVER STAGE AND FLOW READINGS. SOME PERIODS OF LIGHT SNOW EXPECTED TONIGHT AND THURSDAY. A STRONGER STORM SYSTEM MAY IMPACT THE REGION ON SUNDAY. THE STORM IS EXPECTED TO MOVE NORTH OF THE GREAT LAKES AND DRAG A COLD FRONT ACROSS OUR REGION LATE SUNDAY. AHEAD OF THE FRONT...TEMPERATURES ARE EXPECTED TO RISE ABOVE FREEZING WITH THE WARMEST TEMPERATURES OVER ULSTER...DUTCHESS AND LITCHFIELD COUNTIES. SOME RUNOFF IS EXPECTED ON SUNDAY SOUTH OF I-90 FROM A COMBINATION OF MELT AND RAINFALL. MODEL ENSEMBLES SHOW A 75 PERCENT CHANCE OF A HALF INCH OF RAIN...AND LESS THAN 30 PERCENT CHANCE OF OVER ONE INCH OF RAIN. AT THIS TIME RIVER FLOODING IS NOT EXPECTED BUT THERE IS A THREAT THAT FLOODING COULD DEVELOP...ESPECIALLY OVER SOUTHERN COUNTIES...IF TEMPERATURES TURN OUT WARMER AND RAINFALL IS HEAVIER. LOCALIZED FLOODING IS POSSIBLE IN SOUTHERN URBAN AREAS WHERE STORM DRAINS ARE BLOCKED BY SNOW. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ AVIATION...11 ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1248 AM EST WED DEC 19 2007 .SYNOPSIS... A CLIPPER LOW PRESSURE SYSTEM WILL APPROACH FROM THE UPPER GREAT LAKES REGION TONIGHT. THIS LOW WILL BRING PERIODS OF LIGHT SNOW TO EASTERN NEW YORK AND WESTERN NEW ENGLAND WEDNESDAY AFTERNOON INTO THURSDAY MORNING. AN UPPER LEVEL DISTURBANCE WILL PRODUCE SCATTERED SNOW SHOWERS THURSDAY AFTERNOON. A BROAD AREA OF HIGH PRESSURE WILL RIDGE BACK INTO THE REGION FROM QUEBEC THURSDAY NIGHT INTO FRIDAY. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... THE COMBINATION OF MID LEVEL WARM ADVECTION (AS EVIDENCE PROVIDED BY THE 00Z SOUNDINGS FROM HERE AND AT BUF BETWEEN 800-900MB) UNDERWAY AND SLIGHT Q-VECTOR CONVERGENCE ALONG WITH DEPARTING UPPER JET HAS RESULTED IN MOISTURE CONVERGENCE IN THE FORM OF MID AND HIGH CLOUDS. LATEST RUC13 CONTINUES TO SUPPORT AN INCREASE IN RH FIELDS (ALTHOUGH THERE WILL BE SEVERAL BREAKS) AND WILL ADJUST ACCORDINGLY WITH THE SKY FORECAST/GRIDS. IN ADDITION...THIS WILL HAVE AN IMPACT ON OVERNIGHT LOWS AND WILL RAISE THEM A FEW DEGREES. THIS WAS CAPTURED WELL WITH THE 18Z GFSMOS GUIDANCE AND CURRENT TRENDS SEEN IN THE LAMP NUMBERS. HOWEVER...THE AFOREMENTIONED BREAKS IN THE CLOUDS AND FRESH SNOWPACK WILL PLAY A FACTOR SO WILL CONTINUE TO BE A LITTLE CONSERVATIVE WITH LOW TEMPS. OTHERWISE...UPSTREAM SHORT WAVE CONTINUES TO ADVANCE EAST FROM THE UPPER MISSISSIPPI RIVER VALLEY WITH LITTLE IN WAY OF UPSTREAM OBSERVATIONS REPORTING PRECIP. DTX AND PBZ SOUNDINGS THIS EVENING WERE QUITE DRY SO WILL BE INTERESTING TO SEE HOW THE 00Z GUIDANCE SHOWS THE PRECIP TRENDS FOR WEDNESDAY. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... MID AND HIGH CLOUDS THICKEN THROUGH THE DAY WEDNESDAY IN ADVANCE OF THE NORTHERN STREAM UPPER SYSTEM. BOUNDARY LAYER WARM ADVECTION WILL INCREASE AS SOUTHWESTERLY LOW-LEVEL WINDS INCREASE...ALONG WITH ISENTROPIC LIFT. SNOW WILL BEGIN IN MANY AREAS BY SUNSET...BUT WILL BE LIGHT...THEN CONTINUE PERIODICALLY INTO THE NIGHT...ENDING IN MANY AREAS THURSDAY MORNING. BASED ON THE TRACK OF THE UPPER SYSTEM AND THE 850 MB LOW...MOST OF THE PRECIPITATION WILL FALL IN THE ADIRONDACKS...NORTHERN LAKE GEORGE REGION AND MOUNTAINS OF SOUTHERN VT. THE SYSTEM STRENGTHENS AS IT EXITS NEW ENGLAND...AND A QUICK EASTERLY WIND ANOMALY DEVELOPS THAT NOSES INTO EASTERN AND NORTHERN NEW ENGLAND. THEREFORE...SNOW WILL LINGER IN SOUTHERN VT THROUGH THURSDAY INTO THURSDAY NIGHT. BUT...AFTER THURSDAY MORNING...ANY LINGERING SOUTHERN VT SNOWS WOULD BE LIGHT AND SHOWERY. SOME FLURRY ACTIVITY IS POSSIBLE ANYWHERE THURSDAY...WITH CHANCES FOR MORE SUBSTANTIAL SNOW SHOWER ACTIVITY DOWNWIND FROM LAKE ONTARIO. BASED ON GUIDANCE INCLUDING SREF AND MREF PLUMES...AROUND A QUARTER TO A THIRD OF AN INCH LIQUID EQUIVALENT POSSIBLE IN ADIRONDACKS...NORTHERN LAKE GEORGE REGION AND SOUTHERN VT...WITH LESS FOR POINTS SOUTH. SO...2-4" POSSIBLE IN AREAS OF MAX...WITH PERHAPS AROUND AN INCH OR TWO MOHAWK VALLEY...CAPITAL DISTRICT AND BERKSHIRES AND POINTS SOUTH...WITH A COATING TO AN INCH CATSKILLS...TACONICS AND NW CT. SYSTEM EXITS LATER THURSDAY AND THURSDAY NIGHT...SO GRADUAL CLEARING LATER THURSDAY AND THURSDAY NIGHT. SOME LAKE EFFECT MOISTURE AFFECTING WESTERN AREAS INTO THURSDAY NIGHT WITH NORTHWEST LOW-LEVEL FLOW. DRY WEATHER CONTINUES FRIDAY. TEMPERATURES WILL BE IN THE 20S AND 30S WEDNESDAY THROUGH FRIDAY...SINCE TRUE ARCTIC AIR WILL HAVE RETREATED NORTH. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... THE 500 HPA TROF CONTINUES TO DIG SOUTH AND ADVANCE EAST WITH A CLOSED LOW DEVELOPING NORTH OF THE DAKOTAS AS THE RIDGE OVER THE EASTERN STATES SLOWLY DRIFTS EAST. THE SURFACE HIGH UNDER THE RIDGE BUILDS EAST INTO THE MARITIMES WHILE A FRONTAL SYSTEM ASSOCIATED WITH THE TROF MOVES TO THE MISSISSIPPI VALLEY. THE POSSIBILITY OF OVERRUNNING PRECIPITATION DEVELOPS SATURDAY MORNING AS A LOW LEVEL FLOW FROM THE SOUTH RUNS UP AGAINST THE COLD DOME ASSOCIATED WITH THE HIGH OVER THE MARITIMES. BY MIDDAY TEMPERATURES OVER THE REGION WARM INTO THE MID TO UPPER THIRTIES OVER MOST OF THE AREA FROM THE MOHAWK VALLEY SOUTH...EXCEPT FOR THE HIGHER ELEVATIONS OF THE CATSKILLS...RESULTING IN SNOW NORTH AND OVER THE HIGHER TERRAIN...RAIN OVER THE MID HUDSON REGION...AND A MIX IN BETWEEN. LATE IN THE AFTERNOON TEMPERATURES AT 850 HPA WARM TO AROUND PLUS 2 AND THE WARMING ALOFT CONTINUES THROUGH THE NIGHT WITH 850 HPA TEMPERATURES PLUS 6 TO PLUS 8 BY 12Z SUNDAY. THIS BRINGS ABOUT THE POSSIBILITY OF FREEZING RAIN OVER COLDER AREAS... ESPECIALLY NORTH AND WEST WHERE TEMPERATURES ALOFT ARE EXPECTED TO WARM FASTER FROM THE LOW LEVEL FLOW UP THE OHIO VALLEY. THE PRIMARY LOW ROCKETS INTO CENTRAL QUEBEC WHILE A SECOND LOW DEVELOPS OVER SOUTHERN NEW ENGLAND AS THE FRONT MOVES THROUGH THE REGION SUNDAY AFTERNOON. BEFORE THE FRONT PASSES SURFACE TEMPS ARE EXPECTED TO WARM UP ENOUGH TO TURN THE PRECIPITATION TO RAIN OVER THE ENTIRE FORECAST AREA. AFTER THE FRONT PASSES THE RAIN WILL MIX AND TURN BACK TO SNOW SUNDAY NIGHT...THEN MIX WITH AND CHANGE TO RAIN IN OUR SOUTHERN ZONES LATE MONDAY MORNING BEFORE THE COLD AIR RETURNS AS THE COASTAL LOW LIFTS NORTHEAST BRINGING IN ANOTHER BLAST OF COLD AIR MONDAY EVENING. CHRISTMAS MORNING WILL FIND US BETWEEN A DEEP LOW OVER THE MARITIMES...A WEAK HIGH JUST NORTH OF LAKE HURON...AND A STRONGER HIGH OVER THE OHIO VALLEY. THE GOOD NEWS IS THAT THE HIGH OVER THE OHIO VALLEY IS FORECAST TO BUILD NORTH ENOUGH TO SHIFT THE GRADIENT AND STRONG NORTH WESTERLY WINDS OFF INTO COASTAL NEW ENGLAND...RESULTING IN PARTLY TO MOSTLY CLOUDY SKIES OVER THE REGION AND JUST A SLIGHT CHANCE OF SOME SNOW SHOWERS OVER THE HIGHER TERRAIN WEST OF THE HUDSON VALLEY. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... VFR CONDITIONS EXPECTED TO HOLD THROUGH EARLY TO MID AFTERNOON WITH P6SM BKN120 OVC250 EXPECTED DURING MUCH OF THE PERIOD AS MID AND HIGH CLOUDS OVERSPREAD THE REGION AHEAD OF A CLIPPER TYPE SYSTEM. LIGHT SNOW EXPECTED TO DEVELOP MID TO LATE AFTERNOON AS CLIPPER DIVES SOUTHEAST INTO EASTERN GREAT LAKES REGION. MVFR/IFR EXPECTED AT KGFL AFTER 19Z AND 21Z RESPECTIVELY AS LIGHT SNOW OVERSPREADS THE REGION. MVFR CONDITIONS EXPECTED AT KALB AND KPOU AFTER 20Z AND 21Z RESPECTIVELY WITH JUST VCSH AT KPOU AS VERY LITTLE QPF TO WORK WITH ACROSS SOUTHERN PORTION OF FA. WINDS EXPECTED TO BE LIGHT AND VARIABLE OR SOUTH TO SOUTHEAST AT 5 KTS OR LESS. OUTLOOK... THU...VFR/MVFR CIGS...WDLY SCT SNOW SHOWERS. FRI-SAT...VFR/MVFR...CHANCE -SN KALB/KGFL...-RA/-SN KPOU. SUN...IFR MIXED PCPN. && .HYDROLOGY... NO HYDRO PROBLEMS ARE ANTICIPATED UNTIL THE WEEKEND. ICE WILL CONTINUE TO FORM AND THICKEN ON THE RIVERS. THE ICE IS CAUSING SEVERAL RIVER GAGES...PARTICULARLY MCKEEVER AND PRATTSVILLE... TO READ HIGHER THAN THEY WOULD IF THE CHANNELS WERE CLEAR. STARTING LATE SATURDAY NIGHT...WARM AIR OVERRUNNING THE COLDER AIR IN THE REGION WILL BEGIN PRECIPITATION STARTING AS SNOW BUT LIKELY CHANGING TO FREEZING RAIN AND EVENTUALLY RAIN ALONG WITH A SIGNIFICANT WARM UP BY MIDDAY SUNDAY WITH HIGHS FROM THE UPPER 30S TO THE MID 40S...ALONG WITH STRONG SOUTHERLY WINDS. THE COMBINATION OF RAIN...MELTING SNOW...AND IN SOME CASES RIVER CHANNEL BLOCKAGES WITH ICE...COULD BRING ABOUT SOME SIGNIFICANT RISES IN WATER LEVELS AND POSSIBLY EVEN SOME FLOODING SUNDAY NIGHT INTO MONDAY. AREAS MOSTLY LIKELY TO BE AFFECTED INCLUDE THE CATSKILLS...BERKSHIRES...MID HUDSON REGION OF NY...AND THE HOUSATONIC VALLEY IN WESTERN NEW ENGLAND. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ AVIATION...11 ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 927 PM EST THU DEC 20 2007 .SYNOPSIS... SURFACE HIGH PRES WILL GIVE WAY TO AN APPROACHING UPPER-LEVEL DISTURBANCE WHICH WILL PASS THROUGH THE REGION AND MOVE OFF THE COAST EARLY FRI. THIS WILL ENHANCE A WEDGE PATTERN OVER THE CAROLINAS THAT SHOULD BREAK DOWN ON SUN AS A COLD FRONT APPROACHES FROM THE W. THE FRONT WILL MOVE OFF THE COAST EARLY MON...BUT UNSETTLED WEATHER COULD RETURN BY CHRISTMAS DAY AS ANOTHER UPPER- LEVEL DISTURBANCE IS POSSIBLE. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... SURFACE OBSERVATIONS INDICATE COLD AIR DAMMING IS BEGINNING TO TAKE SHAPE ACROSS INLAND AREAS WHILE COASTAL FRONTOGENESIS IS ONGOING OFFSHORE. THE INLAND WEDGE AND ASSOCIATED COASTAL FRONT WILL STRENGTHEN OVERNIGHT AS THERMAL GRADIENTS INTENSIFY DUE TO DIABATIC COOLING AND INCREASING BAROCLINICITY OFFSHORE NEAR THE WRN WALL OF THE GULF STREAM. OPTED TO RAISE LOW TEMPS A DEG OR TWO MOST AREAS BASED ON THE LATEST RUC-13 WET-BULB PROGNOSTICATIONS BUT STILL EXPECT TEMPS TO BOTTOM OUT IN THE UPR 40S ACROSS WELL INLAND WITH UPR 50S ALONG THE BEACHES. AN AREA OF WDSPRD RAINFALL THAT IS MOVING ACROSS SRN GA IS STEADILY EXPANDING AHEAD OF A SHORTWAVE NOTED ALONG THE CENTRAL GULF COAST. THIS AREA OF RAIN WILL INTENSITY THROUGH THE NGT AS INCRG OMEGA AHEAD OF THE SHORTWAVE COMBINES WITH INCRG ISENTROPIC LIFT ATOP THE WEDGE. POPS NEAR 100 PCNT ARE ON TRACK AND AGREE WELL WITH CURRENT RADAR AND SHORT-TERM MODEL TRENDS. WE ARE CAREFULLY WATCHING THE INTENSIFYING N-S ORIENTED SQUALL LINE THAT IS MOVING ACROSS THE GULF WATERS SOUTH OF THE FL PANHANDLE THIS EVNG. SO FAR THE LINE HAS SHOWN NO SIGNS OF SIGNIFICANTLY DISRUPTING 850MB MOISTURE TRANSPORT N INTO SC/GA. THUS EXPECT THE RAIN TO BECOME LCLLY HEAVY AT TIMES BY EARLY FRI AS LOW-LVL CONVG ALONG THE WEDGE FRONT INCRS AND PWATS CLIMB ABOVE 1.25 INCHES. ALTHOUGH WDSPRD DEEP CONVECTION WILL BE LACKING... BUILDING ASTRONOMICAL TIDES MAY PEAK DURING A PERIOD OF MODERATE TO HEAVY RAINS ACROSS THE COASTAL COUNTIES EARLY FRI MRNG WHICH RAISES THE CONCERN FOR POSSIBLE FRESH WATER FLOODING PROBLEMS... ESPECIALLY IN THE DOWNTOWN CHARLESTON AREA. WILL DEFER THE DECISION FOR A FLOOD WATCH TO THE MIDNGT SHIFT AND MAINTAIN A MENTION OF POSSIBLE FLOODING PROBLEMS IN THE HAZARDOUS WEATHER OUTLOOK. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... THE LOW PRESSURE SYSTEM WILL SHIFT OFF THE GA/SC COASTLINE FRI...WITH RAIN CHANCES SUBSEQUENTLY DECREASING THROUGH THE DAY FROM SW TO NE. THE COASTAL LOW OFFSHORE WILL ACT TO AMPLIFY THE PERSISTENT INLAND SURFACE WEDGE. THICK CLOUD COVER AND RESIDUAL DRIZZLE DIABATICALLY ENHANCING THE COLD AIR DAMMING WILL CREATE CHILLY CONDITIONS FOR THE NORTHERN AND WESTERN COUNTIES. EXPECT HIGHS TO BE SUPPRESSED IN THE LOWER 50S NW ZONES...INCREASING TO THE LOWER TO MID 60S TOWARD THE S. A PINCHED GRADIENT ALONG THE CHARLESTON COUNTY COAST WILL LIKELY SUPPORT BREEZY CONDITIONS THERE FOR MUCH OF THE DAY. LAKE WINDS...A LAKE WIND ADVISORY MAY BE NEEDED FOR LAKE MOULTRIE ON FRIDAY...BUT MUCH WILL DEPEND ON WHERE EXACTLY THE SFC LOW DVLPS. WILL HOLD THE FCST JUST UNDER ADVISORY CRITERIA FOR NOW..BUT HEADLINE THAT AN ADVISORY MAY BE NEEDED. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... SOLID WEDGE WILL BE IN PLACE FRIDAY NIGHT INTO SATURDAY WITH NORTHEAST WINDS...COOL TEMPS...NOT A LOT OF SUN...AND EVEN A FEW LIGHT SHOWERS/DRIZZLE ...MAINLY IN THE NORTHEASTERN HALF OF THE CWA. WENT BELOW GUIDANCE FOR TEMPS ON SATURDAY. WINDS START TO VEER SATURDAY NIGHT AHEAD OF THE NEXT FRONT WITH A WARMER DAY SUNDAY ON SOUTH TO SOUTHWESTERLY WINDS. STILL...THE WEDGE MAY TRY TO HOLD ON FAR NORTH...BUT HAVE NOT GONE WITH THAT SOLUTION. AGAIN...THERE IS A SMALL CHANCE OF SHOWERS AHEAD OF THE FRONT. COLD FRONT GOES THROUGH SUNDAY NIGHT CAUSING THE WINDS TO COME AROUND TO THE NORTHWEST. THIS WILL INTRODUCE SOME DRYING WITH A BETTER CHANCE FOR SUNSHINE MONDAY. TEMPS WILL BE SEASONABLE. FORECAST BECOMES VERY UNCERTAIN FOR THE REMAINDER OF CHRISTMAS WEEK AS MODELS DIFFER SIGNIFICANTLY ON THE EVOLUTION OF A DEVELOP LOW. ONE SET OF SOLUTIONS DEVELOPS THE LOW OFF THE SOUTHEAST COAST AND SETS UP FOR A COOL CHRISTMAS WITH A CHANCE OF RAIN. ANOTHER SET DEVELOPS THE SYSTEM QUITE A BIT FURTHER WEST AND KEEPS US DRY UNTIL WEDNESDAY. FOR NOW...I WENT WITH CONTINUITY WHICH IS MORE PESSIMISTIC FOR CHRISTMAS DAY...BUT I DO NOT HAVE MUCH CONFIDENCE DUE TO THE DIVERGENCE OF MODEL SOLUTIONS. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS WILL DETERIORATE TONIGHT AT BOTH CHS AND SAV TERMINALS. MVFR CIGS AND VSBYS WILL BEGIN BY 07Z AT THE SAV TERMINAL AND 09Z AT THE CHS TERMINAL AS A SYSTEM OF LOW PRESSURE BRINGS RAIN OVER THE AREA. RAIN WILL BE HEAVY AT TIMES BY 12Z AT BOTH TERMINALS. WILL LIKELY SEE IFR CONDITIONS BEGIN BY 10Z AT THE SAV TERMINAL AND 12Z AT THE CHS TERMINAL AS HEAVY PRECIP PUSHES OCCURS. LIFR CIGS OF 400 FEET WILL TEMPORARILY ACCOMPANY HEAVIER RAIN AT BOTH TERMINALS. CONDITIONS WILL BEGIN TO IMPROVE TOMORROW AFTERNOON AS THE COASTAL LOW BEGINS TO SHIFT NORTHEAST. MVFR VSBYS AND CIGS ARE ANTICIPATED THROUGH MOST OF TOMORROW AFTERNOON...WITH ACTIVITY REMAINING OVER THE CHS TERMINAL LONGER THAN THE SAV TERMINAL. HAVE ADDED CB TO THE SAV TERMINAL FROM THE 12Z TO 18Z PERIOD AS INSTABILITY INCREASES BEFORE THE LOW PUSHES EAST. WILL SEE EAST WINDS BACK TO THE NORTHEAST TONIGHT AS THE LOW PUSHES TOWARDS THE ATLANTIC. HAVE ADDED WIND GUSTS UP TO 20 KNOTS OVER THE CHS TERMINAL AS RAIN WILL ALLOW A STRONG GRADIENT WIND TO MIX TO THE SFC DURING THE 12Z TO 20Z TIME FRAME TOMORROW. EXTENDED AVIATION OUTLOOK...A PERIOD MVFR OR IFR POSSIBLE FRIDAY NIGHT INTO SATURDAY NIGHT WITH LOW CLOUDS AND POSSIBLE FOG IN WEDGE CONDITIONS. THERE SHOULD BE SOME IMPROVEMENT BY SUNDAY NIGHT AND MONDAY...BUT ANOTHER ROUND OF LOW CIGS IS POSSIBLE TUESDAY AND TUESDAY NIGHT. && .MARINE... THE PRESSURE GRADIENT IS SLOWLY INTENSIFYING ALONG THE SC COAST THIS EVNG BTWN HIGH PRES BUILDING INLAND AND A DVLPG COASTAL FRONT OFFSHORE. THE GRADIENT WILL CONTINUE TO PINCH ACROSS THE SC WTRS OVRNGT AND INTO FRI AS LOW PRES DVLPS OFF THE SC/GA COAST AND COLD AIR DAMMING STRENGTHS INLAND. THE 21/00Z MODELS ARE BEGINNING TO TRICKLE IN AND STILL SUGGEST THERE IS A POTENTIAL FOR GALE FORCE WINDS...AT LEAST IN FREQUENT GUSTS...ALONG THE CHARLESTON COUNTY COASTAL WATERS OUTSIDE OF THE HARBOR. THEY HAVE BEEN HINTING AT THIS POSSIBILITY FOR THE LAST SEVERAL RUNS SO WILL GO AHEAD AND ISSUE A GALE WATCH FOR THE WATERS N OF EDISTO BEACH BEGINNING AROUND SUNRISE FRI AND CONTINUING THROUGH FRI NGT. THE WATCH MAY BE UPGRADED TO A GALE WARNING WITH THE EARLY MRNG FCST PKG. WHILE GALE FORCE WINDS ARE A POSSIBILITY IN THE CHARLESTON HARBOR... CONFIDENCE IS NOT HIGH ENOUGH ATTM TO JUSTIFY A GALE WATCH THERE. SMALL CRAFT ADVISORIES LOOK GOOD ACROSS THE REMAINDER OF THE MARINE AREA...ALTHOUGH THE START TIME FOR THE CHARLESTON HARBOR NEEDS TO BE MOVE UP TO FRI MRNG BASED ON CURRENT TRENDS. WINDS HAVE DROPPED TO LESS THAN 10 KT ACROSS THE GA NEARSHORE WTRS NEAR THE COASTAL FRONT BUT SHOULD BECOME N-NE 10-15 KT AFTER MIDNGT AS LOW PRES DVLPS JUST OFFSHORE. PINNING DIRECTIONS IN THE GA WATERS WILL BE TRICKY UNTIL THE LOW PRES AREA CONSOLIDATES. WINDS WILL GO SOLIDLY NE ACROSS ALL WATERS BY FRI AFTN AS LOW PRES PULLS AWAY FROM THE AREA AND HIGH PRES WEDGE EXPANDS OFFSHORE. SEAS WILL BUILD QUICKLY NGT AND FRI AS NE WINDS INTENSIFY. FRIDAY NIGHT THROUGH TUESDAY...STRONGEST WINDS THROUGH THE PERIOD ARE EXPECTED FRIDAY NIGHT AND SATURDAY THANKS TO THE WEDGE. SCA CONDITIONS EXPECTED THROUGH A GOOD PART OF THE WEEKEND...AND EVEN INTO EARLY NEXT WEEK FOR THE OUTER GEORGIA WATERS. && .TIDES/COASTAL FLOODING... WILL WATCH FOR THE POTENTIAL OF SOME SHALLOW COASTAL FLOODING AROUND HIGH TIDE FRI MORNING IF HEAVY RAINFALL OCCURS. OTHERWISE... ASTRONOMICALLY HIGH TIDES EARLY SATURDAY MORNING AND AGAIN EARLY SUNDAY MORNING SETS US UP FOR THE POSSIBILITY ON MINOR COASTAL FLOODING EACH MORNING IN THE USUALLY VULNERABLE SPOTS. WIND MAY STILL BE ENOUGH OFFSHORE SATURDAY MORNING TO KEEP FROM HAVING MANY PROBLEMS...BUT A SLIGHT SHIFT TO MORE EASTERLY WOULD CHANGE THAT. ULTIMATELY...RESIDENTS IN THOSE FLOOD PRONE LOCATIONS NEED TO STAY TUNED. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...NONE. SC...NONE. MARINE...SMALL CRAFT ADVISORY FROM 7 AM FRIDAY TO 5 AM EST SATURDAY FOR AMZ330. SMALL CRAFT ADVISORY FROM 10 AM FRIDAY TO 5 AM EST SUNDAY FOR AMZ352. GALE WATCH FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT FOR AMZ350. SMALL CRAFT ADVISORY FROM 1 AM TO 9 AM EST FRIDAY FOR AMZ350. SMALL CRAFT ADVISORY FROM 10 AM FRIDAY TO 11 PM EST MONDAY FOR AMZ374. SMALL CRAFT ADVISORY FROM 5 PM FRIDAY TO 5 AM EST SUNDAY FOR AMZ354. && $$ ST ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 336 PM EST WED DEC 19 2007 .SYNOPSIS... HIGH PRESSURE WILL RIDGE INTO THE FORECAST AREA TODAY THROUGH THURSDAY. WEAKENING LOW PRESSURE WILL TRACK SOUTH OF THE AREA THURSDAY NIGHT. THE LOW WILL BE OFF THE SOUTHEAST COAST FRIDAY. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... THE GFS AND NAM TIME-HEIGHTS SHOW LINGERING LOW-LEVEL MOISTURE OVERNIGHT BUT DRY HIGH PRESSURE BUILDING INTO THE AREA SHOULD BECOME MORE DOMINATE. PLAN TO FORECAST PARTLY CLOUDY SKIES. THE TEMPERATURE GUIDANCE IS CLOSE WITH LOWS IN THE MID TO UPPER 30S. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... THE RIDGE WILL MOVE OFF THE COAST THURSDAY. MOISTURE WILL INCREASE AHEAD OF A LEAD H5 SHORTWAVE TROUGH THURSDAY AFTERNOON BUT EXPECT THIS MOISTURE WILL REMAIN TOO SHALLOW FOR RAIN. ISENTROPIC LIFT ALSO APPEARS VERY WEAK THROUGH THE DAY. PLAN TO KEEP THE POP LESS THAN 20 PERCENT. AGAIN THE TEMPERATURE GUIDANCE IS CLOSE WITH HIGHS NEAR 60. THURSDAY NIGHT THE MOISTURE WILL BEGIN TO PUSH EAST OF THE REGION WITH SOME REMAINING SHOWERS INTO THE DAY FRIDAY. ON FRIDAY THE WEDGE WILL BE IN PLACE OVER THE REGION SO HAVE INCREASED CLOUDS AND LOWERED HIGH TEMPERATURES A FEW DEGREES. WEDGE WILL REMAIN IN PLACE THROUGH FRIDAY NIGHT HOWEVER WITH THE UNCERTAINTY IN THE MODELS HAVE KEPT THE WEDGE PRECIPITATION FREE UNTIL SATURDAY WHEN MOISTURE AHEAD OF THE NEXT SYSTEM BEGINS TO MOVE INTO THE AREA. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... MODELS IN THE LONG TERM HAVE SIGNIFICANT DIFFERENCES WITH TIMING AND INTENSITY OF THE SYSTEM FOR THE WEEKEND AND THE BEGINNING OF THE WEEK. LOW PRESSURE WILL TRACK INTO THE GREAT LAKES REGION ON SATURDAY NIGHT...HOWEVER THE COLD FRONT TRACKING FOR SC WEAKENS BEFORE ARRIVING SUNDAY. HAVE SLOWED THIS SYSTEM A BIT AS THE GFS SUGGESTS A SLOWING TREND. DIFFERENCES CONTINUE WITH THE FRONTAL BOUNDARY AS THE GFS STALLS THE BOUNDARY OVER THE REGION AND OTHER MODELS PUSH THE FRONT OFFSHORE. HAVE KEPT WITH THE FRONT MOVING OFFSHORE AND PRECIPITATION ENDING SUNDAY EVENING. MONDAY AND TUESDAY THE GFS DEVELOPS A STRONG LOW PRESSURE SYSTEM ALONG THE WESTERN GULF COAST AND MARCHES IT NORTHWARD INTO THE GREAT LAKES BY TUESDAY MORNING. OTHER MODELS SUGGEST A WEAK SYSTEM OVER THE REGION MONDAY NIGHT AND TUESDAY...SO AGAIN HAVE KEPT WITH THE DRIER SOLUTIONS AND INCREASED CLOUDS SLIGHTLY TO ACCOUNT FOR UNCERTAINTY. EITHER OF THE SOLUTIONS CURRENTLY PROVE TOO WARM FOR ANY CHANCE OF SNOW FOR THE HOLIDAY. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... SATELLITE PLUS THE LATEST RUC TIME-HEIGHTS SHOW LINGERING LOW- LEVEL MOISTURE AND SUPPORT KEEPING MAINLY VFR CEILINGS THROUGH THE AFTERNOON. EXPECT JUST SCATTERED CLOUDS TONIGHT AS DRY RIDGING BECOMES MORE DOMINATE. EXPECT IFR OR MVFR CEILINGS ASSOCIATED WITH LOW PRESSURE TRACKING SOUTH OF THE REGION THURSDAY NIGHT INTO FRIDAY...OTHERWISE NO SIGNIFICANT AVIATION IMPACTS FORECAST DURING THE EXPECTED PERIOD. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && $$ ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE COLUMBIA SC 943 AM EST WED DEC 19 2007 .SYNOPSIS... AN UPPER-LEVEL DISTURBANCE WILL MOVE THROUGH THE FORECAST AREA TODAY. SURFACE HIGH PRESSURE WILL RIDGE INTO THE FORECAST AREA TODAY THROUGH THURSDAY. WEAKENING LOW PRESSURE WILL TRACK SOUTH OF THE AREA THURSDAY NIGHT. THE LOW WILL BE OFF THE SOUTHEAST COAST FRIDAY. && .NEAR TERM /THROUGH TODAY/... AN H5 SHORTWAVE TROUGH AND H85 WARM ADVECTION WERE SUPPORTS AREAS OF RAIN THIS MORNING. THE LIFT IS WEAK WITH LIMITED MOISTURE. EXPECT COVERAGE WILL REMAIN SCATTERED WITH LIGHT AMOUNTS. SURFACE WET- BULB TEMPERATURES ARE ABOVE FREEZING AREAWIDE. THE MODELS SHOW THE LIFT MOVING OUT OF THE FORECAST EARLY THIS AFTERNOON. RADAR TRENDS SUPPORT THIS TIMING. MADE MINOR ADJUSTMENTS TO THE GRIDS BASED ON CURRENT CONDITIONS. && .SHORT TERM /TONIGHT THROUGH FRIDAY/... DRY RIDGING WILL DOMINATE TONIGHT AND THURSDAY. THE NEXT CHANCE FOR RAIN WILL OCCUR THURSDAY NIGHT INTO FRIDAY MORNING. MODELS HAVE BEEN TRENDING SLOWER AND DRIER WITH THIS SYSTEM...AND PLAN ON GOING WITH ONLY CHANCE POPS. SYSTEM WILL BE MOVING EAST OF THE FORECAST AREA BY FRIDAY MORNING...SO POPS WILL ONCE AGAIN BECOME DRY BY THE AFTERNOON. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... IN THE LONGER TERM...MODELS CONTINUE TO HAVE DIFFICULTY IN TIMING AND INTENSITY. THE NEXT SYSTEM APPEARS TO SLOW DOWN SLIGHTLY...AND WILL ARRIVE SATURDAY NIGHT WITH A COLD FRONT PUSHING ACROSS THE AREA BY SUNDAY NIGHT. HAVE GONE MAINLY WITH THE GFS THIS RUN. WITH THE MODEL DIFFERENCES CONFIDENCE IN TIMING REMAINS LOW...HOWEVER THERE DOES APPEAR TO BE POTENTIAL FOR SIGNIFICANT RAINFALL AS THE COLD FRONT CROSSES THE AREA. HIGH PRESSURE WILL MOVE IN BEHIND THE FRONT WITH SKIES CLEARING AND PRECIPITATION FREE CONDITIONS THROUGH TUESDAY. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... H85 WARM ADVECTION AND H5 SHORTWAVE TROUGH WERE SUPPORTING VFR CEILINGS THIS MORNING. THERE WERE AREAS OF VERY LIGHT RAIN. THE LOW-LEVEL DRY AIR IN PLACE AND JUST WEAK LIFT WERE HELPING TO KEEP THE CEILINGS FROM LOWERING INTO THE MVFR CATEGORY. THE MODELS AND RADAR TRENDS SHOW THE SUPPORT FOR RAIN WILL END EARLY THIS AFTERNOON. THE LATEST RUC TIME-HEIGHTS SHOW LINGERING LOW-LEVEL MOISTURE AND SUPPORT KEEPING VFR CEILINGS THROUGH THE AFTERNOON. EXPECT JUST SCATTERED CLOUDS TONIGHT AS DRY RIDGING BECOMES MORE DOMINATE. EXPECT IFR OR MVFR CEILINGS ASSOCIATED WITH LOW PRESSURE TRACKING SOUTH OF THE REGION THURSDAY NIGHT INTO FRIDAY...OTHERWISE NO SIGNIFICANT AVIATION IMPACTS FORECAST DURING THE EXPECTED PERIOD. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...NONE. GA...NONE. && $$ ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 955 PM EST WED DEC 19 2007 .UPDATE... WILL BE SENDING AN UPDATE SHORTLY TO ACCOUNT FOR RADIATIONAL COOLING AND LOWER TEMPERATURES. SATELLITE SHOWS CIRRUS STREAMING OVER THE AREA BUT A LOOK OUTSIDE SUGGESTS THIS IS CURRENTLY QUITE THIN WITH MOST STARS AND MOON SHINING BRIGHTLY. LOW STRATUS DECK HAS SLOWED TO A CRAWL JUST EAST OF KSBN TO KFWA TO KDFI. HAVE LOWERED TEMPS A FEW DEGREES BELOW CURRENT READINGS IN THE WEST BUT SATELLITE SHOWS THICKER CIRRUS CANOPY OVER ILLINOIS MOVING THIS WAY. THEREFORE DROP SHOULD SLOW AND BECOME STEADY OR SLOWLY RISE LATER. MOS HAS NO CLUE AND MUCH TOO WARM AS IS LAMP GUIDANCE WHERE SKIES CLEARED. RUC40 SURFACE TEMPS THE CLOSEST BUT THOSE LOOK TOO COLD. HAVE SLOWED THE INCREASE IN CLOUDS BY A FEW HOURS AS WELL BASED ON SATELLITE TRENDS. VISIBILITIES BETWEEN 1 AND 3 MILES WHERE LOW CLOUDS HAVE CLEARED. ADDED FREEZING FOG MENTION ALL AREAS WITH LOCALLY DENSE WORDING WEST WHERE SKIES ARE PARTIALLY CLEARED. && .AVIATION FOG AND STRATUS REDEVELOPMENT THE CONCERN FOR AVIATION OVERNIGHT. SATELLITE SHOWS LOW CLOUD DECK JUST EXITING KFWA WHILE KSBN RIGHT ON BACK EDGE. NAM12 LOW LEVEL RH PROGS SUGGEST THIS CLEARING TO CONTINUE WORKING NORTHEAST SO KSBN SHOULD SEE THE LOW CLOUDS CLEAR OUT VERY SHORTLY. WILL START TAFS THAT WAY GIVEN SATELLITE OBSERVATIONS AND TRENDS. MEANWHILE...CROSSOVER TEMPS IN THE MID 20S AND CURRENT READINGS SUGGEST SITES ARE AT OR NEAR THESE VALUES. MVFR AND EVEN IFR VIS ALREADY BEING REPORTED. COMPLICATING FACTOR IS INCREASING HIGH LEVEL CLOUDS OVERNIGHT THAT MAY INHIBIT DEEP RADIATIONAL COOLING AND CONFINE VIS RESTRICTIONS TO THE HIGH END OF IFR. HAVE KEPT TAF SITES AT 2SM FOR OVERNIGHT AT THIS TIME AND WILL WATCH CLOSELY TO SEE HOW CONDITIONS BEHAVE THIS EVENING. CERTAINLY POSSIBLE FOR MUCH LOWER VIS WITH DENSE FOG GIVEN THE RECENT MELTING SNOWPACK COUPLED WITH HIGH PRESSURE AND LIGHT SURFACE WINDS WITH DRY AIR ALOFT. && .SHORT TERM... TONIGHT AND THURSDAY. FOCUS OF SHORT TERM WILL REVOLVE AROUND LOW LVL MSTR ACROSS THE AREA. OTHER THAN FAR SW AREAS...CLOUDY SKIES HAVE PREVAILED UNDER A STRONG INVERSION IN PLACE ACROSS THE REGION. AREA OF CLEARING TO THE SW HAS BEEN FINALLY WORKING NE ACROSS MAINLY SOUTHERN HALF TO 2/3RDS OF THE CWA ALLOWING FOR WHAT WILL LIKELY BE A TEMPORARY BREAK. NAM SOUNDINGS DID BEST JOB CAPTURING THE STRONG INVERSION AND APPROXIMATE HGT OF THE DECK. WILL TEND TO FOLLOW IT MORE SO WITH SOUNDINGS AS DIURNAL SWING IN TEMPS WILL ALLOW FOR INVERSION TO STRENGTHEN FURTHER. ABUNDANT LL MSTR TO REMAIN FROM SLOWLY DECREASING/SUBLIMATING SNOWPACK. HAVE TRIED TO CAPTURE CLEARING TREND AND EVENTUAL FILLING BACK IN TOWARDS MIDNIGHT. WITH CLOUD COVER IN PLACE AGAIN...HAVE INCREASED LOWS A FEW DEGREES...BUT NOT GOING TO INCREASE DRAMATICALLY AT THIS POINT UNTIL FULL MAGNITUDE OF CLOUD COVER IS VISIBLE. WILL ALSO BRING BACK IN WHAT SHOULD JUST END UP BEING NUISANCE FOG AFTER MIDNIGHT. ON THURSDAY...INVERSION LOOKS TO STILL BE HOLDING ON WITH LOW LVL MSTR NOT QUICK TO GO ANYWHERE. WILL TRY TO REMAIN OPTIMISTIC AND KEEP WITH MOSTLY CLOUDY CONDITIONS FOR NOW...BUT THREAT FOR SOLID OVERCAST STILL THERE WITH NO OVERALL CHANGE IN FLOW. TEMPS WILL BE HIGHLY DEPENDANT ON THE CLOUD COVER. IF WE CAN CLEAR OUT IN MANY LOCATIONS...TEMPS COULD EASILY CLIMB INTO THE MID OR POSSIBLY UPPER 30S DESPITE SNOWPACK. FOR NOW WILL STAY THE LOWER END AND SEE HOW THINGS PAN OUT. && .LONG TERM... THURSDAY NIGHT THROUGH WEDNESDAY... FORECAST PERIOD BEGINS WITH SYSTEM MOVING ACROSS THE TENNESSEE VALLEY IN SOUTHERN STREAM...MID LEVEL MOISTURE WILL SPREAD INTO THE AREA AS THIS SYSTEM PASSES TO OUR SOUTH. LITTLE IF ANY FORCING TO GENERATE ANY PRECIP...WOULD LEAN TOWARD DRY FCST BUT WILL SETTLE FOR BACKING DOWN TO PATCHY L/ZL- WITH NO MENTION OF POP. WAA ON FRIDAY AS SOUTHERLY FLOW DEVELOPS AHEAD OF NEXT SYSTEM. DESPITE SNOW COVER WE WERE ABLE TO GET TEMPS INTO THE MID-UPPER 30S YESTERDAY WITH SIMILAR PATTERN SO WITH WARMER 850MB TEMPS FCST FOR FRIDAY EXPECT MOST OF THE CWA TO BE NEAR 40F...WITH PATCHY HAZE/FOG EXPECTED DURING THE DAY FROM ADDED LOW LEVEL MOISTURE FROM SNOW MELT. WAA CONTINUES INTO FRIDAY NIGHT SO WILL KEEP MENTION OF AREAS FOG BUT NO SIGNAL FROM ANY OF THE MODELS FOR PRECIP SO WILL REMOVE SMALL CHANCE POPS. AS THE SYSTEM MOVES INTO THE AREA SATURDAY MODELS NOW FAVORING STRONG NORTHERN STREAM COMPONENT WHICH WOULD TAKE MAIN SFC LOW ACROSS NORTHERN GREAT LAKES/SOUTHERN CANADA...ALTHOUGH OPERATIONAL GFS STILL HANGING ONTO SOME SOUTHERN STREAM ENERGY WITH FRONTAL WAVE MOVING INTO OHIO VALLEY BY 12Z SUNDAY. THIS WILL ALLOW FOR PLENTY OF WARM AIR TO BE IN PLACE AT THE ONSET OF PRECIP...SO RAIN CHANCES REMAIN FOR SATURDAY...SATURDAY NIGHT WILL SEE COLD FRONT PASS THROUGH...NAM12 SUGGESTING PLENTY OF POST-FRONTAL MOISTURE AND WITH SHARPLY COLDER TEMPS BEHIND FRONT WILL SEE RAIN MIX WITH THEN CHANGE OVER TO SNOW BY 12Z SUNDAY. FCST SOUNDINGS SHOW ENTIRE COLUMN COOLS WITH FROPA SO NOT TOO CONCERNED WITH IP/ZR ATTM. LATEST MODEL RUNS ARE MORE AGGRESSIVE WITH MOVING SYSTEM EAST ON SUNDAY...BUT WILL HANG ONTO TO CHANCE OF SNOW SUNDAY AND TRIM BACK TO SMALL CHANCE OF LIGHT SNOW BY SUNDAY NIGHT. COULD STILL SEE SOME LINGERING LAKE EFFECT SHSN IN NORTHERN TIER MONDAY SO WILL KEEP MENTION BUT TRIM AREA A LITTLE FARTHER NORTH. LATEST OPERATIONAL GFS HAS GONE FROM HIGH PRESSURE OVER THE AREA TUESDAY TO DEEP LOW OVER KY...NOT READY TO JUMP ON THAT XMAS SURPRISE...AS ENSEMBLES SHOW THIS IS THE OUTLIER...STAYING WITH DRY FCST DAYS 6 AND 7. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ UPDATE...LASHLEY SHORT TERM/AVIATION...FISHER/LASHLEY LONG TERM...LOGSDON in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 1130 PM CST TUE DEC 18 2007 .UPDATE TO FORECAST AND AVIATION DISCUSSION... AREA OF LOW LEVEL STRATUS AND FOG SLIDING SOUTH QUICKLY OUT OF MINNESOTA...LOOKS TO CLIP THE NORTHEASTERN CORNER OF THE CWA THROUGH EARLY WEDNESDAY MORNING. LATEST RUC ANALYSIS SHOWS MAJORITY OF LOW CLOUDS SLIDING JUST TO THE EAST OF THE CWA...SO HAVE UPDATED TO INCREASE CLOUDS NEAR A KMCW TO KALO LINE THROUGH THE REMAINDER OF THE EVENING INTO THE OVERNIGHT HOURS. ALSO VISIBILITIES DROPPING TO 1 TO 3 MILES BENEATH THE LOW CLOUDS...SO BEGAN ONSET OF FZFG MENTION THIS EVENING IN THE CLOUDY AREAS. OTHERWISE REMAINDER OF FORECAST ON TRACK. .SHORT TERM /TONIGHT/... WEAK COLD FRONT OVR ERN IA AND ASSOCIATED WITH SFC LOW OVER WISCONSIN WILL CONTINUE MOVING EAST TONIGHT. NOT A LOT OF AIRMASS CHANGE BEHIND THE FRONT AS TRUE ARCTIC BOUNDARY IS STALLED ACROSS NORTH CENTRAL MN AND NORTHWEST INTO SRN CANADA. A WEAK HIGH PRESSURE RIDGE WILL CRUISE OVER IOWA TONIGHT. SO WITH AN ESSENTIALLY CLEAR SKY AND LIGHT WINDS...EXPECT TEMPERATURES TO DROP TO AT OR BELOW COLDER GUIDANCE VALUES. ALSO EXPECT THAT WITH LOW LEVEL SATURATION OCCURRING AND STRONG INVERSION JUST ABOVE THE BOUNDARY LAYER...FOG WILL LIKELY DEVELOP LATE. THERE IS THE QUESTION OF LOW CLOUDS ALSO FORMING...BUT FOR NOW WILL JUST STICK WITH THE IDEA OF FOG SINCE I AM NOT CONVINCED LOW LEVEL MOISTURE WILL BE DEEP ENOUGH TO RESULT IN CLOUDS. .LONG TERM ... THERE IS PLENTY TO MULL OVER DURING THIS PERIOD...INCLUDING THE POTENTIAL FOR SIGNIFICANT WINTER WEATHER FRIDAY NIGHT AND SATURDAY. FOR THE NEXT SEVERAL DAYS...MOS TEMPERATURE GUIDANCE CONTINUES TO HANDLE THE SNOW COVER POORLY...AND WILL CONTINUE TO KEEP THE FORECAST AT OR BELOW THE COOLEST MOS WHICH HAS GENERALLY BEEN THE MAV OR MET. A COUPLE OF WEAK SHORT WAVES ARE EXPECTED TO TRAVERSE ACROSS THE STATE WEDNESDAY NIGHT AND THURSDAY. MOISTURE REMAINS QUITE LIMITED AND WITH STRONG DOUBTS ABOUT GETTING ANY MEASURABLE PRECIPITATION...WILL KEEP POPS LIMITED TO SLIGHT CHANCE AT BEST. FREEZING DRIZZLE OR DRIZZLE STILL LOOKS TO BE THE DOMINATE WEATHER. LOOKING AHEAD TO THE WEEKEND SYSTEM...THE MODELS CONTINUE TO SHOW POOR CONSISTENCY AND HAVE PHASING ISSUES WITH NORTHERN AND SOUTHERN STREAM ENERGY. PREVIOUS RUNS OF THE EURO PHASED THE N/S UPPER LOWS AND WAS MUCH SLOWER AND STRONGER. THE PREVIOUS GFS HAD TAKEN THE SFC LOW AND PRECIPITATION FARTHER SE...BUT NOW HAS RETURNED TO LIFTING THE INITIAL SFC LOW THROUGH SE IOWA. BOTH 12Z RUNS ARE ACTUALLY SIMILAR...BOTH MORE PROGRESSIVE WITH LESS QPF...AND LOOKING LESS OMINOUS FOR WARNING CRITERIA SNOWFALL AMOUNTS. BASED ON QPF AND THERMAL PROFILES...THE GFS/ECMWF WOULD BOTH FAVOR THE NW 1/2 TO 2/3 OF THE FORECAST AREA FOR THE HEAVIER SNOWS...BUT STILL BELOW 6 INCH WARNING CRITERIA...WITH A MIX AND LESS SNOW ACROSS THE SOUTHEAST. THE 12Z GEM ALSO PROVIDES SUPPORT FOR THIS SCENARIO. THIS IS SIMILAR TO THE MODEL CONSENSUS YESTERDAY AT THIS TIME...BUT CONFIDENCE IN PRECIP TYPE/AMOUNTS/PLACEMENT IS STILL VERY LOW DUE TO THE INCONSISTENT SOLUTIONS. STILL FEEL THAT THIS SYSTEM MAY END UP BEING STRONGER AND LESS PROGRESSIVE IN LIFTING THE UPPER LOW OUT OF THE SW CONUS...SIMILAR TO WHAT THE EURO WAS SHOWING YESTERDAY. A NUMBER OF EVENTS IN THE RECENT AND MORE DISTANT PAST HAVE RESULTED IN THE HEAVIER SNOW ENDING UP FARTHER NORTHWEST THAN INITIALLY THOUGHT...AND TIME WILL TELL IF THAT WILL BE THE CASE WITH THIS EVENT. POPS WERE INCREASED ANOTHER NOTCH...ESPECIALLY FOR FRIDAY NIGHT AND SATURDAY. THERE MAY BE SOME LINGERING LIGHT SNOW/FLURRIES NORTHEAST ON SUNDAY...OTHERWISE DRY FORECAST MAINTAINED MONDAY AND TUESDAY. && .AVIATION...19/06Z LOW STRATUS AND FOG MOSTLY SKIRTING THE NORTHWESTERN CWA...AND FOR THE MOST PART SHOULD REMAIN EAST OF THE KMCW AND KALO. HOWEVER HAVE INCLUDED A TEMPO GROUP FOR THE POSSIBILITY THAT THE IFR/LIFR CEILINGS AND VSBYS MAKE IT INTO THOSE TERMINAL SITES. REMAINDER OF SITES WILL SEE MVFR/VFR CONDITIONS THROUGH THE NEXT FEW HOURS...WITH VSBYS EXPECTED TO DROP TO 1-3SM BY LATE NIGHT TOWARD SUNRISE. VFR CONDITIONS THEN EXPECTED FOR THE REMAINDER OF WED WITH INCREASING HIGH CLOUDS IN ADVANCE OF THE NEXT SYSTEM PUSHING EAST OUT OF THE ROCKIES. LIGHT NORTHWEST WINDS TO SHIFT TO THE SOUTH TO SOUTHEAST WEDNESDAY INTO WEDNESDAY NIGHT. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...MOYER LONG TERM...KINNEY AVIATION...ALBRECHT ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 750 PM CST THU DEC 20 2007 .DISCUSSION... MUCH DRIER AIR HAS FILTERED IN BEHIND A COLD FRONT/DRY LINE WHICH ACCOMPANIED OUR UPPER LEVEL STORM SYSTEM EARLY THIS MORNING. THE BOUNDARY HAS JUST ABOUT PULLED UP STATIONARY ACROSS OUR EASTERN ZONES THIS EVENING AND IS NOT EXPECTED TO MAKE MUCH MORE EASTWARD PROGRESS OVERNIGHT. WITH THE CLEAR SKIES AND HIGH DEWPOINTS ACROSS THE EAST NOT TO MENTION THE WET GROUND CONDITIONS FROM RAINFALL THIS MORNING...ALREADY STARTING TO SEE VISIBILITIES CRATER AT ELD...MLU AND AEX. FOR THIS REASON...HAVE DECIDED TO POST A DENSE FOG ADVISORY THROUGH 900 AM FRIDAY MORNING RUNNING IT GENERALLY ALONG AND EAST OF A LINE FROM HOPE AND LEWISVILLE ARKANSAS TO MINDEN...COUSHATTA AND NATCHITOCHES LOUISIANA. IF THE LATEST RUC13 DATA IS TO BE BELIEVED...THEN WE COULD SEE THIS FOG ADVECT FURTHER WEST AFTER MIDNIGHT...ENCOMPASSING MUCH OF THE REGION PRIOR TO DAYBREAK FRIDAY. OTHER SHORT TERM PROGS KEEPING ENOUGH DRY AIR OUT WEST TO PRECLUDE FOG DEVELOPMENT BUT WILL HEDGE ON THE SIDE OF CAUTION AND JUST MENTION PATCHY FOG ACROSS NORTHEAST TEXAS AND PATCHY DENSE FOG ACROSS EXTREME NORTHWEST LOUISIANA INTO THE TEXARKANA AREA AND SOUTHEAST OKLAHOMA. WOULD NOT BE SURPRISED IF WE NEED TO EXPAND THE ADVISORY FURTHER WEST LATER TONIGHT BUT WILL CROSS THAT BRIDGE IF AND WHEN IT BECOMES NECESSARY. FCST MIN TEMPERATURES AND ALL OTHER GRIDS IN LINE SO NO OTHER CHANCES NECESSARY ATTM. UPDATE AND ADVISORY OUT SHORTLY...13. && .AVIATION... WATER VAPOR IMAGERY SHOWS TROUGH AXIS ON THE EASTERN SIDE OF THE MS VALLEY...W/00Z KSHV SOUNDING SHOWING A VERY DRY AMS IN PLACE. HOWEVER...W/WET SOILS...DECOUPLING...AND ABUNDANT RADIATIONAL COOLING...EXPECT DETERIORATING CEILINGS/VSBYS TO IFR/LIFR...W/KELD ALREADY IN THE SOUP AT 02Z. LATEST RUC INDICATES SW AR AND LA MOST FAVORED FOR FOG. EXPECT CONDITIONS TO QUICKLY IMPROVE TO VFR AFTER SUNRISE. FORECAST SOUNDINGS INDICATE CONVECTIVE TEMPS FRIDAY AFTERNOON IN THE TRIPLE DIGITS...SO NO CU FIELD EXPECTED. && .PRELIMINARY POINT TEMPS/POPS... SHV 46 73 53 68 / 0 0 20 50 MLU 48 73 53 69 / 0 0 20 60 DEQ 40 69 49 61 / 0 0 10 40 TXK 47 71 53 63 / 0 0 10 50 ELD 46 73 51 70 / 0 0 10 60 TYR 42 75 54 64 / 0 0 20 30 GGG 41 74 52 67 / 0 0 20 40 LFK 41 76 52 72 / 0 0 30 50 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...DENSE FOG ADVISORY UNTIL 9 AM FRIDAY FOR THE FOLLOWING ZONES: COLUMBIA...HEMPSTEAD...LAFAYETTE...NEVADA...AND UNION AR. LA...DENSE FOG ADVISORY UNTIL 9 AM FRIDAY FOR THE FOLLOWING ZONES: BIENVILLE...CALDWELL...CLAIBORNE...GRANT...JACKSON...LA SALLE...LINCOLN...NATCHITOCHES...OUACHITA...RED RIVER...UNION LA...WEBSTER...AND WINN. OK...NONE. TX...NONE. && $$ 13/44 la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 809 PM CST WED DEC 19 2007 .DISCUSSION... WARM FRONT AS OF 02Z HAS PULLED UP STATIONARY...ALONG THE AR/LA BORDER SNAKING WESTWARD TO JUST NORTH OF MOUNT PLEASANT TEXAS. FRONT HAS BEEN IN THIS POSITION FOR THE LAST FOUR HOURS AND AS A RESULT...TEMPERATURES HAVE FALLEN OFF QUICKLY ACROSS SOUTHWEST ARKANSAS AND SOUTHEAST OKLAHOMA. HAVE LOWERED TEMPERATURES A COUPLE OF CATEGORIES NORTH OF THIS BOUNDARY BUT THE THINKING IS THAT THIS BOUNDARY MAY MOVE A LITTLE FURTHER NORTH TONIGHT BUT NOT MUCH PER 00Z RUC. HAVE ALSO ADDED PATCHY DENSE FOG WORDING ACROSS OUR NORTHERN ZONES WITH VISIBILITIES AS LOW AS 1/2 MILE AT ELD ALREADY. CONCERNING CONVECTION...LOW LEVEL JET IS JUST NOW STARTING TO CRANK OUT WEST OF THE REGION PER PALESTINE PROFILER SITE WITH AROUND 30KTS AT 5K. THIS SHOULD CONTINUE TO INCREASE OVERNIGHT WITH SHOWERS AND THUNDERSTORMS EXPECTED TO EXPAND IN COVERAGE AND INTENSITY ACROSS OUR WESTERN ZONES OVER THE NEXT FEW HOURS. DESPITE MOST OF OUR CWA BEING SOUTH OF THE STALLED BOUNDARY...FEEL LIKE ACTIVITY WILL MOSTLY BE ELEVATED IN NATURE THUS SUPPORTIVE OF A HAIL THREAT LATER TONIGHT. MODIFIED MARITIME AIRMASS WILL TRY TO COME NORTHWARD INTO OUR SOUTHERN ZONES LATER TONIGHT AND THIS COULD RESULT IN A WIND/ISOLATED TORNADO THREAT...BUT THIS ALL DEPENDS ON IF THE ACTIVITY CAN BECOME ROOTED BELOW THE BOUNDARY LAYER OR NOT. FOR NOW...HAVE BUMPED POPS TO LIKELY CATEGORY ACROSS OUR EXTREME NORTHWEST ZONES FOR LATER TONIGHT AS INITIAL ROUND OF CONVECTION WILL BE TOO CLOSE TO THIS REGION TO SPLIT HAIRS. UPDATE OUT SHORTLY...13. && .AVIATION... LATEST SURFACE OBS SHOW WARM FRONT RUNNING RIGHT ALONG THE AR/LA BORDER...W/VSBYS APPROACHING VLIFR NORTH OF THE FRONT. 00Z SHV/LCH RAOBS SHOW STEEP MID-LEVEL LRS...BUT OTHERWISE UNIMPRESSIVE. HOWEVER...KSHV VAD PROFILER SHOWS LLJ BEGINNING TO DEVELOP AHEAD OF TROUGH OVER THE TEXAS PANHANDLE...W/CONVECTION ALREADY FORMING WEST OF KLFK. THUS...EXPECT LIFR/VLIFR CEILINGS/VSBYS ALL SITES BY 06Z OR SOONER. AS TROUGH EXITS THURSDAY AFTERNOON...EXPECT SCOURING TO VFR BY 21Z ALL SITES EXCEPT KMLU/KELD. && .PRELIMINARY POINT TEMPS/POPS... SHV 59 71 43 71 / 70 40 10 10 MLU 58 71 45 70 / 70 60 10 10 DEQ 48 67 35 68 / 70 30 10 10 TXK 48 70 44 68 / 70 30 10 10 ELD 48 71 41 70 / 70 30 10 10 TYR 58 70 42 71 / 70 20 10 10 GGG 58 70 42 71 / 70 20 10 10 LFK 60 73 40 74 / 70 30 10 10 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...NONE. LA...NONE. OK...NONE. TX...NONE. && $$ 13/44 la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 936 AM EST WED DEC 19 2007 .SYNOPSIS... LOW PRESSURE WILL TRACK FROM THE GREAT LAKES TO NEAR CAPE COD TONIGHT. MEANWHILE...A TROUGH OF LOW PRESSURE WILL EXTEND BACK ACROSS NORTHERN NEW ENGLAND...SERVING AS A FOCUS FOR SNOWFALL TONIGHT AND THURSDAY. THE LOW WILL MOVE EAST OUT TO SEA THURSDAY NIGHT...WITH HIGH PRESSURE RIDGING FROM THE NORTH FRIDAY AND SATURDAY. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... FOR TODAY...THERE WILL BE TWO WAVES OF PRECIPITATION. THE FIRST...WILL BE WITH THE WEAK WARM FRONT LIFTING ACROSS THE REGION. THUS FAR THIS FRONT CAN BE SEEN ON THE IR SATELLITE WHERE MID-LEVEL WARM AIR ADVECTION HAS CAUSED A LINE OF LOW CLOUDS EXTENDING INTO THE MOUNTAINS OF NEW HAMPSHIRE AND NORTHWESTERN MAINE. EXPECT SOME LIGHT SNOW TO DEVELOP AS THIS FRONT LIFTS NORTH...WITH SNOW ACCUMULATION ONLY A DUSTING WITH THIS WEAK FEATURE. CLOUDS WILL INCREASE IN ALL AREAS THIS AFTERNOON...WITH SNOW BEGINNING IN CENTRAL MAINE AND SOUTHWESTERN NEW HAMPSHIRE...AND QUICKLY SPREADING INTO ALL AREAS BY 00Z. EXPECT PRECIPITATION TO REMAIN ALL SNOW THROUGH 00Z...WITH SNOW ACCUMULATIONS AN INCH OR LESS THROUGH 00Z. STILL...COULD BE A SOMEWHAT MESSY EVENING COMMUTE...ESPECIALLY IN AREAS WHERE SNOW BREAKS OUT FIRST. UPDATE: IT APPEARS THE TROUGH AXIS IS BEGINNING TO SET UP AT 12Z...WITH NE WINDS AT MATINICUS ROCK AND PORTLAND LNB OF AROUND 10 KTS. INLAND WINDS ARE GENERALLY NORTHERLY. ALOFT...12Z GYX SOUNDING SHOWS SSW WINDS AT 10 KTS AT 950 MB...WITH SOUTHERLY WINDS AT THE SURFACE AT CAPE COD. BASED ON THIS...LOOKS AS IF THE BOUNDARY GENERALLY RUNS FROM THE ISLES OF SHOALS BUOY...TO JUST SOUTH OF MATINICUS ROCK. THE BOUNDARY WILL ROUGHLY SERVE AS A RAIN/SNOW LINE...WITH THE BEST LIFT NORTH OF THE BOUNDARY. THIS BOUNDARY IS BEST HANDLED BY BOTH THE 06Z NAM12 AND GFS40...AND IS FORECAST TO SLOWLY LIFT NORTH THIS AFTERNOON...STALLING RIGHT ALONG THE SHORELINE THIS EVENING. FOLLOWING THIS...CURRENT ADVISORIES AND SNOWFALL AMOUNTS STILL ON TRACK. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 AM THURSDAY/... UNUSUALLY GOOD MODEL AGREEMENT FOR THIS NORLUN-TROUGH EVENT. NAM/GFS/GEM ALL SHOW SIGNIFICANT QPF FOOTHILLS SOUTHWARD. THE TROF AXIS IS EXPECTED TO SET UP ACROSS THE REGION...FOCUSING HEAVIEST SNOW ACROSS CENTRAL MAINE TONIGHT. THEN THE AXIS IS FORECAST TO SHIFT SOUTH...WITH THE BAND SHIFTING SOUTHWARD AS WELL. GIVEN THE SUBTLE NATURE OF THIS EVENT...CONFIDENCE REMAINS LESS THAN A LARGER SCALE EVENT. STILL...DYNAMICS OF A MODERATE LAPSE RATE IN THE LOWEST 5000 FT...AND A MOIST ONSHORE FLOW SUPPORT DECENT (ALTHOUGH LESS THAN THE GFS) QPFS. GENERALLY USE A NAM/GFS BLEND FOR MOST PARAMETERS...BUT DO ADJUST FOR ANTICIPATED MESOSCALE FEATURES. THE MAIN ONE IS THE COASTAL FRONT...WHICH IS LIKELY TO SET UP FROM EXETER...TO BIDDEFORD...TO JUST SOUTH OF PORTLAND...TO JUST SOUTH OF ROCKLAND. THUS...SOME BUFKIT SOUNDINGS ALONG THE COAST ARE LIKELY TOO WARM IN THE BOUNDARY LAYER. MODELS SEEM TO FOCUS QPF BULLSEYE SOMEWHERE NEAR IZG...WITH THE SOUTHERN 2/3 OF THE CWA EXPECTED TO GET .50 OR GREATER OF QPF BY THE TIME ALL IS DONE. WILL ISSUE A SNOW ADVISORY FOR THE ENTIRE CWA... MAINE AND NEW HAMPSHIRE FOOTHILLS...6 TO 9 INCHES. THE MOUNTAINS AND WESTERN NEW HAMPSHIRE...3 TO 6 INCHES. MOST OF MAINE COASTLINE...4 TO 7 INCHES. SOUTHEASTERN NEW HAMPSHIRE...3 TO 6 INCHES. COASTAL YORK AND ROCKINGHAM...2 TO 5 INCHES. EXPECT THIS TO BE A LONG LASTING EVENT...TONIGHT THROUGH THURSDAY...BUT THE BEST SNOW RATES WILL LIKELY BE FROM MIDNIGHT TONIGHT THROUGH NOON THURSDAY. STILL...WITH THE EVENT SPREAD OUT OVER A 24 HOUR PERIOD...WILL USE 24 HOUR SNOWFALL CRITERIA. THE TROF AXIS WILL FOCUS SNOWFALL...SO EXPECT SNOW TO VARY FROM LIGHT TO OCCASIONALLY HEAVY AT TIMES. ALSO...ANTICIPATE SOME AREAS MAY NEED TO BE UPGRADED TO WARNINGS...WITH 12 INCHES OF SNOW POSSIBLE WHERE FAVORABLE SNOW BANDS STALL. HOWEVER...LITTLE CONFIDENCE IN THE POSITION OF THESE BANDS...AND EXPECT AREAL COVERAGE OF THIS TO BE A SMALL PERCENTAGE OF THE CWA...SO DO NOT HAVE THE CONFIDENCE TO ISSUE WARNINGS AT THIS TIME. && .LONG TERM /THURSDAY THROUGH TUESDAY/... FOLLOWING SIMILAR THOUGHTS TO WED NIGHT FROM THE SHORT TERM SECTION. WILL BE FOLLOWING THE HIER RESOLUTION...MESOSCALE MODEL TRENDS ON THURSDAY...NAM12/13KM DEV RUC/STONY BROOK MM5...FOR THURSDAY...WHICH ARE IN TURN SUPPORTED ON A LARGER SCALE BY GFS/GEM/HPC WINTER WX DESK. THIS SHIFTS AXIS OF HEAVIEST SNOW FROM PWM-IZG AND POINTS EAST DURING THE MORNING...TO CON-SFM AND POINTS S BY AFTERNOON...AS FLOW TURNS FROM ESE-NNE. SO...HAVE STARTED THE DAY WITH CAT POPS IN ALL BUT THE MTNS...BUT BACKED OFF ON POPS E OF THAT PWM-IZG LINE LATER IN THE DAY. AGAIN...SOME DEVIATION IN HEAVIEST SNOW AXIS REMAINS A DISTINCT POSSIBILITY. ALSO AS WINDS TURN MORE NE...COULD SEE COASTAL MAKE SOME INROADS TO THE SW...AND COULD SEE A CHANGE TO RA IN YORK AND ROCKINGHAM COUNTIES...AND PERHAPS EVEN SERN CUMBERLAND COUNTY /CAPE ELIZABETH-DOWNTOWN PORTLAND AREA/. BY THU EVENING...ACCUMULATION SNOW SHOULD HAVE ENDED IN ALL BUT EXTREME SRN ZONES...AND THAT WILL WIND DOWN QUICKLY AS WELL AFTER SUNSET. AIR BEHIND THIS SYSTEM NOT QUITE AS COLD AS WE/VE SEEN IN THE LAST FEW WEEKS...AND MAX TEMPS FRI/SAT WILL RUN NEAR NORMAL...WITH LOWS SLIGHTLY BLO NORMALS...THANKS TO SNOW COVER. NEXT SYSTEM ARRIVES SAT NIGHT...AND GFS/EURO IN AGREEMENT ON A TRACK WELL TO THE WEST...WHICH WOULD LIKELY LEAD TO EITHER A SN/FZRA TO RA EVENT...OR JUST RAIN...FOR SAT NIGHT INTO SUN EVE. MAX TEMPS ON SUN RISE ABOVE NORMAL. SOME SEASONALLY COLD AIR WILL MOVE BACK IN ON MONDAY...WITH ONLY UPSLOPE SHSN EXPECTED MON-TUE. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... EXPECT VFR CONDITIONS THROUGH 12Z THIS MORNING...WITH CLOUDS SPREADING IN ABOVE 3000 FT. BETWEEN 12Z AND 18Z A BIT MORE UNCERTAIN...AS FLOW BECOMES ONSHORE ARE MARGINALLY CONFIDENT THAT MVFR CIGS WILL MOVE INTO PWM-AUG. THEN SNOW WILL MOVE IN BETWEEN 18Z - 00Z...WITH LOWERING CIGS AND VSBY AT ALL SITES. CONDITIONS WILL BE VARIABLE BEYOND THIS...WITH TAFS FORECAST IN THE MIDDLE OF THE VARIABLE CONDITIONS. IFR/LIFR IN SN REMAINS POSSIBLE INTO THU EVE...WITH VFR EXPECTED FRI/SAT. ANOTHER SYSTEM...WHICH WILL LKLY PRODUCE MOSTLY RAIN...COULD PRODUCE ANOTHER ROUND OF IFR SAT NIGHT AND SUN. && .MARINE... IN THE SHORT TERM...WILL LIKELY NEED A SMALL CRAFT ADVISORY FOR LATE TONIGHT. NAM/GFS NOW AGREE ON LOW PRESSURE PASSING SOUTH TONIGHT...WITH A TIGHTENING NE GRADIENT. GO A BIT ABOVE GUIDANCE...BUT STILL EXPECT SCA CONDITIONS TO HOLD OFF UNTIL LATE TONIGHT...WHEN WINDS SHIFT MORE EASTERLY. UPDATED WINDS TO USE 06Z MODEL DATA...WHICH CAPTURES THE NE FLOW ACROSS MOST OF OUR WATERS. EASTERLY WINDS WILL APPROACH GALES ON THU...AND SHIFT NE THU NIGHT...BEFORE DIMINISHING BY FRI MORNING. GALES WILL AGAIN BE POSSIBLE ON SUNDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...SNOW ADVISORY FROM 4 PM THIS AFTERNOON TO 5 PM EST THURSDAY FOR MEZ007>009-012>014-018>028. NH...SNOW ADVISORY FROM 4 PM THIS AFTERNOON TO 5 PM EST THURSDAY FOR NHZ001>010-013-014. MARINE...NONE. && $$ me AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1235 AM EST WED DEC 19 2007 UPDATED AVIATION DISCUSSION .SHORT TERM (TONIGHT THROUGH THU)... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR PRECIPITATION SATURDAY THROUGH SUNDAY. WATER VAPOR IMAGERY AND RUC SHOWING A CLOSED LOW AND ASSOCIATED TROUGH MOVING OVER EASTERN ONTARIO AND A RIDGE SHIFT INTO THE WESTERN ONTARIO AND MINNESOTA. ANOTHER TROUGH IS DEVELOPING OVER MIDDLE HIGH PLAINS. SURFACE ANALYSIS DEPICTS A LOW OVER THE LOWER GREAT LAKES WITH A BROAD HIGH OVER THE OHIO RIVER VALLEY. A RIDGE RUNS FROM THE HIGH NORTH THROUGH WISCONSIN AND THE WEST PART OF THE FORECAST AREA. A STATIONARY FRONT STRETCHES FROM NEW ENGLAND THROUGH THE LOW TO THE ARROWHEAD OF MINNESOTA. A WARM FRONT RUNS FROM IOWA NORTHWEST TO SOUTHEAST SASKATCHEWAN THEN WEST TO CENTRAL BRITISH COLUMBIA. A LARGE HIGH BLANKETS THE ROCKIES. THE MID LEVEL RIDGE WILL SLIDE OVER THE FORECAST AREA OVERNIGHT WHICH WILL CAUSE THE WINDS TO DROP OFF AND BACK SOUTH. THE TROUGH THAT IS DEVELOPING OVER THE HIGH PLAINS WILL SWEEP ACROSS THE CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI RIVER VALLEY ON THURSDAY. THE WISCONSIN RIDGE WILL SHIFT OVER THE FORECAST AREA BY THIS EVENING AND INTO EASTERN ONTARIO ON THURSDAY. 850MB TEMPERATURES OF AROUND -7C OVER EASTERN LAKE SUPERIOR AND NORTHWEST WINDS WILL SUPPORT SOME LAKE EFFECT SNOW ENHANCEMENT OVER THE PART OF THE EASTERN U.P. TONIGHT. THERE SHOULD BE SOME LIMITED CLEARING TONIGHT AND RADIATIONAL COOLING WILL BRING THE TEMPERATURES DOWN TO THE DEW POINT. SOUTHERLY WINDS WILL ALSO HELP PUSH THE TEMPERATURES UP TO AROUND FREEZING ON THURSDAY. SOUNDING DATA SHOWING DRY AIR AND AN INVERSION SETTLING DOWN TO 950MB OVER THE FORECAST WHICH TOGETHER COULD PRODUCE SOME PATCHY FOG TONIGHT THIS WILL BURN OFF ON THURSDAY WITH SURFACE WARMING. WEAK SHORTWAVE MOVING THROUGH WESTERN LAKE SUPERIOR ON THURSDAY COULD PRODUCE SOME LIGHT SNOW MAINLY OVER THE WESTERN. .LONG TERM (THU NIGHT THROUGH NEXT WED)... MAIN FORECAST CONCERN REMAINS ON POTENTIAL FOR HEAVY SNOW SAT NIGHT INTO SUN. THU NIGHT THROUGH SAT...SOUTHERLY WINDS WILL PREVAIL UNTIL A LOW PRESSURE TROUGH SWINGS ACROSS UPPER MI ON SAT (12Z ECMWF IS SLOWER THAN 12Z GFS). INCREASED HIGH TEMPS ON FRIDAY TO ACCOUNT FOR WAA OUT OF THE SSE. MAY NEED TO INCREASE HIGHS MORE IN FUTURE FORECASTS. AS FAR AS PCPN TYPE GOES...MAINLY KEPT WITH GOING FORECAST. IT LOOKS LIKE UPSLOPE AREAS WITH A SSE WIND (WESTERN AND CENTRAL U.P.) WILL SEE BETTER CHANCE OF FREEZING DRIZZLE...AND OTHER AREAS MAY SEE DRIZZLE. FCST SOUNDINGS IN BUFKIT FOR IRON MOUNTAIN ON FRIDAY SHOW GREATER VALUES OF OMEGA AT LOW LEVELS THAN IN MQT AND HOUGHTON. THE TEMPS IN IRON MOUNTAIN REMAIN NEARLY ISOTHERMALLY AROUND 0C UP THROUGH 850MB. THE MAIN SATURATED LAYER ALSO OCCURS AT TEMPS GREATER THAN -10C...SO DRIZZLE IS ALMOST CERTAIN. FOR MQT AND HOUGHTON...POSITIVE OMEGA VALUES UP TO +5...MID-LEVEL DRY AIR...AND SFC TEMPS AROUND 0C LEAD TO UNCERTAINTY IN THE CHANCES OF FREEZING DRIZZLE VS. SNOW VS. NO PCPN AT ALL FOR FRI. CHANCES FOR PCPN INCREASE ACROSS ALL OF THE U.P. BY SAT MORNING AS THE LOW PRESSURE SYSTEM APPROACHES THE REGION. SAT NIGHT THROUGH WED...MODELS HAVE BECOME IN MUCH BETTER AGREEMENT WITH THE END OF THE WEEKEND SYSTEM...AND AT LEAST UP IN THE GREAT LAKES AREA...ARE IN PRETTY GOOD AGREEMENT THROUGH WED. AT 00Z SUN...06Z MODELS PROG THE UPPER LOW OVER SASKATCHEWAN ON FRI TO DROP DOWN INTO NORTHERN MN ON SAT...WHILE A SHRTWV TROUGH MOVES FROM NEW MEXICO UP INTO SW MISSOURI. THERE STILL REMAINS ISSUES WHETHER OR NOT THE SHRTWV AND UPPER LOW WILL PHASE TOGETHER...AS NOTED BY THE 06Z GFS KEEPING THEM UNPHASED. WILL CONTINUE TO SIDE WITH THE PHASED IDEA OF THE ECMWF/CANADIAN...WHICH PHASE THEM TOGETHER NEAR LAKE HURON ON SUNDAY. THIS RESULTS IN A 1007MB LOW OVER ILLINOIS SAT EVENING TO LIFT N AND DEEPEN RAPIDLY...REACHING NORTHERN LAKE HURON AT 12Z SUN WITH A PRESSURE AROUND 990MB. THE LOW WILL THEN TRACK UP INTO NE ONTARIO LATER SUN AND INTO QUEBEC ON MONDAY. FOR UPPER MI...THE TRACK IS FAVORABLE FOR HEAVY SYNOPTIC SNOW...WITH Q-VECTOR CONVERGENCE PROGS SUGGESTING FROM THE NORTHERN U.P. UP TO JAMES BAY. LOOKS LIKE TOO THAT AT LEAST AFTER 00Z SUN...MUCH OF THE PCPN WILL SWITCH OVER TO SNOW AS COLD AIR MOVES IN. THERE ARE TWO OTHER ASPECTS OF THIS EVENT TOO. AS THE UPPER LOW APPROACHES SAT NIGHT...850MB TEMPS PLUMMET COMPARED TO 12Z SAT...WITH READINGS DROPPING TO -8C EAST TO -15C WEST BY 12Z SUN. THUS LAKE ENHANCEMENT LOOKS LIKE A PRETTY GOOD BET. GIVEN THE LOW TRACK...SURFACE AND 850MB WIND FIELDS SUGGEST RIGHT NOW THAT THE BEST ENHANCEMENT IS OVER NORTHWEST SNOW-BELTS. THE OTHER ASPECT TO THIS SYSTEM IS WIND...WITH THE 00Z ECMWF SHOWING 850MB WINDS INCREASING TO 45-50 KT BY 00Z MON. THUS SOME BLOWING AND DRIFTING SNOW IS LIKELY... BEGINNING SAT NIGHT. SYNOPTIC SNOW SHOULD CHANGE OVER TO A PURE LAKE EFFECT REGIME LATER SUN NIGHT AS THE UPPER AND SURFACE LOWS PULL AWAY...WHILE 850MB TEMPS SLOWLY WARM TO AROUND -10C BY 12Z MON. WILL DRY OUT CHRISTMAS EVE A BIT MORE NOW...SINCE MOST MODELS PROG UPPER AND SURFACE RIDGING TO MOVE INTO THE CWA. ONLY LAKE EFFECT CHANCES WILL REMAIN IN NW SNOWBELTS. SHOULD THE SCENARIO OF THE UPPER LOW AND SHRTWV NOT PHASE TOGETHER AS SHOWN BY THE 06Z GFS...THE EVENT WILL TURN OUT WITH MORE PURE LAKE EFFECT SNOW FOR WEST AND NW SNOWBELTS...ALONG WITH BLOWING SNOW. THUS...GIVEN THE DIFFERENCES BETWEEN THE ECMWF AND GFS...ANYONE TRAVELING THIS WEEKEND SHOULD CONTINUE TO MONITOR LATER FORECASTS. FOR CHRISTMAS EVE NIGHT INTO CHRISTMAS DAY...THE WEATHER LOOKS PRETTY TRANQUIL...WITH ONLY A WEAK SHRTWV TROUGH CROSSING CHRISTMAS EVE NIGHT. THE ECMWF AND GFS DEPICT LITTLE IF ANY PCPN FROM THIS...AND THUS WILL NOT INCLUDE ANY IN THE FORECAST. ALSO...WITH SW FLOW DURING THIS PERIOD AND 850MB TEMPS CLIMBING TO -4 TO -6C BY 00Z WED...NO NEED FOR ANY LAKE EFFECT PCPN CHANCES. A NORTHERN STREAM SHRTWV TROUGH IS SHOWN BY THE GFS AND ECMWF TO APPROACH THE CWA TUE NIGHT AND WED. WILL BRING IN SOME SNOW CHANCES ON TUE NIGHT OVER WESTERN LAKE SUPERIOR...THEN ACROSS THE CWA ON WEDNESDAY AS THE TROUGH MOVES THROUGH AND 850MB TEMPS DROP TO GENERATE LAKE EFFECT SNOW. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... LOOK FOR MVFR CIGS AT BOTH LOCATIONS TO LOWER TO IFR AS FLOW BECOMES SE (UPSLOPE AT BOTH LOCATIONS) AND DRYING/SUBSIDENCE ALOFT KEEPS MOISTURE TRAPPED AT LOW-LEVELS. MOIST UPSLOPE FLOW MAY ALSO CONTRIBUTE TO TEMPORARY IFR VBSYS LATE TONIGHT AT KSAW. EXPECT SOME IMPROVEMENT AT KCMX BY LATE THU MORNING WHERE FLOW WILL SHIFT SSE WHICH IS NOT AS FAVORED AN UPSLOPE DIRECTION. SSE FLOW SHOULD CONTINUE TO KEEP KSAW SOCKED IN UNDER MVFR CIGS. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... THE PRESSURE GRADIENT UNDER A RIDGE THAT EXTENDS FROM FROM QUEBEC INTO NORTHERN LAKE SUPERIOR WAS PRODUCING LIGHT NE TO N WINDS. AS THE RIDGE MOVES OFF TO THE EAST ON THURSDAY...SOUTHERLY FLOW WILL INCREASE ON LAKE SUPERIOR WITH WINDS TO NEAR 30 KT BY THURSDAY NIGHT INTO EARLY FRIDAY. A STRONG SURFACE LOW IS EXPECTED TO MOVE TOWARDS THE UPPER GREAT LAKES ON SATURDAY. DEPENDING ON THE TRACK AND TIMING...GALE FORCE WINDS COULD DEVELOP FROM LATE SATURDAY INTO SUNDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...DLG LONG TERM...AJ/MRC AVIATION...VOSS MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1152 PM EST WED DEC 19 2007 .AVIATION...LOW LEVEL MOISTURE REMAINING TRAPPED BELOW INVERSION LEADING TO WIDESPREAD MVFR STRATUS DECK ACROSS THE TAF SITES THIS MORNING...ESPECIALLY OVER KAPN AND KPLN. MIST FORMATION A LITTLE SLOW GETTING GOING THIS EVENING AND HAVE BACKED OFF THIS POSSIBILITY SOMEWHAT...ONLY SHOWING A SLIGHT DROP IN VISIBILITIES. HAVE GONE A LITTLE MORE OPTIMISTIC TOMORROW...HAVING SKIES SCATTER OUT DURING THE MORNING/EARLY AFTERNOON...LEADING TO VFR CONDITIONS. WINDS WILL REMAIN LIGHT AND VARIABLE TONIGHT...BECOMING LIGHT SOUTHEAST THURSDAY. MSB && .UPDATE...ISSUED 955 PM PER 11U-3.9U SATELLITE IMAGERY...EXPANSIVE SUB 2KFT STRATUS DECK OVER THE NORTHERN LAKES REGION THIS EVENING AS REMNANT LOW LEVEL MOISTURE (WITH SOME ADDITIONAL NORTHWEST FLOW MOISTURE FLUX FROM THE BIG LAKES) REMAINS TRAPPED BELOW STRENGTHENING SUBSIDENCE INVERSION. JUST ENOUGH OVER WATER INSTABILITY TO PRODUCE SCATTERED FLURRIES OVER FAVORED NORTHWEST FLOW AREAS OF NORTHERN LOWER MICHIGAN. HOWEVER...EXPECT THIS TO DIMINISH DURING THE NEXT SEVERAL HOURS AS WAA OVERSPREADS THE LAKES. EXPECT CLOUD SHIELD TO PRETTY MUCH REMAIN STATUS QUO OVER MUCH OF THE AREA...WITH THE EXCEPTION OF FAR SOUTH PARTS OF THE AREA WHERE MODEL PROGS SHOW JUST ENOUGH DRYING TO POTENTIALLY SCOUR OUT SOME OF THE CLOUD DECK. NOCTURNAL TEMPERATURE RESPONSE RATHER SLOW ONCE AGAIN THIS EVENING...WITH TEMPERATURES SEVERAL DEGREES WARMER THAN INITIALLY PROGGED. GIVEN THIS SLOWER THAN ANTICIPATED DROP...WILL GO AHEAD AND BUMP TEMPERATURES UP A COUPLE DEGREES ACROSS THE BOARD. OTHERWISE...STILL EXPECTING PATCHY/AREAS OF FOG DEVELOPMENT WITH FURTHER BOUNDARY LAYER COOLING. RECENT BELLAIRE OBSERVATION THAT TEMPORARY DROPPED TO A QUARTER MILE IN FOG ADDS CONFIDENCE TO THIS SCENARIO. BESIDES AFOREMENTIONED TEMPERATURE ADJUSTMENT...REST OF FORECAST IN GREAT SHAPE WITH LITTLE CHANGES WARRANTED. UPDATED GRIDS/NEARSHORES/ZONES OUT SHORTLY. MSB && .DISCUSSION...ISSUED 400 PM LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW SHORTWAVE TROUGHING ACROSS THE GREAT LAKES WITH AN ASSOCIATED SURFACE LOW MOVING ACROSS SE ONTARIO. WEAK SURFACE TROUGH EMANATING FROM THIS LOW IS EXTENDING ACROSS THE STRAITS REGION...BUT APPEARS TO BE LOOSING ITS INFLUENCE OVERALL ACROSS NORTHERN MICHIGAN. CONVERGENCE ALONG THIS TROUGH AND GENERAL CYCLONIC FLOW HAS HELPED MAINTAIN IFR TO MVFR CLOUD DECK ACROSS THE AREA...BUT SHALLOW AND MARGINAL OVER-LAKE INSTABILITY HAS NOT BEEN ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS WITHIN NW FLOW REGIMES. RADAR RETURNS ARE REALLY SPOTTY AND LIGHT AT THIS HOUR WITH PERHAPS ONLY FLURRIES OR EVEN LIGHT DRIZZLE PRESENT AS SFC TEMPS HAVE WARMED ABOVE FREEZING THIS AFTERNOON. SURFACE RIDGE AXIS UPSTREAM OVER WISCONSIN WILL HAVE ITS SIGHTS SET ON NORTHERN MICHIGAN OVERNIGHT...BUT STILL PLENTY OF LOW CLOUDS AND FOG RESIDE FROM NORTHERN MICHIGAN ON WEST TO THE RIDGE AXIS. LOW LEVEL CLOUDS CLEAR OUT TO THE WEST OF THE RIDGE AXIS...BUT MID-LEVEL WARM ADVECTION CLOUDS ALREADY PUSHING EAST INTO THE UPPER MIDWEST. CLOUDS AND TEMPS ARE THE MAIN FORECAST CONCERNS TONIGHT. TONIGHT...SURFACE LOW WILL CONTINUE TO PUSH OFF TO THE EAST INTO THE NEW ENGLAND STATES WHILE THE LOW LEVEL RIDGE AXIS BUILDS IN ACROSS NORTHERN MICHIGAN OVERNIGHT. PRIOR TO THE ARRIVAL OF THE RIDGE AXIS...LIGHT NORTHWEST WINDS COMBINED WITH SHALLOW OVER-WATER INSTABILITY (LAKE-900MB TEMP DIFFERENCE AROUND -10C) WILL SPELL SCT LAKE EFFECT FLURRIES IN THE SNOWBELTS DURING THE EVENING. OTHERWISE...INCREASING SHORTWAVE RIDGING ALOFT WILL PROMOTE DRYING IN THE MID-LEVELS AND DECREASING INVERSION HEIGHTS. LOW LEVEL MOISTURE REALLY DOES NOT HAVE ANYWHERE TO GO OVERNIGHT SINCE THE MOISTURE IS TRAPPED BENEATH THE INVERSION AND LOW LEVEL ADVECTIONS WILL BE RATHER LIGHT. NAM12 925-850MB RH DETAILS SOME DRYING TAKING PLACE IN THE WESTERN ZONES...BUT THAT MAY BE A FUNCTION OF LOWERING INVERSION HEIGHTS AND NOT INDICATIVE OF THE ACTUAL AMOUNT OF LOW CLOUDS THAT ARE PRESENT. PLENTY OF LOW CLOUDS UPSTREAM NEAR THE SURFACE RIDGE AXIS ACROSS WISCONSIN...IN ADDITION TO ONSHORE AND UPSLOPE FLOW WITH THE NW WINDS AND A LINGERING LOW LEVEL CONVERGENCE AXIS THAT SETS UP ACROSS NORTHEAST LOWER AND EASTERN UPPER...AND EVAPORATIVE COOLING AT THE TOP OF THE LOW LEVEL MOIST LAYER SUPPORTS GOING MOSTLY CLOUDY TO CLOUDY THE ENTIRE NIGHT...WITH LOWERING OF THE LOW LEVEL CLOUD BASE. WITH COOLING OF THE BL AND ADDED MOISTURE TO THE BL FROM ABOVE FREEZING SURFACE TEMPS THE PAST TWO AFTERNOONS...PATCHY FOG SHOULD DEVELOP POSSIBLY BECOMING MORE WIDESPREAD ACROSS THE HIGHER TERRAIN DEPENDING UPON HOW MUCH CLOUD BASES LOWER. LOWS WILL RANGE FROM THE UPPER TEENS NEAR CAD AND HTL TO THE MID 20S ALONG THE GREAT LAKES SHORELINES. MPC THURSDAY...WEAK CONVERGENCE AXIS ACROSS NRN LAKE HURON WILL WANE AS SFC RIDGE AXIS SLIDES EAST OF THE REGION IN THE MORNING. TRAPPED LOW CLOUDS ASSOCIATED WITH THIS TROUGH MAY BREAK APART FOR A BRIEF TIME IN THE MORNING...BUT AS WINDS TURN AROUND TO THE SOUTH WITH CONTINUING SHALLOW OVERLAKE INSTABILITY...CLOUDS SHOULD FILL BACK IN ACROSS EASTERN UPPER. ELSEWHERE...SHALLOW/SUB 1500KFT MOISTURE WITH ADDED SFC MOISTURE FROM SNOWMELT...WILL KEEP AREAS OF FOG AND LOW CLOUD AROUND FOR A GOOD DEAL OF THE MORNING. WONDERING HOW MUCH OF THE LOW CLOUD AND FOG WILL ACTUALLY GET TRAPPED IN FOR MUCH OF THE DAY. THIS ONE IS A TOUGH CALL. THERE WILL BE 925 MB WARM ADVECTION THAT INCREASES THROUGH THE DAY...AND WILL LIKELY BRING SOME PARTLY CLOUDY SKIES TO THE SW CWA BY AFTERNOON. OVERALL...BELIEVE THAT A MOSTLY CLOUDY FORECAST WITH LINGERING AREAS OF FOG INTO THE EARLY AFTERNOON IS THE BEST CALL...ESPECIALLY WITH MID TO UPPER LEVEL CLOUDS ADVANCING ITO THE CWA IN THE AFTERNOON. HIGHS AGAIN IN THE LOW TO MIDDLE 30S. THURSDAY NIGHT...WITH THE CONTINUED MILD TEMPERATURES...MORE SNOWMELT WILL CONTINUE TO CREATE QUITE THE SOUPY BL. WOULD NOT BE SURPRISED TO SEE AT LIGHT FOG NEVER REALLY ERODING FROM THURSDAY AFTERNOON...AND JUST CONTINUE INTO THURSDAY NIGHT. DIFFICULT TO DISCERN HOW MUCH MID/UPPER CLOUD WILL BE AROUND. MID LEVEL WEAK WARM ADVECTION/ISENTROPIC UPGLIDE (290-295K) PERSISTS THROUGH THE NIGHT...BUT WEAK MID LEVEL SHORTWAVE DEPARTS EAST BY 12Z WITH SOME MID LEVEL RIDGING. THIS COULD ALLOW FOR SOME DRIER AIR ALOFT TO ARRIVE LATE...HELPING TO PROMOTE THICKENING FOG. EITHER WAY...FOG IN SOME FASHION WILL BE AROUND...AND WHETHER OR NOT AREAS OF/PATCHY IS USED CAN BE SAVED FOR TOMORROW`S FORECAST PACKAGE. AM NOT EXPECTING MUCH OF A TEMP FALL UNDER THE CLOUDS/WARM ADVECTION...LOWS GENERALLY IN THE MIDDLE 20S CAN BE EXPECTED. FRIDAY AND FRIDAY NIGHT...HEIGHTS CONTINUE TO RISE IN THE MID LEVELS AS SRN/NRN JET STREAM ENERGY RIPS INTO THE ROCKIES. THE SOUTHERLY FLOW ACROSS THE GREAT LAKES INCREASES RESULTING IN BETTER/STRONGER WARM AND MOIST AIR ADVECTION. WINDS OF DEEPER H8-H5 MOISTURE SWINGS THROUGH THE CWA FRIDAY. FORECAST SOUNDINGS NO INDICATIVE OF ANY MEASURABLE PRECIPITATION...BUT RATHER LOW LEVEL MOISTURE THICKENING TO NEAR 750MB...ALL WARMER THAN -10C. THIS IS LOOKING MORE AND MORE LIKE A DRIZZLE SCENARIO...HINTED AT YESTERDAY. WILL BRING AREAS OF DRIZZLE INTO THE REGION STARTING FRIDAY AFTERNOON...THEN PROGRESSING THROUGH ALL OF THE CWA FRIDAY NIGHT. OF COURSE...FOG WILL ACCOMPANY THE DRIZZLE. AS FAR AS TEMPS...MID TO UPPER 30S FOR HIGHS ON FRIDAY WITH NEAR STEADY TEMPERATURES THROUGH THE NIGHT. FEEL AS IF ALL AREAS WILL BE ABOVE 32F...SO NO NEED ATTM TO MENTION FREEZING DRIZZLE. SATURDAY...THERE ARE SOME COMMONALITIES IN THE MODELS IN THIS TIME PERIOD. NRN AND SRN STREAM ENERGY WORK THEIR WAY NEAR THE MISSISSIPPI VALLEY...REMAINING SEPARATE SYSTEMS WITH NO APPARENT PHASING (YET?). THE MORNING...IF TIMING IS CORRECT...WILL START OFF DRIZZLY AND FOGGY...BEFORE SFC LOW PRESSURE WORKS INTO THE WESTERN GREAT LAKES...ALONG WITH FORCING FROM SHORTWAVES. WILL KEEP THIS PERIOD SORT OF GENERAL. WILL GO WITH LIKELY RAIN FOR NRN LOWER AS AIR MASS LOOKS TO STAY WARM. LEFT A MIX IN FOR EASTERN UPPER...AND IN LINE WITH NEIGHBORING OFFICES. THESE DETAILS WILL BECOME CLEARER TOMORROW. SATURDAY NIGHT ONWARD...BOY...STILL LOOKING LIKE A COMMON SOLUTION BETWEEN THE MODELS IS JUST A LITTLE TOO FAR AWAY. OVERALL CONSENSUS IS TO STAY WITH THE ECMWF...AS THE GFS KEEPS THE TWO JET BRANCHES SEPARATE. THE 18Z NAM HAS NOW ALLOWED FOR THE TWO BRANCHES TO PHASE TOGETHER...SUCH AS THE 12Z ECMWF. THIS SCENARIO WOULD PULL THE EXPECTED STRONG STORM SYSTEM FURTHER BACK TO THE NW...WHILE RAPIDLY DEEPENING THE SFC LOW. AREAS OF RAIN WOULD PERSIST ACROSS THE NE CWA INTO THE EVENING WHILE STRONG COLD ADVECTION BLOWS IN FROM THE SW. THERE ARE JUST TOO MANY UNCERTAINTIES STILL. FOR AT LEAST ONE MORE TIME...WILL GO WITH RAIN AND SNOW IN THE EVENING...MOST AREAS...THEN CHANGE TO ALL SNOW OVERNIGHT WITH WINDS BECOMING QUITE BRISK SUNDAY/SUNDAY NIGHT). EXPECT CHANGES TO THIS FORECAST AS MORE DETAILED TIMING/STRENGTH AND EVOLUTION OF THIS STORM WILL COME IN DUE TIME. DID INCREASE CHANCES FOR PRECIPITATION TO LIKELY. THAT LOOKS LIKE THE SAFEST BET. THE POTENTIAL FOR HAZARDOUS TRAVEL IS CERTAINLY STILL THERE OVER THE WEEKEND PRIOR TO THE CHRISTMAS HOLIDAY...SO STAY TUNED FOR THE DETAILS TO ARRIVE IN LATER FORECASTS. A RATHER BRIEF PERIOD OF LAKE EFFECT SNOWS ARE EXPECTED ON THE BACKSIDE OF THIS STORM SYSTEM AS IT PULLS EAST SUNDAY NIGHT INTO MONDAY. QUITE A BIT OF DRY AIR IS ACTUALLY FORECAST TO SPREAD IN BY MONDAY NIGHT. SMD && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 624 PM EST WED DEC 19 2007 .AVIATION...WEAK NORTHWEST FLOW LAKE MICHIGAN MOISTURE FLUX TRAPPED BENEATH STRONG INVERSION LEADING TO EXTENSIVE MVFR CIGS/VISIBILITIES IN LOW CLOUDS AND MIST. EXPECT PRETTY MUCH STATUS QUO INTO THE MORNING HOURS...WITH PERHAPS A LOWERING IN BOTH CIGS/VISIBILITIES OVERNIGHT AS INVERSION HEIGHT LOWERS AND BOUNDARY LAYER COOLS. MODEL MOISTURE PROGS SHOW GOOD POTENTIAL FOR MIXING OUT OF THE LOW CLOUD DECK THURSDAY MORNING/AFTERNOON OVER KPLN AND KTVC...WITH ABUNDANT LOW LEVEL MOISTURE LINGERING AT KAPN. WINDS WILL REMAIN LIGHT THROUGH THE PERIOD. MSB && .DISCUSSION...ISSUED 400 PM LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW SHORTWAVE TROUGHING ACROSS THE GREAT LAKES WITH AN ASSOCIATED SURFACE LOW MOVING ACROSS SE ONTARIO. WEAK SURFACE TROUGH EMANATING FROM THIS LOW IS EXTENDING ACROSS THE STRAITS REGION...BUT APPEARS TO BE LOOSING ITS INFLUENCE OVERALL ACROSS NORTHERN MICHIGAN. CONVERGENCE ALONG THIS TROUGH AND GENERAL CYCLONIC FLOW HAS HELPED MAINTAIN IFR TO MVFR CLOUD DECK ACROSS THE AREA...BUT SHALLOW AND MARGINAL OVER-LAKE INSTABILITY HAS NOT BEEN ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS WITHIN NW FLOW REGIMES. RADAR RETURNS ARE REALLY SPOTTY AND LIGHT AT THIS HOUR WITH PERHAPS ONLY FLURRIES OR EVEN LIGHT DRIZZLE PRESENT AS SFC TEMPS HAVE WARMED ABOVE FREEZING THIS AFTERNOON. SURFACE RIDGE AXIS UPSTREAM OVER WISCONSIN WILL HAVE ITS SIGHTS SET ON NORTHERN MICHIGAN OVERNIGHT...BUT STILL PLENTY OF LOW CLOUDS AND FOG RESIDE FROM NORTHERN MICHIGAN ON WEST TO THE RIDGE AXIS. LOW LEVEL CLOUDS CLEAR OUT TO THE WEST OF THE RIDGE AXIS...BUT MID-LEVEL WARM ADVECTION CLOUDS ALREADY PUSHING EAST INTO THE UPPER MIDWEST. CLOUDS AND TEMPS ARE THE MAIN FORECAST CONCERNS TONIGHT. TONIGHT...SURFACE LOW WILL CONTINUE TO PUSH OFF TO THE EAST INTO THE NEW ENGLAND STATES WHILE THE LOW LEVEL RIDGE AXIS BUILDS IN ACROSS NORTHERN MICHIGAN OVERNIGHT. PRIOR TO THE ARRIVAL OF THE RIDGE AXIS...LIGHT NORTHWEST WINDS COMBINED WITH SHALLOW OVER-WATER INSTABILITY (LAKE-900MB TEMP DIFFERENCE AROUND -10C) WILL SPELL SCT LAKE EFFECT FLURRIES IN THE SNOWBELTS DURING THE EVENING. OTHERWISE...INCREASING SHORTWAVE RIDGING ALOFT WILL PROMOTE DRYING IN THE MID-LEVELS AND DECREASING INVERSION HEIGHTS. LOW LEVEL MOISTURE REALLY DOES NOT HAVE ANYWHERE TO GO OVERNIGHT SINCE THE MOISTURE IS TRAPPED BENEATH THE INVERSION AND LOW LEVEL ADVECTIONS WILL BE RATHER LIGHT. NAM12 925-850MB RH DETAILS SOME DRYING TAKING PLACE IN THE WESTERN ZONES...BUT THAT MAY BE A FUNCTION OF LOWERING INVERSION HEIGHTS AND NOT INDICATIVE OF THE ACTUAL AMOUNT OF LOW CLOUDS THAT ARE PRESENT. PLENTY OF LOW CLOUDS UPSTREAM NEAR THE SURFACE RIDGE AXIS ACROSS WISCONSIN...IN ADDITION TO ONSHORE AND UPSLOPE FLOW WITH THE NW WINDS AND A LINGERING LOW LEVEL CONVERGENCE AXIS THAT SETS UP ACROSS NORTHEAST LOWER AND EASTERN UPPER...AND EVAPORATIVE COOLING AT THE TOP OF THE LOW LEVEL MOIST LAYER SUPPORTS GOING MOSTLY CLOUDY TO CLOUDY THE ENTIRE NIGHT...WITH LOWERING OF THE LOW LEVEL CLOUD BASE. WITH COOLING OF THE BL AND ADDED MOISTURE TO THE BL FROM ABOVE FREEZING SURFACE TEMPS THE PAST TWO AFTERNOONS...PATCHY FOG SHOULD DEVELOP POSSIBLY BECOMING MORE WIDESPREAD ACROSS THE HIGHER TERRAIN DEPENDING UPON HOW MUCH CLOUD BASES LOWER. LOWS WILL RANGE FROM THE UPPER TEENS NEAR CAD AND HTL TO THE MID 20S ALONG THE GREAT LAKES SHORELINES. MPC THURSDAY...WEAK CONVERGENCE AXIS ACROSS NRN LAKE HURON WILL WANE AS SFC RIDGE AXIS SLIDES EAST OF THE REGION IN THE MORNING. TRAPPED LOW CLOUDS ASSOCIATED WITH THIS TROUGH MAY BREAK APART FOR A BRIEF TIME IN THE MORNING...BUT AS WINDS TURN AROUND TO THE SOUTH WITH CONTINUING SHALLOW OVERLAKE INSTABILITY...CLOUDS SHOULD FILL BACK IN ACROSS EASTERN UPPER. ELSEWHERE...SHALLOW/SUB 1500KFT MOISTURE WITH ADDED SFC MOISTURE FROM SNOWMELT...WILL KEEP AREAS OF FOG AND LOW CLOUD AROUND FOR A GOOD DEAL OF THE MORNING. WONDERING HOW MUCH OF THE LOW CLOUD AND FOG WILL ACTUALLY GET TRAPPED IN FOR MUCH OF THE DAY. THIS ONE IS A TOUGH CALL. THERE WILL BE 925 MB WARM ADVECTION THAT INCREASES THROUGH THE DAY...AND WILL LIKELY BRING SOME PARTLY CLOUDY SKIES TO THE SW CWA BY AFTERNOON. OVERALL...BELIEVE THAT A MOSTLY CLOUDY FORECAST WITH LINGERING AREAS OF FOG INTO THE EARLY AFTERNOON IS THE BEST CALL...ESPECIALLY WITH MID TO UPPER LEVEL CLOUDS ADVANCING ITO THE CWA IN THE AFTERNOON. HIGHS AGAIN IN THE LOW TO MIDDLE 30S. THURSDAY NIGHT...WITH THE CONTINUED MILD TEMPERATURES...MORE SNOWMELT WILL CONTINUE TO CREATE QUITE THE SOUPY BL. WOULD NOT BE SURPRISED TO SEE AT LIGHT FOG NEVER REALLY ERODING FROM THURSDAY AFTERNOON...AND JUST CONTINUE INTO THURSDAY NIGHT. DIFFICULT TO DISCERN HOW MUCH MID/UPPER CLOUD WILL BE AROUND. MID LEVEL WEAK WARM ADVECTION/ISENTROPIC UPGLIDE (290-295K) PERSISTS THROUGH THE NIGHT...BUT WEAK MID LEVEL SHORTWAVE DEPARTS EAST BY 12Z WITH SOME MID LEVEL RIDGING. THIS COULD ALLOW FOR SOME DRIER AIR ALOFT TO ARRIVE LATE...HELPING TO PROMOTE THICKENING FOG. EITHER WAY...FOG IN SOME FASHION WILL BE AROUND...AND WHETHER OR NOT AREAS OF/PATCHY IS USED CAN BE SAVED FOR TOMORROW`S FORECAST PACKAGE. AM NOT EXPECTING MUCH OF A TEMP FALL UNDER THE CLOUDS/WARM ADVECTION...LOWS GENERALLY IN THE MIDDLE 20S CAN BE EXPECTED. FRIDAY AND FRIDAY NIGHT...HEIGHTS CONTINUE TO RISE IN THE MID LEVELS AS SRN/NRN JET STREAM ENERGY RIPS INTO THE ROCKIES. THE SOUTHERLY FLOW ACROSS THE GREAT LAKES INCREASES RESULTING IN BETTER/STRONGER WARM AND MOIST AIR ADVECTION. WINDS OF DEEPER H8-H5 MOISTURE SWINGS THROUGH THE CWA FRIDAY. FORECAST SOUNDINGS NO INDICATIVE OF ANY MEASURABLE PRECIPITATION...BUT RATHER LOW LEVEL MOISTURE THICKENING TO NEAR 750MB...ALL WARMER THAN -10C. THIS IS LOOKING MORE AND MORE LIKE A DRIZZLE SCENARIO...HINTED AT YESTERDAY. WILL BRING AREAS OF DRIZZLE INTO THE REGION STARTING FRIDAY AFTERNOON...THEN PROGRESSING THROUGH ALL OF THE CWA FRIDAY NIGHT. OF COURSE...FOG WILL ACCOMPANY THE DRIZZLE. AS FAR AS TEMPS...MID TO UPPER 30S FOR HIGHS ON FRIDAY WITH NEAR STEADY TEMPERATURES THROUGH THE NIGHT. FEEL AS IF ALL AREAS WILL BE ABOVE 32F...SO NO NEED ATTM TO MENTION FREEZING DRIZZLE. SATURDAY...THERE ARE SOME COMMONALITIES IN THE MODELS IN THIS TIME PERIOD. NRN AND SRN STREAM ENERGY WORK THEIR WAY NEAR THE MISSISSIPPI VALLEY...REMAINING SEPARATE SYSTEMS WITH NO APPARENT PHASING (YET?). THE MORNING...IF TIMING IS CORRECT...WILL START OFF DRIZZLY AND FOGGY...BEFORE SFC LOW PRESSURE WORKS INTO THE WESTERN GREAT LAKES...ALONG WITH FORCING FROM SHORTWAVES. WILL KEEP THIS PERIOD SORT OF GENERAL. WILL GO WITH LIKELY RAIN FOR NRN LOWER AS AIR MASS LOOKS TO STAY WARM. LEFT A MIX IN FOR EASTERN UPPER...AND IN LINE WITH NEIGHBORING OFFICES. THESE DETAILS WILL BECOME CLEARER TOMORROW. SATURDAY NIGHT ONWARD...BOY...STILL LOOKING LIKE A COMMON SOLUTION BETWEEN THE MODELS IS JUST A LITTLE TOO FAR AWAY. OVERALL CONSENSUS IS TO STAY WITH THE ECMWF...AS THE GFS KEEPS THE TWO JET BRANCHES SEPARATE. THE 18Z NAM HAS NOW ALLOWED FOR THE TWO BRANCHES TO PHASE TOGETHER...SUCH AS THE 12Z ECMWF. THIS SCENARIO WOULD PULL THE EXPECTED STRONG STORM SYSTEM FURTHER BACK TO THE NW...WHILE RAPIDLY DEEPENING THE SFC LOW. AREAS OF RAIN WOULD PERSIST ACROSS THE NE CWA INTO THE EVENING WHILE STRONG COLD ADVECTION BLOWS IN FROM THE SW. THERE ARE JUST TOO MANY UNCERTAINTIES STILL. FOR AT LEAST ONE MORE TIME...WILL GO WITH RAIN AND SNOW IN THE EVENING...MOST AREAS...THEN CHANGE TO ALL SNOW OVERNIGHT WITH WINDS BECOMING QUITE BRISK SUNDAY/SUNDAY NIGHT). EXPECT CHANGES TO THIS FORECAST AS MORE DETAILED TIMING/STRENGTH AND EVOLUTION OF THIS STORM WILL COME IN DUE TIME. DID INCREASE CHANCES FOR PRECIPITATION TO LIKELY. THAT LOOKS LIKE THE SAFEST BET. THE POTENTIAL FOR HAZARDOUS TRAVEL IS CERTAINLY STILL THERE OVER THE WEEKEND PRIOR TO THE CHRISTMAS HOLIDAY...SO STAY TUNED FOR THE DETAILS TO ARRIVE IN LATER FORECASTS. A RATHER BRIEF PERIOD OF LAKE EFFECT SNOWS ARE EXPECTED ON THE BACKSIDE OF THIS STORM SYSTEM AS IT PULLS EAST SUNDAY NIGHT INTO MONDAY. QUITE A BIT OF DRY AIR IS ACTUALLY FORECAST TO SPREAD IN BY MONDAY NIGHT. SMD && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 425 PM EST WED DEC 19 2007 .SHORT TERM (TONIGHT THROUGH THU)... THE MAIN CONCERN WITH THIS FORECAST PACKAGE IS THE POTENTIAL FOR PRECIPITATION SATURDAY THROUGH SUNDAY. WATER VAPOR IMAGERY AND RUC SHOWING A CLOSED LOW AND ASSOCIATED TROUGH MOVING OVER EASTERN ONTARIO AND A RIDGE SHIFT INTO THE WESTERN ONTARIO AND MINNESOTA. ANOTHER TROUGH IS DEVELOPING OVER MIDDLE HIGH PLAINS. SURFACE ANALYSIS DEPICTS A LOW OVER THE LOWER GREAT LAKES WITH A BROAD HIGH OVER THE OHIO RIVER VALLEY. A RIDGE RUNS FROM THE HIGH NORTH THROUGH WISCONSIN AND THE WEST PART OF THE FORECAST AREA. A STATIONARY FRONT STRETCHES FROM NEW ENGLAND THROUGH THE LOW TO THE ARROWHEAD OF MINNESOTA. A WARM FRONT RUNS FROM IOWA NORTHWEST TO SOUTHEAST SASKATCHEWAN THEN WEST TO CENTRAL BRITISH COLUMBIA. A LARGE HIGH BLANKETS THE ROCKIES. THE MID LEVEL RIDGE WILL SLIDE OVER THE FORECAST AREA OVERNIGHT WHICH WILL CAUSE THE WINDS TO DROP OFF AND BACK SOUTH. THE TROUGH THAT IS DEVELOPING OVER THE HIGH PLAINS WILL SWEEP ACROSS THE CENTRAL PLAINS INTO THE MIDDLE MISSISSIPPI RIVER VALLEY ON THURSDAY. THE WISCONSIN RIDGE WILL SHIFT OVER THE FORECAST AREA BY THIS EVENING AND INTO EASTERN ONTARIO ON THURSDAY. 850MB TEMPERATURES OF AROUND -7C OVER EASTERN LAKE SUPERIOR AND NORTHWEST WINDS WILL SUPPORT SOME LAKE EFFECT SNOW ENHANCEMENT OVER THE PART OF THE EASTERN U.P. TONIGHT. THERE SHOULD BE SOME LIMITED CLEARING TONIGHT AND RADIATIONAL COOLING WILL BRING THE TEMPERATURES DOWN TO THE DEW POINT. SOUTHERLY WINDS WILL ALSO HELP PUSH THE TEMPERATURES UP TO AROUND FREEZING ON THURSDAY. SOUNDING DATA SHOWING DRY AIR AND AN INVERSION SETTLING DOWN TO 950MB OVER THE FORECAST WHICH TOGETHER COULD PRODUCE SOME PATCHY FOG TONIGHT THIS WILL BURN OFF ON THURSDAY WITH SURFACE WARMING. WEAK SHORTWAVE MOVING THROUGH WESTERN LAKE SUPERIOR ON THURSDAY COULD PRODUCE SOME LIGHT SNOW MAINLY OVER THE WESTERN. .LONG TERM (THU NIGHT THROUGH NEXT WED)... MAIN FORECAST CONCERN REMAINS ON POTENTIAL FOR HEAVY SNOW SAT NIGHT INTO SUN. THU NIGHT THROUGH SAT...SOUTHERLY WINDS WILL PREVAIL UNTIL A LOW PRESSURE TROUGH SWINGS ACROSS UPPER MI ON SAT (12Z ECMWF IS SLOWER THAN 12Z GFS). INCREASED HIGH TEMPS ON FRIDAY TO ACCOUNT FOR WAA OUT OF THE SSE. MAY NEED TO INCREASE HIGHS MORE IN FUTURE FORECASTS. AS FAR AS PCPN TYPE GOES...MAINLY KEPT WITH GOING FORECAST. IT LOOKS LIKE UPSLOPE AREAS WITH A SSE WIND (WESTERN AND CENTRAL U.P.) WILL SEE BETTER CHANCE OF FREEZING DRIZZLE...AND OTHER AREAS MAY SEE DRIZZLE. FCST SOUNDINGS IN BUFKIT FOR IRON MOUNTAIN ON FRIDAY SHOW GREATER VALUES OF OMEGA AT LOW LEVELS THAN IN MQT AND HOUGHTON. THE TEMPS IN IRON MOUNTAIN REMAIN NEARLY ISOTHERMALLY AROUND 0C UP THROUGH 850MB. THE MAIN SATURATED LAYER ALSO OCCURS AT TEMPS GREATER THAN -10C...SO DRIZZLE IS ALMOST CERTAIN. FOR MQT AND HOUGHTON...POSITIVE OMEGA VALUES UP TO +5...MID-LEVEL DRY AIR...AND SFC TEMPS AROUND 0C LEAD TO UNCERTAINTY IN THE CHANCES OF FREEZING DRIZZLE VS. SNOW VS. NO PCPN AT ALL FOR FRI. CHANCES FOR PCPN INCREASE ACROSS ALL OF THE U.P. BY SAT MORNING AS THE LOW PRESSURE SYSTEM APPROACHES THE REGION. SAT NIGHT THROUGH WED...MODELS HAVE BECOME IN MUCH BETTER AGREEMENT WITH THE END OF THE WEEKEND SYSTEM...AND AT LEAST UP IN THE GREAT LAKES AREA...ARE IN PRETTY GOOD AGREEMENT THROUGH WED. AT 00Z SUN...06Z MODELS PROG THE UPPER LOW OVER SASKATCHEWAN ON FRI TO DROP DOWN INTO NORTHERN MN ON SAT...WHILE A SHRTWV TROUGH MOVES FROM NEW MEXICO UP INTO SW MISSOURI. THERE STILL REMAINS ISSUES WHETHER OR NOT THE SHRTWV AND UPPER LOW WILL PHASE TOGETHER...AS NOTED BY THE 06Z GFS KEEPING THEM UNPHASED. WILL CONTINUE TO SIDE WITH THE PHASED IDEA OF THE ECMWF/CANADIAN...WHICH PHASE THEM TOGETHER NEAR LAKE HURON ON SUNDAY. THIS RESULTS IN A 1007MB LOW OVER ILLINOIS SAT EVENING TO LIFT N AND DEEPEN RAPIDLY...REACHING NORTHERN LAKE HURON AT 12Z SUN WITH A PRESSURE AROUND 990MB. THE LOW WILL THEN TRACK UP INTO NE ONTARIO LATER SUN AND INTO QUEBEC ON MONDAY. FOR UPPER MI...THE TRACK IS FAVORABLE FOR HEAVY SYNOPTIC SNOW...WITH Q-VECTOR CONVERGENCE PROGS SUGGESTING FROM THE NORTHERN U.P. UP TO JAMES BAY. LOOKS LIKE TOO THAT AT LEAST AFTER 00Z SUN...MUCH OF THE PCPN WILL SWITCH OVER TO SNOW AS COLD AIR MOVES IN. THERE ARE TWO OTHER ASPECTS OF THIS EVENT TOO. AS THE UPPER LOW APPROACHES SAT NIGHT...850MB TEMPS PLUMMET COMPARED TO 12Z SAT...WITH READINGS DROPPING TO -8C EAST TO -15C WEST BY 12Z SUN. THUS LAKE ENHANCEMENT LOOKS LIKE A PRETTY GOOD BET. GIVEN THE LOW TRACK...SURFACE AND 850MB WIND FIELDS SUGGEST RIGHT NOW THAT THE BEST ENHANCEMENT IS OVER NORTHWEST SNOW-BELTS. THE OTHER ASPECT TO THIS SYSTEM IS WIND...WITH THE 00Z ECMWF SHOWING 850MB WINDS INCREASING TO 45-50 KT BY 00Z MON. THUS SOME BLOWING AND DRIFTING SNOW IS LIKELY... BEGINNING SAT NIGHT. SYNOPTIC SNOW SHOULD CHANGE OVER TO A PURE LAKE EFFECT REGIME LATER SUN NIGHT AS THE UPPER AND SURFACE LOWS PULL AWAY...WHILE 850MB TEMPS SLOWLY WARM TO AROUND -10C BY 12Z MON. WILL DRY OUT CHRISTMAS EVE A BIT MORE NOW...SINCE MOST MODELS PROG UPPER AND SURFACE RIDGING TO MOVE INTO THE CWA. ONLY LAKE EFFECT CHANCES WILL REMAIN IN NW SNOWBELTS. SHOULD THE SCENARIO OF THE UPPER LOW AND SHRTWV NOT PHASE TOGETHER AS SHOWN BY THE 06Z GFS...THE EVENT WILL TURN OUT WITH MORE PURE LAKE EFFECT SNOW FOR WEST AND NW SNOWBELTS...ALONG WITH BLOWING SNOW. THUS...GIVEN THE DIFFERENCES BETWEEN THE ECMWF AND GFS...ANYONE TRAVELING THIS WEEKEND SHOULD CONTINUE TO MONITOR LATER FORECASTS. FOR CHRISTMAS EVE NIGHT INTO CHRISTMAS DAY...THE WEATHER LOOKS PRETTY TRANQUIL...WITH ONLY A WEAK SHRTWV TROUGH CROSSING CHRISTMAS EVE NIGHT. THE ECMWF AND GFS DEPICT LITTLE IF ANY PCPN FROM THIS...AND THUS WILL NOT INCLUDE ANY IN THE FORECAST. ALSO...WITH SW FLOW DURING THIS PERIOD AND 850MB TEMPS CLIMBING TO -4 TO -6C BY 00Z WED...NO NEED FOR ANY LAKE EFFECT PCPN CHANCES. A NORTHERN STREAM SHRTWV TROUGH IS SHOWN BY THE GFS AND ECMWF TO APPROACH THE CWA TUE NIGHT AND WED. WILL BRING IN SOME SNOW CHANCES ON TUE NIGHT OVER WESTERN LAKE SUPERIOR...THEN ACROSS THE CWA ON WEDNESDAY AS THE TROUGH MOVES THROUGH AND 850MB TEMPS DROP TO GENERATE LAKE EFFECT SNOW. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... BOTH LOCATIONS ARE EXPECTED TO SEE A GRADUAL IMPROVEMENT LATE IN THE DAY AS A SFC RIDGE BUILDS INTO THE AREA. WITH LIGHT WINDS AND DRYING ABOVE THE MOIST BOUNDARY LAYER...EXPECT SOME FOG WILL DEVELOP OVERNIGHT WITH VSBY INTO THE IFR RANGE. GUIDANCE SHOWING AN INVERSION AND LESS SATURATED CONDITIONS AROUND 925MB A5 15Z ON THURSDAY AT KSAW AND IMPROVED CONDITIONS AROUND 9Z AT KCMX. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... THE PRESSURE GRADIENT UNDER A RIDGE THAT EXTENDS FROM FROM QUEBEC INTO NORTHERN LAKE SUPERIOR WAS PRODUCING LIGHT NE TO N WINDS. AS THE RIDGE MOVES OFF TO THE EAST ON THURSDAY...SOUTHERLY FLOW WILL INCREASE ON LAKE SUPERIOR WITH WINDS TO NEAR 30 KT BY THURSDAY NIGHT INTO EARLY FRIDAY. A STRONG SURFACE LOW IS EXPECTED TO MOVE TOWARDS THE UPPER GREAT LAKES ON SATURDAY. DEPENDING ON THE TRACK AND TIMING...GALE FORCE WINDS COULD DEVELOP FROM LATE SATURDAY INTO SUNDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...DLG LONG TERM...AJ/MRC AVIATION/MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 400 PM EST WED DEC 19 2007 .DISCUSSION...LATEST RUC ANALYSIS AND VIS/IR/WV/RADAR IMAGERY SHOW SHORTWAVE TROUGHING ACROSS THE GREAT LAKES WITH AN ASSOCIATED SURFACE LOW MOVING ACROSS SE ONTARIO. WEAK SURFACE TROUGH EMANATING FROM THIS LOW IS EXTENDING ACROSS THE STRAITS REGION...BUT APPEARS TO BE LOOSING ITS INFLUENCE OVERALL ACROSS NORTHERN MICHIGAN. CONVERGENCE ALONG THIS TROUGH AND GENERAL CYCLONIC FLOW HAS HELPED MAINTAIN IFR TO MVFR CLOUD DECK ACROSS THE AREA...BUT SHALLOW AND MARGINAL OVER-LAKE INSTABILITY HAS NOT BEEN ENOUGH TO GENERATE LAKE EFFECT SNOW SHOWERS WITHIN NW FLOW REGIMES. RADAR RETURNS ARE REALLY SPOTTY AND LIGHT AT THIS HOUR WITH PERHAPS ONLY FLURRIES OR EVEN LIGHT DRIZZLE PRESENT AS SFC TEMPS HAVE WARMED ABOVE FREEZING THIS AFTERNOON. SURFACE RIDGE AXIS UPSTREAM OVER WISCONSIN WILL HAVE ITS SIGHTS SET ON NORTHERN MICHIGAN OVERNIGHT...BUT STILL PLENTY OF LOW CLOUDS AND FOG RESIDE FROM NORTHERN MICHIGAN ON WEST TO THE RIDGE AXIS. LOW LEVEL CLOUDS CLEAR OUT TO THE WEST OF THE RIDGE AXIS...BUT MID-LEVEL WARM ADVECTION CLOUDS ALREADY PUSHING EAST INTO THE UPPER MIDWEST. CLOUDS AND TEMPS ARE THE MAIN FORECAST CONCERNS TONIGHT. TONIGHT...SURFACE LOW WILL CONTINUE TO PUSH OFF TO THE EAST INTO THE NEW ENGLAND STATES WHILE THE LOW LEVEL RIDGE AXIS BUILDS IN ACROSS NORTHERN MICHIGAN OVERNIGHT. PRIOR TO THE ARRIVAL OF THE RIDGE AXIS...LIGHT NORTHWEST WINDS COMBINED WITH SHALLOW OVER-WATER INSTABILITY (LAKE-900MB TEMP DIFFERENCE AROUND -10C) WILL SPELL SCT LAKE EFFECT FLURRIES IN THE SNOWBELTS DURING THE EVENING. OTHERWISE...INCREASING SHORTWAVE RIDGING ALOFT WILL PROMOTE DRYING IN THE MID-LEVELS AND DECREASING INVERSION HEIGHTS. LOW LEVEL MOISTURE REALLY DOES NOT HAVE ANYWHERE TO GO OVERNIGHT SINCE THE MOISTURE IS TRAPPED BENEATH THE INVERSION AND LOW LEVEL ADVECTIONS WILL BE RATHER LIGHT. NAM12 925-850MB RH DETAILS SOME DRYING TAKING PLACE IN THE WESTERN ZONES...BUT THAT MAY BE A FUNCTION OF LOWERING INVERSION HEIGHTS AND NOT INDICATIVE OF THE ACTUAL AMOUNT OF LOW CLOUDS THAT ARE PRESENT. PLENTY OF LOW CLOUDS UPSTREAM NEAR THE SURFACE RIDGE AXIS ACROSS WISCONSIN...IN ADDITION TO ONSHORE AND UPSLOPE FLOW WITH THE NW WINDS AND A LINGERING LOW LEVEL CONVERGENCE AXIS THAT SETS UP ACROSS NORTHEAST LOWER AND EASTERN UPPER...AND EVAPORATIVE COOLING AT THE TOP OF THE LOW LEVEL MOIST LAYER SUPPORTS GOING MOSTLY CLOUDY TO CLOUDY THE ENTIRE NIGHT...WITH LOWERING OF THE LOW LEVEL CLOUD BASE. WITH COOLING OF THE BL AND ADDED MOISTURE TO THE BL FROM ABOVE FREEZING SURFACE TEMPS THE PAST TWO AFTERNOONS...PATCHY FOG SHOULD DEVELOP POSSIBLY BECOMING MORE WIDESPREAD ACROSS THE HIGHER TERRAIN DEPENDING UPON HOW MUCH CLOUD BASES LOWER. LOWS WILL RANGE FROM THE UPPER TEENS NEAR CAD AND HTL TO THE MID 20S ALONG THE GREAT LAKES SHORELINES. MPC THURSDAY...WEAK CONVERGENCE AXIS ACROSS NRN LAKE HURON WILL WANE AS SFC RIDGE AXIS SLIDES EAST OF THE REGION IN THE MORNING. TRAPPED LOW CLOUDS ASSOCIATED WITH THIS TROUGH MAY BREAK APART FOR A BRIEF TIME IN THE MORNING...BUT AS WINDS TURN AROUND TO THE SOUTH WITH CONTINUING SHALLOW OVERLAKE INSTABILITY...CLOUDS SHOULD FILL BACK IN ACROSS EASTERN UPPER. ELSEWHERE...SHALLOW/SUB 1500KFT MOISTURE WITH ADDED SFC MOISTURE FROM SNOWMELT...WILL KEEP AREAS OF FOG AND LOW CLOUD AROUND FOR A GOOD DEAL OF THE MORNING. WONDERING HOW MUCH OF THE LOW CLOUD AND FOG WILL ACTUALLY GET TRAPPED IN FOR MUCH OF THE DAY. THIS ONE IS A TOUGH CALL. THERE WILL BE 925 MB WARM ADVECTION THAT INCREASES THROUGH THE DAY...AND WILL LIKELY BRING SOME PARTLY CLOUDY SKIES TO THE SW CWA BY AFTERNOON. OVERALL...BELIEVE THAT A MOSTLY CLOUDY FORECAST WITH LINGERING AREAS OF FOG INTO THE EARLY AFTERNOON IS THE BEST CALL...ESPECIALLY WITH MID TO UPPER LEVEL CLOUDS ADVANCING ITO THE CWA IN THE AFTERNOON. HIGHS AGAIN IN THE LOW TO MIDDLE 30S. THURSDAY NIGHT...WITH THE CONTINUED MILD TEMPERATURES...MORE SNOWMELT WILL CONTINUE TO CREATE QUITE THE SOUPY BL. WOULD NOT BE SURPRISED TO SEE AT LIGHT FOG NEVER REALLY ERODING FROM THURSDAY AFTERNOON...AND JUST CONTINUE INTO THURSDAY NIGHT. DIFFICULT TO DISCERN HOW MUCH MID/UPPER CLOUD WILL BE AROUND. MID LEVEL WEAK WARM ADVECTION/ISENTROPIC UPGLIDE (290-295K) PERSISTS THROUGH THE NIGHT...BUT WEAK MID LEVEL SHORTWAVE DEPARTS EAST BY 12Z WITH SOME MID LEVEL RIDGING. THIS COULD ALLOW FOR SOME DRIER AIR ALOFT TO ARRIVE LATE...HELPING TO PROMOTE THICKENING FOG. EITHER WAY...FOG IN SOME FASHION WILL BE AROUND...AND WHETHER OR NOT AREAS OF/PATCHY IS USED CAN BE SAVED FOR TOMORROW`S FORECAST PACKAGE. AM NOT EXPECTING MUCH OF A TEMP FALL UNDER THE CLOUDS/WARM ADVECTION...LOWS GENERALLY IN THE MIDDLE 20S CAN BE EXPECTED. FRIDAY AND FRIDAY NIGHT...HEIGHTS CONTINUE TO RISE IN THE MID LEVELS AS SRN/NRN JET STREAM ENERGY RIPS INTO THE ROCKIES. THE SOUTHERLY FLOW ACROSS THE GREAT LAKES INCREASES RESULTING IN BETTER/STRONGER WARM AND MOIST AIR ADVECTION. WINDS OF DEEPER H8-H5 MOISTURE SWINGS THROUGH THE CWA FRIDAY. FORECAST SOUNDINGS NO INDICATIVE OF ANY MEASURABLE PRECIPITATION...BUT RATHER LOW LEVEL MOISTURE THICKENING TO NEAR 750MB...ALL WARMER THAN -10C. THIS IS LOOKING MORE AND MORE LIKE A DRIZZLE SCENARIO...HINTED AT YESTERDAY. WILL BRING AREAS OF DRIZZLE INTO THE REGION STARTING FRIDAY AFTERNOON...THEN PROGRESSING THROUGH ALL OF THE CWA FRIDAY NIGHT. OF COURSE...FOG WILL ACCOMPANY THE DRIZZLE. AS FAR AS TEMPS...MID TO UPPER 30S FOR HIGHS ON FRIDAY WITH NEAR STEADY TEMPERATURES THROUGH THE NIGHT. FEEL AS IF ALL AREAS WILL BE ABOVE 32F...SO NO NEED ATTM TO MENTION FREEZING DRIZZLE. SATURDAY...THERE ARE SOME COMMONALITIES IN THE MODELS IN THIS TIME PERIOD. NRN AND SRN STREAM ENERGY WORK THEIR WAY NEAR THE MISSISSIPPI VALLEY...REMAINING SEPARATE SYSTEMS WITH NO APPARENT PHASING (YET?). THE MORNING...IF TIMING IS CORRECT...WILL START OFF DRIZZLY AND FOGGY...BEFORE SFC LOW PRESSURE WORKS INTO THE WESTERN GREAT LAKES...ALONG WITH FORCING FROM SHORTWAVES. WILL KEEP THIS PERIOD SORT OF GENERAL. WILL GO WITH LIKELY RAIN FOR NRN LOWER AS AIR MASS LOOKS TO STAY WARM. LEFT A MIX IN FOR EASTERN UPPER...AND IN LINE WITH NEIGHBORING OFFICES. THESE DETAILS WILL BECOME CLEARER TOMORROW. SATURDAY NIGHT ONWARD...BOY...STILL LOOKING LIKE A COMMON SOLUTION BETWEEN THE MODELS IS JUST A LITTLE TOO FAR AWAY. OVERALL CONSENSUS IS TO STAY WITH THE ECMWF...AS THE GFS KEEPS THE TWO JET BRANCHES SEPARATE. THE 18Z NAM HAS NOW ALLOWED FOR THE TWO BRANCHES TO PHASE TOGETHER...SUCH AS THE 12Z ECMWF. THIS SCENARIO WOULD PULL THE EXPECTED STRONG STORM SYSTEM FURTHER BACK TO THE NW...WHILE RAPIDLY DEEPENING THE SFC LOW. AREAS OF RAIN WOULD PERSIST ACROSS THE NE CWA INTO THE EVENING WHILE STRONG COLD ADVECTION BLOWS IN FROM THE SW. THERE ARE JUST TOO MANY UNCERTAINTIES STILL. FOR AT LEAST ONE MORE TIME...WILL GO WITH RAIN AND SNOW IN THE EVENING...MOST AREAS...THEN CHANGE TO ALL SNOW OVERNIGHT WITH WINDS BECOMING QUITE BRISK SUNDAY/SUNDAY NIGHT). EXPECT CHANGES TO THIS FORECAST AS MORE DETAILED TIMING/STRENGTH AND EVOLUTION OF THIS STORM WILL COME IN DUE TIME. DID INCREASE CHANCES FOR PRECIPITATION TO LIKELY. THAT LOOKS LIKE THE SAFEST BET. THE POTENTIAL FOR HAZARDOUS TRAVEL IS CERTAINLY STILL THERE OVER THE WEEKEND PRIOR TO THE CHRISTMAS HOLIDAY...SO STAY TUNED FOR THE DETAILS TO ARRIVE IN LATER FORECASTS. A RATHER BRIEF PERIOD OF LAKE EFFECT SNOWS ARE EXPECTED ON THE BACKSIDE OF THIS STORM SYSTEM AS IT PULLS EAST SUNDAY NIGHT INTO MONDAY. QUITE A BIT OF DRY AIR IS ACTUALLY FORECAST TO SPREAD IN BY MONDAY NIGHT. SMD && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GAYLORD MI 117 PM EST WED DEC 19 2007 .UPDATE...AREAS OF FREEZING DRIZZLE HAVE DISSIPATED EARLY THIS AFTERNOON...WHILE TEMPERATURES HAVE WARMED AT OR ABOVE FREEZING. ALTHOUGH PATCHY FREEZING DRIZZLE MAY STILL EXIST PARTICULARLY ACROSS THE HIGHER TERRAIN OF NORTHERN LOWER...WARMING TEMPERATURES THIS AFTERNOON WILL PREVENT MUCH IN THE WAY OF ACCUMULATIONS. THEREFORE...HAVE CANCELLED THE WINTER WEATHER ADVISORY FOR AREAS SOUTH OF M-32. ALSO MADE ONE OTHER CHANGE TO THIS AFTERNOONS FORECAST. EARLY BATCH OF PRECIP OVER SOUTHERN LAKE SUPERIOR HAS DISSIPATED OVER THE PAST COUPLE HOURS...AND IT APPEARS THAT MARGINAL OVER-LAKE INSTABILITY IS NOT ENOUGH TO GENERATE ANY LAKE EFFECT SNOW SHOWERS. HAVE THUS CHANGED PRECIP TYPE TO FLURRIES FOR THE REMAINDER OF THE AFTERNOON. NEW ZONES HAVE ALREADY BEEN SENT. MPC && .AVIATION... /ISSUED 1203 PM EST WED DEC 19 2007/ AREAS OF LIGHT FREEZING DRIZZLE AND SNOW ASSOCIATED WITH A SURFACE LOW MOVING EAST OVER LAKE HURON WILL COME TO AN END EARLY THIS AFTERNOON AT ALL TAF SITES. HOWEVER...MVFR VSBYS AND CIGS LOOK TO PERSIST THROUGH TOMORROW MORNING BEFORE DRIER LOW LEVEL AIR MAKES INTO NORTHERN MICHIGAN. SOME VERY LIGHT SNOW SHOWERS MAY MOVE ACROSS TVC/PLN...BUT NOT WORTH PUTTING PREDOMINATELY IN THE FORECAST. MPC && .PREV UPDATE... /ISSUED 1030 AM EST WED DEC 19 2007/ UPDATE....12Z SURFACE/RAOB/RUC ANALYSIS AND IR/WV/RADAR IMAGERY SHOW A SHORTWAVE AND ASSOCIATED SURFACE LOW MOVING ACROSS NE LOWER...A COLD FRONT EXTENDING FROM THIS LOW SOUTH TOWARDS LANSING...AND A SURFACE TROUGH EXTENDED NW TOWARDS MQT. LIGHT RADAR RETURNS CONTINUE TO MOVE SE ON THE WESTERN FLANK OF THE SURFACE LOW...ENHANCED A BIT BY THE AFOREMENTIONED SURFACE TROUGH. NUMEROUS LOCATIONS ARE STILL REPORTING LIGHT FREEZING DRIZZLE...MIXED WITH FLURRIES OR LIGHT SNOW AT TIMES ACROSS NORTHERN LOWER...AND THE 12Z APX SOUNDING SUGGESTS WHY WITH THE MOISTURE DEPTH ONLY REACHING UP TO -11C. ACARS SOUNDING OUT OF KINROSS SHOWS DEEPER MOISTURE UP TO -15C WHICH EXPLAINS ALL SNOW BEING REPORTED ACROSS EASTERN UPPER. NW WINDS BEHIND THE LOW ARE FUNNELING IN SLIGHTLY COOLER 850MB TEMPS THAN THE MODELS PORTRAY...GIVING RISE TO POTENTIAL LAKE EFFECT PRECIP HEADING INTO THE AFTERNOON. BUT FIRST...HAVE TO DEAL WITH TIMING OF NUISANT -FZDZ COMING TO AN END. MAIN AREA OF -FZDZ MIXED WITH LIGHT SNOW WILL CONTINUE SOUTH ACROSS THE CWA THROUGH EARLY AFTERNOON. EXIT TIMING BASED ON RADAR AND SATELLITE LOOPS IS AROUND 18Z ACROSS THE FAR SE CWA...BUT THERE MAY BE SOME LINGERING FZDZ BASED ON LOWER VSBYS ACROSS THE TIP OF THE MITT SO HAVE EXTENDED WINTER WEATHER ADVISORY THROUGH 19Z. ALTHOUGH THE PRIMARY ROADS ARE PROBABLY OK BY NOW...UNTREATED SECONDARY ROADS MAY STILL BE A LITTLE ICY. THEREAFTER...NW FLOW BECOMES ESTABLISHED (ALREADY TAKING SHAPE ACROSS LAKE SUPERIOR) WITH MARGINAL DELTA T/S AROUND 13-14C AND EXPECT A TRANSITION TO LIGHT NW FLOW LAKE EFFECT FROM MID-AFTERNOON ONWARD. INSTABILITY IS ONLY MARGINAL...SO ACCUMULATIONS SHOULD BE A HALF INCH OR LESS...WHICH THE CURRENT FORECAST DISPLAYS WELL. CLOUD COVER WILL REMAIN CLOUDY ALL DAY...AND TEMPERATURES THEREFORE WILL NOT INCREASE TOO MUCH. SO HIGHS IN THE LOW-MID 30S LOOKS GOOD. MPC && .PREVIOUS DISCUSSION...ISSUED 510 AM ON THE LATEST SURFACE WEATHER MAP...1009 MB LOW PRESSURE WAS CENTERED ACROSS NORTHERN LAKE MICHIGAN. SATELLITE LOOPS AND SURFACE OBSERVATIONS INDICATED THAT A STRATOCU DECK HAD OVERSPREAD THE REGION. APX RADAR CONTINUED TO SHOW 16-20 DBZ RETURNS FROM THE TIP OF THE MITT INTO EASTERN UPPER OF THE LAST FEW HOURS. MEANWHILE...A BROAD AREA OF 4-8 DBZ RETURNS DEVELOPED ACROSS SOUTHWEST AND SOUTH CENTRAL COUNTIES A COUPLE OF HOURS AGO WITH A SLOW PROGRESSION TO THE EAST. THE MAIN FORECAST CONCERNS REVOLVE AROUND EXTENT OF FREEZING DRIZZLE AND POSSIBLE HEADLINES THIS MORNING...POPS THURSDAY NIGHT AND HOW MUCH TO TWEAK THE DETAILS OF THE POTENTIAL MAJOR STORM SYSTEM THIS WEEKEND. CLIPPER AND ASSOCIATED AREA OF DIVQ WILL CONTINUE TO MOVE ACROSS FAR NORTHERN ZONES THIS MORNING. SO FAR ONLY LIGHT SNOW (NO FREEZING DRIZZLE) HAS BEEN REPORTED ACROSS THE TIP OF THE MITT AND EASTERN UPPER. MEANWHILE TO THE SOUTH LIGHT RETURNS CORRESPOND TO RECENT REPORTS OF FREEZING DRIZZLE AND DEVELOPING ICY CONDITIONS. MODEL SOUNDINGS/CROSS SECTIONS MOISTEN UP THE COLUMN THROUGH BETWEEN -12 AND -14 C THIS MORNING WHICH WOULD MEAN THAT ANY PRECIPITATION THAT FALLS WOULD BE IN THE FORM OF SNOW. HOWEVER...WITH THE TRACK OF THE CLIPPER (ACROSS THE FAR NORTH) ITS HARD TO BELIEVE THAT IT WOULD MOISTEN UP THIS MUCH SOUTH OF THE SURFACE LOW TRACK. THIS IS BORNE OUT WITH THE INCREASING NUMBER OF FREEZING DRIZZLE REPORTS. THEREFORE WILL ISSUE A WINTER WEATHER ADVISORY FOR THIS MORNING ACROSS ALL ZONES IN NORTHERN LOWER WITH THE EXCEPTION OF THE COUNTIES IN THE TIPP OF THE MITT WHERE MAINLY LIGHT SNOW IS EXPECTED. AS FAR AS SNOW AMOUNTS ACROSS THE FAR NORTH...ONLY EXPECTING LESS THAN AN INCH OF ACCUMULATION. WINDS VEER INTO THE NORTHWEST THIS AFTERNOON AND OVER LAKE INSTABILITY APPEARS TO BE MARGINALLY SUFFICIENT TO SUPPORT LIGHT LAKE EFFECT SNOW SHOWERS (LAKE-850 MB DELTA TS INCREASE TO BETWEEN 13 TO 14) WITH 900-700 MB RH STILL 60 TO 80 PERCENT AND. SO WILL ADD IN NUMEROUS LIGHT SNOW SHOWERS WITH AN INCH OR LESS OF ACCUMULATION INTO FAVORED NW FLOW AREAS. CLOUDS ARE EXPECTED TO HANG IN ALL DAY WITH MODEST COLD AIR ADVECTION. TEMPERATURES SHOULD REMAIN NEARLY STEADY OR FALL BY A COUPLE OF DEGREES (GENERALLY AROUND 30 TO THE LOWER 30S). TONIGHT...NAM LINGERS OVER LAKE INSTABILITY/MOISTURE WELL INTO THIS EVENING WHILE THE GFS HAS PRONOUNCED DRYING (MEAN 900-700 MB RH <40 PERCENT) AND WARMING (850 TEMPS INCREASE BY A FEW DEGREES). AT THIS POINT WILL GO WITH A COMPROMISE SOLUTION WITH ONLY A CHANCE OF LIGHT LAKE EFFECT SNOW SHOWERS IN NORTHWEST FLOW AREAS THROUGH MIDNIGHT AS MEAN SURFACE-850 MB WINDS BARELY SUPPORT ORGANIZED LAKE EFFECT (10 KNOTS OR SO). INCREASING RIDGING/SUFFICIENT WARMING/DRYING OVERNIGHT SHOULD PUT THE KABOSH ON ANY LINGERING ACTIVITY. LOWS TONIGHT IN THE MIDDLE TEENS TO LOWER 20S. THURSDAY...RIDGING AT THE SURFACE AND ALOFT FOR MUCH OF THE DAY. GFS IS FASTER THAN THE NAM WITH MOISTURE RETURN WITH DEVELOPING SOUTHERLY FLOW BUT THIS APPEARS TO BE A BIT QUICK. FOR NOW WILL CONTINUE WITH PARTLY CLOUDY AND MILD CONDITIONS WITH INCREASING CLOUDINESS LATE IN THE DAY. HIGHS IN THE MILD LOWER AND MIDDLE 30S. THURSDAY NIGHT...WARM ADVECTION SHOULD INCREASE PER NAM/GFS LEADING TO THICKENING CLOUD DECK. MOISTURE DEPTH IS QUESTIONABLE FOR PRECIPITATION PRODUCTION BUT WILL ADD IN A CHANCE OF FLURRIES OVERNIGHT. THERE EVEN COULD BE SOME FREEZING DRIZZLE ONCE AGAIN BUT WILL LET THE DAYSHIFT TAKE A BETTER LOOK AT THAT SCENARIO DUE TO LIMITED TIME CONSTRAINT`S AT THE MOMENT. LOWS IN THE LOWER AND MIDDLE 20S. FRIDAY...CONTINUED SOUTHERLY FLOW WITH DRY MID LEVELS SO A MOSTLY CLOUDY DAY IS EXPECTED WITH HIGHS GENERALLY IN THE MIDDLE 30S. FRIDAY NIGHT THROUGH SUNDAY...COMPLEX WEATHER SITUATION SHAPING UP WITH ENERGY IN THE SOUTHERN JET STREAM MOVING NORTHEAST OUT OF THE DESERT SOUTHWEST WHILE ENERGY IN THE NORTHERN JET STREAM DROPS DOWN OUT OF CENTRAL CANADA. EXTENDED MODELS THIS RUN ARE IN BETTER AGREEMENT THAT THE SOUTHERN ENERGY IMPACTS THE AREA FIRST WITH LOW PRESSURE MOVING BY TO OUR WEST WHICH WOULD LEAD TO MAINLY RAIN FOR SATURDAY. THE NORTHERN STREAM ENERGY IS SHOWN TO BE VERY IMPRESSIVE AND IT MERGES WITH THE SOUTHERN STREAM ENERGY SATURDAY NIGHT INTO SUNDAY WHICH WOULD LEAD TO FALLING TEMPERATURES...INCREASING WINDS AND RAIN CHANGING TO SNOW SATURDAY NIGHT AND CONTINUING INTO SUNDAY. MODELS HAVE BEEN WAVERING OVER THE DETAILS OVER THE LAST COUPLE OF DAYS BUT WILL MAKE A FEW ADJUSTMENTS TO CURRENT FORECAST WHICH LINE UP WITH SURROUNDING OFFICES...LIKE INCREASING POPS AND GOING WITH A CHANGEOVER TO ALL SNOW SATURDAY NIGHT INTO SUNDAY. SULLIVAN && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE MARQUETTE MI 1245 PM EST WED DEC 19 2007 .SHORT TERM... .DISCUSSION...THE MAIN CONCERN WITH THIS UPDATE IS THE POTENTIAL FOR PRECIPITATION THIS AFTERNOON AND TONIGHT. WATER VAPOR IMAGERY AND RUC SHOWING A LOW OVER EAST CENTRAL ONTARIO AND A RIDGE OVER THE DAKOTAS AND MANITOBA. A SURFACE LOW IS OVER LAKE HURON WITH A STATIONARY FRONT RUNNING THROUGH IT FROM NORTHERN NEW YORK STATE TO WINNIPEG. CYCLONIC WINDS AROUND THE LOW ARE KEEPING THE WINDS OUT OF THE NORTH ACROSS THE AREA. DRIER AIR IS ADVECTING INTO THE AREA FROM THE WEST CAUSING THE SNOW TO DIMINISH. A SURFACE LOW IS DEEPENING OVER ALBERTA WITH A WEAK TROUGH EXTENDING SOUTH INTO EASTERN COLORADO. COOLER AIR SETTLING OVER THE NORTHERN PLAINS AND THE UPPER MISSISSIPPI RIVER VALLEY IS PRODUCING CONSIDERABLE AMOUNTS OF FOG OVER MINNESOTA AND WISCONSIN THIS MORNING. LOW LEVEL MOISTURE AND TEMPERATURES ARE A LITTLE COOLER THAN ANY OF THE MODEL DEPICT AT THIS TIME. PRECIPITATION HAS ENDED OVER THE WEST HALF OF CWA AND WEAKEN CONSIDERABLY OVER THE EAST AS THE LOW MOVES EAST. THE MID LEVEL LOW WILL BECOME MORE FOCUSED JUST NORTHEAST OF GEORGIAN BAY TODAY AND SHIFT INTO EXTREME SOUTHEAST ONTARIO TONIGHT WHILE THE RIDGE OVER THE DAKOTAS WANDERS INTO MINNESOTA THIS AFTERNOON AND INTO THE WESTERN U.P. TONIGHT. THE SNOW WILL CONTINUE TO END ACROSS THE U.P. AS THE SYSTEM MOVES EAST TODAY. THE LAKE-850MB DELTA-T IS ONLY AROND 11C OVER THE CENTRAL AND EASTERN LAKE SUPERIOR. THIS SHOULD BE ENOUGH TO PRODUCE SOME LAKE ENHANCEMENT IN THE FORECASTS ESPECIALLY OVER THE EAST. CLOUD COVER WILL HOLD TEMPERATURES DOWN TODAY. DRIER AIR WILL GIVE SOME CLEARING THIS EVENING WHICH WILL ALLOW TEMPERATURES TO FALL RAPIDLY EARLY...THEN IT SHOULD TAPER OFF AS CLOUD COVER INCREASES. GUIDANCE LOOKS REASONABLE. .LONG TERM... THURSDAY...THE RIDGE OVER THE DAKOTAS TODAY WILL SLIDE OVERHEAD BY 12Z THURSDAY. THE TROUGH OVER THE WESTERN STATES WILL HAVE MOVED TO THE VICINITY OF MINNESOTA AND IOWA...WEAKENING AS IT SLIDES OVER WESTERN LAKE SUPERIOR LATE THURSDAY AFTERNOON. THE MAIN FEATURE OF INTEREST...THE WEEKEND SYSTEM...WILL BE COMING ONSHORE OVER THE WESTERN STATES THURSDAY MORNING. FRIDAY...THE MIDLEVEL HIGH WILL GET SHIFTED TO THE EAST OF THE CWA AS THE SINKING TROUGH FORMS A CUT-OFF LOW OVER ALBERTA BY 12Z FRIDAY. SATURDAY...MUCH OF THE ATTENTION WILL BE PLACED JUST TO OUR WEST...AS THE MID LEVEL LOW OVER SOUTHERN MANITOBA AND THE DAKOTAS HEADS OUR WAY. THE 00Z NAM HAS JUMPED TO THE SOUTH WHEN COMPARED TO ITS PREVIOUS 12Z RUN...WITH THE 500MB LOW CENTERED OVER CENTRAL SOUTH DAKOTA AT 12Z. THIS WAS MUCH FARTHER SOUTH THAN THE CONSENSUS OF THE REMAINING MODELS. AS A RESULT...THE NAM WAS NOT UTILIZED IN THIS FORECAST BEYOND FRIDAY MORNING. UP UNTIL THAT TIME THE MODELS ARE IN PRETTY GOOD AGREEMENT ACROSS UPPER MICHIGAN. AS FOR SPECIFICS...IT LOOKS LIKE FREEZING DRIZZLE WILL BE A GOOD BET AT ERY UNTIL ABOUT 06-09Z SATURDAY WHEN SOUNDINGS OFF OF THE GFS WOULD SUGGEST RAIN. 850MB TEMPERATURES WILL RISE TO 0 TO 2C EAST FROM 00Z SATURDAY THROUGH 00Z SUNDAY...BEFORE COLD AIR SLIDES BACK IN. SUNDAY...BY 12Z SUNDAY THE MODELS ARE FAIRLY WELL LINED UP...SAYING THAT THE 500MB LOW WILL BE SOMEWHERE BETWEEN STANNARD ROCK AND LA CROSSE WISCONSIN. THE 18Z GFS MORE IN LINE WITH THE NAM TREND WAS THE FARTHEST SOUTH AT THIS POINT...POSITIONED OVER CENTRAL IOWA. AT THE SURFACE AT 12Z SUNDAY...MODELS WERE IN GOOD AGREEMENT POSITIONING THE SURFACE LOW JUST EAST OF LAKE SUPERIOR. THIS WAS A CHANGE FROM PREVIOUS RUNS...QUICKER TO PUSH NORTHEASTWARD. FOR EXAMPLE...THE 18/00Z RUN OF THE GFS HAD THE LOW OVER MILWAUKEE...ROUGHLY 350 MILES SSW OF THE LATEST ECMWF AND CANADIAN RUNS. THE 19/00Z GFS HAS SLID A LITTLE MORE SOUTH OF CONSENSUS...BUT IS STILL 320 MILES NE OF 2 RUNS AGO. STEADY TO FALLING TEMPERATURES CAN BE EXPECTED SUNDAY. PLENTY OF COLD AIR WILL ONCE AGAIN FILTER INTO THE REGION DURING THE DAY SUNDAY. IT LOOKS LIKE 850MB TEMPERATURES OF -18C TO -20C WILL BE SHORT LIVED DURING THE DAYLIGHT HOURS SUNDAY...WITH LAKE EFFECT SNOW SHOWERS LIKELY ACROSS COMMUNITIES FAVORED BY W TO NW WINDS THROUGH MONDAY NIGHT. OVERALL...QUICKER IS THE WAY TO GO...RESULTING IN COOLER TEMPERATURES TO WRAP UP THE WORK WEEK AS WELL AS PLENTY OF WEATHER/POP CHANGES. WINDS WILL NEED TO BE FURTHER ADJUSTED BY LATER SHIFTS. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... BOTH LOCATIONS ARE EXPECTED TO SEE A GRADUAL IMPROVEMENT LATE IN THE DAY AS A SFC RIDGE BUILDS INTO THE AREA. WITH LIGHT WINDS AND DRYING ABOVE THE MOIST BOUNDARY LAYER...EXPECT SOME FOG WILL DEVELOP OVERNIGHT WITH VSBY INTO THE IFR RANGE. GUIDANCE SHOWING AN INVERSION AND LESS SATURATED CONDITIONS AROUND 925MB A5 15Z ON THURSDAY AT KSAW AND IMPROVED CONDITIONS AROUND 9Z AT KCMX. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... THE PRESSURE GRADIENT OVER LAKE SUPERIOR BETWEEN LOW PRESSURE OVER NORTHERN LOWER MICHIGAN AND A RIDGE FROM QUEBEC INTO NORTHERN ONTARIO WAS PRODUCING NE TO N WINDS INTO THE 15 TO 25 KT RANGE. WINDS WILL DIMINISH TODAY AS THE LOW MOVES TO THE EAST AND A RIDGE BUILDS INTO THE AREA FROM MN. AS THE RIDGE MOVES OFF TO THE EAST ON THURSDAY...SOUTHERLY FLOW WILL INCREASE ON LAKE SUPERIOR WITH WINDS TO NEAR 30 KT BY THURSDAY NIGHT INTO EARLY FRIDAY. A STRONG SURFACE LOW IS EXPECTED TO MOVE TOWARDS THE UPPER GREAT LAKES ON SATURDAY. DEPENDING ON THE TRACK AND TIMING...GALE FORCE WINDS COULD DEVELOP FROM LATE SATURDAY INTO SUNDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...DLG LONG TERM...KF AVIATION/MARINE...JLB mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1203 PM EST WED DEC 19 2007 .AVIATION...AREAS OF LIGHT FREEZING DRIZZLE AND SNOW ASSOCIATED WITH A SURFACE LOW MOVING EAST OVER LAKE HURON WILL COME TO AN END EARLY THIS AFTERNOON AT ALL TAF SITES. HOWEVER...MVFR VSBYS AND CIGS LOOK TO PERSIST THROUGH TOMORROW MORNING BEFORE DRIER LOW LEVEL AIR MAKES INTO NORTHERN MICHIGAN. SOME VERY LIGHT SNOW SHOWERS MAY MOVE ACROSS TVC/PLN...BUT NOT WORTH PUTTING PREDOMINATELY IN THE FORECAST. MPC && .PREV DISCUSSION... /ISSUED 1030 AM EST WED DEC 19 2007/ UPDATE....12Z SURFACE/RAOB/RUC ANALYSIS AND IR/WV/RADAR IMAGERY SHOW A SHORTWAVE AND ASSOCIATED SURFACE LOW MOVING ACROSS NE LOWER...A COLD FRONT EXTENDING FROM THIS LOW SOUTH TOWARDS LANSING...AND A SURFACE TROUGH EXTENDED NW TOWARDS MQT. LIGHT RADAR RETURNS CONTINUE TO MOVE SE ON THE WESTERN FLANK OF THE SURFACE LOW...ENHANCED A BIT BY THE AFOREMENTIONED SURFACE TROUGH. NUMEROUS LOCATIONS ARE STILL REPORTING LIGHT FREEZING DRIZZLE...MIXED WITH FLURRIES OR LIGHT SNOW AT TIMES ACROSS NORTHERN LOWER...AND THE 12Z APX SOUNDING SUGGESTS WHY WITH THE MOISTURE DEPTH ONLY REACHING UP TO -11C. ACARS SOUNDING OUT OF KINROSS SHOWS DEEPER MOISTURE UP TO -15C WHICH EXPLAINS ALL SNOW BEING REPORTED ACROSS EASTERN UPPER. NW WINDS BEHIND THE LOW ARE FUNNELING IN SLIGHTLY COOLER 850MB TEMPS THAN THE MODELS PORTRAY...GIVING RISE TO POTENTIAL LAKE EFFECT PRECIP HEADING INTO THE AFTERNOON. BUT FIRST...HAVE TO DEAL WITH TIMING OF NUISANT -FZDZ COMING TO AN END. MAIN AREA OF -FZDZ MIXED WITH LIGHT SNOW WILL CONTINUE SOUTH ACROSS THE CWA THROUGH EARLY AFTERNOON. EXIT TIMING BASED ON RADAR AND SATELLITE LOOPS IS AROUND 18Z ACROSS THE FAR SE CWA...BUT THERE MAY BE SOME LINGERING FZDZ BASED ON LOWER VSBYS ACROSS THE TIP OF THE MITT SO HAVE EXTENDED WINTER WEATHER ADVISORY THROUGH 19Z. ALTHOUGH THE PRIMARY ROADS ARE PROBABLY OK BY NOW...UNTREATED SECONDARY ROADS MAY STILL BE A LITTLE ICY. THEREAFTER...NW FLOW BECOMES ESTABLISHED (ALREADY TAKING SHAPE ACROSS LAKE SUPERIOR) WITH MARGINAL DELTA T/S AROUND 13-14C AND EXPECT A TRANSITION TO LIGHT NW FLOW LAKE EFFECT FROM MID-AFTERNOON ONWARD. INSTABILITY IS ONLY MARGINAL...SO ACCUMULATIONS SHOULD BE A HALF INCH OR LESS...WHICH THE CURRENT FORECAST DISPLAYS WELL. CLOUD COVER WILL REMAIN CLOUDY ALL DAY...AND TEMPERATURES THEREFORE WILL NOT INCREASE TOO MUCH. SO HIGHS IN THE LOW-MID 30S LOOKS GOOD. MPC && DISCUSSION...ISSUED 510 AM ON THE LATEST SURFACE WEATHER MAP...1009 MB LOW PRESSURE WAS CENTERED ACROSS NORTHERN LAKE MICHIGAN. SATELLITE LOOPS AND SURFACE OBSERVATIONS INDICATED THAT A STRATOCU DECK HAD OVERSPREAD THE REGION. APX RADAR CONTINUED TO SHOW 16-20 DBZ RETURNS FROM THE TIP OF THE MITT INTO EASTERN UPPER OF THE LAST FEW HOURS. MEANWHILE...A BROAD AREA OF 4-8 DBZ RETURNS DEVELOPED ACROSS SOUTHWEST AND SOUTH CENTRAL COUNTIES A COUPLE OF HOURS AGO WITH A SLOW PROGRESSION TO THE EAST. THE MAIN FORECAST CONCERNS REVOLVE AROUND EXTENT OF FREEZING DRIZZLE AND POSSIBLE HEADLINES THIS MORNING...POPS THURSDAY NIGHT AND HOW MUCH TO TWEAK THE DETAILS OF THE POTENTIAL MAJOR STORM SYSTEM THIS WEEKEND. CLIPPER AND ASSOCIATED AREA OF DIVQ WILL CONTINUE TO MOVE ACROSS FAR NORTHERN ZONES THIS MORNING. SO FAR ONLY LIGHT SNOW (NO FREEZING DRIZZLE) HAS BEEN REPORTED ACROSS THE TIP OF THE MITT AND EASTERN UPPER. MEANWHILE TO THE SOUTH LIGHT RETURNS CORRESPOND TO RECENT REPORTS OF FREEZING DRIZZLE AND DEVELOPING ICY CONDITIONS. MODEL SOUNDINGS/CROSS SECTIONS MOISTEN UP THE COLUMN THROUGH BETWEEN -12 AND -14 C THIS MORNING WHICH WOULD MEAN THAT ANY PRECIPITATION THAT FALLS WOULD BE IN THE FORM OF SNOW. HOWEVER...WITH THE TRACK OF THE CLIPPER (ACROSS THE FAR NORTH) ITS HARD TO BELIEVE THAT IT WOULD MOISTEN UP THIS MUCH SOUTH OF THE SURFACE LOW TRACK. THIS IS BORNE OUT WITH THE INCREASING NUMBER OF FREEZING DRIZZLE REPORTS. THEREFORE WILL ISSUE A WINTER WEATHER ADVISORY FOR THIS MORNING ACROSS ALL ZONES IN NORTHERN LOWER WITH THE EXCEPTION OF THE COUNTIES IN THE TIPP OF THE MITT WHERE MAINLY LIGHT SNOW IS EXPECTED. AS FAR AS SNOW AMOUNTS ACROSS THE FAR NORTH...ONLY EXPECTING LESS THAN AN INCH OF ACCUMULATION. WINDS VEER INTO THE NORTHWEST THIS AFTERNOON AND OVER LAKE INSTABILITY APPEARS TO BE MARGINALLY SUFFICIENT TO SUPPORT LIGHT LAKE EFFECT SNOW SHOWERS (LAKE-850 MB DELTA TS INCREASE TO BETWEEN 13 TO 14) WITH 900-700 MB RH STILL 60 TO 80 PERCENT AND. SO WILL ADD IN NUMEROUS LIGHT SNOW SHOWERS WITH AN INCH OR LESS OF ACCUMULATION INTO FAVORED NW FLOW AREAS. CLOUDS ARE EXPECTED TO HANG IN ALL DAY WITH MODEST COLD AIR ADVECTION. TEMPERATURES SHOULD REMAIN NEARLY STEADY OR FALL BY A COUPLE OF DEGREES (GENERALLY AROUND 30 TO THE LOWER 30S). TONIGHT...NAM LINGERS OVER LAKE INSTABILITY/MOISTURE WELL INTO THIS EVENING WHILE THE GFS HAS PRONOUNCED DRYING (MEAN 900-700 MB RH <40 PERCENT) AND WARMING (850 TEMPS INCREASE BY A FEW DEGREES). AT THIS POINT WILL GO WITH A COMPROMISE SOLUTION WITH ONLY A CHANCE OF LIGHT LAKE EFFECT SNOW SHOWERS IN NORTHWEST FLOW AREAS THROUGH MIDNIGHT AS MEAN SURFACE-850 MB WINDS BARELY SUPPORT ORGANIZED LAKE EFFECT (10 KNOTS OR SO). INCREASING RIDGING/SUFFICIENT WARMING/DRYING OVERNIGHT SHOULD PUT THE KABOSH ON ANY LINGERING ACTIVITY. LOWS TONIGHT IN THE MIDDLE TEENS TO LOWER 20S. THURSDAY...RIDGING AT THE SURFACE AND ALOFT FOR MUCH OF THE DAY. GFS IS FASTER THAN THE NAM WITH MOISTURE RETURN WITH DEVELOPING SOUTHERLY FLOW BUT THIS APPEARS TO BE A BIT QUICK. FOR NOW WILL CONTINUE WITH PARTLY CLOUDY AND MILD CONDITIONS WITH INCREASING CLOUDINESS LATE IN THE DAY. HIGHS IN THE MILD LOWER AND MIDDLE 30S. THURSDAY NIGHT...WARM ADVECTION SHOULD INCREASE PER NAM/GFS LEADING TO THICKENING CLOUD DECK. MOISTURE DEPTH IS QUESTIONABLE FOR PRECIPITATION PRODUCTION BUT WILL ADD IN A CHANCE OF FLURRIES OVERNIGHT. THERE EVEN COULD BE SOME FREEZING DRIZZLE ONCE AGAIN BUT WILL LET THE DAYSHIFT TAKE A BETTER LOOK AT THAT SCENARIO DUE TO LIMITED TIME CONSTRAINT`S AT THE MOMENT. LOWS IN THE LOWER AND MIDDLE 20S. FRIDAY...CONTINUED SOUTHERLY FLOW WITH DRY MID LEVELS SO A MOSTLY CLOUDY DAY IS EXPECTED WITH HIGHS GENERALLY IN THE MIDDLE 30S. FRIDAY NIGHT THROUGH SUNDAY...COMPLEX WEATHER SITUATION SHAPING UP WITH ENERGY IN THE SOUTHERN JET STREAM MOVING NORTHEAST OUT OF THE DESERT SOUTHWEST WHILE ENERGY IN THE NORTHERN JET STREAM DROPS DOWN OUT OF CENTRAL CANADA. EXTENDED MODELS THIS RUN ARE IN BETTER AGREEMENT THAT THE SOUTHERN ENERGY IMPACTS THE AREA FIRST WITH LOW PRESSURE MOVING BY TO OUR WEST WHICH WOULD LEAD TO MAINLY RAIN FOR SATURDAY. THE NORTHERN STREAM ENERGY IS SHOWN TO BE VERY IMPRESSIVE AND IT MERGES WITH THE SOUTHERN STREAM ENERGY SATURDAY NIGHT INTO SUNDAY WHICH WOULD LEAD TO FALLING TEMPERATURES...INCREASING WINDS AND RAIN CHANGING TO SNOW SATURDAY NIGHT AND CONTINUING INTO SUNDAY. MODELS HAVE BEEN WAVERING OVER THE DETAILS OVER THE LAST COUPLE OF DAYS BUT WILL MAKE A FEW ADJUSTMENTS TO CURRENT FORECAST WHICH LINE UP WITH SURROUNDING OFFICES...LIKE INCREASING POPS AND GOING WITH A CHANGEOVER TO ALL SNOW SATURDAY NIGHT INTO SUNDAY. SULLIVAN && .APX WATCHES/WARNINGS/ADVISORIES... MI...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR MIZ019>036-041-042. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1030 AM EST WED DEC 19 2007 .UPDATE....12Z SURFACE/RAOB/RUC ANALYSIS AND IR/WV/RADAR IMAGERY SHOW A SHORTWAVE AND ASSOCIATED SURFACE LOW MOVING ACROSS NE LOWER...A COLD FRONT EXTENDING FROM THIS LOW SOUTH TOWARDS LANSING...AND A SURFACE TROUGH EXTENDED NW TOWARDS MQT. LIGHT RADAR RETURNS CONTINUE TO MOVE SE ON THE WESTERN FLANK OF THE SURFACE LOW...ENHANCED A BIT BY THE AFOREMENTIONED SURFACE TROUGH. NUMEROUS LOCATIONS ARE STILL REPORTING LIGHT FREEZING DRIZZLE...MIXED WITH FLURRIES OR LIGHT SNOW AT TIMES ACROSS NORTHERN LOWER...AND THE 12Z APX SOUNDING SUGGESTS WHY WITH THE MOISTURE DEPTH ONLY REACHING UP TO -11C. ACARS SOUNDING OUT OF KINROSS SHOWS DEEPER MOISTURE UP TO -15C WHICH EXPLAINS ALL SNOW BEING REPORTED ACROSS EASTERN UPPER. NW WINDS BEHIND THE LOW ARE FUNNELING IN SLIGHTLY COOLER 850MB TEMPS THAN THE MODELS PORTRAY...GIVING RISE TO POTENTIAL LAKE EFFECT PRECIP HEADING INTO THE AFTERNOON. BUT FIRST...HAVE TO DEAL WITH TIMING OF NUISANT -FZDZ COMING TO AN END. MAIN AREA OF -FZDZ MIXED WITH LIGHT SNOW WILL CONTINUE SOUTH ACROSS THE CWA THROUGH EARLY AFTERNOON. EXIT TIMING BASED ON RADAR AND SATELLITE LOOPS IS AROUND 18Z ACROSS THE FAR SE CWA...BUT THERE MAY BE SOME LINGERING FZDZ BASED ON LOWER VSBYS ACROSS THE TIP OF THE MITT SO HAVE EXTENDED WINTER WEATHER ADVISORY THROUGH 19Z. ALTHOUGH THE PRIMARY ROADS ARE PROBABLY OK BY NOW...UNTREATED SECONDARY ROADS MAY STILL BE A LITTLE ICY. THEREAFTER...NW FLOW BECOMES ESTABLISHED (ALREADY TAKING SHAPE ACROSS LAKE SUPERIOR) WITH MARGINAL DELTA T/S AROUND 13-14C AND EXPECT A TRANSITION TO LIGHT NW FLOW LAKE EFFECT FROM MID-AFTERNOON ONWARD. INSTABILITY IS ONLY MARGINAL...SO ACCUMULATIONS SHOULD BE A HALF INCH OR LESS...WHICH THE CURRENT FORECAST DISPLAYS WELL. CLOUD COVER WILL REMAIN CLOUDY ALL DAY...AND TEMPERATURES THEREFORE WILL NOT INCREASE TOO MUCH. SO HIGHS IN THE LOW-MID 30S LOOKS GOOD. MPC && .AVIATION... /ISSUED 632 AM EST WED DEC 19 2007/ ABUNDANT LOW LEVEL MOISTURE ASSOCIATED WITH WEAK SURFACE LOW PRESSURE MOVING ACROSS FAR NORTHERN LOWER MICHIGAN EARLY THIS MORNING IS RESULTING IN LOW END MVFR CIGS AND VISIBILITIES IN BR AND LIGHT FREEZING DRIZZLE AT TVC AND APN AND FREEZING DRIZZLE AND SNOW AT PLN. EXPECT THESE CONDITIONS TO PERSIST THROUGH MUCH OF THIS MORNING UNTIL SLIGHTLY DRIER AIR FILTERING INTO THE REGION HELPS PUT AN END TO THE FREEZING DRIZZLE. HOWEVER...LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED TO DEVELOP THIS AFTERNOON...BUT MUCH OF THIS ACTIVITY WILL FALL BETWEEN TAF SITES. WINDS WILL PICK UP OUT OF THE NORTHWEST LATER THIS MORNING INTO THIS AFTERNOON BUT DIMINISH THIS EVENING. AJS && DISCUSSION...ISSUED 510 AM ON THE LATEST SURFACE WEATHER MAP...1009 MB LOW PRESSURE WAS CENTERED ACROSS NORTHERN LAKE MICHIGAN. SATELLITE LOOPS AND SURFACE OBSERVATIONS INDICATED THAT A STRATOCU DECK HAD OVERSPREAD THE REGION. APX RADAR CONTINUED TO SHOW 16-20 DBZ RETURNS FROM THE TIP OF THE MITT INTO EASTERN UPPER OF THE LAST FEW HOURS. MEANWHILE...A BROAD AREA OF 4-8 DBZ RETURNS DEVELOPED ACROSS SOUTHWEST AND SOUTH CENTRAL COUNTIES A COUPLE OF HOURS AGO WITH A SLOW PROGRESSION TO THE EAST. THE MAIN FORECAST CONCERNS REVOLVE AROUND EXTENT OF FREEZING DRIZZLE AND POSSIBLE HEADLINES THIS MORNING...POPS THURSDAY NIGHT AND HOW MUCH TO TWEAK THE DETAILS OF THE POTENTIAL MAJOR STORM SYSTEM THIS WEEKEND. CLIPPER AND ASSOCIATED AREA OF DIVQ WILL CONTINUE TO MOVE ACROSS FAR NORTHERN ZONES THIS MORNING. SO FAR ONLY LIGHT SNOW (NO FREEZING DRIZZLE) HAS BEEN REPORTED ACROSS THE TIP OF THE MITT AND EASTERN UPPER. MEANWHILE TO THE SOUTH LIGHT RETURNS CORRESPOND TO RECENT REPORTS OF FREEZING DRIZZLE AND DEVELOPING ICY CONDITIONS. MODEL SOUNDINGS/CROSS SECTIONS MOISTEN UP THE COLUMN THROUGH BETWEEN -12 AND -14 C THIS MORNING WHICH WOULD MEAN THAT ANY PRECIPITATION THAT FALLS WOULD BE IN THE FORM OF SNOW. HOWEVER...WITH THE TRACK OF THE CLIPPER (ACROSS THE FAR NORTH) ITS HARD TO BELIEVE THAT IT WOULD MOISTEN UP THIS MUCH SOUTH OF THE SURFACE LOW TRACK. THIS IS BORNE OUT WITH THE INCREASING NUMBER OF FREEZING DRIZZLE REPORTS. THEREFORE WILL ISSUE A WINTER WEATHER ADVISORY FOR THIS MORNING ACROSS ALL ZONES IN NORTHERN LOWER WITH THE EXCEPTION OF THE COUNTIES IN THE TIPP OF THE MITT WHERE MAINLY LIGHT SNOW IS EXPECTED. AS FAR AS SNOW AMOUNTS ACROSS THE FAR NORTH...ONLY EXPECTING LESS THAN AN INCH OF ACCUMULATION. WINDS VEER INTO THE NORTHWEST THIS AFTERNOON AND OVER LAKE INSTABILITY APPEARS TO BE MARGINALLY SUFFICIENT TO SUPPORT LIGHT LAKE EFFECT SNOW SHOWERS (LAKE-850 MB DELTA TS INCREASE TO BETWEEN 13 TO 14) WITH 900-700 MB RH STILL 60 TO 80 PERCENT AND. SO WILL ADD IN NUMEROUS LIGHT SNOW SHOWERS WITH AN INCH OR LESS OF ACCUMULATION INTO FAVORED NW FLOW AREAS. CLOUDS ARE EXPECTED TO HANG IN ALL DAY WITH MODEST COLD AIR ADVECTION. TEMPERATURES SHOULD REMAIN NEARLY STEADY OR FALL BY A COUPLE OF DEGREES (GENERALLY AROUND 30 TO THE LOWER 30S). TONIGHT...NAM LINGERS OVER LAKE INSTABILITY/MOISTURE WELL INTO THIS EVENING WHILE THE GFS HAS PRONOUNCED DRYING (MEAN 900-700 MB RH <40 PERCENT) AND WARMING (850 TEMPS INCREASE BY A FEW DEGREES). AT THIS POINT WILL GO WITH A COMPROMISE SOLUTION WITH ONLY A CHANCE OF LIGHT LAKE EFFECT SNOW SHOWERS IN NORTHWEST FLOW AREAS THROUGH MIDNIGHT AS MEAN SURFACE-850 MB WINDS BARELY SUPPORT ORGANIZED LAKE EFFECT (10 KNOTS OR SO). INCREASING RIDGING/SUFFICIENT WARMING/DRYING OVERNIGHT SHOULD PUT THE KABOSH ON ANY LINGERING ACTIVITY. LOWS TONIGHT IN THE MIDDLE TEENS TO LOWER 20S. THURSDAY...RIDGING AT THE SURFACE AND ALOFT FOR MUCH OF THE DAY. GFS IS FASTER THAN THE NAM WITH MOISTURE RETURN WITH DEVELOPING SOUTHERLY FLOW BUT THIS APPEARS TO BE A BIT QUICK. FOR NOW WILL CONTINUE WITH PARTLY CLOUDY AND MILD CONDITIONS WITH INCREASING CLOUDINESS LATE IN THE DAY. HIGHS IN THE MILD LOWER AND MIDDLE 30S. THURSDAY NIGHT...WARM ADVECTION SHOULD INCREASE PER NAM/GFS LEADING TO THICKENING CLOUD DECK. MOISTURE DEPTH IS QUESTIONABLE FOR PRECIPITATION PRODUCTION BUT WILL ADD IN A CHANCE OF FLURRIES OVERNIGHT. THERE EVEN COULD BE SOME FREEZING DRIZZLE ONCE AGAIN BUT WILL LET THE DAYSHIFT TAKE A BETTER LOOK AT THAT SCENARIO DUE TO LIMITED TIME CONSTRAINT`S AT THE MOMENT. LOWS IN THE LOWER AND MIDDLE 20S. FRIDAY...CONTINUED SOUTHERLY FLOW WITH DRY MID LEVELS SO A MOSTLY CLOUDY DAY IS EXPECTED WITH HIGHS GENERALLY IN THE MIDDLE 30S. FRIDAY NIGHT THROUGH SUNDAY...COMPLEX WEATHER SITUATION SHAPING UP WITH ENERGY IN THE SOUTHERN JET STREAM MOVING NORTHEAST OUT OF THE DESERT SOUTHWEST WHILE ENERGY IN THE NORTHERN JET STREAM DROPS DOWN OUT OF CENTRAL CANADA. EXTENDED MODELS THIS RUN ARE IN BETTER AGREEMENT THAT THE SOUTHERN ENERGY IMPACTS THE AREA FIRST WITH LOW PRESSURE MOVING BY TO OUR WEST WHICH WOULD LEAD TO MAINLY RAIN FOR SATURDAY. THE NORTHERN STREAM ENERGY IS SHOWN TO BE VERY IMPRESSIVE AND IT MERGES WITH THE SOUTHERN STREAM ENERGY SATURDAY NIGHT INTO SUNDAY WHICH WOULD LEAD TO FALLING TEMPERATURES...INCREASING WINDS AND RAIN CHANGING TO SNOW SATURDAY NIGHT AND CONTINUING INTO SUNDAY. MODELS HAVE BEEN WAVERING OVER THE DETAILS OVER THE LAST COUPLE OF DAYS BUT WILL MAKE A FEW ADJUSTMENTS TO CURRENT FORECAST WHICH LINE UP WITH SURROUNDING OFFICES...LIKE INCREASING POPS AND GOING WITH A CHANGEOVER TO ALL SNOW SATURDAY NIGHT INTO SUNDAY. SULLIVAN && .APX WATCHES/WARNINGS/ADVISORIES... MI...WINTER WEATHER ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR MIZ019>036-041-042. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE MARQUETTE MI 1235 AM EST WED DEC 19 2007 UPDATED AVIATION DISCUSSION .SHORT TERM... THE MAIN CONCERN WITH THE SHORT TERM PORTION OF THE FORECAST PACKAGE IS THE POTENTIAL FOR SNOW AND FREEZING DRIZZLE TONIGHT. WATER VAPOR IMAGERY AND RUC SHOWING A WEAK TROUGH OVER MINNESOTA...A WEAK RIDGE OVER THE UPPER GREAT LAKES AND ANOTHER OVER THE NORTHERN HIGH PLAINS. ANOTHER TROUGH IS DIGGING OVER THE PACIFIC NORTHWEST. SURFACE ANALYSIS DEPICTS A LOW OVER CENTRAL WISCONSIN WITH A STATIONARY FRONT EXTENDING EAST FROM THIS INTO NORTHERN LAKE MICHIGAN...AND NORTHWEST THROUGH NORTHERN MINNESOTA. A WEAK SURFACE TROUGH EXTENDS SOUTH FROM THIS LOW THROUGH THE CENTRAL MISSISSIPPI RIVER VALLEY. A RIDGE BLANKETS MUCH OF CENTRAL AND SOUTHERN PLAINS. THE MID LEVEL TROUGH WILL REACH CENTRAL U.P. BY MIDNIGHT...NORTHERN LAKE HURON BY SUNRISE AND EASTERN ONTARIO BY LATE AFTERNOON. THE SURFACE LOW WILL MOVE THROUGH SOUTHERN U.P. AND NORTHERN LAKE MICHIGAN...REACHING NORTHERN LAKE HURON BY SUNRISE. THE BEST ISENTROPIC ASCENT AND DEEPER MOISTURE WITH THIS SYSTEM WILL BE THIS EVENING OVER THE U.P. THIS HEAVIEST PRECIPITATION WILL MOVE INTO EASTERN LAKE SUPERIOR LATE. A RIDGE WITH DRIER AIR WILL PUSH INTO THE WESTERN U.P. ON WEDNESDAY CAUSING THE SNOW TO DIMINISH. .LONG TERM (WED NIGHT THROUGH NEXT TUE)... MAIN FORECAST CONCERN AND WILL CONTINUE FOR THE REST OF THE WEEK IS A WINTER STORM THAT COULD AFFECT THE CWA THIS WEEKEND. PEOPLE TRAVELING THIS WEEKEND SHOULD MONITOR FORECASTS DAILY AS MODELS COME INTO BETTER AGREEMENT. WED NIGHT THROUGH FRI...MUCH OF THIS PERIOD WILL GENERALLY BE QUIET WITH ONLY SOME LIGHT PCPN CHANCES FOR THU AND FRI. ON WED NIGHT...UPPER RIDGING IS PROGGED OVER THE AREA WHILE A SHRTWV APPROACHES DULUTH AROUND 12Z THU. SUBSIDENCE UNDER THE UPPER RIDGE SHOULD KEEP MUCH OF THE CWA DRY...AND APPEARS TO BE STRONG ENOUGH PER MODEL SOUNDINGS TO REMOVE ANY CLOUDS. GENERAL LIGHT WINDS IN THE EVENING ASSOCIATED WITH A SURFACE HIGH PRESSURE RIDGE...ALONG WITH PRECIPITABLE WATER VALUES BELOW 0.3 OF AN INCH...WILL ALLOW TEMPS TO DROP THROUGH THE DEWPOINTS AND PROMOTE SOME FOG DEVELOPMENT. GOING FORECAST LOW TEMPS SEEM REASONABLE. ON THU...THE SHRTWV NEAR DULUTH LIFTS NE INTO NORTHERN ONTARIO WHILE RIDGING REMAINS LOCKED IN OVER THE EASTERN CWA. THUS...HAVE RESTRICTED ANY PCPN CHANCES ASSOCIATED WITH DPVA FROM THE SHRTWV TO THE WEST HALF OF THE CWA. THESE PCPN CHANCES ARE SMALL...THOUGH...SINCE THE SHRTWV HAS LITTLE MOISTURE TO WORK WITH...PRIMARILY DUE TO THE LOW PRECIPITABLE WATER AIRMASS THAT MOVED IN WED NIGHT. AN INCREASE IN MID/HIGH CLOUDS IS LIKELY ACROSS THE CWA...THOUGH...WHICH SHOULD PREVENT TEMPS FROM CLIMBING TOO HIGH (STILL MAKING IT NEAR FREEZING). ANOTHER WEAK SHRTWV MAY MOVE ACROSS THE CWA THU NIGHT IN THE SW FLOW ALOFT BETWEEN TROUGHING OUT WEST AND RIDGING BUILDING IN THE EAST. EITHER THIS SHRTWV OR WARM ADVECTION ASSOCIATED WITH THE RIDGE COULD TOUCH OFF SOME LIGHT PCPN...PARTICULARLY IN THE WEST HALF WHERE MORE MOISTURE IS PRESENT. LOW CONFIDENCE IN FORCING MAINTAINS POPS AT 20. MUCH OF THE MOISTURE TOO IS SITUATED BELOW THE -10C ISOTHERM...AND THUS INCLUDE A MENTION OF FREEZING DRIZZLE. A MENTION OF FREEZING DRIZZLE WITH SLIGHT CHANCE POPS FOR SNOW CONTINUES INTO FRIDAY WITH PLENTY OF LOW LEVEL MOISTURE AROUND...AND A WEAK WARM ADVECTION PATTERN. IF FREEZING DRIZZLE OCCURS...IT COULD SWITCH OVER TO JUST DRIZZLE AS TEMPERATURES ARE EXPECTED TO CLIMB TO AROUND FREEZING. FRI NIGHT THROUGH CHRISTMAS... MODEL DIFFERENCES.. THE BIG QUESTION THROUGH THIS TIME RANGE IS WHAT HAPPENS WITH THE SPLIT LONG WAVE TROUGH THAT STRETCHES FROM SASKATCHEWAN TO ARIZONA/NEW MEXICO AT 00Z SAT. THIS LONG WAVE TROUGH CONSISTS OF AN UPPER LOW IN SOUTHERN SASKATCHEWAN AND A POTENT SHRTWV IN SOUTHERN ARIZONA/NEW MEXICO. WARM ADVECTION AHEAD OF THE LONG WAVE TROUGH SHOULD PRODUCE A FAIRLY STRONG RIDGE FROM THE GULF COAST NORTHWARD INTO MI BY FRI EVENING. THE STRENGTH OF THIS RIDGE WILL DETERMINE WHETHER THE TWO FEATURES IN THE LONG WAVE TROUGH PHASE TOGETHER... RESULTING IN A SLOWER AND DEEPER LOW HEADING TOWARDS UPPER MI...OR IF THEY STAY UNPHASED AND PRODUCE A MORE PROGRESSIVE AND WEAKER LOW THAT HEADS EAST OF THE AREA. THE 00Z CANADIAN/ECMWF FALL INTO THE SLOWER AND DEEPER CAMP...BRINGING A LOW NORTHWARD FROM NEAR SPRINGFIELD MISSOURI AT 00Z SUN INTO CENTRAL UPPER MI AROUND 00Z MON. THE FASTER CAMP SUGGESTED BY THE 00Z/06Z GFS WOULD BRING A LOW UP FROM WESTERN KY AT 00Z SUN TO GEORGIAN BAY AT 00Z MON. THE 00Z UKMET CONSISTS OF PROPERTIES FROM BOTH CAMPS...BRINGING A LOW TO NE WI AT 00Z SUN AND THEN LIFTS INTO QUEBEC AT 00Z MON. GIVEN THE OTHER OPERATIONAL MODELS AND PREVIOUS RUNS...THE 00Z UKMET CAN BE THROWN OUT AS AN OUTLIER. HOWEVER...DECIDING WHETHER THE SLOWER OR FASTER CAMP IS THE CORRECT IDEA PROVES MUCH MORE DIFFICULT...AND FOR NOW WILL STICK WITH HPCS PLAN AND TO PRESERVE CONTINUITY BY FOLLOWING THE ECMWF. NOTE TOO THAT MODEL BIASES ARE USUALLY TOO FAST WITH EJECTING LONG WAVE TROUGHS OUT OF THE WEST...WHICH MAY LEAD SOME CREDENCE TO THE SLOWER IDEA. BY THE WAY...THE MAIN SHRTWV RESPONSIBLE FOR THE DEEP LOW IS STILL OUT AT THE WEST END OF THE ALEUTIANS...THUS LEAVING ROOM FOR OTHER POSSIBLE SOLUTIONS (SEE 12Z UKMET WHICH CUTS OFF THE SOUTHERN STREAM SHRTWV ENTIRELY). DETAILS.. FOR FRI NIGHT...THE ECMWF SHOWS A SHRTWV MOVING INTO WESTERN WI BY 12Z SAT WITH A NORTH/SOUTH SURFACE TROUGH ASSOCIATED WITH IT. DPVA AHEAD OF THIS SHRTWV COULD BRING SOME LIGHT PCPN INTO THE AREA. 925MB TEMPS AROUND 0C WOULD SUGGEST A BETTER LIKELIHOOD OF RAIN. ON SAT...THIS SURFACE TROUGH SHOULD MOVE INTO THE CWA AND STALL AS THE STRONG SYSTEM BEGINS DEVELOPS IN MISSOURI. MORE LIGHT PCPN COULD FALL ALONG THE TROUGH...WITH RAIN IN THE EAST AND A RAIN/SNOW MIX CENTRAL AND WEST. ON SAT NIGHT...THE SURFACE LOW IN MISSOURI WILL DEEPEN AS IT HEADS TOWARDS THE AREA IN RESPONSE TO THE SOUTHERN FEATURE MERGING WITH THE UPPER LOW COMING OUT OF SASKATCHEWAN. THE PHASING OF THE UPPER FEATURES OCCURS OVER IOWA AT 12Z SUN WITH A LOW MOVING UP TO MILWAUKEE. THE PHASING SHOULD ALSO PRODUCE A LARGE WIDESPREAD AREA OF PCPN FROM WI AND INTO UPPER MI LATER IN THE NIGHT. 925MB TEMPS CONTINUE TO SHOW THAT BI-SECTION OF RAIN AND SNOW OVER THE AREA...WITH BEST CHANCE FOR RAIN EAST AND THE SNOW TO THE WEST. ON SUN...THE PHASED UPPER LOW HEADS UP TOWARD GREEN BAY AND CAUSES THE LOW NEAR MILWAUKEE TO BECOME OCCLUDED NEAR MNM. THIS OCCLUSION SHOULD RESULT IN ENOUGH COOLING TO TO CHANGE ANY RAIN TO SNOW OVER THE CWA...ESPECIALLY OVER THE WEST AND CENTRAL. IF THE 00Z ECMWF/CANADIAN SOLUTION IS CORRECT...THERE IS A VERY BIG CONCERN THAT A WINTER STORM/BLIZZARD COULD OCCUR SUNDAY INTO SUNDAY NIGHT ACROSS THE WEST HALF OF UPPER MI...ESPECIALLY SINCE 850MB TEMPS COOL DRAMATICALLY IN THE WEST DURING THE DAY WHICH WOULD RESULT IN LAKE ENHANCEMENT. WINTER STORM CONDITIONS COULD ALSO OCCUR IN THE EAST...PROBABLY SUNDAY AFTERNOON INTO SUNDAY NIGHT. NOTE THAT SINCE THE SYSTEM HAS A STRONG GULF OF MEXICO FEED...A HEAVY WET SNOW WOULD OCCUR. HOWEVER...DO NOT HAVE 100 PERCENT CONFIDENCE ON A BIG SYNOPTIC SNOW GIVEN THE 12Z UKMET. AGAIN...STAY TUNED TO LATER FORECASTS. AS THE UPPER LOW PULLS OUT CHRISTMAS EVE...EXPECT THE SYNOPTIC PCPN TO CHANGE OVER TO LAKE EFFECT WITH 850MB TEMPS ONLY RISING TO -10 TO -13C BY 00Z TUE. UPPER TROUGHING LINGERS OVER THE AREA ON CHRISTMAS...BUT 850MB TEMPS DO MANAGE TO RISE TO AROUND -8C AS HIGH PRESSURE BUILDS IN FROM THE WEST. THESE TEMPS ARE MARGINALLY COLD ENOUGH FOR LAKE EFFECT...BUT WILL LEAVE LAKE EFFECT CHANCES IN JUST IN CASE THE WEEKEND STORM IS SLOWER. IT COULD TURN OUT THAT CHRISTMAS IS DRY. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... SFC LOW LOCATED OVER THE CENTRAL UPPER PENINSULA CONTINUES TO DRIFT E THIS AM. BACK EDGE OF WRAP AROUND SNOW MOVING THROUGH KCMX...WITH VSBY IMPROVING AS SNOW INTENSITY LESSENS. PRES GRADIENT TO ALSO GRADUALLY SLACKENS AT KCMX BRINGING AN END TO GUSTY CONDITIONS THERE. CIGS TO VARY BETWEEN MVFR AND IFR AS INVERSION STRENGTHENS OVERNIGHT WITH WEAK RIDGING MOVING IN BEHIND THE LOW. THERE REMAINS A POTENTIAL FOR FREEZING DRIZZLE AS BUFKIT SOUNDINGS SHOW LOW LEVELS REMAIN SATURATED UNDER THE INVERSION THROUGH THE REMAINDER OF THE MORNING AT KCMX AND KSAW. BOTH LOCATIONS TO SEE A GRADUALL IMPROVEMENT LATE IN THE DAY AS THE SFC RIDGE PUSHES IN. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... THE PRESSURE GRADIENT OVER LAKE SUPERIOR CAUSING NE WINDS INTO THE 15 TO 25 KT RANGE BY THIS EVENING. WINDS SHOULD DIMINISH LATE TONIGHT AND WED AS THE LOW MOVES AWAY FROM LAKE SUPERIOR AND A RIDGE OF HIGH PRESSURE BUILDS INTO THE REGION. AS THIS RIDGE MOVES OFF TO THE EAST ON THURSDAY...SOUTHERLY FLOW WILL INCREASE ON LAKE SUPERIOR WITH WINDS TO NEAR 30 KT BY THURSDAY NIGHT INTO EARLY FRIDAY. A STRONG SURFACE LOW IS EXPECTED TO MOVE TOWARDS THE UPPER GREAT LAKES ON SATURDAY. DEPENDING ON THE TRACK AND TIMING...GALE FORCE WINDS CLOUD DEVELOP. RIGHT NOW THE BEST POSSIBILITY FOR GALES APPEARS TO BE VERY LATE SATURDAY NIGHT AND INTO THE DAY ON SUNDAY AS THE LOW CROSSES WHITEFISH BAY SUNDAY MORNING. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...DLG LONG TERM...AJ AVIATION...RJT MARINE...DLG mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1145 PM EST TUE DEC 18 2007 .AVIATION...ABUNDANT LOW LEVEL MOISTURE ASSOCIATED WITH WEAK SURFACE LOW PRESSURE APPROACHING FROM CENTRAL UPPER MICHIGAN WILL CONTINUE TO OVERSPREAD THE AREA TONIGHT...RESULTING IN LOW END MVFR CIGS AND VISIBILITIES IN BR AND LIGHT FREEZING DRIZZLE AND SNOW. EXPECT THESE CONDITIONS TO PERSIST THROUGH MUCH OF TOMORROW MORNING UNTIL SLIGHTLY DRIER FILTERING INTO THE REGION HELPS SCOUR OUT SOME OF THE LOW LEVEL MOISTURE AND ACCOMPANYING LIGHT PRECIP. WINDS WILL REMAIN LIGHT THROUGH THE DURATION OF THE FORECAST PERIOD. MSB && .UPDATE...ISSUED 1020 PM LATEST ANALYSIS SHOWS A 1010 MB LOW CENTERED NEAR MARQUETTE OUT AHEAD OF LOW AMPLITUDE SHORTWAVE CUTTING EAST ACROSS NORTHERN WISCONSIN. MODEST LOW AND MID LEVEL SOUTHWEST FLOW ISENTROPIC UPGLIDE ALONG AND AHEAD OF THESE FEATURES AND NORTH OF A WARM FRONT EXTENDING FROM THE LOW INTO THE STRAITS REGION HELPING KICK A SHIELD OF LIGHT...TO OCCASIONALLY MODERATE...SNOW OVER CENTRAL AND WESTERN SECTIONS OF THE UPPER PENINSULA. SOUTH OF THIS SNOW SHIELD LIES AN EXTENSIVE 2KFT TO 3KFT LOW CLOUD DECK...WHICH EXTENDS ACROSS MUCH OF WISCONSIN AND HAS RECENTLY MADE INROADS INTO WESTERN SECTIONS OF OUR FORECAST AREA. AS ALWAYS...NOCTURNAL TEMPERATURE RESPONSE A PRODUCT OF CLOUD COVER...WITH TEMPERATURES RANGING FROM THE MID 30S NEAR FRANKFORT AND MANISTEE TO THE UPPER TEENS AND LOW 20S WHERE SKIES HAVE CLEARED OUT IN SOUTHEAST SECTIONS OF THE CWA. CURRENT TRENDS SUPPORT ONGOING FORECAST...WITH LIGHT SNOW AND POSSIBLE PATCHY FREEZING DRIZZLE OVERSPREADING MUCH OF EASTERN UPPER MICHIGAN AND THE STRAITS REGION LATER THIS EVENING INTO THE MORNING HOURS AS UPSTREAM LOW PRESSURE CUTS ALONG THE TIP OF THE MITT. SOUTH OF THIS AREA...LATEST MODEL SOUNDING GUIDANCE STILL SUPPORTING THE DEVELOPMENT OF FREEZING DRIZZLE (ESPECIALLY OVER THE HIGHER TERRAIN AREAS WITH THE HELP OF LIGHT UPSLOPE FLOW) WITH SATURATED CONDITIONS FALLING SHORT OF THE FAVORABLE ICE NUCLEATION -10C TEMPERATURE. AS FOR A WINTER WEATHER ADVISORY...WILL HOLD OF FOR NOW...ESPECIALLY IN LIGHT OF LACK OF UPSTREAM OBS REPORTING FREEZING DRIZZLE AT THIS TIME. WHILE SLOW TO DEVELOP THIS EVENING...FOG FORMATION IS STILL EXPECTED AS SURFACE TEMPERATURE SLOWLY COOL. BASED OF CURRENT TRENDS...BASICALLY ONLY COSMETIC CHANGES NEEDED ON GRIDS...WITH MAIN EMPHASIS ON MINOR TIMING ADJUSTMENTS AND OVERNIGHT TEMPERATURE TRENDS. UPDATED GRIDS/ZONES/NEARSHORES OUT SHORTLY. MSB && .DISCUSSION...ISSUED 351 PM LATEST SURFACE/RUC ANALYSIS AND VIS/IR/WV IMAGERY SHOW MORE OR LESS ZONAL FLOW ACROSS NORTH AMERICA WITH A SHORTWAVE NOTED OVER THE PACIFIC NW AND WEAKER WAVES OVER MN AND LAKE WINNIPEG. 290-295K ISENTROPIC LIFT AHEAD OF THESE DUAL WAVES HAS LED TO A THINNING MID-HIGH LEVEL CLOUD DECK THAT IS MOVING ACROSS THE CWA. LINGERING LOW LEVEL MOISTURE BENEATH THE SUBSIDENCE INVERSION STILL IS CONTRIBUTING TO A LOW END MVFR CLOUD DECK THAT HAS JUST ERODED ACROSS CAD/HTL...WHILE MOISTURE FLUXES AND VERY SHALLOW OVER WATER INSTABILITY OFF LAKE MICHIGAN HAS KEPT THE CLOUDS NEAR MBL/FKS AND ACROSS EASTERN UPPER. WITH THE THINNING CLOUD DECK...TEMPERATURES HAVE WARMED ABOVE FREEZING ACROSS MUCH OF NORTHERN MICHIGAN. MEANWHILE...MVFR CLOUDS OVER NORTHERN WI HAVE BEEN BLOSSOMING THIS AFTERNOON AND MOVING EAST AHEAD OF A WEAK SURFACE LOW OVER WESTERN WI. AS THIS SURFACE LOW MOVES ACROSS NORTHERN MICHIGAN TONIGHT AND LOW LEVEL MOISTURE INCREASES...MAIN FORECAST CONCERNS INCLUDE PRECIP CHANCES AND TYPE...WHICH THEN LASTS THROUGH TOMORROW. TONIGHT...MN SHORTWAVE AND ASSOCIATED WEAK SURFACE LOW WILL APPROACH NORTHERN LAKE MICHIGAN THIS EVENING AND PASS ACROSS THE TIP OF THE MITT OVERNIGHT. MOISTURE DEPTH WILL BE INITIALLY BELOW 900MB...TO START THE EVENING...THEN STEADILY INCREASE AS THE NIGHT WEARS ON. WATCHING TRENDS THIS AFTERNOON...THE 12KM NAM APPEARS TO HAVE A GOOD BEAD ON THINGS AND HAVE FOLLOWED ITS SOLUTION MORE CLOSELY. THIS MOISTURE DEPTH DOES NOT APPROACH THE -10C ISOTHERM UNTIL AFTER ABOUT 04Z AND THATS MOSTLY NORTH OF M-68. AS MOISTURE INCREASES DURING THE EVENING...HAVE INTRODUCED PATCHY FOG AND FREEZING DRIZZLE ACROSS MOST OF NW LOWER AND EASTERN UPPER. BELIEVE SOME PRECIP MAY JUST BE ALL LIQUID RIGHT ALONG THE LAKE MICHIGAN SHORELINE SINCE TEMPERATURES THIS AFTERNOON HAVE RISEN TO 40F AT TVC. AS TEMPERATURES COOL BY MID TO LATE EVENING...ANY DRIZZLE SHOULD TURN INTO THE FREEZING VARIETY...WHILE INTRODUCED OCCASIONAL LIGHT SNOW FROM THE TIP OF THE MITT ON NORTH SINCE THE PROBABILITY OF ICE NUCLEATION INCREASES BY THIS TIME. THESE PRECIP TYPES THEN MAINTAIN CONTINUITY OVERNIGHT (OCCASIONAL LIGHT SNOW MIXED WITH PATCHY FREEZING DRIZZLE AND FOG FROM THE TIP OF THE MITT ON NORTH...AREAS OF FREEZING DRIZZLE AND FOG FROM THE TIP OF THE MITT ON SOUTH). HAVE ALSO THROWN IN AREAS OF FOG SINCE VISIBILITIES TODAY HAVE BEEN REALLY SLOW TO IMPROVE BEYOND 6SM AND VSBYS OVER WI ARE IN THE 3-5SM RANGE. ADDED MOISTURE FROM LOCALIZED MELTING SNOW WILL ALSO HELP IN FOG FORMATION AS TEMPERATURES COOL TONIGHT. WITH ANY WINTRY PRECIP...THERE IS POTENTIAL FOR A HEADLINE LATER TONIGHT...BUT WILL HOLD OFF FOR NOW AND THE EVENING CREW CAN SEE HOW THE FORECAST DEVELOPS. MPC WEDNESDAY...SFC LOW PRESSURE SCOOTING ACROSS NRN LAKE HURON IN THE MORNING WITH WRAP AROUND DEEPER MOISTURE SWINGING ACROSS THE REGION IN ASSOCIATION WITH STRONG H7-H5 -DIVQ. THIS IS LIKELY TO BRING AT LEAST A PERIOD OF LIGHT SNOW TO NRN MICHIGAN NORTH OF M-72. SOUTH OF THERE...THE MOISTURE OFF VARIOUS FORECAST SOUNDINGS NEVER TOUCHES THE MAGICAL -10C ISOTHERM. WILL GO WITH JUST AREAS OF FOG AND FREEZING DRIZZLE SOUTH OF M-72...AND WILL GO WITH OCCASIONAL LIGHT SNOW/FLURRIES WITH AREAS OF FREEZING DRIZZLE NORTH OF M-72. WITH SFC LOW OVERHEAD...AND RESULTANT CONVERGENCE AND DEEP LOW LEVEL MOISTURE ADVECTION...FEEL AS THOUGH THE DRIZZLE OCCURRENCE IS RATHER LIKELY. ANY POTENTIAL HEADLINES (FREEZING RAIN ADVISORY) THAT MAY BE NEEDED BY EVENING CREW TONIGHT...WOULD BE NEEDED INTO WEDNESDAY MORNING. AS THIS SFC LOW DEPARTS FURTHER EAST IN THE AFTERNOON...MOISTURE REALLY BEGINS TO STRIP OUT. THE LOSS OF CONVERGENCE/WIND SHEAR IN THE SHALLOWING MOIST LAYER CEASES...AND CHANCES FOR DRIZZLE ARE SEEMINGLY GONE. FEEL THAT SKIES WILL JUST REMAIN RATHER CLOUDY BUT WILL INCLUDE A CHANCE FOR FLURRIES...AND REMAIN CONSISTENT WITH PREVIOUS FORECAST. WEDNESDAY NIGHT...SFC RIDGE AXIS/COL REGION SLIPS IN OVERHEAD. MOST AREAS CONTINUE TO DRY...SHALLOW OUT THE LOW LEVEL MOISTURE. THERE IS SOME TRAPPED SHALLOW MOISTURE SEEN ON FORECAST SOUNDINGS...MAINLY ACROSS NE LOWER NEAR 925MB CONVERGENCE AXIS. FEEL THAT MOSTLY CLOUDY/CLOUDY SKIES WILL RULE THIS REGION FOR MOST...IF NOT ALL OF THE NIGHT. A NE WIND ACROSS EASTERN UPPER...MAY HELP SKIES CLEAR OUT DUE TO DOWNSLOPING OUT OF ONTARIO...AND SHALLOW OVERLAKE INSTABILITY DOES NOT LOOK SUBSTANTIAL ENOUGH TO OFFSET THE AMOUNT OF DRYING ACROSS NW LOWER. WILL GO WITH LOW END PARTLY CLOUDY FOR NOW. COULD SEE A WEAK LAND BREEZE DEVELOP OVERNIGHT IF WE CLEAR...AND TEMPS WILL FALL INTO THE TEENS IN SPOTS. THESE COLDER TEMPS WITH LIGHT WINDS FROM SFC RIDGE COULD HELP FOG DEVELOP TOO. RECENT WARMER TEMPERATURES HAVE ALSO ADDED MOISTURE TO THE BL...WHICH COULD AID THE FOG DEVELOPMENT. WILL GO WITH PATCHY FOG FOR NOW IN THOSE AREAS EXPECTED TO CLEAR SOME. THURSDAY THROUGH FRIDAY...SFC RIDGE AXIS SLIDES EAST WHILE STRONGER TROUGHING DEVELOPS OVER THE PAC NW. MID LEVEL HEIGHTS RISE OVER NRN MICHIGAN WHICH SPELLS MORE MODERATION OF THE TEMPERATURES. TEMPS THROUGH THE PERIOD WILL REACH THE LOWER AND MIDDLE 30S...AS DEEP SNOWPACK SHOULD KEEP TEMP RISES IN CHECK. A SOUTHERLY FLOW WILL RESULT IN WARMING ALOFT THOUGH...AND A WEAKISH LOOKING WARM FRONT WILL IN FACT WORK ITS WAY THROUGH HERE THURSDAY NIGHT AND FRIDAY. A WING OF MOISTURE AHEAD OF THIS FEATURE WILL RESULT IN MID LEVEL CLOUDINESS WHICH WILL LIKELY LOWER THROUGH FRIDAY AFTERNOON. LOWS THROUGH THURSDAY NIGHT WILL NOT GO FAR WITH INCREASING CLOUDINESS AND INCREASES SOUTH LOW LEVEL FLOW. WILL ONLY DIP READINGS INTO THE 28-31F RANGE. THESE MILDER TEMPERATURES WILL KEEP ADDING MOISTURE TO THE BL...AND LIGHT FOG MAY BE PRESENT FOR A GOOD DEAL OF THE TIME. THERE MAY EVENTUALLY BE SOME LIGHT PRECIPITATION CONCERNS LATE THURSDAY NIGHT AND FRIDAY...BUT WILL KEEP A PRECIP FREE FORECAST FOR NOW AS ANY AMOUNTS WOULD BE VERY LIGHT. THE BETTER CHANCES FOR DEVELOPING PRECIPITATION WILL HOLD OFF UNTIL FRIDAY NIGHT ONWARD. FRIDAY NIGHT ONWARD...ISSUES IN THIS TIME FRAME REVOLVE AROUND STRONG STORM SYSTEM FOR THE WEEKEND LIFTING OUT OF TEXAS. LONG RANGE MODELS SUGGEST THAT ECMWF REMAINS THE MODEL OF CHOICE. OVERALL WEATHER DEVELOPMENT STILL HAS UNCERTAINTIES CONSIDERING THE TIMEFRAME IS QUESTION (5-6 DAYS OUT). THERE IS NOT MUCH CHANGE IN WHAT IS EXPECTED AT THIS POINT...FRIDAY NIGHT WEATHER COULD HAVE A PLETHORA OF WEATHER TYPES DUE TO SFC TEMPERATURES HOLDING AROUND 32F AS MOISTURE INCREASES FROM ABOVE AND BELOW THE COLUMN. THIS WOULD SUGGEST DRIZZLE OR FREEZING DRIZZLE...OR JUST FLAT OUT RAIN. TRENDS KEEP RAIN IN THE FORECAST...BUT A COLDER SCENARIO WOULD SUPPORT SNOW AS WELL...AND WE JUST DO NOT KNOW THOSE SPECIFICS YET. WILL KEEP RAIN AND SNOW IN THE FORECAST ONE MORE TIME...THROUGH SUNDAY MORNING THEN FOLLOW CLOSER TO THE ECMWF. THIS WOULD THEN SUGGEST STRONG COLD ADVECTION (UNDER SOUTHERLY WINDS)...WITH SNOW ENTERING THE PICTURE FOR THE AFTERNOON. SNOW SHOWERS WILL THEN BE LIKELY THROUGH SUNDAY NIGHT. SCATTERED SNOW SHOWERS IN NW FLOW REGIMES MONDAY INTO TUESDAY...BUT WITH MODERATING H8 TEMPS WARMER THAN -10C BY TUESDAY. SMD && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...NONE. LH...NONE. LS...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 850 PM CST THU DEC 20 2007 .DISCUSSION... DENSE FOG CONTINUES TO SPREAD TO THE WEST UNDER INFLUENCE OF A VERY WEAK SURFACE FLOW AROUND LOW PRESSURE TROUGH IN EASTERN MISSOURI AT THIS TIME. MODELS SHOW THIS TROUGH BREAKING DOWN AS STRONGER TROUGHING IN HIGH PLAINS STARTS TO TAKE SHAPE OVERNIGHT WITH LOW LEVEL FLOW BECOMING SOUTHEAST. THIS SHOULD SLOW THE WESTWARD PROGRESSION AFTER MIDNIGHT BUT MAY SPREAD IT MORE INTO NORTHWEST MISSOURI...WHICH IS ALREADY EXPERIENCING PATCHY DENSE FOG UNDER THE CLEAR SKIES AND LIGHT WINDS. BOTH NAM AND RUC 950 MB DEPICTIONS OF THIS MOISTURE WOULD SUGGEST IT MAKING TO NEAR THE MISSOURI KANSAS BORDER IN NORTHWEST MISSOURI OVERNIGHT AND INTO EASTERN PORTIONS OF THE KANSAS CITY METRO AREA. FOR NOW...WILL GO AHEAD AND EXPAND THE ADVISORY TO INCLUDE AREAS THAT ARE SEEING THE WIDESPREAD DENSE FOG SPREADING IN AT THIS TIME...AND KEEP AN EYE ON THE TRENDS...ADDING COUNTIES AS NEEDED. PC && .PREV DISCUSSION... /720 PM CST THU DEC 20 2007/ HAVE MADE SEVERAL PHONE CALLS TO AREAS JUST WEST OF WHERE WE HAD FOG ADVISORY IN EFFECT...AND THEY ARE VERIFYING THE SATELLITE TREND OF THE LOWER VISIBILITIES SPREADING BACK TO THE WEST. WILL EXPAND THE DENSE FOG ADVISORY FURTHER TO THE WEST TO COVER. ESPECIALLY CONCERNED FOR THE INTERSTATES INCLUDING I70 FROM CONCORDIA EASTWARD AND I35 IN HARRISON COUNTY. PC /414 PM CST THU DEC 20 2007/ FORECAST CONCERNS FOR THE FIRST HALF OF THE FORECAST ARE TWO FOLD. TONIGHT WE ARE LOOKING AT CONTINUED DENSE FOG ACROSS AREAS FROM NORTH CENTRAL AND NORTH EAST MISSOURI SOUTH THROUGH CENTRAL MISSOURI. THE SECOND FORECAST CONCERN IS THE WINTER STORM EXPECTED THIS WEEKEND. MOISTURE TRAPPED IN THE BOUNDARY LAYER...AND LIGHT WINDS ASSOCIATED WITH A SURFACE TROUGH...HAVE CONSPIRED TODAY TO KEEP THE EASTERN THIRD OF THE FORECAST AREA UNDER DENSE FOG. CONDITIONS ARE NOT EXPECTED TO CHANGE ACROSS THAT AREA OVERNIGHT. SURFACE TROUGH WILL SLIDE EAST A LITTLE...BUT ONLY ENOUGH TO ALLOW SURFACE WINDS TO SWITCH TO THE SOUTHEAST...ADVECTING MORE MOISTURE IN AT THE SURFACE. HAVE GONE WITH A DENSE FOG ADVISORY FOR THE REST OF THE AFTERNOON THROUGH 10 AM FRIDAY MORNING AS A RESULT. FARTHER WEST SKIES CLEARED TODAY AND THE FOG THAT SET IN DISSIPATED RATHER QUICKLY. TONIGHT WILL SEE THE INVERSION TRAP ABUNDANT MOISTURE AT THE SURFACE AGAIN...BUT WINDS JUST ABOVE THE INVERSION WILL STAY A LITTLE HIGHER IN RESPONSE TO THE DEEPENING TROUGH IN THE WESTERN CONUS. EXPECT THIS SLIGHTLY HIGHER WIND ABOVE THE INVERSION TO INDUCE ENOUGH MIXING OVERNIGHT TO PREVENT THE FOG FROM BECOMING AS DENSE ACROSS THE WESTERN TWO THIRDS OF THE FORECAST AREA. IN FACT...HAVE KEPT FOG OUT OF THE FORECAST FOR AREAS FROM THE KANSAS CITY METRO ON SOUTH AS MODEL SOUNDINGS SHOW THE SURFACE MOISTURE TO BE PARTICULARLY SHALLOW. THIS WILL NEED TO BE WATCHED OVERNIGHT THOUGH IN CASE RADIATION FOG BEGIN TO DEVELOP UNDER THE CLEAR SKIES. ATTENTION THEN TURNS TOWARDS FRIDAY NIGHT AND SATURDAY AS THE DEEPENING WEST CONUS TROUGH SWEEPS EAST THROUGH THE PLAINS. GFS AND ECMWF HAVE CONTINUED TO CONVERGE TOWARDS ONE SOLUTION FOR THIS WEEKENDS SYSTEM...AND THE NAM-WRF SEEMS TO BE MOVING IN THE SAME DIRECTION. THE EARLY WEEKEND SHORTWAVE TROUGH WILL ACTUALLY CONSIST OF A NORTHERN AND SOUTHERN STREAM WAVES PHASING AS THEY THEY MOVE THROUGH MISSOURI. THERE IS A STRONG SHOT OF COLD AIR THAT WILL QUICKLY SPREAD ACROSS THE FORECAST AREA SATURDAY. THIS SYSTEM WILL BE BRINGING THE BULK OF ITS MOISTURE FROM THE PACIFIC...SO THE EXPECTATION IS THAT MUCH OF THE PRECIPITATION WILL BE POST FRONTAL...IN THE DEFORMATION ZONE BEHIND THE SURFACE LOW. WITH THE SOLUTIONS FROM THE GFS/ECMWF/AND NAM-WRF ALL CONVERGING I HAVE NOT HAD TO MAKE MANY ADJUSTMENTS TO THE GOING FORECAST FOR FRIDAY NIGHT INTO SATURDAY. DID KEEP SOME LIKELY POPS ACROSS THE EASTERN HALF OF THE FORECAST AREA FOR SATURDAY EVENING AS THE WEIGHT OF THE CONSENSUS SLOWS THE SYSTEM A LITTLE. OTHERWISE...EXPECT MUCH OF THE PRECIPITATION FALLING FROM THE SKY TO BE SNOW BY THE AFTERNOON HOURS. FREEZING RAIN AND SLEET ARE GOING TO BE MINOR AS THE SPEED WITH WHICH THE COLD AIR RUSHES IN SHOULD PRECLUDE MUCH OPPORTUNITY FOR MIXED PRECIP. CURRENT SNOWFALL TOTALS STILL LOOK RANGE BETWEEN 1 TO 4 INCHES OF ACCUMULATION...IN PART DUE TO THE PROGRESSIVE NATURE OF THE SYSTEM. ALSO...WIND BEHIND THE FRONT LOOKS TO BE SUSTAINED AS HIGH AS 20 TO 30 MPH WITH HIGHER GUSTS. THEREFORE...ADDED BLOWING SNOW TO THE FORECAST WEATHER FOR THE DAY SATURDAY AND SATURDAY NIGHT. CUTTER EXTENDED...(SUNDAY-THURSDAY) THE NORTHERN AND SOUTHERN SHORTWAVE BRANCHES WILL CONTINUE TO PHASE AT THE START OF THE EXTENDED FORECAST ON SUNDAY. THE PHASING SYSTEM WILL QUICKLY DEPART TO THE NORTHEAST...WITH SHORTWAVE RIDGING/SURFACE HIGH PRESSURE SPREADING EAST IN ITS WAKE. A SERIES OF PACIFIC SHORTWAVE TROUGHS WILL CONTINUE TO HEAD EAST THROUGH THE MEAN FLOW ACROSS THE CONUS NEXT WEEK. MODEL AGREEMENT DIMINISHES QUICKLY BY EARLY NEXT WEEK WITH REGARD TO THESE SHORTWAVE FEATURES. AS SUCH...THERE IS LOW CONFIDENCE FOR PRECIPITATION CHANCES. IF ONE MODEL WERE TO BE CHOSEN OVER ANOTHER...WOULD HAVE TO SIDE WITH THE MORE CONSISTENT ECMWF. THE ECMWF STILL BRINGS A CLIPPER SYSTEM FURTHER SOUTH THAN THE GFS ON MONDAY...BUT WITH LITTLE MOISTURE TO WORK WITH MEASURABLE PRECIPITATION IS NOT EXPECTED FOR OUR NECK OF THE WOODS. THE NEXT IN THE SERIES OF PROGRESSIVE SHORTWAVES IS PROGGED TO AFFECT THE REGION TOWARD WEDNESDAY. STOFLET && .AVIATION... /535 PM CST THU DEC 20 2007/ FOR THE 00Z TAF CYCLE...SOUNDINGS SHOW ANOTHER INVERSION SETTING UP ACROSS THE KANSAS/MISSOURI BORDER REGION TONIGHT...WITH A MODEST AND MOIST SOUTHEAST SURFACE FLOW. HOWEVER...THE WIND JUST OFF THE SURFACE IS EXPECTED TO REMAIN A LITTLE STRONGER EARLY FRIDAY MORNING THAN IT WAS THIS MORNING. THOUGHTS ARE THAT THIS WILL KEEP THE SURFACE LAYER MIXED A LITTLE MORE WITH THE DRY LAYER ABOVE PREVENTING A DRASTIC DECREASE IN VISIBILITIES IN THE MORNING. BIGGEST CONCERN WILL BE AT KSTJ WITH ITS SLIGHTLY LOWER ELEVATION ISOLATING IT A BIT MORE FROM THE EFFECTS OF DRIER AIR MIXING IN OVER TOP. WILL GO WITH A TEMPO CATEGORY FOR IFR CONDITIONS LATE TONIGHT AT THAT SITE. PC && .EAX WATCHES/WARNINGS/ADVISORIES... MO...DENSE FOG ADVISORY UNTIL 10 AM FRIDAY FOR MOZ003-MOZ004- MOZ005-MOZ006-MOZ007-MOZ008-MOZ013-MOZ014-MOZ015-MOZ016- MOZ017-MOZ022-MOZ023-MOZ024-MOZ025-MOZ030-MOZ031-MOZ032- MOZ033-MOZ038-MOZ039-MOZ040-MOZ044-MOZ045-MOZ046-MOZ054. KS...NONE. $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 925 AM EST WED DEC 19 2007 .SYNOPSIS... A WEAK TROUGH OF LOW PRESSURE WILL CONTINUE TO LINGER WHILE WEAKENING JUST OFF THE COAST TODAY. A FAST MOVING SYSTEM WILL BRING A CHANCE OF SHOWERS LATE THURSDAY AND EARLY FRIDAY. A RIDGE OF HIGH PRESSURE WILL SPREAD INTO THE CAROLINAS FROM THE NORTH ON SATURDAY WITH THE POSSIBLE DEVELOPMENT OF ANOTHER COASTAL TROUGH. FINALLY...A STRONG COLD FRONT WILL MOVE ACROSS THE REGION LATE SUNDAY...QUICKLY FOLLOWED BY ANOTHER SYSTEM ON CHRISTMAS DAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 3 AM WEDNESDAY..HIGH PRESSURE AXIS OVER EASTERN NORTH CAROLINA AT 06 UTC WITH ONLY MID LEVEL CLOUDINESS. THE LATEST RUC SHOWS THE COASTAL TROUGH SITUATED JUST TO THE SOUTH OF THE AREA. THE 00 UTC RUNS OF THE GFS AND NAM ALONG WITH THE 21 UTC SREF ALL ARE PROJECTING A COASTAL TROUGH TO CONTINUE TO DEVELOP NORTHWARD BUT REMAIN OFFSHORE AND MINIMAL IMPACT EXPECTED. THE SREF PRECIPITATION PROBABILITY FIELDS SHOW ALL PRECIPITATION STAYS EAST OF THE FORECAST AREA. SO EXPECT AREA TO REMAIN DRY WITH THE LIMITED MOISTURE SEEN IN THE VERTICAL PROFILES. FOR TEMPERATURES WENT WITH A CONSENSUS FORECAST OF THE STATISTICAL GUIDANCE PRODUCTS. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... AS OF 3 AM WEDNESDAY...THE MAIN QUESTION IS THE SENSIBLE WX EFFECT OF A PROGRESSIVE SOUTHERN STREAM SYSTEM...WHICH IS EXPECTED TO MOVE EAST ACROSS THE CAROLINAS THU NIGHT. MOISTURE FEED AHEAD OF THIS SYSTEM IS SLOW TO DEVELOP...AND THE RUN-TO-RUN TREND IS A BIT SLOWER YET. THE OTHER TRICKY FACTOR WILL BE THE DRY NNE FLOW AND HOW MUCH EVAPORATION WILL OCCUR. BEST SHOT FOR PRECIP WILL BE 06-12Z FRI...WITH THE MAIN ENERGY STAYING FAR ENOUGH SOUTH TO WARRANT A GRADIENT FROM LOW CHANCE IN THE NORTH...TO HIGH CHANCE IN THE SOUTH. MOISTURE IS SLOW TO EXIT ON FRIDAY SO WILL TAPER POPS DOWN THRU THE DAY. TEMPS ARE HIGHLY DEPENDENT ON CLOUD COVER IN THIS PERIOD. FORECAST HIGHS IN THE UPPER 50S ON THU REPRESENT THE BEST-CASE SCENARIO AND AN EARLIER ARRIVAL OF CLOUDINESS WILL REALLY HOLD TEMPS BACK. MODELS ARE HINTING THAT FRIDAY TEMPS WILL ALSO BE LIMITED BY LOW CLOUDS...BUT CONFIDENCE IS STILL QUITE LOW AT THIS POINT. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 3 AM WEDNESDAY...PATTERN REMAINS FAIRLY PROGRESSIVE BUT THE MAIN COMPLICATION IS THAT EXTENDED GFS MOS IS QUITE BULLISH WITH PRECIP CHANCES...ADVERTISING POPS WELL ABOVE CLIMO AND SOLIDLY IN THE CHANCE CATEGORY THROUGH MOST OF THE PERIOD. FOR NOW AM NOT BUYING WHAT THE GFS IS SELLING...ESPECIALLY IN THE ONGOING DROUGHT. HAVE FOCUSED INSTEAD ON PERIODS THAT SEEM TO HAVE A LEGIT CHANCE OF PRECIP...THUS CARRYING 30-40 POPS SAT NIGHT THROUGH SUN NIGHT AS A STRONG COLD FRONT CROSSES THE AREA. TEMPS ABOVE CLIMO FOR THE WEEKEND AND INTO MONDAY UNDER FLAT UPPER RIDGING...THEN WE GET KNOCKED BACK TO NEAR OR BELOW CLIMO NUMBERS BEHIND THE COLD FRONT. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... MID LEVEL CLOUDINESS IS APPROACHING THE TAF SITES THIS MORNING. THE LATEST SURFACE ANALYSIS SHOWS HIGH PRESSURE STILL OVER THE FORECAST AREA WITH COASTAL TROUGH FORMED JUST SOUTH OF THE MYR AND CRE TAF SITS. 06 UTC GFS... 06 UTC NAM AND 03 UTC SREF ALL ARE STILL IN AGREEMENT ON DEVELOPING TROUGH FARTHER NORTH AND OFF THE COAST. LATEST 11-3.9 MICRON SATELLITE IMAGERY IS SHOWING MID LEVEL CLOUDINESS MOVING TOWARDS THE COAST AND LATEST BUFR SOUNDING CONTINUE TO SHOW MOISTURE BUILDING FROM 10K TO 5K FT. WINDS WILL BE LIGHT AND VARIABLE OVER THE NEXT 9 HOURS WITH SOUTHWEST WINDS EXPECTED AFTER 15 UTC AS RIDGE SHIFTS EASTWARD. LOW PRESSURE MOVES ALONG THE SOUTHEASTERN STATES THURSDAY NIGHT INTO FRIDAY...WITH POSSIBLE LOW CEILINGS AND PRECIP. && .MARINE... NEAR TERM /THROUGH 7 AM THURSDAY/... AS OF 900 AM WEDNESDAY...COASTAL TROUGH SITUATED WITHIN A BROAD RIDGE BARELY DISTINGUISHABLE OFFSHORE BASED ON SURFACE AND BUOY OBS AND SATELLITE PICS. GRADIENT VERY SLACK WITH WINDS ESSENTIALLY LIGHT AND VARIABLE OVER THE COASTAL ZONES. SEAS CURRENTLY 2 FT OR LESS. WINDS WILL PICK UP A BIT FROM THE SW THIS AFTERNOON AS A COLD FRONT IN FORMATION APPROACHES...SHIFTING NW TONIGHT AFTER FROPA...BECOMING N BY DAYBREAK. SHORT TERM /THURSDAY 7 AM THROUGH FRIDAY/... AS OF 3 AM WEDNESDAY...NE GRADIENT WILL GRADUALLY TIGHTEN UP THRU THE PERIOD. WIND SPEEDS REMAIN FAIRLY LIGHT MOST OF THURSDAY...BUT INCREASE INTO THE 15-20 KT RANGE...WHERE SMALL TWEAKS IN DIRECTION BECOME CRITICAL TO SEA GROWTH. THE CURRENTLY ADVERTISED 040-050 DIRECTION SHOULD BE EXPOSED ENOUGH TO BUILD SEAS TO 5 FT AWAY FROM SHORE ON FRIDAY...BUT IF THE GRADIENT REMAINS MORE NORTHERLY THE NEAR-SHORE ALLOWANCES WILL NEED TO BE LARGER. LONG TERM/FRIDAY NIGHT THROUGH SUNDAY/... AS OF 3 AM WEDNESDAY...NE FLOW WILL SHIFT TO THE SOUTH ON SATURDAY AS MODELS ARE HINTING AT A WEAKENING COASTAL TROF OR WARM FRONT. EVEN IF THE NE FLOW HANGS ON INTO SAT NIGHT...WILL SEE THE SW FLOW AHEAD OF THE FRONT BECOME DOMINANT BY SUNDAY EITHER WAY. SCA WINDS AND SEAS ARE LIKELY ON SUNDAY AHEAD OF THE FRONT...BUT WE ARE STILL TALKING 5 DAYS OUT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...REK NEAR TERM...REK nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 735 AM EST WED DEC 19 2007 .SYNOPSIS...A WEAK SURFACE TROUGH WILL MOVE ACROSS THE AREA TODAY...FOLLOWED BY ANOTHER DRY HIGH PRESSURE SYSTEM BUILDING OVER THE AREA ON THURSDAY. A LOW PRESSURE SYSTEM IS EXPECTED TO TRACK ACROSS THE DEEP SOUTH THURSDAY AND THURSDAY NIGHT. && .NEAR TERM /THROUGH TODAY/... AS OF 730 AM... A QUICK UPDATE HAS BEEN SENT FOR THE BAND OF PRECIPITATION CURRENTLY MOVING THROUGH THE FAR WESTERN PIEDMONT. THIS LOOKS TO BE SUPPORTED BY UPPER DIVERGENCE ASSOCIATED WITH A DIVING 110+ KT JET AND MID LEVEL DIFFERENTIAL POSITIVE VORTICITY ADVECTION WITH THE SHORTWAVE TROUGH NOW DROPPING INTO THE MOUNTAINS. THE WET BULB PROFILE ON THE 12Z GSO SOUNDING IS ALMOST ENTIRELY BELOW ZERO BUT WITH MARGINAL MOISTURE... HOWEVER THE 12Z RNK SOUNDING SHOWS SUFFICIENT SATURATION IN THE -10 TO -15C LAYER FOR THE POSSIBILITY OF A LIGHT MIXTURE OF SNOW AND RAIN THROUGH THE MORNING. TEMPS MAY STRUGGLE TO CLIMB THROUGH THE 40S TODAY.-GIH AS OF 230 AM WEDNESDAY...SFC ANALYSIS THIS MORNING SHOWS 1029 MB HIGH PRESSURE OFF THE MID-ATLANTIC COAST...WITH SFC RIDGING EXTENDING SOUTHWEST THROUGH NC INTO GA/AL/FL. A 1009 MB SURFACE LOW WAS LOCATED OVER LAKE MICHIGAN. A WEAKER SURFACE LOW WAS LOCATED NEAR THE LA/TX/AR BORDER. A RELATIVELY WARM/MOIST AIRMASS (TEMPS IN THE 50S TO LOWER 60S AND DEWPOINTS IN THE 40S AND 50S) AHEAD OF THE SFC LOW WAS BEGINNING TO SPREAD NORTH FROM THE GULF OF MEXICO INTO THE DEEP SOUTH AS FAR NORTH AS WESTERN TN. ALOFT...00Z RAOB ANALYSIS AND CURRENT WV IMAGERY SHOW SEVERAL SHORTWAVES EMBEDDED IN THE FLOW UPSTREAM OF THE AREA...THE STRONGEST OF WHICH WAS LOCATED IN SOUTHERN IL/MO. A WEAKER SHORTWAVE WAS LOCATED IN EASTERN TN/KY. THE 00Z GSO SOUNDING HAD A PWAT OF 0.24". CURRENT REGIONAL RADAR IMAGERY SHOWS AN AREA OF SHOWERS ASSOC/W AN UPPER LEVEL SHORTWAVE AND ISENTROPIC LIFT APPROACHING THE SOUTHERN APPALACHIANS. THESE SHOWERS ARE REACHING THE GROUND WEST OF THE MOUNTAINS...FALLING OUT OF BKN/OVC 5-8 KFT CEILINGS. NEITHER THE 00Z GFS NOR THE NAM SEEM TO HAVE PICKED UP ON THE CORRECT TIMING OR LOCATION OF THIS PRECIP...WITH THE 00-06Z QPF FROM BOTH MODELS TOO FAR WEST OF WHERE THE CURRENT ACTIVITY IS LOCATED. THE ATMOSPHERE ACROSS CENTRAL NC IS VERY DRY THIS MORNING...WITH PWAT VALUES AROUND A QUARTER OF AN INCH AND SFC DEWPOINTS IN THE TEENS TO 20S. THE LIKELIHOOD OF ANY SHOWER ACTIVITY REACHING THE GROUND IN THE DRY ATMOSPHERE EAST OF THE MOUNTAINS THIS MORNING IS VERY SLIM. HOWEVER...GIVEN THAT CURRENT WETBULB TEMPERATURES ARE BELOW FREEZING (27-31F)...AND SHOULD REMAIN SO THROUGH SUNRISE...ANY PRECIP THAT DOES REACH THE GROUND EAST OF THE MOUNTAINS...EVEN A TRACE...COULD POTENTIALLY BE A PROBLEM IF IT FALLS AS FZRA. FCST SOUNDINGS FOR THIS MORNING SHOW ABOVE FREEZING TEMPS IN THE LOWEST 5-7 KFT...WITH A 40F WARM NOSE PROGGED AT AROUND 1 KFT AGL. GIVEN THE AMOUNT OF DRY AIR IN THE LOWER LEVELS...ANY EVAPORATIVE COOLING ASSOC/W FALLING PRECIP COULD ALTER THE THERMAL STRUCTURE TO ONE MORE FAVORABLE FOR FROZEN PRECIP. THE 0637Z SFC OB IN ATLANTA THIS MORNING WAS REPORTING SLEET AND RAIN WITH A TEMP OF 39 AND A DEWPOINT OF 28. THE SHORTWAVE THAT IS AIDING SHOWER ACTIVITY APPROACHING THE MOUNTAINS IS LOCATED IN EASTERN TN/KY BASED ON WATER VAPOR IMAGERY AND RUC H5 HEIGHT/VORT FIELDS. EXTRAPOLATION OF THE MOVEMENT OF THIS FEATURE SHOW THE SHORTWAVE ALONG THE NC/VA BORDER NEAR DANVILLE BY 12Z. NAM/GFS ISENTROPIC ANALYSIS SHOWS ISENTROPIC LIFT INCREASING ACROSS THE AREA TOWARD SUNRISE AS WELL. AT THIS TIME PREFER TO LEAVE OUT ANY POPS THIS MORNING GIVEN THE VERY DRY ATMOSPHERE ACROSS THE AREA...HOWEVER...THIS WILL BE VERY CLOSELY MONITORED OVER THE NEXT FEW HOURS GIVEN THE BELOW FREEZING WETBULB TEMPERATURES. EXPECT MOSTLY CLOUDY SKIES DEVELOPING ACROSS THE AREA FROM WEST TO EAST BY OR SHORTLY AFTER SUNRISE. THE SURFACE BOUNDARY ASSOC/W THE LOW PRESSURE SYSTEM OVER THE GREAT LAKES IS PROGGED TO CROSS CENTRAL NC DURING THE AFTERNOON HOURS. THE STRONGER SHORTWAVE CURRENTLY OVER MO/IL IS PROGGED TO DROP ESE INTO THE AREA THIS AFTERNOON IN CONCERT WITH THE WEAK SFC TROUGH / BOUNDARY. GFS/NAM FCST SOUNDINGS SHOW CEILINGS BETWEEN 5-12 KFT TODAY WITH A DRY SUB-CLOUD LAYER. NEITHER MODEL PRODUCES MEASURABLE PRECIP ACROSS THE AREA THIS AFTERNOON...AND PROBABILITIES OF MEASURABLE PRECIP OFF THE SREF REMAIN LESS THAN 25%. ALTHOUGH AN ISOLATED SPRINKLE OR LIGHT SHOWER CANNOT BE RULED OUT THIS AFTERNOON...AT THIS TIME PROBABILITIES APPEAR TOO LOW TO INTRODUCE PRECIP INTO THE FORECAST. WILL KNOCK DOWN HIGH TEMPS AT LEAST SEVERAL DEGREES TODAY GIVEN 12Z THICKNESSES BETWEEN 1310-1320 METERS...00Z THICKNESSES PROGGED BETWEEN 1320-1330 METERS...AND A GOOD DEAL OF CLOUD COVER EXPECTED INTO AT LEAST EARLY/MID AFTERNOON...ALL OF WHICH ARGUE FOR HIGH TEMPS IN THE MID TO UPPER 40S IN MOST LOCATIONS...LOWER 50S PERHAPS IN THE FAR SOUTHERN PORTIONS OF THE AREA. THIS IS AT THE LOW END OR BELOW THE LATEST 00Z MAV/MET MOS GUIDANCE. -VINCENT && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...SFC HIGH PRESSURE OVER THE MIDWEST STATES MOVES EAST INTO THE MID-ATLANTIC TONIGHT...REMAINING OVER THE AREA DURING THE DAY ON THURSDAY. A VIGOROUS SOUTHERN STREAM TROUGH...CURRENTLY OVER SOUTHERN CALIFORNIA...WILL TRAVERSE THE COUNTRY AND INITIATE CYCLOGENESIS IN THE LEE OF THE ROCKIES TONIGHT...WITH THE UPPER LEVEL TROUGH AND ASSOC SFC LOW APPROACHING THE DEEP SOUTH DURING THE DAY THURSDAY. ACROSS CENTRAL NC...WITH HIGH PRESSURE IN CONTROL... EXPECT MOSTLY CLEAR SKIES AT THE BEGINNING OF THE DAY...WITH INCREASING CLOUD COVER LATER IN THE AFTERNOON/EVENING IN ADVANCE OF THE APPROACHING SHORTWAVE AND SFC LOW. ALTHOUGH THICKNESSES ON THURSDAY ARE PROGGED TO BE ONLY SLIGHTLY WARMER THAN TODAY...CLEAR OR MOSTLY CLEAR SKIES ARE EXPECTED THROUGH THE MORNING AND MOST OF THE AFTERNOON...AND THIS SHOULD ALLOW TEMPS TO REACH THE MID 50S ACROSS THE AREA. DIFFICULT FORECAST ON TAP FOR THURSDAY NIGHT AND FRIDAY. BOTH THE GFS/NAM CONTINUE TO TAKE THE SOUTHERN STREAM WAVE AND SURFACE LOW SOUTH OF THE AREA. SFC RIDGING IS PROGGED TO DEVELOP IN ADVANCE OF THIS SYSTEM ACROSS THE CAROLINAS ON THURSDAY...WITH THE SOUTHERN PORTION OF THE WEDGE OVER GA/SC/NC FURTHER STRENGTHENING THU NIGHT AS ISENTROPIC LIFT BEGINS TO INCREASE AND PRECIP ADVANCES TOWARD THE AREA FROM THE SOUTHWEST. BOTH THE GFS/NAM SHOW A MILLER TYPE-B SCENARIO WHERE THE INLAND SFC LOW OVER NORTHERN AL OR SOUTHERN TN JUMPS EAST OF THE WEDGE TO THE GA/FL COAST OR EVEN OFFSHORE FRIDAY MORNING. AT THIS TIME THE BEST LIFT REMAINS SOUTH OF THE AREA...AND LITTLE IF ANY PRECIP IS EXPECTED ACROSS CENTRAL NC. THE 00Z GFS SHOWS 0.05 TO 0.10" FALLING ALONG/SOUTH OF HIGHWAY 64 BETWEEN 06-12Z FRIDAY MORNING...WHILE THE 00Z NAM DOES NOT GENERATE ANY MEASURABLE PRECIP ACROSS CENTRAL NC IN ASSOC/W THIS SYSTEM. THE SREF SHOWS LESS THAN 25% PROBABILITIES OF MEASURABLE PRECIP ACROSS MOST OF CENTRAL NC...EXCEPT ALONG THE NC/SC BORDER AND IN THE FAR WESTERN PIEDMONT WHERE PROBABILITIES ARE AS HIGH AS 45%. AT THIS TIME THE BEST CHANCE FOR PRECIP APPEARS TO BE ALONG THE NC/SC BORDER BETWEEN 06-17Z FRIDAY...AND WILL THEREFORE CONFINE A LOW CHANCE (30%) OF SHOWERS TO THOSE LOCATIONS DURING THAT TIME PERIOD...WITH A SLIGHT CHANCE EXTENDING NORTH TO HIGHWAY 64 AND INTO THE TRIAD. THE LATEST FCST SOUNDINGS SHOW THERMAL PROFILES SUPPORTIVE OF ALL LIQUID PRECIP...HOWEVER...IF PRECIP ASSOC/W THE SYSTEM IS HEAVIER AND SPREADS FURTHER NORTH THAN ANTICIPATED...OR IF THE ANTECEDENT SFC RIDGING/WEDGE IS STRONGER THAN EXPECTED...P-TYPE PROBLEMS WOULD BE POSSIBLE...AND THIS WILL NEED TO BE MONITORED CLOSELY OVER THE NEXT 24-36 HOURS. DIFFICULT LOW TEMP FORECAST FRIDAY MORNING...SINCE THIS WILL DEPEND ON THE AMOUNT OF CLOUD COVER...THE STRENGTH OF THE ANTECEDENT SFC RIDGING AND WHETHER OR NOT PRECIP IS FALLING INTO COOL/DRY AIR AT THE SURFACE. AT THIS TIME WILL ADVERTISE LOWER/MID 30S NORTH TO UPPER 30S SOUTH. THICKNESSES ON FRIDAY ARE EXPECTED TO RANGE BETWEEN 1305-1330 METERS...SIMILAR TO TODAY/THU. WITH FULL SUN TEMPERATURES WOULD BE SIMILAR TO WHAT IS EXPECTED THURSDAY...ALTHOUGH WITH SIGNIFICANT CLOUD COVER TEMPERATURES WOULD BE MORE SIMILAR TO WHAT IS EXPECTED TODAY. AT THIS TIME...WILL TREND CLOSE TO MOS GUIDANCE...WITH HIGHS RANGING FROM THE MID 40S NORTH TO LOWER 50S SOUTH. LOW TEMPS FRIDAY NIGHT IN THE MID 30S NORTH TO LOWER 40S SOUTH. -VINCENT && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 AM EST... THE WEEKEND LOOKS TO BE CLOUDY AND WET. ON SATURDAY BOTH THE 00Z/19 GFS AND 00Z/19 ECMWF SHOW HIGH PRESSURE LOCATED OVER THE EASTERN PORTION OF MAINE EXTENDING INTO THE AREA. WEAK ISENTROPIC LIFT DEPICTED BY THE MODELS MAY PRODUCE SOME LIGHT PRECIP ON SATURDAY AND SATURDAY NIGHT. THUS...WILL CARRY A SLIGHT CHANCE FOR RAIN ON SATURDAY AND INCREASE THE POPS TO CHANCE DURING THE OVERNIGHT HOURS FROM WEST TO EAST. HIGHS SATURDAY WILL BE CATEGORY ABOVE NORMAL. LOWS SUNDAY MORNING WILL RUN 10 TO 15 DEGREES ABOVE NORMAL...AS THE HIGH PRESSURE RIDGE BEGINS TO RETREAT AND WINDS BECOME SOUTHERLY IN ADVANCE OF THE FRONT. A FAIRLY IMPRESSIVE UPPER LEVEL TROUGH WILL APPROACH THE AREA FROM THE WEST ON SUNDAY WITH A SURFACE COLD FRONT CROSSING THE AREA SUNDAY AFTERNOON INTO THE EVENING. TIMING FOR THE SURFACE FRONT IS LOOKING BETTER AS THE THE 00Z/19 GFS AND ECMWF ARE COMING INTO BETTER AGREEMENT... WITH BOTH SHOWING THE FRONT CROSSING THE AREA DURING THE AFTERNOON INTO THE EVENING ON SUNDAY. BOTH THE GFS AND ECMWF DEPICT A FAIRLY STRONG UPPER LEVEL JET ASSOCIATED WITH THIS SYSTEM. AT THIS TIME WE APPEAR TO BE IN THE FAVORED RIGHT ENTRANCE REGION OF THE JET... WHICH WOULD INCREASE LIFT AND COUPLED WITH GOOD SOUTHERLY FLOW IN ADVANCE OF THE SURFACE FRONT SHOULD INCREASE THE LIKELIHOOD OF A MORE SUBSTANTIAL RAIN EVENT. THUS...WILL INCREASE POPS TO 50% FOR SUNDAY AFTERNOON INTO THE EARLY EVENING ACROSS THE CWA. WILL LIKELY NEED TO UP POPS IN LATER FORECASTS IF THE SYSTEM CONTINUES TO SHOW CONSISTENCY IN THE MODELS FROM RUN TO RUN. HIGHS SUNDAY WILL BE WELL ABOVE AVERAGE WITH TEMPS RANGING FROM THE UPPER 50S NORTHWEST TO THE UPPER 60S IN THE SOUTHEAST. LOWS MONDAY WILL RANGE FROM THE MID 30S NORTHWEST TO THE MID 40S IN THE EAST. MONDAY WILL BE NOTICEABLY COOLER AS HIGH PRESSURE BUILDS INTO THE REGION AT THE SURFACE. HOWEVER...HIGH TEMPS WILL STILL BE NEAR NORMAL FOR THIS TIME OF YEAR. MODELS BEGIN TO DIVERGE IN THEIR SOLUTIONS BEYOND MONDAY...AS THE 00Z/19 GFS BRINGS A UPPER LEVEL SHORTWAVE ACROSS THE REGION ON TUESDAY...WHILE THE 00Z/19 ECMWF DEVELOPS A CUT OFF UPPER LEVEL LOW OVER NORTHERN PORTIONS OF THE GULF COAST STATES. THUS...WITH MODEL DIFFERENCES AT THIS TIME WILL STICK CLOSE TO CLIMATOLOGY AND KEEP ANY MENTION OF PRECIP OUT OF THE FORECAST FOR NOW. -BSD && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... AS OF 630 AM WEDNESDAY...VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A WEAK SHORTWAVE WILL CROSS CENTRAL NORTH CAROLINA TODAY UNDER FAST ZONAL FLOW ALOFT. THIS SHORTWAVE IS IS PRODUCING BKN/OVC DECK OF CLOUDS AT 6 TO 8 KFT AT ALL SITE AS OF 1130Z... EXCEPT KRWI... WHERE THESE CLOUDS SHOULD MOVE IN BETWEEN 13-14Z THIS MORNING. THIS DECK SHOULD BEGIN TO SCATTER OUT IN THE AFTERNOON... WITH SKIES BECOMING MOSTLY CLEAR IN THE EVENING. IN ADDITION... AN ISOLATED SHOWER OR TWO WILL BE POSSIBLE THIS MORNING AS WELL. MVFR TO IFR CONDITIONS ARE POSSIBLE WITH A STORM SYSTEM PASSING JUST SOUTH OF THE AREA THURSDAY NIGHT...PRIMARILY AT FAY WITH THE BEST MOISTURE STAYING SOUTH OF GSO/INT/RDU/RWI. ISENTROPIC LIFT WILL INCREASE BY SATURDAY MORNING AS LOW LEVEL RIDGING MOVES OFFSHORE IN ADVANCE OF A STRENGTHENING STORM SYSTEM OVER THE CENTRAL U.S. MVFR TO IFR CONDITIONS WILL BE POSSIBLE DURING THIS TIME. THIS STORM SYSTEM WILL PUSH A COLD FRONT THROUGH CENTRAL NORTH ON SUNDAY...RESULTING IN A GOOD LIKELIHOOD OF SHOWERS ALONG WITH OCCASIONALLY MVFR TO IFR CONDITIONS. -BSD && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...HARTFIELD/VINCENT SHORT TERM...VINCENT LONG TERM...BSD AVIATION...BSD nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON NC 605 AM EST WED DEC 19 2007 .SYNOPSIS... A WEAK COASTAL TROUGH WILL CONTINUE TO DEVELOP OFF THE COAST AND MOVE AWAY FROM THE AREA TONIGHT. ANOTHER FAST MOVING SYSTEM JUST TO THE SOUTH OF THE REGION WILL BRING A CHANCE OF SHOWERS LATE THURSDAY AND EARLY FRIDAY. HIGH PRESSURE WILL PREVAIL ON SATURDAY...FOLLOWED BY A STRONG COLD FRONT LATE SUNDAY. && .NEAR TERM /THROUGH 7 AM THURSDAY/... AS OF 3 AM WEDNESDAY..HIGH PRESSURE AXIS OVER EASTERN NORTH CAROLINA AT 06 UTC WITH ONLY MID LEVEL CLOUDINESS. THE LATEST RUC SHOWS THE COASTAL TROUGH SITUATED JUST TO THE SOUTH OF THE AREA. THE 00 UTC RUNS OF THE GFS AND NAM ALONG WITH THE 21 UTC SREF ALL ARE PROJECTING A COASTAL TROUGH TO CONTINUE TO DEVELOP NORTHWARD BUT REMAIN OFFSHORE AND MINIMAL IMPACT EXPECTED. THE SREF PRECIPITATION PROBABILITY FIELDS SHOW ALL PRECIPITATION STAYS EAST OF THE FORECAST AREA. SO EXPECT AREA TO REMAIN DRY WITH THE LIMITED MOISTURE SEEN IN THE VERTICAL PROFILES. FOR TEMPERATURES WENT WITH A CONSENSUS FORECAST OF THE STATISTICAL GUIDANCE PRODUCTS. && .SHORT TERM /THURSDAY 7 AM THROUGH FRIDAY/... AS OF 3 AM WEDNESDAY...THE MAIN QUESTION IS THE SENSIBLE WX EFFECT OF A PROGRESSIVE SOUTHERN STREAM SYSTEM...WHICH IS EXPECTED TO MOVE EAST ACROSS THE CAROLINAS THU NIGHT. MOISTURE FEED AHEAD OF THIS SYSTEM IS SLOW TO DEVELOP...AND THE RUN-TO-RUN TREND IS A BIT SLOWER YET. THE OTHER TRICKY FACTOR WILL BE THE DRY NNE FLOW AND HOW MUCH EVAPORATION WILL OCCUR. BEST SHOT FOR PRECIP WILL BE 06-12Z FRI...WITH THE MAIN ENERGY STAYING FAR ENOUGH SOUTH TO WARRANT A GRADIENT FROM LOW CHANCE IN THE NORTH...TO HIGH CHANCE IN THE SOUTH. MOISTURE IS SLOW TO EXIT ON FRIDAY SO WILL TAPER POPS DOWN THRU THE DAY. TEMPS ARE HIGHLY DEPENDENT ON CLOUD COVER IN THIS PERIOD. FORECAST HIGHS IN THE UPPER 50S ON THU REPRESENT THE BEST-CASE SCENARIO AND AN EARLIER ARRIVAL OF CLOUDINESS WILL REALLY HOLD TEMPS BACK. MODELS ARE HINTING THAT FRIDAY TEMPS WILL ALSO BE LIMITED BY LOW CLOUDS...BUT CONFIDENCE IS STILL QUITE LOW AT THIS POINT. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 3 AM WEDNESDAY...PATTERN REMAINS FAIRLY PROGRESSIVE BUT THE MAIN COMPLICATION IS THAT EXTENDED GFS MOS IS QUITE BULLISH WITH PRECIP CHANCES...ADVERTISING POPS WELL ABOVE CLIMO AND SOLIDLY IN THE CHANCE CATEGORY THROUGH MOST OF THE PERIOD. FOR NOW AM NOT BUYING WHAT THE GFS IS SELLING...ESPECIALLY IN THE ONGOING DROUGHT. HAVE FOCUSED INSTEAD ON PERIODS THAT SEEM TO HAVE A LEGIT CHANCE OF PRECIP...THUS CARRYING 30-40 POPS SAT NIGHT THROUGH SUN NIGHT AS A STRONG COLD FRONT CROSSES THE AREA. TEMPS ABOVE CLIMO FOR THE WEEKEND AND INTO MONDAY UNDER FLAT UPPER RIDGING...THEN WE GET KNOCKED BACK TO NEAR OR BELOW CLIMO NUMBERS BEHIND THE COLD FRONT. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... MID LEVEL CLOUDINESS IS APPROACHING THE TAF SITES THIS MORNING. THE LATEST SURFACE ANALYSIS SHOWS HIGH PRESSURE STILL OVER THE FORECAST AREA WITH COASTAL TROUGH FORMED JUST SOUTH OF THE MYR AND CRE TAF SITS. 06 UTC GFS... 06 UTC NAM AND 03 UTC SREF ALL ARE STILL IN AGREEMENT ON DEVELOPING TROUGH FARTHER NORTH AND OFF THE COAST. LATEST 11-3.9 MICRON SATELLITE IMAGERY IS SHOWING MID LEVEL CLOUDINESS MOVING TOWARDS THE COAST AND LATEST BUFR SOUNDING CONTINUE TO SHOW MOISTURE BUILDING FROM 10K TO 5K FT. WINDS WILL BE LIGHT AND VARIABLE OVER THE NEXT 9 HOURS WITH SOUTHWEST WINDS EXPECTED AFTER 15 UTC AS RIDGE SHIFTS EASTWARD. LOW PRESSURE MOVES ALONG THE SOUTHEASTERN STATES THURSDAY NIGHT INTO FRIDAY...WITH POSSIBLE LOW CEILINGS AND PRECIP. && .MARINE... NEAR TERM /THROUGH 7 AM THURSDAY/... AS OF 300 AM WEDNESDAY...SURFACE ANALYSIS AND RUC MODEL SHOW COASTAL TROUGH DEVELOPING JUST SOUTH OF THE WATER AT THIS TIME. TROUGH SHOULD BUILD NORTHWARD AND JUST EAST OF THE COASTAL WATERS THROUGHOUT THE DAY. WINDS ARE VARIABLE AT THIS TIME WITH WINDS SPEEDS LESS THAN 10 KNOTS. WINDS ARE EXPECTED TO SHIFT TO THE SOUTHWEST THIS AFTERNOON AND NORTHWESTERLY TONIGHT. WINDS SPEED ARE ONLY EXPECTED TO INCREASE TO 15 KNOTS TONIGHT. LATEST WAVEWATCH III AND REEFCAST ALL ARE SHOWING SEAS 1 TO 2 FEET THROUGH TODAY WITH A SLIGHT INCREASE IN SEAS OFFSHORE WITH THE INCREASED NORTHWESTERLY WINDS TONIGHT. SHORT TERM /THURSDAY 7 AM THROUGH FRIDAY/... AS OF 3 AM WEDNESDAY...NE GRADIENT WILL GRADUALLY TIGHTEN UP THRU THE PERIOD. WIND SPEEDS REMAIN FAIRLY LIGHT MOST OF THURSDAY...BUT INCREASE INTO THE 15-20 KT RANGE...WHERE SMALL TWEAKS IN DIRECTION BECOME CRITICAL TO SEA GROWTH. THE CURRENTLY ADVERTISED 040-050 DIRECTION SHOULD BE EXPOSED ENOUGH TO BUILD SEAS TO 5 FT AWAY FROM SHORE ON FRIDAY...BUT IF THE GRADIENT REMAINS MORE NORTHERLY THE NEAR-SHORE ALLOWANCES WILL NEED TO BE LARGER. LONG TERM/FRIDAY NIGHT THROUGH SUNDAY/... AS OF 3 AM WEDNESDAY...NE FLOW WILL SHIFT TO THE SOUTH ON SATURDAY AS MODELS ARE HINTING AT A WEAKENING COASTAL TROF OR WARM FRONT. EVEN IF THE NE FLOW HANGS ON INTO SAT NIGHT...WILL SEE THE SW FLOW AHEAD OF THE FRONT BECOME DOMINANT BY SUNDAY EITHER WAY. SCA WINDS AND SEAS ARE LIKELY ON SUNDAY AHEAD OF THE FRONT...BUT WE ARE STILL TALKING 5 DAYS OUT. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...NONE. NC...NONE. MARINE...NONE. && $$ SYNOPSIS...DRH NEAR TERM...DRH SHORT TERM...RAS LONG TERM...RAS AVIATION...DRH nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 325 AM EST WED DEC 19 2007 .SYNOPSIS...HIGH PRESSURE CENTERED JUST OFF THE VIRGINIA COAST WILL CONTINUE TO EXTEND SOUTHWESTWARD THROUGH THE CAROLINAS TONIGHT. A WEAK SURFACE TROUGH WILL MOVE ACROSS THE AREA ON WEDNESDAY...FOLLOWED BY ANOTHER DRY HIGH PRESSURE SYSTEM BUILDING OVER THE AREA ON THURSDAY. A LOW PRESSURE SYSTEM IS EXPECTED TO TRACK ACROSS THE DEEP SOUTH THURSDAY AND THURSDAY NIGHT. && .NEAR TERM /THROUGH TODAY/... AS OF 230 AM WEDNESDAY...SFC ANALYSIS THIS MORNING SHOWS 1029 MB HIGH PRESSURE OFF THE MID-ATLANTIC COAST...WITH SFC RIDGING EXTENDING SOUTHWEST THROUGH NC INTO GA/AL/FL. A 1009 MB SURFACE LOW WAS LOCATED OVER LAKE MICHIGAN. A WEAKER SURFACE LOW WAS LOCATED NEAR THE LA/TX/AR BORDER. A RELATIVELY WARM/MOIST AIRMASS (TEMPS IN THE 50S TO LOWER 60S AND DEWPOINTS IN THE 40S AND 50S) AHEAD OF THE SFC LOW WAS BEGINNING TO SPREAD NORTH FROM THE GULF OF MEXICO INTO THE DEEP SOUTH AS FAR NORTH AS WESTERN TN. ALOFT...00Z RAOB ANALYSIS AND CURRENT WV IMAGERY SHOW SEVERAL SHORTWAVES EMBEDDED IN THE FLOW UPSTREAM OF THE AREA...THE STRONGEST OF WHICH WAS LOCATED IN SOUTHERN IL/MO. A WEAKER SHORTWAVE WAS LOCATED IN EASTERN TN/KY. THE 00Z GSO SOUNDING HAD A PWAT OF 0.24". CURRENT REGIONAL RADAR IMAGERY SHOWS AN AREA OF SHOWERS ASSOC/W AN UPPER LEVEL SHORTWAVE AND ISENTROPIC LIFT APPROACHING THE SOUTHERN APPALACHIANS. THESE SHOWERS ARE REACHING THE GROUND WEST OF THE MOUNTAINS...FALLING OUT OF BKN/OVC 5-8 KFT CEILINGS. NEITHER THE 00Z GFS NOR THE NAM SEEM TO HAVE PICKED UP ON THE CORRECT TIMING OR LOCATION OF THIS PRECIP...WITH THE 00-06Z QPF FROM BOTH MODELS TOO FAR WEST OF WHERE THE CURRENT ACTIVITY IS LOCATED. THE ATMOSPHERE ACROSS CENTRAL NC IS VERY DRY THIS MORNING...WITH PWAT VALUES AROUND A QUARTER OF AN INCH AND SFC DEWPOINTS IN THE TEENS TO 20S. THE LIKELIHOOD OF ANY SHOWER ACTIVITY REACHING THE GROUND IN THE DRY ATMOSPHERE EAST OF THE MOUNTAINS THIS MORNING IS VERY SLIM. HOWEVER...GIVEN THAT CURRENT WETBULB TEMPERATURES ARE BELOW FREEZING (27-31F)...AND SHOULD REMAIN SO THROUGH SUNRISE...ANY PRECIP THAT DOES REACH THE GROUND EAST OF THE MOUNTAINS...EVEN A TRACE...COULD POTENTIALLY BE A PROBLEM IF IT FALLS AS FZRA. FCST SOUNDINGS FOR THIS MORNING SHOW ABOVE FREEZING TEMPS IN THE LOWEST 5-7 KFT...WITH A 40F WARM NOSE PROGGED AT AROUND 1 KFT AGL. GIVEN THE AMOUNT OF DRY AIR IN THE LOWER LEVELS...ANY EVAPORATIVE COOLING ASSOC/W FALLING PRECIP COULD ALTER THE THERMAL STRUCTURE TO ONE MORE FAVORABLE FOR FROZEN PRECIP. THE 0637Z SFC OB IN ATLANTA THIS MORNING WAS REPORTING SLEET AND RAIN WITH A TEMP OF 39 AND A DEWPOINT OF 28. THE SHORTWAVE THAT IS AIDING SHOWER ACTIVITY APPROACHING THE MOUNTAINS IS LOCATED IN EASTERN TN/KY BASED ON WATER VAPOR IMAGERY AND RUC H5 HEIGHT/VORT FIELDS. EXTRAPOLATION OF THE MOVEMENT OF THIS FEATURE SHOW THE SHORTWAVE ALONG THE NC/VA BORDER NEAR DANVILLE BY 12Z. NAM/GFS ISENTROPIC ANALYSIS SHOWS ISENTROPIC LIFT INCREASING ACROSS THE AREA TOWARD SUNRISE AS WELL. AT THIS TIME PREFER TO LEAVE OUT ANY POPS THIS MORNING GIVEN THE VERY DRY ATMOSPHERE ACROSS THE AREA...HOWEVER...THIS WILL BE VERY CLOSELY MONITORED OVER THE NEXT FEW HOURS GIVEN THE BELOW FREEZING WETBULB TEMPERATURES. EXPECT MOSTLY CLOUDY SKIES DEVELOPING ACROSS THE AREA FROM WEST TO EAST BY OR SHORTLY AFTER SUNRISE. THE SURFACE BOUNDARY ASSOC/W THE LOW PRESSURE SYSTEM OVER THE GREAT LAKES IS PROGGED TO CROSS CENTRAL NC DURING THE AFTERNOON HOURS. THE STRONGER SHORTWAVE CURRENTLY OVER MO/IL IS PROGGED TO DROP ESE INTO THE AREA THIS AFTERNOON IN CONCERT WITH THE WEAK SFC TROUGH / BOUNDARY. GFS/NAM FCST SOUNDINGS SHOW CEILINGS BETWEEN 5-12 KFT TODAY WITH A DRY SUB-CLOUD LAYER. NEITHER MODEL PRODUCES MEASURABLE PRECIP ACROSS THE AREA THIS AFTERNOON...AND PROBABILITIES OF MEASURABLE PRECIP OFF THE SREF REMAIN LESS THAN 25%. ALTHOUGH AN ISOLATED SPRINKLE OR LIGHT SHOWER CANNOT BE RULED OUT THIS AFTERNOON...AT THIS TIME PROBABILITIES APPEAR TOO LOW TO INTRODUCE PRECIP INTO THE FORECAST. WILL KNOCK DOWN HIGH TEMPS AT LEAST SEVERAL DEGREES TODAY GIVEN 12Z THICKNESSES BETWEEN 1310-1320 METERS...00Z THICKNESSES PROGGED BETWEEN 1320-1330 METERS...AND A GOOD DEAL OF CLOUD COVER EXPECTED INTO AT LEAST EARLY/MID AFTERNOON...ALL OF WHICH ARGUE FOR HIGH TEMPS IN THE MID TO UPPER 40S IN MOST LOCATIONS...LOWER 50S PERHAPS IN THE FAR SOUTHERN PORTIONS OF THE AREA. THIS IS AT THE LOW END OR BELOW THE LATEST 00Z MAV/MET MOS GUIDANCE. -VINCENT && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... AS OF 300 AM WEDNESDAY...SFC HIGH PRESSURE OVER THE MIDWEST STATES MOVES EAST INTO THE MID-ATLANTIC TONIGHT...REMAINING OVER THE AREA DURING THE DAY ON THURSDAY. A VIGOROUS SOUTHERN STREAM TROUGH...CURRENTLY OVER SOUTHERN CALIFORNIA...WILL TRAVERSE THE COUNTRY AND INITIATE CYCLOGENESIS IN THE LEE OF THE ROCKIES TONIGHT...WITH THE UPPER LEVEL TROUGH AND ASSOC SFC LOW APPROACHING THE DEEP SOUTH DURING THE DAY THURSDAY. ACROSS CENTRAL NC...WITH HIGH PRESSURE IN CONTROL... EXPECT MOSTLY CLEAR SKIES AT THE BEGINNING OF THE DAY...WITH INCREASING CLOUD COVER LATER IN THE AFTERNOON/EVENING IN ADVANCE OF THE APPROACHING SHORTWAVE AND SFC LOW. ALTHOUGH THICKNESSES ON THURSDAY ARE PROGGED TO BE ONLY SLIGHTLY WARMER THAN TODAY...CLEAR OR MOSTLY CLEAR SKIES ARE EXPECTED THROUGH THE MORNING AND MOST OF THE AFTERNOON...AND THIS SHOULD ALLOW TEMPS TO REACH THE MID 50S ACROSS THE AREA. DIFFICULT FORECAST ON TAP FOR THURSDAY NIGHT AND FRIDAY. BOTH THE GFS/NAM CONTINUE TO TAKE THE SOUTHERN STREAM WAVE AND SURFACE LOW SOUTH OF THE AREA. SFC RIDGING IS PROGGED TO DEVELOP IN ADVANCE OF THIS SYSTEM ACROSS THE CAROLINAS ON THURSDAY...WITH THE SOUTHERN PORTION OF THE WEDGE OVER GA/SC/NC FURTHER STRENGTHENING THU NIGHT AS ISENTROPIC LIFT BEGINS TO INCREASE AND PRECIP ADVANCES TOWARD THE AREA FROM THE SOUTHWEST. BOTH THE GFS/NAM SHOW A MILLER TYPE-B SCENARIO WHERE THE INLAND SFC LOW OVER NORTHERN AL OR SOUTHERN TN JUMPS EAST OF THE WEDGE TO THE GA/FL COAST OR EVEN OFFSHORE FRIDAY MORNING. AT THIS TIME THE BEST LIFT REMAINS SOUTH OF THE AREA...AND LITTLE IF ANY PRECIP IS EXPECTED ACROSS CENTRAL NC. THE 00Z GFS SHOWS 0.05 TO 0.10" FALLING ALONG/SOUTH OF HIGHWAY 64 BETWEEN 06-12Z FRIDAY MORNING...WHILE THE 00Z NAM DOES NOT GENERATE ANY MEASURABLE PRECIP ACROSS CENTRAL NC IN ASSOC/W THIS SYSTEM. THE SREF SHOWS LESS THAN 25% PROBABILITIES OF MEASURABLE PRECIP ACROSS MOST OF CENTRAL NC...EXCEPT ALONG THE NC/SC BORDER AND IN THE FAR WESTERN PIEDMONT WHERE PROBABILITIES ARE AS HIGH AS 45%. AT THIS TIME THE BEST CHANCE FOR PRECIP APPEARS TO BE ALONG THE NC/SC BORDER BETWEEN 06-17Z FRIDAY...AND WILL THEREFORE CONFINE A LOW CHANCE (30%) OF SHOWERS TO THOSE LOCATIONS DURING THAT TIME PERIOD...WITH A SLIGHT CHANCE EXTENDING NORTH TO HIGHWAY 64 AND INTO THE TRIAD. THE LATEST FCST SOUNDINGS SHOW THERMAL PROFILES SUPPORTIVE OF ALL LIQUID PRECIP...HOWEVER...IF PRECIP ASSOC/W THE SYSTEM IS HEAVIER AND SPREADS FURTHER NORTH THAN ANTICIPATED...OR IF THE ANTECEDENT SFC RIDGING/WEDGE IS STRONGER THAN EXPECTED...P-TYPE PROBLEMS WOULD BE POSSIBLE...AND THIS WILL NEED TO BE MONITORED CLOSELY OVER THE NEXT 24-36 HOURS. DIFFICULT LOW TEMP FORECAST FRIDAY MORNING...SINCE THIS WILL DEPEND ON THE AMOUNT OF CLOUD COVER...THE STRENGTH OF THE ANTECEDENT SFC RIDGING AND WHETHER OR NOT PRECIP IS FALLING INTO COOL/DRY AIR AT THE SURFACE. AT THIS TIME WILL ADVERTISE LOWER/MID 30S NORTH TO UPPER 30S SOUTH. THICKNESSES ON FRIDAY ARE EXPECTED TO RANGE BETWEEN 1305-1330 METERS...SIMILAR TO TODAY/THU. WITH FULL SUN TEMPERATURES WOULD BE SIMILAR TO WHAT IS EXPECTED THURSDAY...ALTHOUGH WITH SIGNIFICANT CLOUD COVER TEMPERATURES WOULD BE MORE SIMILAR TO WHAT IS EXPECTED TODAY. AT THIS TIME...WILL TREND CLOSE TO MOS GUIDANCE...WITH HIGHS RANGING FROM THE MID 40S NORTH TO LOWER 50S SOUTH. LOW TEMPS FRIDAY NIGHT IN THE MID 30S NORTH TO LOWER 40S SOUTH. -VINCENT && .LONG TERM /SATURDAY THROUGH TUESDAY/... AS OF 300 AM EST... THE WEEKEND LOOKS TO BE CLOUDY AND WET. ON SATURDAY BOTH THE 00Z/19 GFS AND 00Z/19 ECMWF SHOW HIGH PRESSURE LOCATED OVER THE EASTERN PORTION OF MAINE EXTENDING INTO THE AREA. WEAK ISENTROPIC LIFT DEPICTED BY THE MODELS MAY PRODUCE SOME LIGHT PRECIP ON SATURDAY AND SATURDAY NIGHT. THUS...WILL CARRY A SLIGHT CHANCE FOR RAIN ON SATURDAY AND INCREASE THE POPS TO CHANCE DURING THE OVERNIGHT HOURS FROM WEST TO EAST. HIGHS SATURDAY WILL BE CATEGORY ABOVE NORMAL. LOWS SUNDAY MORNING WILL RUN 10 TO 15 DEGREES ABOVE NORMAL...AS THE HIGH PRESSURE RIDGE BEGINS TO RETREAT AND WINDS BECOME SOUTHERLY IN ADVANCE OF THE FRONT. A FAIRLY IMPRESSIVE UPPER LEVEL TROUGH WILL APPROACH THE AREA FROM THE WEST ON SUNDAY WITH A SURFACE COLD FRONT CROSSING THE AREA SUNDAY AFTERNOON INTO THE EVENING. TIMING FOR THE SURFACE FRONT IS LOOKING BETTER AS THE THE 00Z/19 GFS AND ECMWF ARE COMING INTO BETTER AGREEMENT... WITH BOTH SHOWING THE FRONT CROSSING THE AREA DURING THE AFTERNOON INTO THE EVENING ON SUNDAY. BOTH THE GFS AND ECMWF DEPICT A FAIRLY STRONG UPPER LEVEL JET ASSOCIATED WITH THIS SYSTEM. AT THIS TIME WE APPEAR TO BE IN THE FAVORED RIGHT ENTRANCE REGION OF THE JET... WHICH WOULD INCREASE LIFT AND COUPLED WITH GOOD SOUTHERLY FLOW IN ADVANCE OF THE SURFACE FRONT SHOULD INCREASE THE LIKELIHOOD OF A MORE SUBSTANTIAL RAIN EVENT. THUS...WILL INCREASE POPS TO 50% FOR SUNDAY AFTERNOON INTO THE EARLY EVENING ACROSS THE CWA. WILL LIKELY NEED TO UP POPS IN LATER FORECASTS IF THE SYSTEM CONTINUES TO SHOW CONSISTENCY IN THE MODELS FROM RUN TO RUN. HIGHS SUNDAY WILL BE WELL ABOVE AVERAGE WITH TEMPS RANGING FROM THE UPPER 50S NORTHWEST TO THE UPPER 60S IN THE SOUTHEAST. LOWS MONDAY WILL RANGE FROM THE MID 30S NORTHWEST TO THE MID 40S IN THE EAST. MONDAY WILL BE NOTICEABLY COOLER AS HIGH PRESSURE BUILDS INTO THE REGION AT THE SURFACE. HOWEVER...HIGH TEMPS WILL STILL BE NEAR NORMAL FOR THIS TIME OF YEAR. MODELS BEGIN TO DIVERGE IN THEIR SOLUTIONS BEYOND MONDAY...AS THE 00Z/19 GFS BRINGS A UPPER LEVEL SHORTWAVE ACROSS THE REGION ON TUESDAY...WHILE THE 00Z/19 ECMWF DEVELOPS A CUT OFF UPPER LEVEL LOW OVER NORTHERN PORTIONS OF THE GULF COAST STATES. THUS...WITH MODEL DIFFERENCES AT THIS TIME WILL STICK CLOSE TO CLIMATOLOGY AND KEEP ANY MENTION OF PRECIP OUT OF THE FORECAST FOR NOW. -BSD && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... AS OF 1230 AM WEDNESDAY...VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. A WEAK SHORTWAVE WILL APPROACH CENTRAL NORTH CAROLINA THIS MORNING UNDER FAST ZONAL FLOW ALOFT. THIS SHORTWAVE IS ALREADY PRODUCING A DECK OF CLOUDS WITH BASES BETWEEN 4-5 KFT ACROSS TN/AL/MS/GA. THIS MOISTURE WILL SPREAD ACROSS THE REGION LATER THIS MORNING...WITH SKIES LIKELY GOING BROKEN AT GSO/INT BETWEEN 12-13Z...AND A FEW HOURS LATER AT RDU/FAY/RWI. CEILINGS SHOULD STAY VFR...AVERAGING 5 KFT. THIS DECK SHOULD BEGIN TO SCATTER OUT IN THE AFTERNOON...WITH SKIES BECOMING MOSTLY CLEAR IN THE EVENING. MVFR TO IFR CONDITIONS ARE POSSIBLE WITH A STORM SYSTEM PASSING JUST SOUTH OF THE AREA THURSDAY NIGHT...PRIMARILY AT FAY WITH THE BEST MOISTURE STAYING SOUTH OF GSO/INT/RDU/RWI. ISENTROPIC LIFT WILL INCREASE BY SATURDAY MORNING AS LOW LEVEL RIDGING MOVES OFFSHORE IN ADVANCE OF A STRENGTHENING STORM SYSTEM OVER THE CENTRAL U.S. MVFR TO IFR CONDITIONS WILL BE POSSIBLE DURING THIS TIME. THIS STORM SYSTEM WILL PUSH A COLD FRONT THROUGH CENTRAL NORTH ON SUNDAY...RESULTING IN A GOOD LIKELIHOOD OF SHOWERS ALONG WITH OCCASIONALLY MVFR TO IFR CONDITIONS. -BSD && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...BSD AVIATION...BSD nc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND FORKS ND 930 AM CST THU DEC 20 2007 .SHORT TERM... ONCE AGAIN TEMPERATURES AND FOG CONTINUE BE FORECAST CHALLENGES FOR REMAINDER OF DAY. PATCHY BR...LOCALLY DENSE...PERSISTS FROM RED RIVER VALLEY INTO NW MN. ASSOCIATED STRATUS DECK LOOKS TO BE EXPANDING ACROSS NW MN AND BEING TRAPPED UNDER SHARP INVERSION MAY BE TOUGH TO ERODE. WILL AGAIN EXTEND BR THROUGH AM HOURS AND HOPE INCREASING MIXING WILL DISSIPATE MOST FOG. REMAINDER OF FA SHOULD SEE FAIR AMOUNT OF SOLAR WITH ONLY UPSTREAM SCT-BKN CI/AC. TEMPERATURES WILL ALSO POSE CHALLENGES. COLDEST READINGS THIS AM WEST OF VALLEY WHERE SKIES WERE CLEAR. WEAK WARM ADVECTION CONTINUES TODAY WITH RUC INDICATING AN INCREASE IN MIXING AS SURFACE GRADIENT TIGHTENS A BIT. WITH WARM COLUMN AND SOLAR WESTERN AREAS SHOULD NOT HAVE ANY PROBLEM REACHING FORECAST HIGHS. MAX TEMPERATURES OVER REMAINDER OF FA UNDER BR AND STRATUS WILL HINGE ON MIXING/SOLAR. BEING PESSIMISTIC AREAS ADJACENT TO VALLEY IN NW/WEST CENTRAL MN MAY SEE LIMITED RECOVERY WITH FAR EAST ALREADY CLOSE TO EXPECTED HIGHS BUT NOT LIKELY TO SEE MUCH IMPROVEMENT IN LOW CIGS. WILL LOWER MAX TEMPERATURES SLIGHTLY ACROSS MN ADJACENT TO VALLEY AND LEAVE REMAINDER AS IS. && .AVIATION... IFR/MVFR CIGS/VSBY FROM VALLEY EAST. MODELS SUGGEST INCREASED MIXING WHICH MAY IMPROVE VSBYS IN BR LATE AM INTO EARLY AFTERNOON. NOT QUITE AS CONFIDENT IN LOSING LOWER CIGS OVER MN. MOISTURE REMAINS TRAPPED BLO SHARP INVERSION AND CONFIDENCE NOT REAL HIGH ON CIGS ERODING. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ VOELKER nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE WILMINGTON OH 1019 AM EST WED DEC 19 2007 .SYNOPSIS... A WEAK COLD FRONT WILL PASS ACROSS THE REGION TODAY...WASHING OUT SOUTH OF THE OHIO RIVER THIS EVENING. HIGH PRESSURE WILL THEN BUILD INTO THE AREA THROUGH THURSDAY MORNING...FOLLOWED BY A WEAK UPPER LEVEL SHORTWAVE WHICH WILL PASS SOUTH OF THE REGION THURSDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... COMPLICATED NEAR TERM FORECAST. A WEAK COLD FRONT WILL CONTINUE TO PASS ACROSS THE REGION THROUGH THIS AFTERNOON. AS IT DOES...SFC TEMPS WILL ACTUALLY WARM SOME ACRS THE SE CWFA...BUT COOL OR REMAIN STEADY ACRS THE REMAINDER OF THE REGION. WILL USED A BLEND OF THE LATEST RUC AND NAM-WRF FOR TEMPERATURES THROUGH THIS EVENING. SKIES SHOULD REMAIN MOSTLY CLOUDY. ZONES/GRIDS WILL BE ISSUED SOON. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/... AS THERMAL TROUGH PUSHES OFF TO THE EAST OVERNIGHT...SHOULD SEE AT LEAST SOME PARTIAL CLEARING WORK ITS WAY ACROSS OUR AREA FROM THE WEST. SFC HIGH WILL SHIFT EAST OF THE REGION THURSDAY MORNING WHICH BRINGS RETURN FLOW AND A WARM UP...ESPECIALLY ACROSS THE SRN HALF OF THE CWA. WEAK H5 SHORTWAVE STILL PROGGED TO PASS SOUTH OF THE REGION THURS NIGHT. BEST FORCING AND PRECIP CHANCES WILL REMAIN WELL SOUTH OF THE CWA. BUT WITH A LITTLE BIT OF H8 MOISTURE SKIRTING THE SOUTHERN TIER OF COUNTIES IN WEAK WAA REGIME...A FEW STRAY SHRA OR SPRINKLES MAY MAKE IT INTO FAR SRN PORTIONS OF THE CWA. OTHERWISE...EXPECT DRY WEATHER AND A CONTINUED WARMING TREND TO CONTINUE INTO FRI AND FRI NIGHT AS UPPER RIDGE BUILDS OVERHEAD...AND RETURN SRLY FLOW CONTINUES AHEAD OF WEEKEND SYSTEM. && .LONG TERM /SATURDAY THROUGH TUESDAY/... MAIN FOCUS THIS PERIOD IS A STRENGTHENING STORM SYSTEM FORECAST TO PASS THROUGH THE REGION SATURDAY NIGHT. MODELS SLOWLY TRENDING TOWARD A CONSENSUS...KEEPING THE UPPER WAVE MORE AMPLIFIED ACROSS THE WRN US BEFORE IT PHASES WITH NRN STREAM ENERGY OVER THE GREAT LAKES LATE ON SATURDAY. THIS BRINGS THE SFC LOW TRACK A BIT FURTHER SOUTH AND EAST...BUT STILL KEEPS OUR CWA WARM SECTORED UNTIL FRONTAL PASSAGE SAT NIGHT WHICH MEANS A RAIN EVENT AREAWIDE. GIVEN GOOD RUN TO RUN CONTINUITY...BELIEVE LIKELY POPS ARE WARRANTED ALONG AND AHEAD OF THE FRONT. GFS FORECAST SOUNDINGS INDICATE SEASONABLY STRONG ELEVATED INSTABILITY (NR 1000 J/KG) SO THUNDER IS A POSSIBILITY SAT NIGHT. HOWEVER...WILL WAIT FOR BETTER RUN TO RUN CONSISTENCY BEFORE INTRODUCING LATE DECEMBER THUNDERSTORMS. THOUGH MOST PRECIP SHOULD BE PRE-FRONTAL...ANY LINGERING MOISTURE WOULD MIX WITH AND CHANGE TO SNOW HEADING INTO SUN MORNING. LITTLE IF ANY SNOW ACCUM. TEMPS SHOULD BE SLOW TO WARM ON SUNDAY WITH STRONG CAA BEHIND THE FRONT. NO OTHER MAJOR SYSTEMS EXPECTED TO IMPACT THE REGION THROUGH CHRISTMAS DAY SO FORECAST IS DRY INTO EARLY NEXT WEEK. LARGE SCALE TROUGHING ACROSS THE EASTERN HALF OF THE COUNTRY SHOULD KEEP TEMPS BELOW AVG. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... CLOUD DECK HAS DROPPED TO MVFR ACROSS MUCH OF THE AREA THIS MORNING AND CLOUDS HAVE BEEN SLOWLY FILLING IN BACK TO OUR WEST ACROSS EASTERN INDIANA. COMBINATION OF THIS AND THE FACT THAT THE 925-850 MB THERMAL TROUGH WILL BE PIVOTING ACROSS THE AREA THROUGH EARLY AFTERNOON...SHOULD KEEP MVFR CIGS THROUGH MUCH OF THE AFTERNOON AND INTO EARLY EVENING. AS THERMAL TROUGH PUSHES OFF TO THE EAST AND LOW LEVEL FLOW BEGINS TO BACK...EXPECT CLOUDS TO ERODE FROM SOUTHWEST TO NORTHEAST ACROSS OUR AREA TONIGHT. OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE SATURDAY AFTERNOON INTO SUNDAY. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...NONE. KY...NONE. IN...NONE. && $$ SYNOPSIS...HICKMAN NEAR TERM...HICKMAN SHORT TERM...HAWBLITZEL/JGL LONG TERM...HAWBLITZEL AVIATION...JGL oh AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC 1010 PM EST THU DEC 20 2007 .SYNOPSIS... WEAK HIGH PRESSURE WILL GIVE WAY TO AN AREA OF LOW PRESSURE TONIGHT. COOL AND UNSETTLED NORTHEAST FLOW WILL REMAIN INTO THE WEEKEND AS A WEDGE OF HIGH PRESSURE LINGERS. A COLD FRONT IS EXPECTED TO CROSS THE AREA ON SUNDAY. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... MOST OF THE SIGNIFICANT PRECIPITATION DURING THE REMAINDER OF THE OVERNIGHT PERIOD WILL REMAIN WELL TO THE SOUTH OF THE CWA IN THE VICINITY OF THE SURFACE LOW PRESSURE SYSTEM MOVING EASTWARD ALONG THE GULF COAST TOWARD NORTHERN FL. RUC DEPICTS SOME LIGHT RAIN SPREADING ACROSS EXTREME NORTHEAST GA AND WESTERN CAROLINAS BETWEEN 05Z AND 08Z AS SHORT WAVE TROUGH APPROACHES AND ISENTROPIC LIFT STRENGTHENS A LITTLE OVER SOUTHERN PERIPHERY OF HIGH PRESSURE SYSTEM EXTENDING SOUTHWARD FROM EASTERN CANADA AND NEW ENGLAND. OVERNIGHT FORCING IS RATHER WEAK AND CURRENT RADAR DEPICTION SHOWS THAT EXISTING PRECIPITATION IS NOT EXTENSIVE IN COVERAGE. SO... HAVE LOWERED POPS SOMEWHAT FROM PREVIOUS FORECAST BUT MOST OF CWA WILL STILL HAVE LIKELY OR CATEGORICAL. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... AS OF 200 PM THURSDAY...PRECIPITATION FROM SOUTHERN STREAM SHORT WAVE AND ATTENDANT SURFACE LOW WILL BE AFFECTING THE FORECAST AREA FRIDAY MORNING. HOWEVER...EXPECT RAINFALL TO BE ON THE LIGHT SIDE AS BEST FORCING WILL BE TO THE SOUTH. ALSO...EXPECT THAT CONVECTION TO THE SOUTH WILL ROB MOISTURE INFLUX. NEVERTHELESS...IT LOOKS LIKE WIDESPREAD LIGHT RAIN (CATEGORICAL POPS) WILL BE OVER THE SOUTHERN PIEDMONTS EARLY FRIDAY...BUT WILL TAPER POPS OFF RAPIDLY TO THE NORTH. THIS SYNOPTIC SCALE PRECIP WILL MOVE OUT THE REGION BY MIDDAY AS SHORT WAVE MOVES OFF THE SE COAST. HOWEVER...NO CLEARING IS EXPECTED AS COLD HIGH OVER NEW ENGLAND WEDGES SOUTHWARD ALONG AND EAST OF THE APPALACHIANS. MODELS INDICATE THAT CAD WILL PERSIST THROUGH SAT ALONG WITH WEAK UPSLOPE COMPONENT IN THE MOUNTAINS.. HENCE...EXPECT CLOUDY CONDITIONS TO PREVAIL THROUGH SAT. AREAS OF LIGHT RAIN/DRIZZLE ARE A GOOD BEST ALONG THE ESCARPMENT THROUGH SAT. PATCHY DRIZZLE A GOOD BET ELSEWHERE FRI NIGHT. BETTER UPSLOPE COMPONENT AND MOISTURE TRANSPORT WILL SUPPORT INCREASING CHANCES OF RAIN...ESPECIALLY OVER THE MOUNTAINS SAT NIGHT. APPROACHING COLD FRONT LATE SAT NIGHT WILL ALSO BOOST PRECIP CHANCES IN THE MOUNTAINS. WILL STAY ON THE LOW END OF GUIDANCE FOR MAX TEMPS BOTH FRI AND SAT. TEMPS WILL PROBABLY SHOW A NON-DIURNAL TREND SAT NIGHT AS CAD ERODES AND WARM ADVECTION KICKS IN. USED 3 HOURLY GMOS TO POPULATE TEMPERATURE GRIDS WHICH KEEPS SAT NIGHT LOWS ESSENTIALLY IN THE UPPER 40S EAST OF THE MOUNTAINS AND LOW TO MID 40S IN MOUNTAINS. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 230 PM THURSDAY...NAM/GFS IN GOOD AGREEMENT THAT COLD FRONT WILL CROSS THE FORECAST AREA ON SUNDAY. HIGHEST POPS WILL BE IN THE MOUNTAINS (LIKELY FOR NOW) WITH CHANCE POPS TO THE EAST. THERE MAY BE ENOUGH FORCING FOR WIDESPREAD SHOWERS EVERYWHERE...BUT FOR NOW WILL JUST SHOW CHANCE TYPE POPS TO EAST OF THE MOUNTAINS AS FLOW DOES VEER TO THE SW WHICH MAY TEND TO DIMINISH SHOWER CHANCES E OF MOUNTAINS. EXPECT RAPID CLEARING BEHIND THE FRONT BY SUN EVENING. HIGH PRESSURE WILL BUILD OVER THE REGION ON MONDAY WHICH SHOULD PRODUCE A VERY NICE DAY. SUNDAY AND MONDAY LOOK TO BE MILD WITH TEMPS ONE TO TWO CATEGORIES ABOVE NORMAL. THINGS GET MURKY RATHER QUICKLY AFTER MONDAY AS THE MEDIUM RANGE GUIDANCE CONTINUES TO BE IN FLUX. THE ECWMF AND GFS SOLUTIONS ARE QUITE DIFFERENT FOR CHRISTMAS ONWARD. AFTER CONSULTATION WITH NEIGHBORING OFFICES...IT WAS DETERMINED THAT HPC GUIDANCE WOULD BE UTILIZED WHICH LEANS HEAVILY ON THE ECWMF SOLUTION. THIS SOLUTION BRINGS A SHORT WAVE ACROSS THE AREA ON TUE WITH CYCLOGNESIS ALONG THE COAST. THIS WOULD SPARE THE SOUTHERN APPALACHIANS FROM MUCH IN THE WAY OF SIGNIFICANT PRECIP. MAYBE JUST SOME WIDELY SCATTERED/SCATTERED SHOWERS (POSSIBLY MIXED WITH SNOW AT HIGHER ELEVATIONS IN MOUNTAINS). THEN A DRY DAY WEDNESDAY. THE BEST THREAT FOR PRECIP THEN BECOMES THURSDAY AS A COLD FRONT APPROACHES FROM THE W. GFS ON THE OTHER HAND DEVELOPS A SWATH OF OVERRUNNUNG PRECIP OVER THE FORECAST AREA BY LATE TUE USING THE OLD BOUNDARY TO THE S. IT KEEPS THIS SWATH OF MOISTURE/PRECIP ACROSS THE REGION INTO THU ALONG THE STATIONARY FRONT...WITH A SOUTHERN STREAM LOW THEN EJECTING NE DURING THU TO THE W OF APPALACHIANS. HOPEFULLY WE WILL GET BETTER AGREEMENT AS WE DRAW CLOSER. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... CEILINGS WILL LOWER INTO MVFR RANGE AS WARM ADVECTION/ISENTROPIC LIFT OVER SOUTHERN PERIPHERY OF DAMMING HIGH STRENGTHENS THROUGH THE NIGHT. THERMAL ADVECTION AND LIFT... PLUS A LITTLE HELP FROM WEAK UPSLOPE WIND COMPONENT... APPEAR TO BE PROMOTING DEVELOPMENT OF RAIN AREA FROM UPSTATE SC INTO WESTERN NC. HOWEVER... PRIMARY AREA OF PRECIPITATION OVERNIGHT LIKELY TO REMAIN WELL TO OUR SOUTH NEAR SURFACE LOW THAT WILL MOVE STEADILY EASTWARD. BY 06Z TO 08Z... EXPECT SOME IFR CEILINGS AND VISIBILITIES TO APPEAR AS ISENTROPIC LIFT NEARS ITS MAXIMUM... BUT PRECIPITATION SHOULD REMAIN RATHER LIGHT. IFR AND LOW MVFR CEILING AND VISIBILITY WILL IMPROVE SOMEWHAT BETWEEN 15Z AND 18Z AS STRONGEST FORCING FOR PRECIPITATION EXITS THE REGION... BUT MVFR CEILING WILL CONTINUE. AVIATION OUTLOOK...CIG AND VSBY RESTRICTIONS ARE EXPECTED THROUGH SUNDAY AS MOISTURE LINGERS IN THE PERSISTENT COLD AIR DAMMING REGION. A COLD FRONTAL PASSAGE SHOULD SCOUR THE COLD WEDGE BY MON WITH COOL HIGH PRESSURE BUILDING IN BEHIND IT. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...NONE. NC...NONE. SC...NONE. && $$ SYNOPSIS...BSH NEAR TERM...LGL SHORT TERM...LG LONG TERM...LG AVIATION...LGL sc AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 817 PM CST WED DEC 19 2007 .UPDATE... LATEST RUC SOUNDINGS...COMBINED WITH NAM12 925MB COND PRES DEF PLOTS...SHOW THAT FOG IS A POSSIBILITY TONIGHT ACROSS THE CWA. BY 0215UTC...KETH IS AT 5SM BR...WITH KABR AT 4SM BR. HAVE UPDATED WX GRIDS TO REFLECT FOG THROUGH 14Z. BASED ON DWPTS...CURRENT LOWS LOOK OK...ALTHO MAY BE A TAD TO LOW IN THE JAMES RIVER VALLEY...BUT WILL LEAVE AS IS FOR NOW. UPDATED ZONES HAVE BEEN SENT. UPDATED AVIATION DISCUSSION BELOW. && .PREV DISCUSSION... .SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT MAIN CHALLENGE IN THE SHORT TERM IS TEMPERATURES. A WEAK UPPER LEVEL TROUGH WILL SLIDE ACROSS THE PLAINS TONIGHT. THE UPPER FLOW BECOMES NEARLY ZONAL ON THURSDAY...THEN SHIFTS TO SOUTHWESTERLY AS A STRONG TROUGH DIGS DOWN THE WEST SIDE OF THE ROCKIES. AT THE SURFACE...A TROUGH/WARM FRONT ASSOCIATED WITH LOW PRESSURE OVER SOUTHWEST CANADA SLIDES ACROSS THE CWA TONIGHT. GFS HINTING AT SOME FLURRIES POSSIBLE ACROSS THE NORTHEASTERN CWA...BUT CLOUD BASES WILL BE PRETTY HIGH AND HAVE OPTED TO NOT MENTION THEM. THE SOUTHWEST CANADA LOW TRACKS TO SOUTHERN SASK ON THURSDAY...THEN ELONGATES OVER THE NORTHERN AND CENTRAL PLAINS THURSDAY NIGHT WITH A COLD FRONT JUST APPROACHING THE WESTERN CWA BY FRIDAY MORNING. EXPECT A PERIOD OF MOSTLY CLEAR SKIES TONIGHT...THEN WILL SEE MORE MID TO HIGH CLOUDS PUSH IN THURSDAY AHEAD OF THE APPROACHING LOW PRESSURE SYSTEM. NO SIGNIFICANT ENERGY OR MOISTURE AROUND...SO WILL LEAVE THE SHORT TERM DRY. MILD TEMPERATURES WILL CONTINUE WITH H85 TEMPS STAYING ABOVE ZERO THROUGH LATE THURSDAY NIGHT. EXPECT LOWS TONIGHT AND THURSDAY TO BE IN THE TEENS WITH THURSDAY HIGHS A GOOD CATEGORY OR TWO ABOVE NORMAL. .LONG TERM...FRIDAY MORNING THROUGH THURSDAY LOTS TO DISCUSS CONCERNING PROGRESSION OF WEATHER DURING THE WEEKEND AND THE FIRST HALF OF NEXT WEEK. WILL BEGIN WITH A WINTER STORM...FOLLOWED BY A RAPID TEMPERATURE DROP IN THE WAKE OF THE SYSTEM...A RETURN TO WARMER TEMPERATURES...AND END WITH A WEAK WEATHER SYSTEM LATE IN THE PERIOD. UPPER TROUGH SET UP ACROSS THE FRONT RANGE WITH AN INTENSE UPPER LOW DROPPING SOUTHWARD ACROSS THE NORTHERN CWA SATURDAY AM. THIS DEVELOPS STRONG BAROCLINIC FLOW ACROSS THE SOUTHEASTERN CWA. DECENT CONTINUITY EXISTS BETWEEN GFS/GFS ENSEMBLE AND ECMWF RUNS IN TIMING OF SYSTEM THOUGH EARLY SATURDAY. SOLUTIONS DIVERGE LATE SATURDAY...WITH ECMWF SLOWER THAN GFS/GFS ENSEMBLES. AS FOR POP TOTALS...ENSEMBLES DEPICT MAJORITY OF LIQUID IS IN THE NORTHEAST AND SOUTH CENTRAL CWA...ACCUMULATING AFTER FRIDAY AFTERNOON. WITH SLOWER ECMWF SOLUTION WOUND NOT BE SURPRISED TO SEE LINGERING SNOW SHOWERS THROUGH EARLY SATURDAY. SNOW ACCUMLATIONS BETWEEN 1 TO 3 INCHES THE MOST LIKELY OUTCOME. WILL CONTINUE TREND FOR ANOMALOUSLY WARM TEMPERATURES WITH H925 LAYER ABOVE FREEZING FOR THE START OF THE PERIOD. CAA REGIME DEVELOPS WELL BEHIND PASSAGE OF WEAK TROUGH FRIDAY...AND PERSIST INTO SUNDAY AM. ONCE COLD BUBBLE AT H925 DRIFTS INTO MINNESOTA...WILL SEE WEAK WAA DEVELOP BY SUNDAY AM. NOT EXPECTING THIS TO ALLOW FOR DRASTIC WARM UP IN THE JAMES VALLEY WITH WEAK GRADIENT AND SOUTHERLY FLOW NEAR THE SURFACE...ALONG WITH ADDED SNOWFALL FROM THE WEEKEND. THE WESTERN CWA WILL SET UP FOR WARMER TEMPERATURES AS SNOW COVER IS EXPECTED TO REMAIN THIN AND WITH A SOUTHWESTERLY FLOW. CONCERNING A MID WEEK WEATHER SYSTEM. NORMALLY WOULD NOT EVEN INCLUDE SAVE FOR THE CONTINUITY BETWEEN GFS AND ECMWF DETERMINISTIC RUNS AS WELL AS GFS ENSEMBLE MEMBERS BRINGING A SHORTWAVE THOUGH THE CWA. WILL LIMIT MENTION TO SLIGHT CHANCE OF PRECIPITATION FOR NOW. && .AVIATION... MVFR CIGS/VSBYS POSSIBLE FROM 03Z TO 14Z FOR KABR AND KATY TAF SITES AS FOG IS EXPECTED TO DEVELOP AND/OR IS CURRENTLY DEVELOPING. P6SM/SKC CONDS EXPECTED THROUGH 18Z FOR KPIR AND KMBG TAF LOCATIONS. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ UPDATE...HINTZ SHORT TERM...PARKIN LONG TERM...CONNELLY AVIATION...HINTZ WEATHER.GOV/ABERDEEN sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CORPUS CHRISTI TX 826 PM CST THU DEC 20 2007 .UPDATE...THE NAM/GFS DETERMINISTIC SOLNS PROGD 00Z FRI SFC DEW POINTS 5-10C DEGRESS GREATER THAN METAR VALUES. THE LOCAL MM5 PROGD THE LOWEST 00Z FRI SFC DEW POINTS OVR THE NERN CWFA... INCONSISTENT WITH THE 00Z FRI OBSERVATIONS. YET...THE RUC SOLN PERFORMED MUCH BETTER IN THIS RESPECT...AND THUS MORE CONFIDENT IN THIS SOLN. HWR...ALTHOUGH THE RUC PROGS 12Z FRI SFC TEMPS HIGHER THAN THE CURRENT FCST...WL DEFER TO THE CURRENT FCST. ANTICIPATE THAT LIGHT WIND/EXTREMELY DRY CONDITIONS/DECOUPLING CONDITIONS WL ALLOW FOR SFC TEMPS TO MOVE CLOSER TO THE SFC DEW POINTS. THUS... WL RETAIN THE CURRENT TEMP FCST. CAVEAT...THE NAM/GFS PROG WEAK ONSHORE WIND AFT 09Z FRI...WHICH COULD RESULT IN HIGHER MIN TEMPS OVR THE COASTAL COUNTIES. && .AVIATION...VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD. && .PRELIMINARY POINT TEMPS/POPS... CORPUS CHRISTI 83 45 80 63 77 / 0 0 0 10 10 VICTORIA 81 43 78 58 72 / 0 0 0 20 20 LAREDO 82 45 84 56 75 / 0 0 0 0 10 ALICE 84 43 83 59 77 / 0 0 0 10 10 ROCKPORT 82 49 76 63 75 / 0 0 0 20 20 COTULLA 81 41 81 53 72 / 0 0 0 0 10 KINGSVILLE 84 43 82 61 79 / 0 0 0 10 10 NAVY CORPUS 82 50 78 65 76 / 0 0 0 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ WC/87...SHORT TERM JR/19...AVIATION tx AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE LA CROSSE WI 927 PM CST THU DEC 20 2007 .UPDATE... LATEST RUC SOUNDINGS INDICATE LOW LEVEL MOISTURE DEPTH TO DECREASE FROM WEST TO EAST TONIGHT ACROSS THE AREA. SO GREATEST THREAT FOR FZDZ LOOKS TO REMAIN TO THE EAST OF THE MISSISSIPPI RIVER. RADAR RETURNS OVER THE PAST HOUR HAVE BEEN DIMINISHING ACROSS THE EASTERN COUNTIES...BUT CALLS STILL INDICATE VERY LIGHT RAIN/DRIZZLE/FREEZING DRIZZLE STILL OCCURRING WITH MOST OF THE SUB-FREEZING TEMPERATURES FOUND NORTH OF HIGHWAY 29. VISIBILITIES HAVE HELD UP IN THE ONE HALF TO ONE MILE RANGE ACROSS THE NORTHERN HALF OF THE DENSE FOG ADVISORY AREA FOR MOST OF THE EVENING. BUT ACROSS NORTHEAST IOWA ONE QUARTER OR LESS IS BEING REPORTED. WITH CONTINUED SOUTHEAST FLOW STILL EXPECT WIDESPREAD DENSE FOG ACROSS THE WESTERN ZONES OVERNIGHT AND INTO FRIDAY MORNING. ALL IN ALL GRIDS LOOKS TO BE IN GOOD SHAPE AND PLAN NO MAJOR CHANGES TO ONGOING FORECAST. && JLR .PREV DISCUSSION... .SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT FORECAST CONCERNS THIS PACKAGE...DENSE FOG/DZ/FZDZ TONIGHT... POTENTIAL WINTER STORM CENTERED ON SAT/SAT NIGHT. DATA ANALYSIS AT 18Z HAD ONE LOW PRESSURE CENTERED OVER ALB AND A WEAKER ONE OVER THE LA/AR AREA. BROAD SOUTH/SOUTHEAST FLOW AHEAD OF THESE LOWS WAS PUSHING WARM/MORE MOIST AIR NORTH INTO THE REGION. DEW POINTS INTO THE UPPER 20S/LOW 30S ACROSS MUCH OF IA/SOUTHERN WI/NORTHERN IL. FOG-PRODUCT/VIS IMAGERY/SFC OBS SHOWING LOW STRATUS DECK ADVECTING/EXPANDING NORTH ACROSS AREA ALONG AND EAST OF I-35. VSBYS ALREADY LESS THAN 2SM IN FOG OVER THE WEST HALF OF THE FORECAST AREA AS THE INCREASING MOIST AIRMASS IS ADVECTED NORTH OVER THE SNOW COVERED LANDSCAPE. EARLY AFTERNOON TEMPS IN THE LOW/MID 30S...ADDING TO THE BOUNDARY LAYER MOISTURE WITH SOME MELTING SNOW. NO MAJOR ERRORS NOTED WITH 20/12Z NAM/GFS INITIALIZATIONS...WITH SOLUTIONS MORE SIMILAR TO EACH OTHER THAN THEIR RUNS OF 12 AND 24HRS AGO. GFS TRENDING TOWARD THE STRONGER...MORE PHASED ECMWF/UKMET/NAM SOLUTIONS WITH THE TROUGH AS IT LIFTS THRU THE UPPER MIDWEST SAT/ SUN. NAM STILL THE STRONGEST...WITH GFS/ECMWF/UKMET OFFERING A RATHER GOOD CONSENSUS AT THE SFC/500MB AT 12Z SUN. DPROG/DT OF 500MB HGTS AT 20/12Z SHOWED NAM/GFS RUNS OF 18/12Z AND 19/12Z VERIFIED REASONABLY WELL ACROSS NOAM/EASTERN PAC. MODELS HAVE TRENDED TOWARD THE STRONGER LOOK OF NAM WITH THE ENERGY OFF THE CA COAST WHILE TRENDING TOWARD THE GFS WITH THE NORTHERN STREAM ENERGY OVER BC. THRU 36HRS...NAM SHOWS THE BETTER RUN-TO-RUN CONSISTENCY WIT THE SOUTHERN STREAM ENERGY INTO AZ/NM WHILE GFS SHOWS THE BETTER CONSISTENCY WITH THE NORTHERN STREAM ENERGY INTO MT/SASKAT. FOR 36- 84HRS MODELS HAVE CONVERGED ON A COMMON SOLUTION WITH THE SOUTHERN STREAM ENERGY LIFTING TO MO/AR WHILE CONSIDERABLE DIFFERENCE STILL REMAIN WITH THE NORTHERN STREAM/DEVELOPING UPPER LOW OVER THE NORTHERN PLAINS/WESTERN GREAT LAKES. TREND IS TOWARD ECMWF IN THIS TIME-FRAME...WITH 20/00Z ECMWF OFFERING A REASONABLE COMPROMISE OF LATEST NAM/GFS SOLUTIONS AT 60/72HRS AS NORTHERN/SOUTHERN STREAM PHASE. CHECK OF OBS VS. MODEL DATA AT 18Z SHOWED NAM/GFS REASONABLE WITH THE SFC MASS FIELDS ACROSS CENTRAL NOAM. PER WV IMAGERY... MODELS LOOK TO HAVE GOOD DEPICTIONS OF THE SHORTWAVE FEATURES OVER NOAM/EASTERN PAC...WITH A MODEL COMPROMISE PERHAPS A BIT BETTER THAN EITHER NAM/GFS ALONE. GOOD DARKENING SEEN IN WV IMAGERY WITH THE SHORTWAVE COMING ON THE CA COAST. WITH ALL THE MODEL VARIABILITY OF LATE AND 18Z DATA TENDING TO SUPPORT A MODEL COMPROMISE...PREFER THAT SOLUTION THIS CYCLE. GIVEN DEPENDENCE OF FORECAST ON NUANCES OF NORTHERN/SOUTHERN STREAM PHASING...SHORT-TERM FORECAST CONFIDENCE AVERAGE AT BEST. FOR THE SHORT TERM...SOUTH/SOUTHEAST WINDS TONIGHT WILL CONTINUE TO ADVECT MOISTURE NORTHWARD ACROSS THE AREA...OVER THE SNOW PACK AND UNDER AN INVERSION NEAR 850MB. WITH VSBYS ALREADY LOW AND THE CONTINUED LOADING OF THE SUB-INVERSION LAYER WITH MOISTURE...WILL ISSUE A DENSE FOG ADVISORY FOR TONIGHT INTO FRI MORNING FOR AREAS WEST OF THE MS RIVER. LOW CLOUD/FOG BLANKET AND CONTINUED LOW LEVEL WARM ADVECTION...TEMPS TO BE NEARLY STEADY TONIGHT NEAR THE FREEZING MARK. WITH WEAK CONVERGENCE/LIFT IN THE MOIST SFC-850MB LAYER...PATCHY DZ/FZDZ STILL LOOKS REASONABLE TONIGHT. AS DEPTH OF MOISTURE DECREASES FROM WEST TO EAST LATER TONIGHT...THREAT OF DZ/FZDZ WILL DIMINISH AS WELL...AND THIS ALREADY DEPICTED IN GRIDS. WITH CONTINUED MOIST SOUTH WINDS OVER THE SNOW COVER FRI...FOG WILL PERSIST THRU MUCH OF THE DAY AND ADVISORY MAY NEED TO BE EXTENDED INTO THE EARLY AFTERNOON...MUCH LIKE WED. ATTENTION QUICKLY TURNS TO WEEKEND SYSTEM AND POTENTIAL FOR SIGNIFICANT SNOW FOLLOWED BY STRONG WEST/NORTHWEST WINDS. LATEST MODEL SUITE/ENSEMBLES HAVE TRENDED STRONGER/MORE PHASED WITH THE NORTHERN/SOUTHERN STREAMS AS THE SHORTWAVES CROSS THE MID MS VALLEY AND UPPER MIDWEST. THIS MORE PHASED SOLUTION BRINGS DEEPER MOISTURE /4-5 G/KG/ AND DEEPER/STRONGER 850-500MB FN/QG CONVERGENCE NORTHWARD INTO THE FORECAST AREA CENTERED ON 00Z SUN. THIS COUPLED WITH STRONGER PV ADVECTION AND 300MB AGEOSTROPHIC FLOW/DIVERGENCE ALOFT. SOUNDINGS INITIALLY SUPPORT PRECIP AS SNOW OVER THE NORTHWEST HALF OF THE FORECAST AREA SAT MORNING...TO RAIN OVER THE SOUTHEAST END. APPEARS TO BE ONLY SMALL CHANCES OF MIXED/FREEZING PRECIP TYPES WITH THIS SYSTEM AS SOUNDINGS SHOW AIRMASS WARMER THAN 0C MIXED TO THE SFC. DEEP DYNAMIC LIFT/COOLING OF THE AIRMASS AHEAD OF THE EJECTING SOUTHERN STREAM SHORTWAVE THEN LOOKS TO QUICKLY COOL THE COLUMN FROM THE TOP DOWN AND CHANGE AND RA/SN MIX TO ALL SNOW LATE SAT MORNING/AFTN. GIVEN VERY DYNAMIC TREND OF THIS SYSTEM /SFC LOW DEEPENS ABOUT 14MB FROM 00Z SUN TO 12Z SUN/...THE TREND TOWARD A STRONGER MORE PHASED SOLUTION...AND POTENTIAL IMPACT ON A MAJOR HOLIDAY TRAVEL WEEKEND...ISSUED A WINTER STORM WATCH FOR THE SOUTHERN THIRD OF THE FORECAST AREA FOR SAT AFTERNOON/NIGHT AS A START. AS DETAILS BECOME CLEARER...POTENTIAL FOR THE WATCH TO BE EXPANDED NORTH/EAST WITH LATER ISSUANCES. WITH THE RAPIDLY DEEPENING LOW SAT NIGHT PRESSURE GRADIENT OVER THE AREA INCREASES BY 12Z SUN WITH STRONG/GUSTY WEST/NORTHWEST WINDS IN THE WAKE OF THE LOW FOR LATE SAT NIGHT/MUCH OF SUNDAY. MAY NEED TO EXPEND WATCH OR ANY LATER HEADLINES INTO SUNDAY DUE TO STRONG WINDS CREATING BLOWING/DRIFTING SNOW. WITH A BETTER CONSENSUS FOR THE STRONGER SYSTEM...RAISED POPS FOR MUCH THE SAT/SAT NIGHT PERIOD INTO LIKELY/CATEGORICAL RANGES. POTENTIAL FOR WRAP-AROUND DEFORMATION BAND OF -SN TO REMAIN OVER THE AREA ON SUN AND RAISED -SN CHANCES ON SUN AS WELL. WITH CLOUD/FOG BLANKET...FAVORED WARMER OF GUIDANCE LOWS TONIGHT WITH NEAR STEADY TEMPS. WITH CLOUDS/FOG FRI...TRENDED TOWARD COOLER OF GUIDANCE HIGHS. FAVORED A BLEND OF GUIDANCE LOWS/HIGHS FRI NIGHT/SAT...WITH FALLING TEMPS DURING THE DAY SAT. TRENDED TOWARD COLDER OF GUIDANCE LOWS SAT NIGHT AS COLD AIR POURS IN AND THE UPPER LOW DROPS ACROSS THE REGION. PREFERRED A BLEND OF GFS MEX/ ENSEMBLE MOS AND HPC GUIDANCE FOR HIGHS/LOWS SUN/SUN NIGHT. .LONG TERM...MONDAY THROUGH THURSDAY 20/00Z MEDIUM RANGE MODELS/ENSEMBLE MEAN OFFER A MODEST CONSENSUS WITH EACH OTHER FOR MON-THU...BUT DIFFERENCES IN TIMING/STRENGTH OF THE SHORTWAVE TROUGHS INCREASES THRU THE PERIOD. RUN-TO-RUN CONSISTENCY OF TIMING/STRENGTH DETAILS BY TUE AND BEYOND IS QUITE LOW. THIS NOT UNEXPECTED GIVEN MODELS STILL STRUGGLING WITH THE NORTHERN/SOUTHERN STREAM BALANCE OF ENERGY WITH THE SYSTEM THIS WEEKEND AND NUMEROUS STRONGER SHORTWAVE TROUGHS ACROSS THE CONUS FOR NEXT WEEK. THUS...FORECAST CONFIDENCE IN THE LONG TERM ON THE LOW SIDE THIS CYCLE. GFS ENSEMBLE MEAN DOES TREND TOWARD A MODEL BLEND/ COMPROMISE OF THE GFS/ECMWF/UKMET RUNS...AT LEAST WITH TIMING OF FEATURES. WHAT MODEL CONSENSUS THERE IS INDICATES A RATHER ACTIVE FLOW PATTERN ACROSS NOAM THRU NEXT WEEK...ESPECIALLY THE SOUTHERN STREAM. UPPER MIDWEST LOOKS TO BE CAUGHT UNDER SPLIT FLOW MON/TUE WITH A COLD SFC HIGH PRESSURE RIDGE SLIDING ACROSS THE REGION...FOR DRY...QUIET WEATHER. FOR WED/THU ECMWF AND TO A LESSER DEGREE GFS ENSEMBLE MEAN TRENDING TOWARD SOME PHASING OF THE NORTHERN/SOUTHERN STREAMS AND A SIGNIFICANT TROUGH LIFTING NORTHEAST ACROSS THE CENTRAL CONUS. UKMET/CAN GEM/20/06Z GFS RUN LOOK TO MAINTAIN MORE OF A SPLIT FLOW AND BULK OF THE ACTIVE WEATHER SOUTH OF THE AREA. HPC TRENDED TOWARD A MODEL COMPROMISE WEIGHTED TOWARD THE USUALLY BETTER ECMWF AND ENSEMBLES FOR WED/THU. SMALL SNOW CHANCES WED INTO THU LOOKS REASONABLE FOR NOW GIVEN RANGE MODEL SOLUTIONS AND LOWER FORECAST CONFIDENCE BY DAYS 6/7 FOR ANY ONE PARTICULAR OUTCOME. FAVORED A BLEND OF GFS MEX/ENSEMBLE MOS AND HPC GUIDANCE MAXES/MINS THRU THE PERIOD. && .AVIATION...TONIGHT AND FRIDAY LOW CLOUDS AND/OR FOG EXPECTED TO PERSIST ACROSS THE AREA THROUGH TONIGHT AND INTO FRIDAY. THIS BASED ON EXPANSE OF STRATUS CONTINUING TO MOVE NORTHWARD FROM IOWA AND ILLINOIS. IN FACT...BASED ON CURRENT CONDITIONS AND LOCAL STUDY OF DENSE FOG EVENTS...FORECAST CONFIDENCE WAS HIGH FOR KRST TAF SITE TO HAVE VISIBILITY NEAR 1/4 MILE DURING LARGE PORTIONS OF 18Z 20DEC07 TAF VALID TIME. SOME IMPROVEMENT SHOULD OCCUR AFTER 16Z 21DEC07. LOOKING AHEAD...POTENTIAL FOR WINTRY PRECIPITATION EVENT TO IMPACT BOTH KRST AND KLSE TAF SITES AND IN FACT MOST OF THE AIRPORTS IN THE FORECAST AREA THIS WEEKEND. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR WIZ053-WIZ054-WIZ055-WIZ061. MN...DENSE FOG ADVISORY UNTIL 10 AM CST FRIDAY FOR MNZ079-MNZ086- MNZ087-MNZ088-MNZ094-MNZ095-MNZ096. IA...DENSE FOG ADVISORY UNTIL 10 AM CST FRIDAY FOR IAZ008-IAZ009- IAZ010-IAZ011-IAZ018-IAZ019-IAZ029-IAZ030. WINTER STORM WATCH FROM SATURDAY AFTERNOON THROUGH LATE SATURDAY NIGHT FOR IAZ008-IAZ009-IAZ010-IAZ011-IAZ018- IAZ019-IAZ029-IAZ030. && $$ SHORT/LONG TERM...RRS AVIATION..........THOMPSON wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 1026 AM CST THU DEC 20 2007 .UPDATE...PRIMARY CONCERN WAS WITH DENSE FOG ACROSS PARTS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA TODAY. SATELLITE IMAGERY INDICATED STRATUS EXPANDING STEADILY NORTHWARD INTO FORECAST AREA THIS MORNING. VISIBILITY LOWERS TO AS LOW AS 1/4 MILE PER 16Z OBSERVATION AT KOLZ. LATEST RUC AND 12Z 20DEC07 NAM/WRF SUPPORTED LOW CLOUDS AND FOG TO CONTINUE PUSHING NORTHWARD TODAY ACROSS THE ENTIRE FORECAST AREA. BASED ON CURRENT OBSERVATIONS...INCLUDED FOG ACROSS PARTS OF SOUTHEAST MINNESOTA AND NORTHEAST IOWA REST OF TODAY. WILL CONTINUE TO MONITOR VISIBILITY TRENDS IN CASE WIDESPREAD 1/4 MILE SCENARIO DEVELOPS. FOR NOW...HAVE UPDATED CURRENT DATA BASE AND WILL UPDATE ZONE FORECASTS FOR LATEST TRENDS. && THOMPSON .PREV DISCUSSION... /ISSUED 340 AM CST THU DEC 20 2007/ SHORT TERM...TODAY THROUGH SATURDAY NIGHT FORECAST FOCUS IN THE SHORT-TERM CENTERS ON THE PCPN CHANCES FOR TODAY...AND THEN WHAT THE WEEKEND SYSTEM WILL DO. TODAY...A RELATIVE WEAK AND PROGRESSIVE 500 MB SHORTWAVE TROUGH WILL TRACK EAST ACROSS THE REGION. DESPITE ITS NON-DESCRIPT APPEARANCE...THIS FEATURE WILL BRING SOME QG CONVERGENCE THROUGH THE LAYERS WITH IT...ALONG WITH SOME BROAD LOW LEVEL WARMING ON THE 925:700 MB SFCS. SOME ISENTROPIC UPGLIDE IS ALSO INDICATED AHEAD OF THE SHORTWAVE TROUGH...IN THE 285:300 K SFCS. THE THERMODYNAMIC LIFT PEAKS THIS AFTERNOON ALONG AND EAST OF THE MISSISSIPPI RIVER...GENERALLY EXITING EAST BETWEEN 00-06Z. SO...THERE IS SOME LIFT TO WORK WITH...AND POTENTIALLY SOME PCPN...ALL DEPENDING ON HOW MUCH SATURATION THERE WILL BE. A WEST-EAST RUNNING X-SECTION HAS THE CURRENT HIGH/MID LEVEL SATURATION PUSHING EAST BY THIS AFTERNOON...WITH AN INCREASE IN THE LOW LEVEL MOISTURE //800MB TO THE SFC// THIS AFTERNOON. THE MOISTURE ISN/T DEEP ENOUGH TO SUPPORT ANY SIGNIFICANT PCPN PROCESSES...BUT IT IS FOR DRIZZLE/FREEZING DRIZZLE. SO...WITH SOME BROADSCALE LIFT THROUGH THE TOP OF THIS LAYER...PATCHY DRIZZLE/FREEZING DRIZZLE WILL BE POSSIBLE...MOSTLY THIS AFTERNOON AND EARLY EVENING...AND MOSTLY ALONG AND EAST OF THE MISSISSIPPI RIVER. NOW...ON TO THE MUCH TALKED ABOUT STORM SYSTEM FOR THE WEEKEND. THE MODELS HAVE CERTAINLY HAD THEIR FUN WITH US...WHILE CONTINUING TO BRING THE REGION SOME PCPN...WHAT AND WHERE HAS VARIED ALMOST ON A DAY TO DAY...RUN TO RUN BASIS. NOW THAT THE SYSTEM HAS MOVED INTO THE SHORT-TERM...VARIANCES CONTINUE. I CERTAINLY DIDN/T ASK SANTA FOR THIS. ANYWAY...THE MODELS DO SEEM TO BE SETTLING MORE ON A SPLIT 500 MB FLOW TYPE SYSTEM...THAT MERGES TOGETHER AS IT PASSES INTO THE GREAT LAKES...STRENGTHENING FOR ITS TREK ACROSS THE NEW ENGLAND STATES. HOWEVER...THE DEVELOPMENT OF THEIR SFC LOWS ARE DIFFERENT...AND SO IS THEIR RESULTING QPF. THE NAM AND EC WOULD DEVELOP A SINGLE LOW CENTER...OVER WI/ILL BY 00Z SUN. THE GFS KEEPS THIS SYSTEM SPLIT YET...WITH LOW CENTERS OVER SOUTHERN CANADA AND ARK. EVENTUALLY THESE SOLUTION COME TOGETHER AS THE STORM MOVES EAST. THE 21Z SREF IS SIMILAR TO THE GFS WITH PLACEMENT OF ITS LOW CENTERS. THE GFS HAS BEEN FAIRLY CONSISTENT WITH A TWO-HEADED SYSTEM AS IT MOVES THROUGH THE GREAT LAKE STATES...ALTHOUGH A BIT SLOWER OVER ITS PAST FEW RUNS. THE EC HAS BEEN VARIABLE...BUT HAS MOVED FROM TWO LOWS TO ONE AS IT MOVES ACROSS THE REGION...WHILE THE NAM HAS HAD ONE LOW...JUST MOVED IT FARTHER SOUTH. IT WOULD SEEM THAT THE GFS HAS BEEN MORE CONSISTENT...AND IS FAVORED BY THE ENSEMBLES. THE DIFFERENCES ARE SIGNIFICANT IN THAT THE NAM/EC WOULD BRING STRONGER FORCING ACROSS THE FORECAST AREA...ALONG WITH THE DEFORMATION PCPN BAND WEST/NORTH OF THE SFC LOW. AS A RESULT...MORE QPF AND MORE SNOW POTENTIAL. THE GFS...CONVERSELY...IS MUCH LESS IN ITS QPF. WITH THE NAM...COBB OUTPUT WOULD PUT 3-5 INCHES ACROSS MUCH OF THE AREA. THE GFS IS LESS THAN AN INCH. THE SREF WOULD SUGGEST 1-2 INCHES...AND THE EC 2-4. DON/T THINK GOING TOWARD THE HIGH END...OR THE LOW END...IS THE WAY TO GO. WITH SUCH VARIABILITY IN THE MODEL SOLUTIONS...WILL OPT WITH SOMETHING IN THE MIDDLE...AND ALLOW LATER FORECASTS TO ADJUST UP OR DOWN...AS THE CASE MAY BE. ONE THING THE MODELS DO AGREE ON IS THAT SATURDAY/SAT EVENING WILL BE THE BEST TIME FOR SOME ACCUMULATING PCPN. BEFORE GETTING TO SNOW AMOUNTS...OR LACK THERE OFF...PRECIPITATION TYPE NEEDS TO BE QUESTIONED. AS THEY HAVE BEEN DOING...THE MODELS CONTINUE TO PULL CONSIDERABLE WARM AIR NORTHWARD AHEAD OF THE SYSTEM...AND THEN A QUICK COOL DOWN BEHIND THE ASSOCIATED COLD FRONT. LOOKING AT A NORTHWEST-SOUTHEAST RUNNING X-SECTION...THE NAM IS BY FAR THE WARMEST MODEL...SURGING +4 C AIR IN THE 900:850 MB LAYER NORTH OF RST AT 00Z SAT...WITH THE EC/GFS CLOSER TO +1. THE MODELS COOL THIS LAYER DOWN AS THE SYSTEM TRANSITIONS EAST... BUT THE NAM STILL STAYS FAIRLY WARM...WITH A DEEP //800 MB TO THE SFC// ABOVE ZERO LAYER FROM LSE TO THE SOUTHEAST AT 18Z SAT. BY 00Z ALL MODELS ARE COOL. THINK THE NAM MIGHT BE TOO AGGRESSIVE WITH THIS WARMING...AND WILL LEAN TOWARD THE EC/GFS IN THIS STEAD. STILL...THE TEMP PROFILES POINT TO SOME RAIN...OR RAIN/SNOW FOR PARTS OF NORTHEAST IOWA/SOUTHWEST WISCONSIN AS THIS SYSTEM MOVES IN...GRADUALLY CHANGING OVER TO SNOW BY SAT AFTERNOON. THIS TREND IS SHOWN WELL IN THE 21Z SREF DOMINANT PCPN TYPE DEPICTION. AS HAS BEEN THE CASE OVER THE PAST SEVERAL DAYS...THESE TEMP PROFILES SUPPORT EITHER RAIN OR SNOW...AND NOT SLEET OR FREEZING RAIN. AS FOR SNOW TOTALS...THE GREATER TOTALS WILL COME WHERE THE BEST FORCING COMES TOGETHER WITH THE COLDER AIR. SEEING AS THE FORECAST AREA WILL LIKELY LIE IN THIS TRANSITION ZONE ADDS FURTHER DIFFICULTLY IN TRYING TO PINPOINT TOTALS. AS MENTIONED PREVIOUSLY...SAT/SAT EVENING APPEARS TO BE THE BEST TIME FOR ACCUMULATIONS...AND WILL TAKE A MIDDLE OF THE ROAD APPROACH FOR AMOUNTS FOR NOW. 2 TO 4 INCHES SEEMS TO BE A REASONABLE PLACE TO START. LATEST HPC GUIDANCE IS FOLLOWING THE EC...WHICH WOULD PUT THE BETTER ACCUMS OVER CENTRAL/EASTERN WI INTO EASTERN IA. IF THE NAM HAS ITS WAY...IT WOULD BE OVER NORTHWEST WI INTO CENTRAL IA. TOUGH CALL...AND HATE TO BE WISHY WASHY...BUT MODEL CONFIDENCE DOES NOT LEND ITSELF TO ANYTHING TOO SPECIFIC AT THIS MOMENT. SO...CONFIDENCE REMAINS HIGH THAT THE REGION WILL RECEIVE SOME PRECIPITATION WITH THIS SYSTEM...CONFIDENCE ON AMOUNTS ARE NOT. A SNOW OR SNOW/RAIN OR EVEN JUST RAIN FOR AWHILE ALSO APPEARS QUITE LIKELY. JUST HOW FAR WEST AND NORTH THIS MIX OR RAIN WILL EXTEND IS NOT AS CLEAR. IT CERTAINLY HAS BEEN A VERY INTERESTING...BUT FRUSTRATING...SYSTEM TO TRY TO FORECAST. LONG TERM...SUNDAY THROUGH WEDNESDAY THE STORM SYSTEM CONTINUES TO PULL OFF TO THE EAST ON SUNDAY. SOME LIGHT SNOW/FLURRIES WILL BE POSSIBLE POST THE SYSTEM...IN THE WRAP AROUND REGION OF THE LOW...BUT MOSTLY TO THE NORTH AND EAST OF THE LOCAL AREA. HIGH PRESSURE THEN LOOKS TO BUILD IN FOR XMAS EVE/XMAS...AND SHOULD BRING SOME QUIET AND MOSTLY CLEAR CONDITIONS FOR THE HOLIDAY. FOR WED...A 500 MB TROUGH WILL START TO APPROACH THE REGION...HOWEVER CURRENT INDICATIONS BY THE GFS/EC IS TO TAKE THE BULK OF THE ASSOCIATED SHORTWAVE ENERGY EITHER NORTH OR SOUTH OF THE LOCAL AREA. AVIATION... A WEAK SHORT WAVE TROUGH WILL MOVE ACROSS THE AREA THIS AFTERNOON AND EVENING. ENOUGH FORCING WILL OCCUR FROM THIS WAVE TO POSSIBLY PRODUCE SOME LIGHT PRECIPITATION. FORECAST SOUNDINGS INDICATE THAT MVFR CEILINGS SHOULD DEVELOP THIS AFTERNOON AS THE WAVE APPROACHES. THE CLOUD LAYER DOES NOT LOOK TO RESIDE IN COLD ENOUGH TEMPERATURES TO HAVE ICE IN IT...SO ANY PRECIPITATION THAT DEVELOPS WILL EITHER BE DRIZZLE OR FREEZING DRIZZLE DEPENDING ON SURFACE TEMPERATURES. SOUTH TO SOUTHEAST WINDS WILL PUMP WARMER AND MOIST AIR INTO THE AREA OVERNIGHT WHICH IS EXPECTED TO RESULT IN IFR CEILINGS DEVELOPING. VISIBILITIES SHOULD REMAIN EITHER IFR OR MVFR THROUGH TODAY AND TONIGHT. 04 && .ARX WATCHES/WARNINGS/ADVISORIES... WI...NONE. MN...NONE. IA...NONE. && $$ RIECK wi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 1225 AM EST FRI DEC 21 2007 .SYNOPSIS... HIGH PRESSURE OVER QUEBEC WILL BUILD SOUTH INTO NEW ENGLAND AND NEW YORK TODAY. SATURDAY IT WILL SLIDE OFFSHORE AND A SOUTHERLY FLOW OF MILDER AIR WILL BECOME ESTABLISHED OVER THE EASTERN SEABOARD. A STORM WILL ORGANIZE IN THE MID MISSISSIPPI VALLEY SATURDAY AFTERNOON AND INTENSIFY AS IT MOVES THROUGH THE GREAT LAKES REGION TO HUDSON`S BAY SUNDAY. AHEAD OF IT INCREASING MOISTURE WILL BRING A WINTRY MIX OF PRECIPITATION AT FIRST...BUT IT WILL WARM ENOUGH TO CHANGE THE PRECIPITATION TO RAIN...WHICH WILL BE HEAVY AT TIMES SUNDAY AFTERNOON. THE STORMS COLD FRONT WILL SWEEP TROUGH THE REGION SUNDAY NIGHT...AND IT WILL TURN MUCH COLDER. CHRISTMAS EVE AN UPPER LEVEL DISTURBANCE WILL PASS ACROSS THE REGION AND IN THE CHILLY NORTHWEST FLOW WILL TRIGGER SCATTERED SNOW SHOWERS. HIGH PRESSURE WILL BUILD INTO THE REGION FROM ONTARIO CHRISTMAS DAY. && .NEAR TERM /UNTIL 6 AM FRIDAY/... IT SEEMS A NARROW YET PERSIST/INTERMITTENT BAND OF LIGHT SNOW CONTINUES TO IMPACT WESTERN NEW ENGLAND AND ATTEMPTING TO CROSS INTO EASTERN NEW YORK (NORTH OF THE MID HUDSON VALLEY). LATEST RUN OF THE RUC13 AND 00Z NAM/WRF INDICATE THIS IS RESPONSE TO LOW LEVEL CONVERGENCE AND DEFORMATION WHICH IS EXPECTED TO BE INTERMITTENT THROUGH TONIGHT. WILL UPDATE POPS ACCORDINGLY BUT KEEP IT IN THE SLIGHT CHANCE CATEGORY. WHERE IT HAS SNOWED...VISIBILITIES HAVE DROPPED BACK 1-3 MILES...MAINLY ACROSS THE HIGHER ELEVATIONS. THE OTHER CONCERN IS THE TEMPERATURES OVERNIGHT. WITH PERSISTENT CLOUD COVER AND LACK OF ADVECTION...WILL RAISE OVERNIGHT LOWS SEVERAL DEGREES WHICH CORRESPONDS WELL WITH THE 00Z RUN OF THE GFS LAMP. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... THE SURFACE HIGH WILL BE CENTERED TO OUR EAST AND WILL SHIFT OFF THE NEW ENGLAND COAST FRIDAY NIGHT. IT WILL KEEP US DRY WITH A DEVELOPING SOUTHEAST FLOW. LOW LEVEL CLOUDS WILL LIFT FRIDAY BUT HIGH LEVEL CLOUDS WELL IN ADVANCE OFF OF THE SYSTEM FOR THE WEEKEND WILL BE STREAMING IN...SO NOT MUCH SUN EXPECTED. TEMPERATURES WILL BE SEASONABLE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... HIGH PRESSURE SLIDES OFF THE ATLC COAST SATURDAY...AND SOUTHERNLY FLOW INCREASES THROUGH THE DAY. 500HPA RIDGE OVER THE EASTERN SEABOARD. CLOUDS WILL BE VARIABLE AS WAA PRODUCES MID AND HI CLOUDS. MEANWHILE THE LOW LEVEL SOUTHEAST FLOW WILL ALSO BRING MOISTURE INTO THE REGION AND CONSIDERABLE LOW LEVEL MOISTURE REMAINS THAT HAS LINGERED SINCE THURSDAY. SO ALOT OF CLOUDS AND BY SAT AFTN AND EVENING SPOTTY LIGHT DRIZZLE...FREEZING DRIZZLE AND FLURRIES. TEMPERATURES MAY FALL A BIT DURING THE EVENING...BUT INCREASING SOUTHERLY FLOW WILL RESULT IN STEADY OR SLOWLY RISING TEMPS OVERNIGHT. TEMPS WILL STILL BE AROUND OR BLO FREEZING IN MANY AREAS AND PTYPE LIKELY TO BE ZR...BUT AMOUNTS WILL BE LIGHT. RAPIDLY DEEPENING SURFACE LOW IN THE GREAT LAKES SUNDAY WILL PUSH A CDFNT INTO NYS SUN AFTERNOON...WHICH SWEEPS EAST ACROSS REGION BY EVENING. WITH RAPIDLY INCREASE SOUTHERNLY INFLOW AHEAD OF THE SYSTEM TEMPS WILL RISE INTO THE 40S...AND KATAFRONT TYPE DYNAMICS OF SHOWERY/SQUALLY RAINS WILL DEVELOP ALONG AND AHEAD OF CDFNT. ENSEMBLE QPF AMOUNTS FM PLUMES OF 1 TO 2 INCHES LIKELY IN 6 TO 9 HOUR PERIOD. SIGNIFICANT SNOWMELT AND RUNOFF LIKELY. SEE HYDRO SECTION FOR PARTICULARS. THE 500HPA CUTOFF...FOLLOWS ACROSS THE REGION SUNDAY NIGHT AS VERY STRONG CAA FLASH FREEZES ANY REMAINING LIQUID...AND MELTED SNOW. ALSO THE PASSAGE OF THE CUT OFF WILL BE ACCOMPANIED BY SECONDARY ARCTIC CDFNT CHRISTMAS EVE WITH SCT -SHSN IN CAA...WITH STRONG UPPER DYNAMICS...BUT NOT IDEAL SETUP FOR LAKE EFFECT IN FCA. FINALLY SURFACE HIGH AND 500HPA RIDGE BUILD ACROSS THE REGION CHRISTMAS DAY...AND SEASONABLE TEMPS AND MAINLY CLEAR SKIES THE RESULT. BEYOND THEN THE SURFACE HIGH PASSES OFFSHORE...AND THE MODELS DIVERGE ON A VARIETY OF PASSING WEATHER SYSTEMS. WITH CUT OFF LOW ORGANIZING OVER GRTLKS REGION..ONE SFC LOW PASSES WELL SOUTH OF REGION OR THROUGH REGION THURSDAY OR FRIDAY. FOR NOW WENT WITH GFS MOS GUIDANCE AND SCT -SHSN AND CHC SNOW AT END OF EFP. AFTER ALL THE 1.5 PVU ANOMALY THAT WILL ORGANIZE THIS SYSTEM IS CURRENTLY NEAR TOKYO JAPAN. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AN EAST/NORTHEASTERLY FLOW AT LOW LEVELS IS RESULTING IN WIDE SPREAD MVFR TO IFR CEILINGS OVER THE REGION WITH BROKEN TO OVERCAST STRATUS 600 TO 2000 FEET AGL AT MANY OF THE METAR SITES...WITH WIDESPREAD IFR/LIFR CEILINGS AND OBSCURATIONS OVER HIGHER TERRAIN. A CONTINUED FLOW OF VERY MOIST AIR OFF THE ATLANTIC WILL RESULT IN IMPROVEMENT BEING SLOW TO OCCUR. WINDS WILL BE LIGHT FROM THE NORTH AND EAST IN THE EARLY MORNING HOURS...AND EASTERLY AROUND 5 KNOTS DURING THE DAY TODAY. OUTLOOK... TONIGHT...MVFR/IFR DUE TO LOW CLOUDS AND/OR FOG. SAT...VFR...NO SIGNIFICANT WEATHER EXPECTED. SUN...IFR MIXED PCPN...STRONG S-SE WINDS. MON...VFR...EXCEPT MVFR/IFR IN LAKE EFFECT SNOW SHOWERS DOWNWIND OF LAKE ONTARIO TUE...VFR...NO SIGNIFICANT WEATHER EXPECTED. && .HYDROLOGY... NO HYDRO PROBLEMS ARE ANTICIPATED THROUGH SATURDAY. A STRONG STORM SYSTEM WILL IMPACT THE REGION ON SUNDAY. STRONG SOUTHERLY WINDS ARE EXPECTED TO DEVELOP ACROSS THE AREA ON SUNDAY. THIS WILL BRING A WARM SURGE OVER A SNOW PACK THAT CONTAINS 1 TO 3 INCHES OF WATER EQUIVALENT FROM ALBANY SOUTH AND 2 TO 4 INCHES OF WATER EQUIVALENT OVER NORTHERN AREAS. A COLD FRONT WILL CROSS THE AREA SUNDAY EVENING. MODELS HAVE TRENDED WETTER BRINGING AROUND AN INCH OF RAIN TO ALL AREAS IN A 6 HOUR PERIOD SUNDAY AFTERNOON OR EVENING. THE UPPER MOHAWK...MOOSE...UPPER HUDSON AND VERMONT BASINS ARE EXPECTED TO SEE A 6 TO 12 HOUR WARM PERIOD LATE SUNDAY...WHICH WILL PROBABLY NOT BE ENOUGH TO RIPEN THE SNOW. NORTHERN SNOW COVER SHOULD ABSORB THE RAIN WITH MINIMAL RUNOFF BEFORE REFREEZING. HOWEVER...SOUTHERN AREAS MAY SEE 18 TO 24 HOURS OF ABOVE FREEZING TEMPERATURES. THE QUESTION IS HOW MUCH SNOW MELTS. LOCAL RIVER MODELS SHOW THAT STREAMS CAN HANDLE AS MUCH AS TWO INCHES OF COMBINED MELT AND RAIN WITH MINIMAL FLOODING. 3 INCHES OR MORE OF MELT AND RAIN WOULD CAUSE SIGNIFICANT FLOODING. THE GROUND HERE AT ALBANY IS FROZEN TO A DEPTH OF 5 INCHES. FROZEN GROUND ENHANCES THE CHANCES THAT FLOODING...AND POSSIBLY FLASH FLOODING...MAY OCCUR. RIVER ICE COVER IS NOT THICK ENOUGH TO CAUSE ICE JAM PROBLEMS. THE HIGHEST CONFIDENCE IS FOR TIDAL FLOODING LATE SUNDAY ALONG THE MID HUDSON RIVER NEAR KINGSTON AND POUGHKEEPSIE DUE TO STRONG SOUTHERLY WINDS. OTHER BASINS AT RISK FOR FLOODING INCLUDES THE SCHOHARIE...THE LOWER MOHAWK...THE ESOPUS...THE BATTEN KILL...THE HOOSIC...WAPPINGERS CREEK AND THE HOUSATONIC AND ITS TRIBUTARIES FROM FALLS VILLAGE DOWN STREAM. FREEZING TEMPERATURES ARE EXPECTED ACROSS THE ENTIRE AREA BY MONDAY MORNING WHICH WILL END THE RUNOFF. IF FLOODING WERE TO OCCUR IT WOULD MOST LIKELY BEGIN SUNDAY AFTERNOON AND LINGER INTO MONDAY. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...NONE. NY...NONE. MA...NONE. VT...NONE. && $$ SYNOPSIS...SNYDER NEAR TERM...BGM SHORT TERM...IAA LONG TERM...SNYDER AVIATION...RCK HYDROLOGY...DIRIENZO WWW.WEATHER.GOV/ALBANY ct AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 1142 PM CST THU DEC 20 2007 .DISCUSSION... /1042 PM CST THU DEC 20 2007/ WILL GO AHEAD AND ISSUE A DENSE FOG ADVISORY FOR REST OF FORECAST AREA EXCEPT FOR THE KANSAS COUNTIES AND CASS AND BATES COUNTIES IN MISSOURI. WILL START THE ADDITIONAL COUNTIES AS OF MIDNIGHT. CURRENT FOG CONTINUES TO SPREAD WESTWARD AT AROUND 5 KTS. DEEPER MOISTURE CAN BE SEEN ON SATELLITE SPREADING INTO NORTHWEST MISSOURI...WHILE FOG IS SHALLOWER BUT STILL STILL PRODUCING LOW VSBYS IN SOUTHWEST MISSOURI. THINK THE SLIGHT INCREASE IN THE LOW LEVEL WINDS LATER TONIGHT WILL HAVE THE MOST IMPACT ON THIS SHALLOWER MOISTURE SO WILL LEAVE SOUTHWEST COUNTIES OUT OF THE ADVISORY AT THIS POINT. PC && .PREV DISCUSSION... /850 PM CST THU DEC 20 2007/ DENSE FOG CONTINUES TO SPREAD TO THE WEST UNDER INFLUENCE OF A VERY WEAK SURFACE FLOW AROUND LOW PRESSURE TROUGH IN EASTERN MISSOURI AT THIS TIME. MODELS SHOW THIS TROUGH BREAKING DOWN AS STRONGER TROUGHING IN HIGH PLAINS STARTS TO TAKE SHAPE OVERNIGHT WITH LOW LEVEL FLOW BECOMING SOUTHEAST. THIS SHOULD SLOW THE WESTWARD PROGRESSION AFTER MIDNIGHT BUT MAY SPREAD IT MORE INTO NORTHWEST MISSOURI...WHICH IS ALREADY EXPERIENCING PATCHY DENSE FOG UNDER THE CLEAR SKIES AND LIGHT WINDS. BOTH NAM AND RUC 950 MB DEPICTIONS OF THIS MOISTURE WOULD SUGGEST IT MAKING TO NEAR THE MISSOURI KANSAS BORDER IN NORTHWEST MISSOURI OVERNIGHT AND INTO EASTERN PORTIONS OF THE KANSAS CITY METRO AREA. FOR NOW...WILL GO AHEAD AND EXPAND THE ADVISORY TO INCLUDE AREAS THAT ARE SEEING THE WIDESPREAD DENSE FOG SPREADING IN AT THIS TIME...AND KEEP AN EYE ON THE TRENDS...ADDING COUNTIES AS NEEDED. PC /720 PM CST THU DEC 20 2007/ HAVE MADE SEVERAL PHONE CALLS TO AREAS JUST WEST OF WHERE WE HAD FOG ADVISORY IN EFFECT...AND THEY ARE VERIFYING THE SATELLITE TREND OF THE LOWER VISIBILITIES SPREADING BACK TO THE WEST. WILL EXPAND THE DENSE FOG ADVISORY FURTHER TO THE WEST TO COVER. ESPECIALLY CONCERNED FOR THE INTERSTATES INCLUDING I70 FROM CONCORDIA EASTWARD AND I35 IN HARRISON COUNTY. PC /414 PM CST THU DEC 20 2007/ FORECAST CONCERNS FOR THE FIRST HALF OF THE FORECAST ARE TWO FOLD. TONIGHT WE ARE LOOKING AT CONTINUED DENSE FOG ACROSS AREAS FROM NORTH CENTRAL AND NORTH EAST MISSOURI SOUTH THROUGH CENTRAL MISSOURI. THE SECOND FORECAST CONCERN IS THE WINTER STORM EXPECTED THIS WEEKEND. MOISTURE TRAPPED IN THE BOUNDARY LAYER...AND LIGHT WINDS ASSOCIATED WITH A SURFACE TROUGH...HAVE CONSPIRED TODAY TO KEEP THE EASTERN THIRD OF THE FORECAST AREA UNDER DENSE FOG. CONDITIONS ARE NOT EXPECTED TO CHANGE ACROSS THAT AREA OVERNIGHT. SURFACE TROUGH WILL SLIDE EAST A LITTLE...BUT ONLY ENOUGH TO ALLOW SURFACE WINDS TO SWITCH TO THE SOUTHEAST...ADVECTING MORE MOISTURE IN AT THE SURFACE. HAVE GONE WITH A DENSE FOG ADVISORY FOR THE REST OF THE AFTERNOON THROUGH 10 AM FRIDAY MORNING AS A RESULT. FARTHER WEST SKIES CLEARED TODAY AND THE FOG THAT SET IN DISSIPATED RATHER QUICKLY. TONIGHT WILL SEE THE INVERSION TRAP ABUNDANT MOISTURE AT THE SURFACE AGAIN...BUT WINDS JUST ABOVE THE INVERSION WILL STAY A LITTLE HIGHER IN RESPONSE TO THE DEEPENING TROUGH IN THE WESTERN CONUS. EXPECT THIS SLIGHTLY HIGHER WIND ABOVE THE INVERSION TO INDUCE ENOUGH MIXING OVERNIGHT TO PREVENT THE FOG FROM BECOMING AS DENSE ACROSS THE WESTERN TWO THIRDS OF THE FORECAST AREA. IN FACT...HAVE KEPT FOG OUT OF THE FORECAST FOR AREAS FROM THE KANSAS CITY METRO ON SOUTH AS MODEL SOUNDINGS SHOW THE SURFACE MOISTURE TO BE PARTICULARLY SHALLOW. THIS WILL NEED TO BE WATCHED OVERNIGHT THOUGH IN CASE RADIATION FOG BEGIN TO DEVELOP UNDER THE CLEAR SKIES. ATTENTION THEN TURNS TOWARDS FRIDAY NIGHT AND SATURDAY AS THE DEEPENING WEST CONUS TROUGH SWEEPS EAST THROUGH THE PLAINS. GFS AND ECMWF HAVE CONTINUED TO CONVERGE TOWARDS ONE SOLUTION FOR THIS WEEKENDS SYSTEM...AND THE NAM-WRF SEEMS TO BE MOVING IN THE SAME DIRECTION. THE EARLY WEEKEND SHORTWAVE TROUGH WILL ACTUALLY CONSIST OF A NORTHERN AND SOUTHERN STREAM WAVES PHASING AS THEY THEY MOVE THROUGH MISSOURI. THERE IS A STRONG SHOT OF COLD AIR THAT WILL QUICKLY SPREAD ACROSS THE FORECAST AREA SATURDAY. THIS SYSTEM WILL BE BRINGING THE BULK OF ITS MOISTURE FROM THE PACIFIC...SO THE EXPECTATION IS THAT MUCH OF THE PRECIPITATION WILL BE POST FRONTAL...IN THE DEFORMATION ZONE BEHIND THE SURFACE LOW. WITH THE SOLUTIONS FROM THE GFS/ECMWF/AND NAM-WRF ALL CONVERGING I HAVE NOT HAD TO MAKE MANY ADJUSTMENTS TO THE GOING FORECAST FOR FRIDAY NIGHT INTO SATURDAY. DID KEEP SOME LIKELY POPS ACROSS THE EASTERN HALF OF THE FORECAST AREA FOR SATURDAY EVENING AS THE WEIGHT OF THE CONSENSUS SLOWS THE SYSTEM A LITTLE. OTHERWISE...EXPECT MUCH OF THE PRECIPITATION FALLING FROM THE SKY TO BE SNOW BY THE AFTERNOON HOURS. FREEZING RAIN AND SLEET ARE GOING TO BE MINOR AS THE SPEED WITH WHICH THE COLD AIR RUSHES IN SHOULD PRECLUDE MUCH OPPORTUNITY FOR MIXED PRECIP. CURRENT SNOWFALL TOTALS STILL LOOK RANGE BETWEEN 1 TO 4 INCHES OF ACCUMULATION...IN PART DUE TO THE PROGRESSIVE NATURE OF THE SYSTEM. ALSO...WIND BEHIND THE FRONT LOOKS TO BE SUSTAINED AS HIGH AS 20 TO 30 MPH WITH HIGHER GUSTS. THEREFORE...ADDED BLOWING SNOW TO THE FORECAST WEATHER FOR THE DAY SATURDAY AND SATURDAY NIGHT. CUTTER EXTENDED...(SUNDAY-THURSDAY) THE NORTHERN AND SOUTHERN SHORTWAVE BRANCHES WILL CONTINUE TO PHASE AT THE START OF THE EXTENDED FORECAST ON SUNDAY. THE PHASING SYSTEM WILL QUICKLY DEPART TO THE NORTHEAST...WITH SHORTWAVE RIDGING/SURFACE HIGH PRESSURE SPREADING EAST IN ITS WAKE. A SERIES OF PACIFIC SHORTWAVE TROUGHS WILL CONTINUE TO HEAD EAST THROUGH THE MEAN FLOW ACROSS THE CONUS NEXT WEEK. MODEL AGREEMENT DIMINISHES QUICKLY BY EARLY NEXT WEEK WITH REGARD TO THESE SHORTWAVE FEATURES. AS SUCH...THERE IS LOW CONFIDENCE FOR PRECIPITATION CHANCES. IF ONE MODEL WERE TO BE CHOSEN OVER ANOTHER...WOULD HAVE TO SIDE WITH THE MORE CONSISTENT ECMWF. THE ECMWF STILL BRINGS A CLIPPER SYSTEM FURTHER SOUTH THAN THE GFS ON MONDAY...BUT WITH LITTLE MOISTURE TO WORK WITH MEASURABLE PRECIPITATION IS NOT EXPECTED FOR OUR NECK OF THE WOODS. THE NEXT IN THE SERIES OF PROGRESSIVE SHORTWAVES IS PROGGED TO AFFECT THE REGION TOWARD WEDNESDAY. STOFLET && .AVIATION... FOR THE 06Z TAFS...WILL BRING IN THE DENSER FOG AT 10Z IN THE KANSAS CITY AREA. COULD BE AS EARLY AS 09Z...BUT AM SEEING SOME SIGNS OF THE WESTWARD PROGRESSION SLOWING INTO THE METRO AREA. FOR KSTJ...VSBYS MAY BOUNCE AROUND FOR A WHILE UNTIL THE DENSE FOG AREA CAN MOVE IN. WILL JUST TEMPO THE QUARTER MILE VISIBILITIES AT THIS POINT...AND LET MIDNIGHT SHIFT FINE TUNE AS TIMING IS MORE CERTAIN. PC && .EAX WATCHES/WARNINGS/ADVISORIES... MO...DENSE FOG ADVISORY UNTIL 10 AM FRIDAY FOR MOZ003-MOZ004-MOZ005- MOZ006-MOZ007-MOZ008-MOZ013-MOZ014-MOZ015-MOZ016-MOZ017- MOZ022-MOZ023-MOZ024-MOZ025-MOZ030-MOZ031-MOZ032-MOZ033- MOZ038-MOZ039-MOZ040-MOZ044-MOZ045-MOZ046-MOZ054. DENSE FOG ADVISORY UNTIL 10 AM FRIDAY FOR MOZ001-MOZ002-MOZ011- MOZ012-MOZ020-MOZ021-MOZ028-MOZ029-MOZ037. KS...NONE. $$ mo AREA FORECAST DISCUSSION...CORRECTION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 1042 PM CST THU DEC 20 2007 .DISCUSSION... WILL GO AHEAD AND ISSUE A DENSE FOG ADVISORY FOR REST OF FORECAST AREA EXCEPT FOR MIAMI AND LINN COUNTIES IN KANSAS AND CASS AND BATES COUNTIES IN MISSOURI. WILL START THE ADDITIONAL COUNTIES AS OF MIDNIGHT. CURRENT FOG CONTINUES TO SPREAD WESTWARD AT AROUND 5 KTS. DEEPER MOISTURE CAN BE SEEN ON SATELLITE SPREADING INTO NORTHWEST MISSOURI...WHILE FOG IS SHALLOWER BUT STILL STILL PRODUCING LOW VSBYS IN SOUTHWEST MISSOURI. THINK THE SLIGHT INCREASE IN THE LOW LEVEL WINDS LATER TONIGHT WILL HAVE THE MOST IMPACT ON THIS SHALLOWER MOISTURE SO WILL LEAVE EXTREME SOUTHWEST COUNTIES OUT OF THE ADVISORY AT THIS POINT. PC && .PREV DISCUSSION... /850 PM CST THU DEC 20 2007/ DENSE FOG CONTINUES TO SPREAD TO THE WEST UNDER INFLUENCE OF A VERY WEAK SURFACE FLOW AROUND LOW PRESSURE TROUGH IN EASTERN MISSOURI AT THIS TIME. MODELS SHOW THIS TROUGH BREAKING DOWN AS STRONGER TROUGHING IN HIGH PLAINS STARTS TO TAKE SHAPE OVERNIGHT WITH LOW LEVEL FLOW BECOMING SOUTHEAST. THIS SHOULD SLOW THE WESTWARD PROGRESSION AFTER MIDNIGHT BUT MAY SPREAD IT MORE INTO NORTHWEST MISSOURI...WHICH IS ALREADY EXPERIENCING PATCHY DENSE FOG UNDER THE CLEAR SKIES AND LIGHT WINDS. BOTH NAM AND RUC 950 MB DEPICTIONS OF THIS MOISTURE WOULD SUGGEST IT MAKING TO NEAR THE MISSOURI KANSAS BORDER IN NORTHWEST MISSOURI OVERNIGHT AND INTO EASTERN PORTIONS OF THE KANSAS CITY METRO AREA. FOR NOW...WILL GO AHEAD AND EXPAND THE ADVISORY TO INCLUDE AREAS THAT ARE SEEING THE WIDESPREAD DENSE FOG SPREADING IN AT THIS TIME...AND KEEP AN EYE ON THE TRENDS...ADDING COUNTIES AS NEEDED. PC /720 PM CST THU DEC 20 2007/ HAVE MADE SEVERAL PHONE CALLS TO AREAS JUST WEST OF WHERE WE HAD FOG ADVISORY IN EFFECT...AND THEY ARE VERIFYING THE SATELLITE TREND OF THE LOWER VISIBILITIES SPREADING BACK TO THE WEST. WILL EXPAND THE DENSE FOG ADVISORY FURTHER TO THE WEST TO COVER. ESPECIALLY CONCERNED FOR THE INTERSTATES INCLUDING I70 FROM CONCORDIA EASTWARD AND I35 IN HARRISON COUNTY. PC /414 PM CST THU DEC 20 2007/ FORECAST CONCERNS FOR THE FIRST HALF OF THE FORECAST ARE TWO FOLD. TONIGHT WE ARE LOOKING AT CONTINUED DENSE FOG ACROSS AREAS FROM NORTH CENTRAL AND NORTH EAST MISSOURI SOUTH THROUGH CENTRAL MISSOURI. THE SECOND FORECAST CONCERN IS THE WINTER STORM EXPECTED THIS WEEKEND. MOISTURE TRAPPED IN THE BOUNDARY LAYER...AND LIGHT WINDS ASSOCIATED WITH A SURFACE TROUGH...HAVE CONSPIRED TODAY TO KEEP THE EASTERN THIRD OF THE FORECAST AREA UNDER DENSE FOG. CONDITIONS ARE NOT EXPECTED TO CHANGE ACROSS THAT AREA OVERNIGHT. SURFACE TROUGH WILL SLIDE EAST A LITTLE...BUT ONLY ENOUGH TO ALLOW SURFACE WINDS TO SWITCH TO THE SOUTHEAST...ADVECTING MORE MOISTURE IN AT THE SURFACE. HAVE GONE WITH A DENSE FOG ADVISORY FOR THE REST OF THE AFTERNOON THROUGH 10 AM FRIDAY MORNING AS A RESULT. FARTHER WEST SKIES CLEARED TODAY AND THE FOG THAT SET IN DISSIPATED RATHER QUICKLY. TONIGHT WILL SEE THE INVERSION TRAP ABUNDANT MOISTURE AT THE SURFACE AGAIN...BUT WINDS JUST ABOVE THE INVERSION WILL STAY A LITTLE HIGHER IN RESPONSE TO THE DEEPENING TROUGH IN THE WESTERN CONUS. EXPECT THIS SLIGHTLY HIGHER WIND ABOVE THE INVERSION TO INDUCE ENOUGH MIXING OVERNIGHT TO PREVENT THE FOG FROM BECOMING AS DENSE ACROSS THE WESTERN TWO THIRDS OF THE FORECAST AREA. IN FACT...HAVE KEPT FOG OUT OF THE FORECAST FOR AREAS FROM THE KANSAS CITY METRO ON SOUTH AS MODEL SOUNDINGS SHOW THE SURFACE MOISTURE TO BE PARTICULARLY SHALLOW. THIS WILL NEED TO BE WATCHED OVERNIGHT THOUGH IN CASE RADIATION FOG BEGIN TO DEVELOP UNDER THE CLEAR SKIES. ATTENTION THEN TURNS TOWARDS FRIDAY NIGHT AND SATURDAY AS THE DEEPENING WEST CONUS TROUGH SWEEPS EAST THROUGH THE PLAINS. GFS AND ECMWF HAVE CONTINUED TO CONVERGE TOWARDS ONE SOLUTION FOR THIS WEEKENDS SYSTEM...AND THE NAM-WRF SEEMS TO BE MOVING IN THE SAME DIRECTION. THE EARLY WEEKEND SHORTWAVE TROUGH WILL ACTUALLY CONSIST OF A NORTHERN AND SOUTHERN STREAM WAVES PHASING AS THEY THEY MOVE THROUGH MISSOURI. THERE IS A STRONG SHOT OF COLD AIR THAT WILL QUICKLY SPREAD ACROSS THE FORECAST AREA SATURDAY. THIS SYSTEM WILL BE BRINGING THE BULK OF ITS MOISTURE FROM THE PACIFIC...SO THE EXPECTATION IS THAT MUCH OF THE PRECIPITATION WILL BE POST FRONTAL...IN THE DEFORMATION ZONE BEHIND THE SURFACE LOW. WITH THE SOLUTIONS FROM THE GFS/ECMWF/AND NAM-WRF ALL CONVERGING I HAVE NOT HAD TO MAKE MANY ADJUSTMENTS TO THE GOING FORECAST FOR FRIDAY NIGHT INTO SATURDAY. DID KEEP SOME LIKELY POPS ACROSS THE EASTERN HALF OF THE FORECAST AREA FOR SATURDAY EVENING AS THE WEIGHT OF THE CONSENSUS SLOWS THE SYSTEM A LITTLE. OTHERWISE...EXPECT MUCH OF THE PRECIPITATION FALLING FROM THE SKY TO BE SNOW BY THE AFTERNOON HOURS. FREEZING RAIN AND SLEET ARE GOING TO BE MINOR AS THE SPEED WITH WHICH THE COLD AIR RUSHES IN SHOULD PRECLUDE MUCH OPPORTUNITY FOR MIXED PRECIP. CURRENT SNOWFALL TOTALS STILL LOOK RANGE BETWEEN 1 TO 4 INCHES OF ACCUMULATION...IN PART DUE TO THE PROGRESSIVE NATURE OF THE SYSTEM. ALSO...WIND BEHIND THE FRONT LOOKS TO BE SUSTAINED AS HIGH AS 20 TO 30 MPH WITH HIGHER GUSTS. THEREFORE...ADDED BLOWING SNOW TO THE FORECAST WEATHER FOR THE DAY SATURDAY AND SATURDAY NIGHT. CUTTER EXTENDED...(SUNDAY-THURSDAY) THE NORTHERN AND SOUTHERN SHORTWAVE BRANCHES WILL CONTINUE TO PHASE AT THE START OF THE EXTENDED FORECAST ON SUNDAY. THE PHASING SYSTEM WILL QUICKLY DEPART TO THE NORTHEAST...WITH SHORTWAVE RIDGING/SURFACE HIGH PRESSURE SPREADING EAST IN ITS WAKE. A SERIES OF PACIFIC SHORTWAVE TROUGHS WILL CONTINUE TO HEAD EAST THROUGH THE MEAN FLOW ACROSS THE CONUS NEXT WEEK. MODEL AGREEMENT DIMINISHES QUICKLY BY EARLY NEXT WEEK WITH REGARD TO THESE SHORTWAVE FEATURES. AS SUCH...THERE IS LOW CONFIDENCE FOR PRECIPITATION CHANCES. IF ONE MODEL WERE TO BE CHOSEN OVER ANOTHER...WOULD HAVE TO SIDE WITH THE MORE CONSISTENT ECMWF. THE ECMWF STILL BRINGS A CLIPPER SYSTEM FURTHER SOUTH THAN THE GFS ON MONDAY...BUT WITH LITTLE MOISTURE TO WORK WITH MEASURABLE PRECIPITATION IS NOT EXPECTED FOR OUR NECK OF THE WOODS. THE NEXT IN THE SERIES OF PROGRESSIVE SHORTWAVES IS PROGGED TO AFFECT THE REGION TOWARD WEDNESDAY. STOFLET && .AVIATION... /535 PM CST THU DEC 20 2007/ FOR THE 00Z TAF CYCLE...SOUNDINGS SHOW ANOTHER INVERSION SETTING UP ACROSS THE KANSAS/MISSOURI BORDER REGION TONIGHT...WITH A MODEST AND MOIST SOUTHEAST SURFACE FLOW. HOWEVER...THE WIND JUST OFF THE SURFACE IS EXPECTED TO REMAIN A LITTLE STRONGER EARLY FRIDAY MORNING THAN IT WAS THIS MORNING. THOUGHTS ARE THAT THIS WILL KEEP THE SURFACE LAYER MIXED A LITTLE MORE WITH THE DRY LAYER ABOVE PREVENTING A DRASTIC DECREASE IN VISIBILITIES IN THE MORNING. BIGGEST CONCERN WILL BE AT KSTJ WITH ITS SLIGHTLY LOWER ELEVATION ISOLATING IT A BIT MORE FROM THE EFFECTS OF DRIER AIR MIXING IN OVER TOP. WILL GO WITH A TEMPO CATEGORY FOR IFR CONDITIONS LATE TONIGHT AT THAT SITE. PC && .EAX WATCHES/WARNINGS/ADVISORIES... MO...DENSE FOG ADVISORY UNTIL 10 AM FRIDAY FOR MOZ003-MOZ004-MOZ005- MOZ006-MOZ007-MOZ008-MOZ013-MOZ014-MOZ015-MOZ016-MOZ017- MOZ022-MOZ023-MOZ024-MOZ025-MOZ030-MOZ031-MOZ032-MOZ033- MOZ038-MOZ039-MOZ040-MOZ044-MOZ045-MOZ046-MOZ054. DENSE FOG ADVISORY UNTIL 10 AM FRIDAY FOR MOZ001-MOZ002-MOZ011- MOZ012-MOZ020-MOZ021-MOZ028-MOZ029-MOZ037. KS...NONE. $$ mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 408 AM MST FRI DEC 21 2007 .SHORT TERM... (TODAY AND TONIGHT) ...SNOW WILL FLY LATER TODAY INTO TONIGHT MOST AREAS... ...RUSH HOUR ACROSS COS AREA WILL BE AFFECTED THIS AFTERNOON... CURRENTLY...WESTERLY SFC WINDS HAVE KEPT TEMPS UP THIS MORNING AS REASDING MOST AREAS ARE IN THE 30S AND 40S. CLOUDS OVER THE SAN LUIS VALLEY (SLV) HAVE EVEN KEPT TEMPS IN THE TEENS (VS NEGATIVE VALUES OF THE LAST WEEK OR SO). COMPOSITE RADAR ACROSS THE STATE INDICATS SNOW IS ALREADY FALLING OVER NW CO AND ECHOES ARE BEGINNING TO SHOW UP OVER NEW MEXICO. SFC CHART/3H P CHANGE SHOWS FRONT STILL UP IN THE C WY AREA. WATER VAPOR/RUC ANALYSIS FIEDLS SHOW TROUGH AXIS EXTENDING FROM SALT LAKE SSW ACROSS S CALIF. MET DISCUSSION...THE "XMAS HOLIDAY WEEK ACTIVE WX PATTERN" WHICH HAS BEEN ADVERTISED BY THIS WFO THE LAST FEW DAYS WILL BEGIN TODAY. FIRST IN A SERIES OF SYSTEMS STILL ON TRACK TO BRING SNOW TO THE REGION TODAY AND TONIGHT. COMBINATION OF STRONG FRONTOGENETICAL FORCING S OF HIWAY 50 AND STRONG NNE WINDS AT 700 MB SHOULB BRING THE HEAVIEST SNOW ACCUMS ACROSS THE WETS/SANGRE MTN RANGES THEN E TOWARDS THE KS BORDER S OF HIWAY 50. SNOW AND BLOWING SNOW WILL ALSO OCCUR ACROSS THE PALMER DIVIDE...BUT WIND MAY BE THE BIGGEST CONCERN OVER THIS REGION. TODAY (THROUGH 18Z)...TWEAKED POPS A BIT HERE. KEPT VERY HITH POPS ALONG CONTDVD REGION BUT CUT BACK ALL OTEHR AREAS AS I DO NOT THINK WE WILL SEE ANY SIGNIF PRECIP E OF THE CONTDVD UNTIL AFTER 18Z. ALSO...WARMED TEMPS UP A BIT THIS MORNING AS FRONT WILL LIKELY NOT CROSS THE PALMER UNTIL AT LEAST NOONISH. LATER TODAY (AFTER 18Z)...AFTER FRONT CROSSES THE PALMER DVD BELIEVE WINDS WILL PICK UP FROM THE N AND BECOME QUITE GUSTY AND TEMPS WILL BEGIN THERE DOWNWARD TREND. PRECIP WILL LIKELY BEGIN ACROSS TELLER COUNTY BY EARLY AFTERNOON AND REACH DOWN ACROSS N EL PASO BY MID TO LATE AFTERNOON. I DO BELIEVE RUSH HOUR WILL BE AFFECTED BY BLOWING SNOW ACROSS THE GREATER COS AREA...AND HAVE INTRODUCED A SNOW AND BLOWING SNOW ADVISORY FOR TELLER/N EL PASO STARTING A 21Z. ATTM...I AM MORE CONCERNED ABOUT THE BLOWING SNOW THAN THE ACCUMULATING SNOW AS WINDS BY LATER THIS AFTERNOON COULD BE IN THE 20-30 MPH RANGE AS LATEST GUIDANCE IS SHOWING 700 MB WINDS IN THE 40-50 KNOT RANGE. AS FOR THE MTNS...SNOWS WILL BE FLYING ACROSS THE CONTDVD WHERE 3-6" OF NEW SNOW SHOULD FALL BY 00Z. TONIGHT...WINTER STORM WARNINGS ARE IN EFFECT FOR THE WETS AND S SANGRE MTN RANGES. S/BS ADVISORIES ARE IN EFFECT FOR THE PLAINS GENERALLY S OF US HIWAY 50. ADVISORIRES ARE ALSO IN EFFECT FOR THE WET MTN VALLEY AND THE N SANGRES. ADVISORIES ARE ONGOING ACROSS N EL PASO/TELLER. THE HEAVIEST SNOW WITH THIS SYSTEM WILL FALL ACROSS THE E FACING SLOPES OF THE WETS AND S SANGRES. THESE AREAS SHOULD SEE 8-12" OF NEW SNOW BY 12Z TOMORROW. OVER THE PLAINS...THE HEAVIEST SNOWS WILL FALL GENERALLY ALONG THE RATON MESA ALONG THE CO/NM BORDER. SOME OF THESE SNOW TOTAL REACHED INTO THE WARNING CATEGORY BUT DECIDED TO GO WITH A S/BS ADVISORY AS MOST OF THE REGION SHOULD SEE TOTALS IN THE 3-6 RANGE. WINDS WILL ALSO BE A CONCERN ACROSS THIS AREA TONIGHT AND TRAVEL WILL BE DIFFICULT ACROSS RATON PASS AND ALONG HIWAY S OF KLAA. AS ALWAYS WITH THESE NE WIND EVENTS...PUEBLO COUNTY WILL BE PROBLEMATIC. I AM CONFIDENT THAT THE S SXNS OF THE COUNTY WILL SEE S/BS CRITERIA BUT THE N PART OF THE COUNTY (INCLUDING PUB) WILL NOT SEE MUCH. PLAN TO MENTION THIS IN DETAIL IN THE HILITE PACKAGE THAT WILL BE ISSUED SHORTLY. SNOW ACROSS THE PALMER DVD SHOULD START TO WIND DOWN AFTER MIDNIGHT...AND ACROSS THE RATON MESA TOWARDS SUNRISE. /HODANISH .LONG TERM... (SATURDAY THROUGH THURSDAY) ...UNSETTLED WEATHER PROBABLE THROUGH THURSDAY... FORECAST MODELS INDICATE THAT A STRING OF FAST MOVING UPPER LEVEL SYSTEMS WILL BE LINED UP TO AFFECT THE REGION THROUGH THURSDAY. MAXIMUM TEMPERATURES ARE EXPECTED TO REMAIN IN THE 20S AND 30S EACH DAY...THEN DROP INTO THE SINGLE DIGITS TO TEENS EACH NIGHT. THE EXCEPTION WILL BE THE SAN LUIS VALLEY...WHERE LOW TEMPS WILL MOST LIKELY DIP WELL BELOW ZERO EACH NIGHT. SATURDAY...THE FIRST UPPER TROUGH WILL BE EXITING THE REGION SAT MORNING...MAKING FOR AN INITIALLY COLD AND BLUSTERY START ACROSS THE FAR E PLAINS. NW FLOW SETTLES IN...WITH LINGERING POTENTIAL FOR ISOLATED SNOW OVER THE CENTRAL MTS WHILE THE PLAINS CLEAR OUT DURING THE AFTN. SUNDAY AND MONDAY...NEXT SYSTEM DROPS DOWN ACROSS THE N ROCKIES...PRODUCING ISOLATED TO SCATTERED SNOW FOR THE CONTDVD THROUGH THE DAY...THEN SPREADING TO THE ENTIRE CWA BY THE EVENING. BY MON MORNING THIS LOW SHOULD BE MOVING OUT...WITH PCPN TAPERING OFF ACROSS THE SE CORNER. A BREAK IN THE ACTIVE PATTERN IS FORECAST FOR THE REST OF MONDAY...BEFORE THE NEXT SYSTEM DROPS DOWN FOR THE NIGHT. MONDAY NIGHT THROUGH TUESDAY NIGHT...LONG RANGE MODELS ARE INDICATING THAT THE NEXT STORM SYSTEM WILL DROP A BIT FURTHER SOUTH THAN PREVIOUS DISTURBANCES. THIS TRANSLATES TO A GREATER CHANCE OF SNOW FOR THE CONTDVD CHRISTMAS EVE...THEN ALL OF THE FORECAST AREA THROUGH CHRISTMAS DAY. WEDNESDAY AND THURSDAY...LOOKS TO BE A REPEAT OF MONDAY AND TUESDAY. ALL OF THESE SYSTEMS DO NOT LOOK TOO IMPRESSIVE WHEN TALKING ABOUT SNOW AMOUNTS...BUT THE RAPID SUCCESSION INCREASES THE POTENTIAL OF IT FEELING LIKE THE HOLIDAY SEASON THROUGH NEXT WEEK. MOORE && .AVIATION... ALL TAF SITES WILL BE IMPACTED BY THIS WX SYSTEM. FRONT SHOULD CROSS KCOS AROUND 18Z AND KPUB BY 19Z. WINDS WILL SHIFT TO THE N AND BECOME QUITE GUSTY...WITH N WINDS 20-30 MPH. ACROSS THE KCOS REGION...SNOW SHOULD BECOME A CONCERN BY LATE IN THE AFTERNOON AND LASTING INTO THE EVENING. ACCUMS SHOULD NOT BE A MAIN CONCERN (1-2")...BUT WINDS WILL BE THE MAIN ISSUE. BY LATER THIS EVENING...NORTHERLY WINDS COULD BE APPROACHING 35 KNOTS. THE SNOW AND WINDS SHOULD BEGIN TO DECREASE AFTER MIDNIGHT. WITH N WINDS...CIGS SHOULD NOT BE A MAJOR CONCERN AND SNOW SHOULD NOT BE HEAVY...EXPECT MAINLY MVFR CONDITIONS THROUGH THE WORST OF IT. HOWEVER..IF SNOWS ACCUM A BIT MORE THAN EXPECTED...AND THINGS START BLOWING THEN VIS COULD BE SEVERELY RESTRICTED THIS EVENING DUE TO THE BLOWING SNOW. KPUB...WINDS AND SNOW WILL BE LESS ACROSS KPUB. MAIN ACTIVITY WILL BE THIS EVENING WITH CIGS MAINLY IN THE BKN020-030 RANGE AND VIS RESTRICTIONS 2-3SM. KALS...EXPECT PERIODS OF SNOW IN THE VALLEL DURING THE EVENING PERIOD. BRIEF HEAVY SNOW COULD CAUSE IFR CONDITIONS AT TIMES. && .PUB WATCHES/WARNINGS/ADVISORIES... SNOW AND BLOWING SNOW ADVISORY FROM 6 PM THIS EVENING TO 5 AM MST SATURDAY FOR COZ072-073-078-086>088-093-094-097>099. SNOW AND BLOWING SNOW ADVISORY UNTIL 8 PM MST THIS EVENING FOR COZ058>061-066-068. WINTER STORM WARNING FROM 6 PM THIS EVENING TO 5 AM MST SATURDAY FOR COZ074-075-079-080. SNOW AND BLOWING SNOW ADVISORY FROM 2 PM THIS AFTERNOON TO 2 AM MST SATURDAY FOR COZ081-082-084. && $$ 34/27 co AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON SC 859 AM EST FRI DEC 21 2007 .SYNOPSIS... A STRONG UPPER-LEVEL DISTURBANCE WHICH WILL PASS THROUGH THE REGION AND MOVE OFF THE COAST TODAY. THIS WILL ENHANCE A WEDGE PATTERN OVER THE CAROLINAS THAT SHOULD HOLD UNTIL BREAKING DOWN ON SUN AS A COLD FRONT APPROACHES FROM THE W. THE FRONT WILL MOVE OFF THE COAST BY EARLY MON...BUT UNSETTLED WEATHER COULD RETURN BY CHRISTMAS DAY AS ANOTHER UPPER LEVEL DISTURBANCE IS POSSIBLE. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 06Z GFS/RUC HAVE CONVERGED ON A SIMILAR SOLUTION WHICH PUTS A SFC LOW NEAR THE W WALL OF THE GULF STREAM SE OF CHARLESTON THIS AFTN. ALMOST A 12 MB PRES GRAD FORECAST INDICATES A WINDY SETUP. NAM SHOWS 60 KT H925 WINDS THIS AFTN...LIKELY OVERDONE BUT WORRISOME. IMPRESSIVE DEFORMATION AXIS ALONG AND JUST W OF I-95 HAS FUELED A ZONE OF 3-6 INCH RNFL AMOUNTS FROM HARDEEVILLE AND PORT WENTWORTH SW TO LONG AND TATTNALL COUNTIES. A FLOOD ADVISORY FOR MINOR FLOODING IS IN EFFECT THROUGH MID MORNING FOR QUITE A FEW OF OUR COUNTIES. ZONES HAVE BEEN UPDATED THIS MORNING TO REFLECT HEAVY RAIN AND INCREASE QPF. RADAR AND GROUND OBSERVATION RECENTLY INDICATED OVER 5 INCHES OF RAIN HAS ALREADY FALLEN AT THE SAVANNAH AIRPORT. THIS RNFL MAX EXTENDS NWD TO AROUND HARDEEVILLE. RAIN ALONG THE NW SIDE OF THE LOW LEVEL WARM FRONT MAY BE A BIT SLOWER TO PULL OUT OF THE ERN PART OF THE FA TODAY. THE EJECTING SFC LOW OFF THE GEORGIA COAST THIS MORNING SHOULD ENHANCE A CLASSIC WEDGE SETUP TODAY. WE INDICATED HIGH TEMPS IN OUR NW TIER WILL OCCUR DURING THIS MORNING...FALLING AFTERNOON. VERY LITTLE CHANGE TO OVERALL TEMPERATURE SCHEME OVERALL. WINDS SHOULD INCREASE THIS AFTERNOON. WILL NEED TO WATCH FOR WIND ADVISORY CRITERIA POSSIBILITIES ALONG THE IMMEDIATE CHARLESTON COUNTY COAST AT SOME POINT LATER TODAY. THE COMBINATION OF STRONG PINCHING...DEEPENING LOW OVER THE ATLC AND RAPID PRES RISES IN ITS WAKE WILL RESULT IN STRONG AND GUSTY WINDS OVER THE COASTAL COUNTIES TODAY. HIGHEST WINDS WILL BE NEAR THE COAST...AND MOST NOTABLY ACROSS CHARLESTON COUNTY. WE HAVE THUS INITIATED A HIGH WIND ADVISORY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... HEAVIER PRECIP SHOULD HAVE TAPERED OFF BY TONIGHT EXCEPT FOR A FEW CONVECTIVE SHOWERS POSSIBLE OVER FAR NE PORTIONS. HOWEVER... CONTINUED WEDGE PATTERN WITH WEAK ISENTROPIC LIFT COULD RESULT IN SOME DRIZZLE THROUGH THE NIGHT IN MANY AREAS. EXTENSIVE CLOUD COVER AND A RATHER CONTIGUOUS AIRMASS IN PLACE SHOULD KEEP TEMPERATURES FAIRLY STEADY THROUGH THE NIGHT OR SLIGHTLY FALLING. GUIDANCE TEMPS FOR SAT SEEM MUCH TOO HIGH OVER THE NORTHERN HALF OF THE AREA. MID TO UPPER 60S IS PRETTY MUCH OUT OF THE QUESTION ASSUMING THE WEDGE OF HIGH PRES REMAINS FIRMLY PLANTED ACROSS THE EASTERN SEABOARD. WE SHOULD HAVE A LARGE TEMP GRADIENT ACROSS THE AREA WITH UPPER 60S FAR S TO UPPER 50S N. DECREASED POPS TO SLIGHT CHANCE OVER SE SC WHERE BEST CHANCE OF SOME ISENTROPIC ALONG THE COASTAL TROUGH WILL EXIST. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... WHILE MODEL SOLUTIONS REMAIN SPLIT FOR MOST OF THE EXTENDED... CONFIDENCE THAT THE GUIDANCE IS RUNNING TOO WARM IS QUITE HIGH. MUCH OF THE LONG-TERM PERIOD WILL BE DOMINATED BY A WEDGE PATTERN WITH HIGH PRES OVER THE NE STATES. AS USUAL WITH PERSISTENT WEDGE PATTERNS IN THIS PART OF THE COUNTRY...THE GFS MOS TEMPS ARE ABOUT TEN DEGREES TOO WARM ON AVERAGE. THIS STILL SEEMS TO BE THE CASE WITH THE 00Z RUN. INHERITED GRIDS SEEM QUITE REASONABLE AND ARE WELL COLLABORATED ON THE WHOLE...THUS DID NOT MAKE SIGNIFICANT CHANGES TO THESE PERIODS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... SFC LOW AT 11Z WAS CLOSE TO MOVING OFF THE GEORGIA COAST S OF KSAV AND WINDS WERE ALREADY BACKING IN NRN CHATHAM COUNTY INDICATING THE LOW IS SLIPPING OF THE SSE. HEAVY RNFL IS PINNED DOWN AROUND THE SAVANNAH AIRPORT AND VSBYS AND CIGS SHOULD CONTINUE TO BOUNCE WITH THE PRECIP LOADING. STRONG LOW LEVEL CONVERGENCE IS INCREASING FURTHER UP THE COAST AND HEAVY RAINS MAY ALSO BECOME PINNED ALONG THE CHARLESTON COUNTY LATER THIS MORNING. IN EITHER CASE...IFR/MVFR CONDITIONS SHOULD BECOME LIFR BY THIS AFTERNOON AS THE WEDGE INVERSION LOWERS AND STRENGTHENS. LIFR CIGS TONIGHT...VERY LOW CONFIDENCE ON VSBYS IN THE WEDGE. AT BOTH TAF SITES...N TO NE WINDS SHOULD BE GUSTY FROM THIS AFTN THROUGH THIS EVENING...HIGHEST AT KCHS. THIS IS DEPENDANT ON THE EVOLUTION OF A VERY COMPLEX SYNOPTIC REGIME. EXTENDED AVIATION OUTLOOK...LIFR OR LOWER CIGS AND REDUCED VSBYS IN FOG SAT MORNING...LIFTING TO MVFR CIGS SAT AFTN. LOW CIGS MAY REDEVELOP SAT NIGHT. THERE SHOULD BE SOME IMPROVEMENT BY SUNDAY NIGHT AND MONDAY...BUT ANOTHER ROUND OF LOW CIGS IS POSSIBLE TUESDAY AND TUESDAY NIGHT. && .MARINE... KJAX SOUNDING SHOWS 35-40 KT BELOW 2K FT THIS MORNING AND STRONG PINCHING IS DEVELOPING AND WILL STRENGTHEN FURTHER AS LOW DEEPENS AS IT REACHES THE GULF STREAM. WITH STRONG PRES RISES IN WAKE OF THE LOW WILL GO AHEAD AND RAISE A GALE WARNING FOR AMZ352-354-374. THUS ALL WATERS ARE NOW UNDER A GALE WARNING. HAVE RAISED SEAS/WAVES ACCORDINGLY. HAVE ALSO ADDED TSTMS TO THE SC WATERS AND LOWERED COVERAGE OVER PRECIP ON THE SE GA WATERS. STRONG GRAD PINCHING IS LIKELY TODAY THROUGH EARLY TONIGHT GIVEN THE DYNAMICS AND THERMAL GRADIENT/DIABATIC EFFECT. WHILE THE NAM MODEL SEEMS A BIT QUESTIONABLE WITH THE TRACK OF THE SFC LOW TODAY... THE GFS REMAINS ON TRACK...ALBEIT WEAK WITH THE WIND SPEEDS GIVEN THE TILTING WEDGE SCENARIO. WE HAVE UPGRADED GALE WATCH TO A WARNING OFF THE CHARLESTON COUNTY COAST AND INCLUDED THE HARBOR FOR TODAY INTO TONIGHT. N WINDS SHOULD TRAP-DOOR DOWN THE BACKSIDE OF THE EJECTING LOW THIS AFTN...SPEEDS AND SEAS INCREASING GEORGIA LEGS. SCA ALL WATERS OUTSIDE OF THE GALE WARNINGS. SEAS COULD BUILD AS HIGH AS 9-10 FT 15-30 NM OFF THE NRN CHARLESTON COUNTY BY 00Z/22. WINDS SHOULD BE ON THE DECREASE TONIGHT AND SAT OVER THE WATERS BUT SEAS WILL REMAIN ELEVATED THROUGH TUE. SMALL CRAFT ADVISORIES CONTINUE THROUGH SAT NIGHT IN THE NEARSHORE WATERS AND THROUGH MON EVENING OVER THE OFFSHORE. LAKE WINDS...RECENT OBSERVATION FROM EADYTOWN AND TIGHTENING OF THE PRES GRAD HAS PROMPTED AN ISSUANCE OF A LAKE WIND ADVISORY FOR LAKE MOULTRIE. WE RAN THE ADVISORY THROUGH TONIGHT AS THE GRAD REMAINS QUITE STRONG. && .TIDES/COASTAL FLOODING... HIGH TIDE AROUND 5-6 AM THIS MORNING FELL BELOW COASTAL FLOOD ADVISORY CRITERIA BUT RAIN LIKELY EXACERBATED SOME MINOR FLOODING. HIGH ASTRONOMICAL TIDES EXPECTED SAT THROUGH TUE MORNINGS. THE QUESTION IS WHEN WE EXPECT METEOROLOGICAL FACTORS TO RESULT IN ENOUGH POSITIVE ANOMALY TO PUSH TIDES ABOVE CRITICAL THRESHOLDS FOR SHALLOW COASTAL FLOODING. SAT MORNING HOLDS A CONSIDERABLE CHANCE ALONG THE SC COAST GIVEN CONTINUED NE WINDS AND SOME SWELL WAVE. SUN AND MON WILL BE CLOSE BUT WINDS WILL EITHER BE DUE S OR DUE N...NEITHER OF WHICH NORMALLY RESULTS IN MUCH OF A RESIDUAL. TUE MORNING WE COULD AGAIN BE PUSHING 7 FT AT CHS IF NE FLOW SETS UP AS FORECAST. && .EQUIPMENT... THERE WAS NO BE NO 12Z UPPER AIR FLIGHT THIS MORNING DUE TO HEAVY PCPN AND GROUND EQUIPMENT ISSUES. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...WIND ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR GAZ119. SC...LAKE WIND ADVISORY UNTIL 5 AM EST SATURDAY FOR SCZ045. WIND ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR SCZ048>051. MARINE...GALE WARNING UNTIL 11 PM EST THIS EVENING FOR AMZ352-354. GALE WARNING UNTIL 5 AM EST SATURDAY FOR AMZ330-350-374. && $$ 33/RVT/JRL ga AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 530 AM CST FRI DEC 21 2007 .UPDATED FOR THE AVIATION FORECAST... .SYNOPSIS... LOW LAYERS SATURATED THIS MORNING WITH LIFR CIGS/VSBYS ALONG AND EAST OF AXA-BNW-LWD LINE AT 09Z. SYS IN QUESTION FOR WEEKEND PUSHING THROUGH WRN CONUS. WEAK SHRT WVS NOTED OVER SD AND UPR MS RIVER VALLEY WITH PATCHY MID/HIGH CLOUDS ABOVE...BUT LITTLE OTHER FORCING IN PLACE FOR THE TIME BEING. && .DISCUSSION... IMMEDIATE CONCERN WILL BE FATE OF DENSE FOG ADVY. WILL LEAVE IT GOING FCST AREA WIDE THROUGH 15Z. VSBYS NOT TOO LOW IN WRN SECTIONS AT 09Z...BUT WITH WEAK SELY FLOW AND DIMINISHING MID/HIGH CLOUDS FEEL POTENTIAL IS CERTAINLY THERE FOR DENSE FOG DEVELOPMENT OVER ENTIRE AREA. WITH PLENTY OF STRATUS UPSTREAM OVER MO...CANNOT SEE ANY REASON WHY LOW VSBYS WILL NOT CONTINUE ERN SECTIONS SO HAVE ADVY GOING THERE TOO TIL 18Z. ATTENTION THEN TURNS TO SIGNIFICANT WEEKEND SYS. NAM/GFS BOTH KEEP AREA LOCKED INTO STRATUS TONIGHT WITH COLUMN NOT REALLY TRYING TO SATURATE UNTIL 09Z AND AFTER. HAVE LOWERED MEASURABLE POPS THROUGH AT LEAST MIDNIGHT WITH FOG AND TRACE MENTIONS OF EITHER DRZL OR FRZG DRZL DEPENDING ON SFC TEMPS WHICH GENERALLY FOLLOWED A BLEND OF AVAILABLE GUIDANCE AND LOW LEVEL TEMPS. TRANSITIONED TO HIGHER POPS BEFORE DAYBREAK AND RAIN OR SNOW WORDING. FORECAST INTO SAT WAS BASICALLY A BLEND OF 00Z GFS/12Z ECMWF. AIRMASS SATURATES WITH ALL SNOW NWRN HALF AND RAIN CHANGING TO SNOW SERN HALF. SFC AND WARM LAYER TEMPS FALL AT GENERALLY THE SAME TIME SO ALTHOUGH THERE COULD BE A BRIEF PERIOD OF SLEET AS WARM LAYERS DIPS TO 1-3C...DO NOT FEEL IT WILL BE LONG ENOUGH OR SIGNIFICANT ENOUGH TO MENTION. DID PUSH START OF WATCH BACK TO 18Z HOWEVER AS BEST UVM DOES NOT ARRIVE UNTIL THAT TIME...AND STILL HAVE RAIN MENTION SE. DENDRITIC LAYER FORCING INCREASES DURING THE AFTERNOON IN 300K ISENT SFC AND H5/H6 PRES LAYER. EXPECT RELATIVELY NARROW SW-NE RIBBON OF SNOW TO DEVELOP INTO CENTRAL IA...THEN MORE WIDESPREAD AND INTENSE UVM CLIPPING SERN PORTIONS AS PRIMARY SHRT WV EJECTS INTO MID MS VALLEY. SNOWFALL INTENSITIES REALLY INCREASE AS FORCING MOVES INTO DVN AREA DURING THE EARLY EVENING. MOISTURE TRANSPORT...FRONTOGENETICAL FORCING AND LOWERING STATIC STABILITIES ALL COME TOGETHER DURING THIS TIME FRAME. CONSIDERING THIS AMOUNT OF FORCING IN DENDRITIC LAYER...HAVE SNOW AMOUNTS IN HIGH END OF COBB OUTPUT WITH AMOUNTS RANGING FROM 1 FAR NW TO 6 FAR SE WHERE UVM IS BEST. QUICK LOOK AT 00Z ECMWF QPF IS NOW HIGHER...BUT LATER SWITCH TO SNOW MAY DIMINISH AMOUNTS SOMEWHAT SE SO PRETTY MUCH STUCK WITH AFOREMENTIONED THINKING FOR THE TIME BEING ALTHOUGH THIS TREND WILL HAVE TO BE WATCHED. THESE AMOUNTS DO NOT JUSTIFY WATCH BY THEMSELVES...BUT WITH BLOWING SNOW CONSIDERED WILL LEAVE HEADLINE GOING AS IS. SOMEWHAT LOW CONFIDENCE ON WRN EDGES...BUT WITH BLOWING SNOW POTENTIAL DID NOT CHANGE ANYTHING AT THE MOMENT BESIDES ALTERATION OF START TIME AND EXTENSION TIL 12Z SUN. ALTHOUGH CONFIDENCE NOT HIGH ENOUGH TO BOOST INTO BLIZZARD WATCH YET...WILL MENTION NEAR BLIZZARD CONDITIONS IN TEXT OF WSW. AS SYS MATURES AROUND 00Z...VSBYS COULD DROP TO 1/4MI WITH WINDS GUSTING TO NEAR 35 MPH. SNOW WILL QUICKLY DIMINISH IN OUR AREA DURING THE EVENING...BUT BLOWING SNOW POTENTIAL CONTINUES OVERNIGHT HENCE WATCH EXTENSION. WINDS SHOULD GUST WELL THROUGH THE 20S FOR AN EXTENDED PERIOD. RAW MODEL AND SREF TEMPS SUGGEST GUIDANCE IS TOO WARM TODAY AND COOL TONIGHT WITH BLANKET OF STRATUS SO HAVE GONE BELOW AND ABOVE MOS TODAY AND TONIGHT RESPECTIVELY. WENT ABOVE SAT MORNING BEFORE TEMPS START CRASHING WITH QUICK SURGE OF WAA. EXPECT LITTLE REBOUND SUN WITH WRAP AROUND STRATUS SO HAVE UNDERCUT GUIDANCE SUN. && .AVIATION...21/12Z LIFR CONDITIONS TO CONTINUE THROUGH 15Z AT ALL TERMINAL SITES...WITH THE EASTERN TERMINALS STILL SEEING LIFR CONDITIONS THROUGH 18Z. VSBYS MAY IMPROVE THROUGHOUT THE AFTERNOON INTO THE IFR/MVFR RANGE...HOWEVER CEILINGS ARE STILL EXPECTED TO REMAIN LOW. ALL MODELS INDICATING A DECENT LAYER OF SATURATION THAT PERSISTS THROUGHOUT THE LOWER LEVELS THROUGH THE DAY. HAVE TRENDED TOWARD A SLIGHTLY INCREASING VSBYS/CIGS IN THE AFTERNOON...AS RUC HINTS A BRIEF TIME PERIOD OF SOME DRIER AIR PUSHING INTO THE WESTERN/SOUTHERN TAF SITES. HOWEVER AM SOMEWHAT SKEPTICAL...AND ALL AREAS MAY REMAIN SOCKED IN WITH FOG/LOW STRATUS THROUGH THE DAY WITH SOUTHEAST FLOW CONTINUING TO ADVECT MOISTURE FROM MISSOURI/FOG AREA INTO THE CWA. && DMX WATCHES/WARNINGS/ADVISORIES... DENSE FOG ADVY ENTIRE AREA THROUGH 15Z...AND ALONG AND EAST OF ALGONA-WEBSTER CITY-DES MOINES-CORYDON LINE TIL 18Z. WINTER STORM WATCH 18Z SAT-12Z SUN ALONG AND EAST OF FOREST CITY-WEBSTER CITY-WINTERSET-CHARITON-CORYDON LINE. && $$ SMALL/ALBRECHT ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAKE CHARLES LA 955 AM CST FRI DEC 21 2007 .UPDATE...DENSE FOG BURN OUT DELAYED ON THE LONGEST NIGHT OF THE YEAR. SHOULD BE SEEING RAPID IMPROVEMENT OVER THE EASTERN ZONES VERY SHORTLY. WILL ISSUE UPDATED ZONES REMOVING PATCHY FOG ACCORDINGLY. OTHERWISE, LOWERED TEMPS TODAY DUE TO BOTH DELAYED BURNOFF AND WEAK SUN USING LATEST UPDATED RUC. && .PREV DISCUSSION... /ISSUED 610 AM CST FRI DEC 21 2007/ DISCUSSION...SHARP MOISTURE GRADIENT ACROSS EXTREME EASTER PARTS OF THE REGION...WHERE DEWPOINTS GO FROM 47 AT KLFT TO 59 AT KBTR. NOT COINCIDENTALLY...THIS ALSO SERVES AS THE DEMARCATION LINE FOR AREAS OF DENSE FOG...WHICH IS PRIMARILY OVER EASTERN PARTS OF LOUISIANA INTO MISSISSIPPI. WILL MENTION AREAS OF FOG WITH DENSE SPOTS OVER THE EXTREME EASTERN TIER OF PARISHES...BUT FOREGO AN ADVISORY WITH VISIBILITY BOUNCING AROUND A BIT...WORSENING A LITTLE JUST WEST OF THE ATCHAFALAYA WHILE IMPROVING EAST OF IT. SUNNY AND WARM CONDITIONS ON TAP FOR TODAY WITH HIGH PRESSURE AT THE SURFACE GRADUALLY SHIFTING EAST WHILE SHORTWAVE RIDGING ALOFT MOVES OVERHEAD. WILL START TO SEE MOISTURE RETURNING TO THE AREA LATE THIS AFTERNOON AND IN EARNEST LATE TONIGHT INTO EARLY SATURDAY ONCE THE SFC HIGH SHIFTS EAST OF THE AREA AND 30-40 LLJ DEVELOPS. THERE ARE DIFFERENCES AMONG THE NAM AND GFS THAT HAVE IMPORTANT IMPLICATIONS ON JUST HOW ACTIVE SATURDAY WILL OR WILL NOT BE. WITHOUT DELVING INTO THE GORY DETAILS...SUFFICE IT TO SAY IN SUMMARY THAT THE GFS OFFERS THE BETTER SEVERE POTENTIAL FROM A TIMING...KINEMATIC...AND THERMODYNAMIC PERSPECTIVE...THOUGH IN BOTH CASES INSTABILITY WILL BE A LIMITING FACTOR. TO THAT END...SPC HAS A "SEE TEXT" DENOTED FOR THE AREA...AND CONCUR WITH THAT ASSESSMENT GIVEN THE PRESENT UNCERTAINTY. WHAT DOES SEEM MORE CERTAIN IS STRONG SOUTHERLY WINDS AHEAD OF THE FRONT...FOLLOWED BY EVEN STRONGER NORTH WINDS BEHIND IT. A LAKE WIND ADVISORY IS POSSIBLE FOR PARTS OF THE AREA ON BOTH SIDES...PARTICULARLY ALONG THE COAST. SHOWERS AND THUNDERSTORMS EXPECTED TO COME TO AN END BY SATURDAY EVENING...WITH SUNDAY DOMINATED BY COLD AIR ADVECTION. FOR THE MEDIUM TO EXTENDED RANGE...HAVE CONTINUED TO LEAN ON THE ECMWF...WITH THE GFS COMING MORE IN LINE WITH ITS SOLUTIONS. IT WOULD SEEM THAT THIS SATURDAY FRONT WILL BE THE END OF THE 70 PLUS DEGREE DAYS FOR A WHILE...WITH THE TRAIN OF SHORTWAVES AMID THE PROGRESSIVE FLOW COMING FAST AND FURIOUS. LOOKS LIKE ABOVE NORMAL RAIN CHANCES ABOUT EVERY TWO DAYS OR SO...WITH THE FIRST SHOT AFTER THIS FRONT COMING MONDAY INTO...YEP...CHRISTMAS. THE HIGHEST POPS FALL ON CHRISTMAS EVE...WITH THINGS HOPEFULLY WINDING DOWN CHRISTMAS DAY AS THE UPPER TROF LIFTS OUT TOWARD THE MID ATLANTIC. ANOTHER WILL BE ON ITS HEELS...HOWEVER...AND WEDNESDAY LOOKS TO BE THE NEXT DECENT CHANCE. AVIATION...EASTERN TERMINALS...KARA...KLFT...AND KAEX...FLIRTING WITH EXPANSIVE AREA OF FOG PRIMARILY OVER SOUTHEAST AND NORTHEAST LOUISIANA THIS MORNING. THERE HAS BEEN SOME WESTWARD EXPANSION OVER THE PAST COUPLE OF HOURS...BUT ANY RESTRICTIONS WILL BE SHORT LIVED AND OCCUR GENERALLY PRIOR TO 13Z. MARINE...SOME PATCHY FOG THIS MORNING OVER THE 0-20NM ZONE FROM INTRACOASTAL CITY TO THE LOWER ATCHAFALAYA. OTHERWISE...LIGHT NORTH WINDS THIS MORNING WILL GRADUALLY BECOME EAST AND FINALLY SOUTH BY THIS AFTERNOON AS HIGH PRESSURE SHIFTS EAST OF THE AREA. SOUTHERLY FLOW WILL STRENGTHEN TONIGHT IN ADVANCE OF A COLD FRONT THAT IS FORECAST TO MOVE THROUGH THE COASTAL WATERS SATURDAY AFTERNOON INTO SATURDAY NIGHT. AN SCEC HEADLINE MAY BE WARRANTED TONIGHT AFTER MIDNIGHT AND SATURDAY PRIOR TO THE FRONT. SHOWERS AND THUNDERSTORMS WILL PRECEDE AND ACCOMPANY THE FRONT...WITH STRONG NORTHERLY WINDS AND BUILDING SEAS EXPECTED ONCE IT PASSES THROUGH. AN SCA SEEMS LIKELY FOR THESE CONDITIONS BEHIND THE FRONT. && .PRELIMINARY POINT TEMPS/POPS... KLCH 72 57 73 42 / 0 20 40 20 KBPT 73 58 72 41 / 0 20 30 10 KAEX 70 54 73 40 / 0 20 50 20 KLFT 72 58 76 43 / 0 20 40 30 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$ 11 la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1117 AM EST FRI DEC 21 2007 .UPDATE...LITTLE TO NONE OF THE RETURNS ON THE RADAR ARE MAKING IT TO THE GROUND. SO HAVE SLASHED THE POPS FOR THE REST OF THE DAYTIME AS MID LEVEL DRY AIR CONTINUES OVER THE REGION. SO FAR, THE NAM AND RUC HAVE THE BETTER HANDLE ON THE 850 MB MOISTURE MOVING IN WHICH LOOKS THE BEST. SO HAVE SCT SPRINKLES IN THE FORECAST FOR THE AFTERNOON. BASED ON THE LOWER CLOUDS (AROUND 1500 FEET) AT ANJ, AS WELL AS BELOW FREEZING TEMPERATURES, PUT PATCHY ZL- IN FOR E UPPER WITH IT CHANGING TO SCT SPRINKLES FOR THE AFTERNOON AS THE TEMEPERATURES WARM AND THE DRY AIR PUSHES THE LOWER CLOUDS OUT. OTHERWISE, TEMPERATURES AND WINDS LOOK GOOD. LUTZ && .PREV DISCUSSION... /ISSUED 738 AM EST FRI DEC 21 2007/ AVIATION...BKN MVFR CIGS ANTICIPATED ACROSS PORTIONS OF NRN LOWER MICHIGAN THIS MORNING...PARTICULARLY AT PLN/APN WITH SE FLOW OFF LAKE HURON PUSHING LOW CLOUD COVER INTO THOSE AREAS. OTHERWISE... SPOTTY ELEVATED SHOWER ACTIVITY WILL BE FOUND ACROSS THE REGION TODAY ALONG ADVANCING NOSE OF WARM AIR AND MOISTURE ALOFT. LOWERING CIGS/VSBYS ALONG WITH AREAS OF DRIZZLE ANTICIPATED TONIGHT LEADING TO MVFR AND EVENTUALLY IFV CONDITIONS AT ALL THREE TAF LOCATIONS. ADAM DISCUSSION...ISSUED AT 509 AM. LONGWAVE TROUGH PATTERN PREVALENT ACROSS NORTH AMERICA WITH A MYRIAD OF AMPLIFYING SHORTWAVES MOVING THROUGH THE FLOW. MOST SIGNIFICANT OF THESE WAVES...AND WHAT WILL BE THE MAIN FOCUS IN THE FORECAST FOR THE WEEKEND...BEGINNING TO TRAVERSE THE EXPANSE OF THE ROCKIES. ONE PIECE OF ENERGY NOW DIGGING INTO THE SW STATES WHILE ANOTHER WAVE IN WESTERN CANADA. OPERATIONAL NAM/GFS SOLUTIONS AS WELL AS THE GFS ENSEMBLES AND ECMWF SOLUTION ALL STILL DEPICTING A TROUGH MERGER BETWEEN THESE TWO SYSTEMS OVER THE UPPER MIDWEST... LATE SATURDAY THROUGH SUNDAY...AND ASSOCIATED RAPID SPIN-UP OF A DEEP SFC LOW OVER NRN MICHIGAN. IN THE MEANTIME...STILL PLENTY TO THINK ABOUT IN THE SHORT TERM. BUILDING MID LEVEL RIDGING DOWNSTREAM OF THIS SYSTEM AND INCREASING LOW LEVEL WARM/MOISTURE ADVECTION INTO THE WESTERN GREAT LAKES EXPECTED TO DOMINATE TODAY THROUGH MUCH OF SATURDAY...WITH CHANCES FOR LIGHT SHOWER AND DRIZZLE/FREEZING DRIZZLE ACTIVITY THE MAIN FORECAST ISSUES. TODAY AND TONIGHT...MID CLOUD COVER AND ELEVATED RADAR RETURNS ALONG ADVANCING MID LEVEL MOISTURE GRADIENT CONTINUE TO PRESS INTO THE REGION FROM THE WEST-SOUTHWEST. HOWEVER...MORE WIDESPREAD LOW CLOUD COVER AND DRIZZLE ACTIVITY STILL WAY BACK ACROSS CENTRAL WISCONSIN INTO WESTERN UPPER MICHIGAN...ALTHOUGH SOME STRATUS HAS DEVELOPED/ EXPANDED ACROSS THE HIGHER TERRAIN OF NE LOWER MICHIGAN OVERNIGHT. THUS FAR...RADAR RETURNS LOOK CONVECTIVE IN NATURE AS AXIS OF STEEPER MID LEVEL LAPSE RATES PRESSES OUT OF WISCONSIN. BUT OUTSIDE OF A COUPLE OBS IN SW LOWER MICHIGAN SHOWING PRECIP OVERNIGHT... NOTHING REALLY GETTING TO THE GROUND THUS FAR. HOWEVER...RADAR RETURNS HAVE INCREASED IN COVERAGE OVER THE LAST HOUR OR SO AND PROBABLY NEED TO CARRY SOME SORT OF PRECIP THIS MORNING AS THE MOISTURE AXIS AND STEEPER LAPSE RATES LIFT UP THROUGH THE REGION. QUESTION IS...WHAT WILL IT BE? FORECAST NAM SOUNDINGS FOR THIS MORNING DEPICT ABOVE FREEZING LAYER ALOFT NOSING INTO THE REGION. BUT GIVEN THE DRY LOW LEVEL AIR STILL IN PLACE AND CONVECTIVE NATURE TO THE PRECIP...THINK ANYTHING THAT DOES REACH THE GROUND WILL BE OF THE FROZEN VARIETY. TIME WILL TELL OF COURSE BUT FOR NOW WILL CARRY CHANCY SNOW SHOWER WORDING THROUGH MIDDAY. THEN BY LATER THIS AFTERNOON THROUGH SATURDAY...LOW LEVEL MOISTURE FINALLY GETS SHOVED INTO THE REGION LATER THIS AFTERNOON AND ESPECIALLY THIS EVENING...SETTING THE STAGE FOR AREAS OF FOG AND DRIZZLE TO DEVELOP. HAVE NOT CHANGED MUCH TO THE GOING FORECAST IN THIS REGARD OTHER THAN SLOWING DOWN THE DEVELOPMENT OF WIDESPREAD FOG AND DRIZZLE UNTIL LATER IN THE EVENING...AND ADDING FREEZING DRIZZLE TO SOME OF THE HIGHER TERRAIN AREAS WHERE TEMPS WILL LIKELY HOVER AROUND FREEZING. SOUPY CONDITIONS THEN EXPECTED TO PERSIST THROUGH SATURDAY ALTHOUGH CONTINUING WARM ADVECTION/MOISTENING ALOFT MAY BRING BETTER CHANCES FOR MEASURABLE PRECIP INTO THE REGION. IN ANY EVENT...A DREARY...DAMP COOL DAY LOOKS ON TAP FOR NRN MICHIGAN WITH TEMPS SLOWLY REACHING THE 35 TO 40 DEGREE MARK. SATURDAY NIGHT THROUGH SUNDAY...TROUGH MERGER SLATED TO TAKE SHAPE OVER THE UPPER MIDWEST BRINGING ABOUT A RAPID SPIN UP OF A DEEP SFC LOW NEARLY OVER THE STATE...TRACKING UP ACROSS EASTERN LAKE SUPERIOR ON SUNDAY. VERY STRONG DYNAMICS COME INTO PLAY IN THIS SCENARIO AND AT THIS POINT CATEGORICAL POPS ARE JUSTIFIED SATURDAY NIGHT INTO SUNDAY WITH A GOOD SWATH OF PRECIP RUNNING UP THROUGH THE REGION. ALSO AT THIS POINT...MAINLY RAIN ANTICIPATED SATURDAY NIGHT WITH THE LOW DEEPENING JUST WEST OF THE REGION AND +4C OR BETTER H8 AIR GETTING SHOVED UP THROUGH EASTERN UPPER MICHIGAN. A RAPID CHANGEOVER TO SNOW AS WELL AS SOUTHWEST-WEST LAKE EFFECT/ENHANCED SNOW SHOWERS EXPECTED TO FOLLOW SUNDAY AS CORE OF -14C OR COLDER H8 AIR ROTATES AROUND INTO LOWER MICHIGAN. A LOT OF WIND AND THE POTENTIAL FOR HEAVY SNOW/NEAR BLIZZARD CONDITIONS WITH THIS SYSTEM SUNDAY AND SUNDAY NIGHT WILL LIKELY WARRANT HEADLINES IN THE NEXT 1 TO 2 FORECAST CYCLES. TBA CHRISTMAS EVE AND CHRISTMAS...LAKE AGGREGATE TROUGHING WILL CONTINUE ACROSS THE GREAT LAKES THROUGH THE DAY ON MONDAY...BEFORE 850MB TEMPERATURES WARM TO AROUND -5C BY 00Z MONDAY. WITH SURFACE TROUGH ROTATING ACROSS NORTHERN MICHIGAN EARLY MONDAY MORNING...EXPECT TO SEE FAIRLY WIDESPREAD SNOW SHOWERS AND BLOWING SNOW. DURING THE DAY ON MONDAY...DEEPER MOISTURE STARTS TO PULL OUT AND PRECIPITATION SLOWLY BECOMES PURELY LAKE EFFECT. FINALLY...AS THE BOUNDARY LAYER WARMS...LAKE EFFECT WILL END MONDAY EVENING. HIGH PRESSURE WILL BECOME ESTABLISHED OVER THE GREAT LAKES BY CHRISTMAS DAY...PROVIDING A FAIRLY PLEASANT DAY WITH HIGHS WARMING INTO THE LOWER 30S UNDER PARTLY SUNNY SKIES AFTER STARTING THE DAY IN THE TEENS. KAS AVIATION... /ISSUED 1154 PM EST THU DEC 20 2007/ MID/HIGH CLOUDS ACROSS NORTHERN MI OVERNIGHT...SOME ST OVER LAKE HURON MAY IMPACT APN THIS EVENING. CLOUD COVER AND PERSISTENT SOUTHEAST FLOW MAY IMPACT FOG POTENTIAL AT TERMINAL SITES OVERNIGHT. CEILINGS WILL LOWER DURING THE DAY FRIDAY...PREVAILING MVFR CONDITIONS EXPECTED. SOME DRIZZLE OR LIGHT RAIN POSSIBLE DURING THE AFTERNOON. JPB && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LMZ341. LH...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LHZ346. LS...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LSZ321. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ST LOUIS MO 615 AM CST FRI DEC 21 2007 .DISCUSSION... LOTS OF WX CONCERNS FOR THE NXT 48 HRS. PRIMARY ISSUE FOR TDA...AT LEAST FOR THIS MRNG...IS DENSE FOG THAT CURRENTLY BLANKETS ENTR FCST AREA. WITH ONLY A MODEST INCR IN MIXING DURG THE DAY...AND WITH SFC/LO LVL TRAJECTORIES CONTINUING TO PUSH HIER DWPT AIR INTO REGION...THINK IMPROVEMENT WILL BE FAIRLY SLOW. PREVIOUSLY ISSUED DENSE FOG ADVISORY RUNS UNTIL 16Z AND HAVE OPTED TO NOT EXTEND IT ATTM AS CLIMO FAVORS SM INCR IN VSBYS...ALBEIT MODEST...IN THE 15-16Z TIME FRAME. IF ST HOLDS ENTR DAY AS SUGGESTED BY INVERSION ON FCST SNDGS...TEMPS ARE GOING TO STRUGGLE TO WRM. BASED ON YSTDAS DIURNAL RECOVERY HV GIVEN MOST AREAS A MAX TEMP ABT 10 DEGREES ABV GOING READINGS. ATTENTION THEN TURNS TO SYSTEM MOVING THROUGH AREA SAT AND SAT NGT. SPEED AND INTENSITY OF SYS CONTS TO VARY A BIT FROM MODEL TO MODEL AND FROM RUN TO RUN. HWVR...IT APRS THAT GFS IS TOO SLOW WITH THE SYSTEM...AND MODEL CONSENSUS OF WRF/NAM...ECMWF...SREF...AND CANADIAN ALL SEEMS TO SUGGEST LEANING TWD A MORE PROGRESSIVE SOLN. FCST FROM 18Z SAT-12Z SUN GENLY FOLLOWS A SREF/WRF-NAM BLEND FOR MOST ELEMENTS. ALTHO INITIALLY ON SAT MRNG MSTR WILL BE LIMITED...INCRG S FLOW AHD OF TROF SHUD RAPIDLY MOISTEN THE AMS AOB 500 MB...AND PCPN SHUD BGN TO BLOSSOM AS UVV ASSOC WITH TROF WORKS INTO MSVLY. COLDER AIR WILL THEN WORK EWD...CHGG RAIN TO SNOW OVR W COUNTIES DURG THE AFTN...AND OVR THE IL COUNTIES ON SAT EVE. ALL MODELS KEEP SYSTEM OPEN...WITH NO WELL-DEFINED SFC OR 850 MB LOW TRACK ON WHICH TO BASE SNOW POTENTIAL. USING CONSENSUS QPF AND MODEL SNDGS TO TIME CHGOVER TO SNOW SUGGESTS BEST CHC FOR ACCUM SNOW WILL BE OVR N/W COUNTIES...RUFLY FROM N OF COU TO NR UIN. SINCE SYSTEM IS MOVING SO FAST DON`T THINK SNOWFALL ACCUMULATIONS WILL BE EXTREMELY HIGH...BUT AM WORRIED ABT THE EFFECT OF VRY STG WNDS IN WAKE OF SYSTEM COMBINING WITH ANY SNOW THAT DOES ACCUMULATE. TO HIGHLIGHT THE THREAT HV CONTD MENTION OF BLOWING AND DRIFTING SNOW IN AREAS THAT APPEAR TO HV A CHC OF OVER AN INCH OF ACCUMULATION...AND WL ALSO EMPHASIZE THIS CONCERN IN HWO. ALL PCPN WITH SYSTEM SHUD END BY 12Z SUN...ALTHO GUSTY WINDS SHUD CONT THRUOUT THE DAY...SPCLY IN N SECTIONS OF THE FA. TRUETT && .AVIATION... FOR THE 12Z TAFS...SHOULD ONLY SEE A SLOW IMPROVEMENT IN VSBYS AND A SLOW RISE IN CEILING HGTS BGNG AT 15Z TO 16Z WITH SLOWLY INCRSG SELY SFC WNDS. WITH FCTS SOUNDINGS SHOWING BNDRY LYR MOISTURE TRAPPED BLW AN INVERSION THRU THE DAY THE STRATUS CEILING SHOULD CONT. THE LATEST RUC FCST DOES SHOW LWRG RH IN THE 925 MB LYR BY 21Z FRI OVR COU. WILL FCST BKN020 IN COU AT 21Z...BUT WILL KEEP AN OVERCAST CEILING AT 700 FT IN UIN...STL AND SUS THRU THE AFTN HRS. WILL IMPROVE THE VSBYS TO 2SM BR BY 16Z...AND THEN TO 4SM BR AT 18Z FRI AT THE TAF SITES. VSBYS SHOULD CONT TO IMPROVE THIS EVNG WITH THE STRATUS LYR CONTG TO SLOWLY RISE WITH MDLS DEPICTING INCRSG LOW LVL S-SELY WNDS...ALTHOUGH THE BNDRY LYR REMAINS VERY MOIST. GKS && .LSX WATCHES/WARNINGS/ADVISORIES... MO...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR AUDRAIN- BOONE-CALLAWAY-COLE-CRAWFORD-FRANKLIN-GASCONADE-IRON- JEFFERSON-KNOX-LEWIS-LINCOLN-MADISON-MARION-MONITEAU-MONROE- MONTGOMERY-OSAGE-PIKE-RALLS-REYNOLDS-SHELBY-ST. CHARLES-ST. FRANCOIS-ST. LOUIS-ST. LOUIS CITY-STE. GENEVIEVE-WARREN- WASHINGTON. IL...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR ADAMS IL- BOND IL-BROWN IL-CALHOUN IL-CLINTON IL-FAYETTE IL-GREENE IL- JERSEY IL-MACOUPIN IL-MADISON IL-MARION IL-MONROE IL- MONTGOMERY IL-PIKE IL-RANDOLPH IL-ST. CLAIR IL-WASHINGTON IL. && $$ WFO LSX mo AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BINGHAMTON NY 1121 AM EST FRI DEC 21 2007 .SYNOPSIS... MARINE MOISTURE WILL RIDE UP THE MOUNTAINS OF NORTHEASTERN PENNSYLVANIA, AND BRING CLOUDS AND PATCHY FREEZING DRIZZLE TO THE REGION TONIGHT. LOW PRESSURE WILL SPREAD STRONG WINDS AND RAIN INTO NY AND PA FOR SUNDAY. BEHIND THE STORM WILL BE COLDER AIR AND LAKE EFFECT SNOW SHOWERS SUNDAY NIGHT INTO MONDAY. && .NEAR TERM /THROUGH TONIGHT/... LOW LEVEL SOUTHEAST FLOW OFF OF ATLANITC KEEPING CLOUDS OVER MOST OF THE CWA TODAY INTO SATURDAY. WITH THE THICK LOW CLOUDS DROPPED THE HIGH TEMPERATURES BY A FEW DEGREES. FEW OTHER CHANGES TO THE NEAR TERM. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... MAIN CONCERN IN THE NEAR TERM IS FOR PATCHY FREEZING DRIZZLE OVERNIGHT, AND EARLY SATURDAY. MARINE LAYER MOISTURE WILL FLOW NORTHWEST THROUGH PA TONIGHT. THE BEST CHANCE FOR FREEZING DRIZZLE WILL BE JUST NORTH OF THE HIGH TERRAIN IN NORTHEASTERN PA, AND ALSO INTO DELAWARE AND OTSEGO COUNTIES, WHERE THE ADDED LIFT SHOULD ALLOW FOR SOME LIGHT DRIZZLE. WE BRING CHC POPS INTO NY/PA SATURDAY AFTERNOON WITH WARM FRONTAL PUSH, THEN QUICKLY RAMP POPS SATURDAY NIGHT INTO SUNDAY. MODELS ARE IN GOOD AGREEMENT REGARDING MOISTURE FLOW AND LIFT. THERE ARE SOME QPF DISCREPANCIES, WHICH COULD COME INTO PLAY ON SUNDAY. WITH 1.50-2.00 INCHES OF LIQUID IN THE SNOW PACK MAINLY EAST OF I-81, AND AN ADDITIONAL 0.75-1.50 INCHES OF PRECIPITATION EXPECTED, THERE IS A POSSIBILITY FOR HYDRO CONCERNS. GIVEN THE STRENGTH OF THE WINDS, THE HIGH DEW POINTS, AND THE MILD TEMPERATURES OVER AN EXTENDED PERIOD OF TIME, A LOT OF SNOW PACK COULD BE MELTED TO RELEASE ITS WATER CONTENT. && .LONG TERM /MONDAY THROUGH THURSDAY/... MEDIUM RANGE GUIDANCE IN GOOD AGREEMENT WITH FEATURES BEHIND THE STRONG LOW PRESSURE AND COLD FROPA SUNDAY NIGHT. CYCLONIC FLOW ALOFT AND CAA ACROSS LAKE ONTARIO WILL MAINTAIN PLENTY OF CLOUDS AND LAKE EFFECT SNOW STREAMERS. MODELS DIVERGE TUES AND WEDNESDAY. ALL MODELS AGREE ON HIGH AMPLITUDE TROF DEVELOPING OVER INTERMOUNTAIN WEST...BUT THE LAST FEW RUNS OF GFS SEEM TO BE OUT ON THEIR OWN WITH MAINTAINING A STRONG RIDGE OVER THE SW ATLANTIC AND SE CONUS.THE GEFS/EC/GGEM/UKMET CAMP...AND EVEN NOGAPS SHOW SOME NRN/SRN STREAM PHASING OF UL LOW PRESSURE OVER THE SOUTHEASTERN STATES ON TUESDAY AND WEDNESDAY. THIS LEADS TO SIGNIFICANT CYCLOGENESIS OFFSHORE. THAT SAID...THIS DOES NOT SEEM TO HAVE MUCH BEARING ON CNY/NEPA WEATHER FOR THE MIDDLE OF NEXT WEEK...BARRING A SIGNIFICANT WWD SHIFT IN MODEL TRACKS OF THE LOW FEATURE. BOTH MODEL CAMPS OFFER UP AT LEAST SOME DERIVATION OF HIGH PRESSURE FORMING OVER THE NORTHEAST WITH FAIR WX BOTH CHRISTMAS DAY...AND WEDNESDAY AND WILL GO WITH THAT FOR NOW. THURSDAY ALSO BECOMES ANOTHER PROBLEM WITH MORE MODEL SPREAD. GFS AND IT/S GEFS ENSEMBLES LIFTS OUT THE INTERMOUNTAIN WEST LOW BY THURSDAY...WHILE EC SEEMS TO HOLD BACK A COUPLE DAYS. CAN GGEM WOULD SUGGEST SOME PRECIP AS EARLY AS THURS. PREV FCST INDICATES CHC...AND WILL STICK WITH THAT CONSIDERING OVERALL LOW PRESSURE INDICATED OVER UPR MIDWEST/GTLKS BY DAY 7 HPC PROG. PRETTY MUCH WENT WITH WHAT 00Z GMOS HAS OFFERED FOR TEMPS. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... ANOTHER DAY...MORE CRAZY FLIGHT CONDITIONS IN CNY/NEPA. LATEST FOG PRODUCT SHOWS PLENTY OF HOLES HAD DEVELOPED IN THE STRATUS LAYER BETWEEN 08Z-11Z...WITH CIGS SCATTERING OUT TO VFR AT BGM-ELM-ITH- RME. ON THE FLIP SIDE...THIS CLEARING HAS ALLOWED MVFR AND BRIEF IFR VSBYS TO DEVELOP. MEANWHILE...MARINE LAYER STRATUS WAS NOT THAT FAR AWAY...AND HAS INVADED AVP WITH MVFR CIGS. NOT EXACTLY SURE WHY ALL THIS HAS TRANSPIRED...BUT COULD BE THAT SELY BLYR FLOW HAS INCREASED WITH A LITTLE DOWNSLOPING WAS OCCURRING FROM THE CATSKILLS AND POCONOS WAS AFFECTING BGM-ELM-ITH...WHILE MOISTURE WAS INCRG ON THE LEE SIDE AT AVP. RUC AND NAM MODELS DO SEEM TO BE CAPTURING THIS IN THE 925 MB RH FIELDS...AND BOTH SUGGEST THAT BKN-OVC MVFR CIGS FROM THE MARINE LAYER WILL RETURN TO THE CLEARED OUT AREAS BY 15Z. SYR REMAINS SOCKED IN LIFR CIG. THINKING IS THAT THEY TOO WILL LIFT THE LOW LAYER TO MVFR BY 13Z OR 14Z. ONCE THE MARINE STRATUS LAYER IS IN...IT IS PROGGED TO STAY THROUGH THIS PERIOD WITH MINOR FLUCTUATIONS. ALSO EXPECT AS LAYER COOLS TONIGHT SOME WEAK UPSLOPE LIFT MAY CAUSE IFR CIGS AGAIN WITH FREEZING DRIZZLE AT AVP AND BGM...WITH LESS OF A CHC AT ELM-ITH AND VRY LITTLE CHC AT RME-SYR. CONFIDENCE IN THE DETAILS OF THIS FCST AT ANY STATION IS VERY LOW...NOT A GOOD DAY FOR VFR ONLY RATED AVIATORS. HIGH PRESSURE STRENGTHENS A LITTLE ON SATURDAY WITH MODELS SHOWING DRYING OF THE LOW LVLS IN THE AFTERNOON. THIS SHOULD AT LEAST ALLOW CIGS TO REACH VFR. THEN...THE NEXT STORM SYSTEM APPCHS LATE SATURDAY NIGHT WITH PCPN DEVELOPING AFTER 06Z SUNDAY. RAIN EXPECTED ON SUNDAY BEFORE STRONG COLD FRONTAL PASSAGE TOWARD EVENING...WITH PRECIPITATION CHANGING OVER TO ALL SNOW. EXPECT VARIABLE MVFR-IFR CIG RESTRICTIONS ON SUNDAY AND SUNDAY NIGHT. WINDS INCREASE OUT OF THE SOUTHEAST SUNDAY MORNING WITH LOW-LEVEL WINDS OF 50+ KTS DURING THE DAY ON SUNDAY WITH LLWS POSSIBLE...FOLLOWED BY BLUSTERY WEST-NW WINDS POST FROPA ON SUNDAY NIGHT. COLD ADVECTIVE NORTHWEST FLOW WILL CAUSE LAKE EFFECT ON MONDAY AND MONDAY NIGHT WITH STRATOCUMULUS MVFR/IFR CIGS...AND ALSO POOR VSBY IN SHSN. HIGH PRESSURE BEGINNING TO BUILD IN ON TUESDAY WILL SHUT LAKE EFFECT OFF BY MID-WEEK. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...NONE. NY...NONE. && $$ SYNOPSIS...TAC NEAR TERM...TAC SHORT TERM...DJP LONG TERM...JAB AVIATION...JAB ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 357 PM EST FRI DEC 21 2007 .SHORT TERM (TONIGHT AND SATURDAY)... FOCUS TONIGHT WILL BE ON ADVANCING AREA OF INCREASED DEWPOINTS AND ANTICIPATED LOWER VISIBILITIES IN FOG. LOCATIONS SEEING DEWPTS IN THE 34 DEGREE OR HIGHER RANGE TO THE SOUTH AND WEST ARE SEEING THE DENSER FOG HOLDING ON. RUC40/NAM12 ALL SHOWING SLOWER ARRIVAL OF HIGHER DEWPOINTS...WITH BEST ADVECTION NOT OCCURRING TILL CLOSER TO 6Z IN THE SW AND SPREADING NORTH OVERNIGHT. AS A RESULT WILL MAKE FURTHER ADJUSTMENTS AND SLOW DOWN ONSET OF FOG AND DRIZZLE. KIWX 88D SHOWS SOME LIGHT RETURNS THAT MAY REACH THE GROUND IN THE FORM OF A BIT OF DRIZZLE OR FLURRIES. SOME CONCERNS AS STUBBORN AS THE DRIER FLOW IS INTO THE AREA THAT FOG MAY STRUGGLE TO GET TOO FAR NORTH. WILL REMAIN OPTIMISTIC AS 925/850 MB WINDS RAMP UP LATER TONIGHT AND SHOULD ALLOW THE MSTR TO GET ON THE MOVE. ON SATURDAY...CONTINUATION OF SNOWMELT AND HIGHER DEWPTS WILL CONTINUE IN INCREASING S TO SW FLOW. NAM/GFS/SREF HAVE ALL TRENDED SLOWER WITH ARRIVAL OF PRECIP NOT BRINGING IN TILL LIKELY OUTSIDE THIS PERIOD. DID NOT WANT TO DROP ALL POPS AT THIS POINT SO WENT DRASTIC DOWNWARD TREND AND REPOSITION OF BEST CHC FOR ANY PRECIP BY LATE AFTERNOON. WITH SLOWER ARRIVAL OF PRECIP...WARMER TEMPS MAY BE POSSIBLE ESPECIALLY IF FOG CAN LIFT OUT SOONER OR DOESN`T MATERIALIZE AS MUCH. FOR NOW HAVE LEFT THINGS ALONE TEMP WISE. && .LONG TERM (SATURDAY NIGHT THROUGH FRIDAY)... SATURDAY NIGHT THROUGH SUNDAY AMPLIFIED PATTERN ACROSS THE CENTRAL AND EASTERN CONUS WITH DEEP TROUGH OVER THE CENTRAL CONUS AND RIDGING ACROSS THE EAST. SFC WAVE MOVING UP FROM MID MS VALLEY TOWARDS LAKE MICHIGAN BY LATE SATURDAY NIGHT INTO EARLY SUNDAY. SFC LOW MOVES THRU THE LP OF MICHIGAN AN NORTH INTO CENTRAL ONTARIO BY SUNDAY AFTERNOON...BEFORE PULLING NORTHEAST INTO NORTHERN QUEBEC BY EARLY MONDAY. THERMAL PROFILE ACROSS THE REGION SUGGESTS ALL RAIN THRU THE OVERNIGHT BEFORE STARTING THE TRANSITION PERIOD AROUND DAYBREAK SUNDAY. MODELS HAVING BEEN SLOWING THE SYSTEM DOWN AND HAVE THEREFORE SLOWED THE PRECIP CHANGEOVER DOWN SOME AS WELL...AS THE H850 TEMPS DROP FROM +5 C TO BELOW 0C ACROSS THE ENTIRE REGION BETWEEN 12-15Z. ANY WRAP AROUND OR LAKE ENHANCED PRECIP WILL BE SNOW THEN THROUGH THE LATE MORNING INTO THE AFTERNOON WITH VERY STRONG CAA INTO THE REGION. TEMPS WILL CONTINUE TO DROP FROM LATE SATURDAY NIGHT THRU SUNDAY NIGHT...FROM 40S LATE SATURDAY NIGHT INTO THE 20S BY SUNDAY AFTERNOON...AND TEENS FOR LOWS OVERNIGHT INTO EARLY MONDAY. SIGNIFICANT AMOUNTS OF MOISTURE FOR THE SYSTEM TO WORK WITH WITH PWATS ABOVE 1 INCH EARLY SUNDAY...LIQUID QPF AMOUNTS WILL PUSH .5 INCHES FOR MOST OF THE AREA...BUT VERY LITTLE SNOW ACCUMS EXPECTED THRU THE PERIOD. MAINLY WITH LAKE ENHANCED OR LAKE EFFECT ACROSS THE FAR NW PORTIONS OF THE AREA AND ACROSS THE FAR NORTHERN TIER OF COUNTIES AS THE FLOW ACROSS THE LAKE BECOME MORE WESTERLY WITH TIME...MAYBE AN INCH OR TWO. UPPER LEVEL LOW STARTS TO PUSH INTO THE GREAT LAKES EARLY SUNDAY AND THRU THE DAY...VERY TIGHT PRESSURE GRADIENT ACROSS THE REGION WITH NORTHWEST/WEST FLOW THROUGH THE DAY. GUSTY WINDS WILL INCREASE FROM EARLY SUNDAY THROUGH SUNDAY AFTERNOON. LAKE EFFECT SNOW ACROSS THE NORTHERN TIER OF THE CWA WILL CONTINUE TO BE A POSSIBILITY WITH DELTA T/S REACHING LEVELS OF -15 OR MORE BY SUNDAY EVENING. MONDAY THROUGH FRIDAY SPLIT FLOW ACROSS THE WEST BECOMES MORE CONFLUENT ACROSS THE EASTERN CONUS...UPPER LEVEL LOW PUSHING EAST THRU THE ST LAW RVR VALLEY WITH ANOTHER SW CONUS SHRTWV PULLING OUT AND WEAKENING AS IT MOVES TO THE NORTHEAST. LARGE SFC HIGH ENTRENCHED ACROSS THE GREAT LAKES/OH AND MS VALLEYS INTO TUESDAY...WITH SOME UPPER LEVEL RIDGING BUILDING ACROSS THE REGION TUESDAY INTO WEDNESDAY WITH ANOTHER UPPER LEVEL LOW OVER THE SW CONUS. BELOW NORMAL TEMPS EXPECTED MONDAY...SLIGHTLY WARMER AND NEAR SEASONAL VALUES OF LOWER TO MID 30S FOR HIGHS. DRY THRU THE PERIOD...A SMALL CHANCE OF LAKE EFFECT ACROSS THE FAR NORTH EARLY MONDAY. MID RANGE MODELS HAVING SOME ISSUES THRU THE END OF THE PERIOD...SIGNIFICANT DISAGREEMENTS WITH RESPECT TO THE STRENGTH AND TIMING BUT THE LATEST GFS AND THE ENSEMBLE MEANS HAVE BEEN SHOWING SOME SIGNIFICANT WINTRY POTENTIAL TOWARDS THE END OF THE MONTH. FIRST POTENTIAL SIGNIFICANT SYSTEM WILL BE WEDNESDAY NIGHT INTO THURSDAY TIMEFRAME. CUT-OFF LOW PUSHES EAST INTO THE RIDGE...POSSIBLE NEG TILT WITH SFC LOW MOVING FROM THE LOWER MS VALLEY INTO THE REGION. MOISTURE SHOULD NOT BE A CONCERN WITH THE GULF APPEARING TO BE OPEN...PWATS AT OR MORE THAN DOUBLE NORMAL FOR THE TIME OF YEAR. THE TRACK STILL UNCERTAIN...WILL LIMIT THE DETAILS...BUT CURRENT BUFKIT AND MODEL THERMAL PROFILES WOULD SUGGEST ALL SNOW. HAVE UPPED POPS TO 50 THRU THE PERIOD WITH HIGHER CONFIDENCE THAT A SYSTEM WILL BE THERE...BUT LOWER CONFIDENCE ON TRACK AND P-TYPE AS THE MODELS THIS SEASON HAVE HAD SOME SIGNIFICANT SHIFTS OVER TIME OF UP TO 300-500 MILES. ANOTHER DIGGING UPPER LEVEL LOW INTO THE SOUTHWEST LATE IN THE WEEK...THURSDAY INTO FRIDAY...WILL START KICK OUT AND WILL ALLOW FOR THE SECOND POTENTIAL WINTER SYSTEM BY THE WEEKEND. PRECIP COULD START AS SOON AS FRI NIGHT/SATURDAY...WITH TRACK AND P-TYPE HIGHLY UNCERTAIN...STILL 6-7 DAYS OR MORE OUT MUCH TO CHANGE MOST LIKELY. STRONG MODEL SUPPORT FROM THE GFS ENSEMBLES. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...FISHER LONG TERM...SCHOTT in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 1214 PM EST FRI DEC 21 2007 .UPDATE... UPDATED GRIDS/ZONES EARLIER TO SLOW DOWN ARRIVAL OF FOG BASED ON TRENDS AND RUC40 DATA. HIGHER DEWPTS SLOWLY COMING IN BUT LOOK TO BE DELAYED UNTIL LATER TODAY INTO TONIGHT. HAVE PUSHED BACK MENTION OF DENSE FOG TO TONIGHT WHEN MOISTURE WILL INCREASE DRAMATICALLY AS LOW LEVEL FLOW BEGINS TO INCREASE. HAVE JUST WENT PATCHY DENSE AT THIS POINT. TEMPS STILL LOOK OK FOR NOW SO HAVE LEFT THEM AND THE REMAINDER OF THE GRIDS ALONE. && .AVIATION... AS MENTIONED IN UPDATE...HAD PREVIOUSLY SLOWED DOWN ARRIVAL OF MAINLY LOWER VSBYS. WILL NEED TO CONTINUE THIS TREND WITH GENERAL MVFR VSBY/IFR CIGS STARTING THE PERIOD THEN DROPPING TO LIFR CONDITIONS BY EARLY EVENING AT KSBN. MAY BE A BIT SLOWER ARRIVAL AT KFWA. ONCE THESE ARRIVE...LITTLE OVERALL CHANGE EXPECTED UNTIL SATURDAY AS WINDS BEGIN TO INCREASE AND ALLOW FOR BETTER MIXING AND INCREASE IN HGTS/VSBYS. && .PREV DISCUSSION... /ISSUED 640 AM EST FRI DEC 21 2007/ SHORT TERM... TODAY AND TONIGHT LOTS OF LOW LEVEL MOISTURE...DRIZZLE AND FOG IS THE STORY FOR TODAY AND TONIGHT. WARM AIR ADVECTION WILL CONTINUE TODAY. THE SNOW COVER ACROSS THE AREA WILL KEEP TEMPERATURES NEAR THE SURFACE COOLER THAN UP ABOVE...SETTING UP A DECENT INVERSION TODAY. THIS WILL HELP TO KEEP THE MOISTURE FROM THE MELTING SNOW TODAY TRAPPED NEAR THE SURFACE...RESULTING IN FOG ACROSS THE AREA. WITH DECENT MOISTURE UP TO ABOUT 5KFT TO 7KFT...DRIZZLE IS ALSO POSSIBLE. THE LARGE DEWPOINT DEPRESSIONS IN THE CWA THIS NIGHT HAVE KEPT THE LIGHT RAIN/DRIZZLE OFF TO THE WEST...BUT THE ATMOSPHERE IS EXPECTED TO BECOME MORE AND MORE SATURATED AS THE HOURS PASS BY...AND EVENTUALLY THE LOWER CEILINGS AND VISIBILITIES WILL MOVE INTO THE CWA. JUST WHEN THESE LOWER CONDITIONS WILL MOVE IN AND WHERE THEY WILL DROP THE MOST HAS BEEN THE TRICKIEST PART OF THE FORECAST FOR TODAY. VISIBILITIES ARE STILL UP ACROSS THE CWA SO HAVE SLOWED DOWN THE FOG MOVING INTO/FORMING IN THE AREA. ALSO TO NOTE WHERE TEMPERATURES ARE AT FREEZING AND BELOW...MAINLY IN THE NORTHEASTERN TO EASTERN PARTS OF THE CWA...EARLY THIS MORNING ANY DRIZZLE WILL BE FREEZING DRIZZLE. BUT TEMPERATURES ARE EXPECTED TO WARM UP ABOVE THE FREEZING MARK ACROSS THE ENTIRE CWA BY MID MORNING. TRICKY YET AS TO HOW FAR EASTWARD AREAS OF DENSE FOG COULD MAKE IT...BUT FOR RIGHT NOW JUST HAVE THE WESTERN PART OF THE CWA SEEING AREAS OF DENSE FOG FORM THIS MORNING. THE WARM AIR ADVECTION WILL CONTINUE THROUGH THIS EVENING AND TONIGHT...RESULTING IN NON DIURNAL TEMPERATURES FOR TONIGHT. TEMPERATURES WILL EITHER REMAIN FAIRLY STEADY OR SLOWLY INCREASE A FEW DEGREES THROUGHOUT THE NIGHT. THEREFORE THIS DAY/S LOW TEMPERATURES ARE EXPECTED TO OCCUR EARLY THIS MORNING. THE ATMOSPHERE IS GOING TO REMAIN FAIRLY WELL SATURATED IN THE LOWER LEVELS THROUGH TONIGHT WITH THE LOW LEVEL INVERSION CONTINUING THROUGH TONIGHT. THEREFORE AREAS OF FOG AND DRIZZLE ARE CONTINUED FOR TONIGHT. LONG TERM... SATURDAY THROUGH THURSDAY MAIN EMPHASIS ON WEST COAST SYSTEM TO ARRIVE SAT NIGHT. NAM FAVORED SOLN WITH INITIALIZATION OF COMPLEX WESTERN TROF WITH ALBERTA ENERGY AND STRATOSPHERIC INTRUSION ACRS WCENTL NV/SOCAL AT 00 UTC. RATHER BROAD TONGUE OF 40F PLUS DEWPOINTS ALREADY POISED NORTH OF OHIO RIVER AND WITH SEVERAL HOURS OF ADDITIONAL SNOWMELT AND ADVECTIVE COMPONENT WILL AID IN TOTAL MOISTURE INCREASE AHEAD OF STRONG FULL LATITUDINAL SYSTEM THAT WILL UNDERGO RAPID INTENSIFICATION. FROM F36-60 RAPID ML HEIGHT FALLS ON ORDER OF 160-190/12 HRS REFLECTS NEAR BOMBO SURFACE CYCLOGENESIS AS RED RIVER VLY SFC LOW AT F36/12 UTC SAT NEAR RED RIVER VLY TX SURGES NE TO 1001 MB CNTL IL THEN TO 987MB OVER CNTL UP. PWAT APPROACH 1 INCH WITH 7.5-7.8 G/KG IN 1000-850MB LAYER WITH TREMENDOUS LOW LEVEL KINEMATICS UPPED POPS TO 90 PERCENT WITH STRONG SIGNALS/MOISTURE...CONSIDERED ISOLD TSRA THOUGH OVERALL CHANCES SLIGHT. DRY SLOT BEHIND FRONT QUICKLY BRING POPS DOWN TO CHC CATEGORY...AND PTYPE QUICKLY TO SNOW LATE SATURDAY NIGHT WEST IN STRONG/DEEP CAA WITH ABRUPT CHANGEOVER THOUGH LITTLE IF ANY ACCUM EXPECTED. RAMPED WINDS SAT THRU SUN NIGHT...ESP SUN GIVEN INTENSITY OF SFC LOW. BEYOND LITTLE CHANGE MADE. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...SMALL CRAFT ADVISORY FROM 1 AM SUNDAY TO 7 AM EST MONDAY FOR LMZ043-046. && $$ SHORT TERM...LOTHAMER LONG TERM...MURPHY AVIATION/UPDATE...FISHER in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GOODLAND KS 200 PM MST FRI DEC 21 2007 .DISCUSSION...FORECAST CONCERNS ARE ON WINDS AND SNOW TONIGHT THROUGH EARLY IN THE DAY SATURDAY. MORE SNOW EXPECTED AGAIN CHRISTMAS DAY INTO WEDNESDAY WITH ANOTHER THURSDAY INTO FRIDAY. .SHORT TERM (TONIGHT-MONDAY NIGHT)... TONIGHT-SATURDAY...UPPER TROUGH AXIS CURRENTLY EXTENDING ALONG THE CONTINENTAL DIVIDE WILL MOVE ACROSS THE AREA OVERNIGHT AND BY 18Z BE EAST OF THE AREA. THE COMBINATION OF 850-500MB MOISTURE/MID LEVEL FRONTOGENESIS AND 250 JET DIVERGENCE WILL FAVOR HIGHEST POPS ACROSS SOUTHERN 2/3 OF THE AREA...HIGHEST ACROSS THE FAR SOUTH. TOTAL ACCUMULATIONS IN THIS AREA WILL RANGE FROM 1 TO 3 INCHES...HIGHEST SOUTH. LATEST NAM/RUC SHOWING SOME ORGANIZATION TO THE SNOW ACROSS INTERSTATE 70 WITH A LULL IN SNOW IN THE DOWNSLOPE AREAS OF CHEYENNE COUNTY COLORADO AND WALLACE KS. WILL ISSUE A SNOW AND BLOWING SNOW ADVISORY AS A RESULT FROM 03Z TONIGHT THROUGH 18Z SATURDAY. ELSEWHERE...WILL UPDATE THE HWO TO TALK ABOUT THE SNOW AND POTENTIAL FOR BLOWING SNOW OUTSIDE THE ADVISORY AREA. WILL KEEP SOME POPS MENTIONED ACROSS THE FAR EAST/SOUTHEAST THROUGH 18Z SATURDAY GIVEN TIMING DIFFERENCES AMONGST THE MODELS WITH REGARD TO HOW FAST THE SYSTEM LEAVES THE AREA. GFS/09Z SREF THE SLOWER OF THE MODELS WITH THE NAM/NGM A BIT QUICKER. AFTER 18Z IT SHOULD BE PRETTY MUCH OVER WITH...EXCEPT THE WIND. ONCE THE SNOW ENDS WE STILL HAVE TO DEAL WITH STRONG WINDS JUST OFF THE SURFACE AND INCREASING SUNSHINE AS THE SYSTEM MOVES EAST. QUESTION BECOMES WHETHER THE WIND WILL FULLY MIX TO THE SURFACE GIVEN EXISTING SNOW COVER AND EXPECTED LIGHT ACCUMULATIONS. FOR NOW WILL NOT ISSUE A WIND ADVISORY FOR THE 18Z- 22Z TIME FRAME GIVEN THE CONCERN LISTED ABOVE. SATURDAY NIGHT-SUNDAY...WILL HAVE A BRIEF PERIOD OF CLEAR SKIES BEFORE MID AND UPPER LEVEL MOISTURE SPREADS ACROSS THE AREA FROM THE NORTHWEST AFTER MIDNIGHT AS ANOTHER QUICK MOVING SYSTEM MAKES ITS WAY TOWARD THE AREA. COLUMN STARTS TO SATURATE IN THE 850-500 LAYER DURING THE DAY SUNDAY FROM NORTHWEST TO SOUTHEAST. DESPITE THE INCREASE IN MOISTURE DYNAMICS AND LIFT ARE LACKING...THUS WILL MAINTAIN A NO POP FORECAST. SUNDAY NIGHT-MONDAY NIGHT...WELL ORGANIZED UPPER DISTURBANCE EMBEDDED IN A DEEP AND COMPACT TROUGH WILL MOVE SOUTH THROUGH THE FRONT RANGE AND EASTERN PLAINS OF COLORADO INTO SOUTHWEST/SOUTH CENTRAL KANSAS BY THE END OF THE PERIOD. LOOKS LIKE THIS SYSTEM WILL SLIDE JUST FAR ENOUGH WEST AND SOUTH OF THE AREA TO KEEP SILENT POPS IN THE FORECAST...GENERALLY ACROSS THE SOUTHWEST PART OF THE AREA. WILL NEED TO KEEP AN EYE ON IT FOR POSSIBLE INCREASE IN POPS FOR SOME LIGHT SNOW...AGAIN GENERALLY ACROSS THE SOUTHWEST 1/3 OF THE AREA SUNDAY NIGHT. LITTLE TO TALK ABOUT MONDAY BUT MONDAY NIGHT FEATURES ANOTHER TROUGH AND INCREASING MOISTURE/CLOUDINESS MOVING TOWARD THE AREA FROM THE NORTHWEST. .LONG TERM (TUESDAY-FRIDAY)... GENERALLY FOLLOWED ECMWF GUIDANCE FOR THE EXTENDED AS IT HAS SHOWN THE BEST RUN TO RUN CONTINUITY AND ALSO RECEIVES SUPPORT FROM THE CANADIAN ENSEMBLE MEAN. APPEARS THE ACTIVE SYNOPTIC SCALE FLOW PATTERN WILL CONTINUE WITH A SERIES OF SHORTWAVE TROUGHS TRAVERSING THE CWA DURING THIS TIME FRAME. THE FIRST SYSTEM LOOKS TO ARRIVE ON CHRISTMAS DAY AS THE H5 RIDGE SLIDES OFF TO THE EAST. WHILE IT APPEARS MAIN AREA OF H85-H7 FRONTOGENESIS WILL STAY SOUTH OF OUR CWA...IT WILL BE CLOSE ENOUGH TO ALLOW AT LEAST SOME LIGHT SNOW TO FALL. WITH H85 WINDS AOB 20KTS...TRAVEL ISSUES DO NOT APPEAR TO BE A CONCERN AT THIS TIME. EC IS SLOWER IN MOVING THE SYSTEM OUT OF THE AREA SO HAVE SLIGHT CHC TO CHC POPS CONTINUING INTO WEDNESDAY. APPEARS WE WILL HAVE A VERY SHORT BREAK BEFORE THE NEXT SHORTWAVE TROUGH MOVES IN AROUND MIDDAY ON THURSDAY. DYNAMICS APPEAR A LITTLE BETTER FOR US WITH THIS STORM AS THE EC TRACKS THE H5 OPEN WAVE TROUGH OVER SOUTHWEST KANSAS. WENT WITH SLIGHT CHC POPS FOR NOW BUT WILL NEED TO MONITOR FUTURE RUNS FOR ANY NECESSARY ADJUSTMENTS. WILL SEE WEAK RIDGING START TO SET BY LATE FRIDAY AS THE SHORTWAVE TROUGH SHIFTS OFF TO THE NORTHEAST AND INTO THE WESTERN GREAT LAKES REGION. && .AVIATION... FOR THE 00Z TAF...NORTHWEST WINDS OF 25 TO 30 KTS WITH HIGHER GUSTS WILL BLOW THROUGH THE TAF PERIOD. SNOWFALL WILL BEGIN IN THE KGLD AREA SHORTLY BEFORE 06Z WHILE KMCK WILL NOT START TIL THE 06-09Z TIME FRAME. THE COMBINATION OF THE WIND AND SNOW WILL PRODUCE REDUCED VISIBILITIES IN SNOW AND BLOWING SNOW THROUGH ROUGHLY 12-15Z SATURDAY MORNING. FROM 15Z-22Z WINDS WILL REMAIN IN THE 20 TO 30 KT RANGE THEN QUICKLY FALL OFF WITH A GRADUAL CLEARING FROM WEST TO EAST. CIGS WILL BE IN THE MVFR/IFR RANGE THROUGH THE PRECIPITATION DURATION. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...SNOW AND BLOWING SNOW ADVISORY FROM 8 PM MST /9 PM CST/ THIS EVENING TO 11 AM MST /12 PM CST/ SATURDAY FOR KSZ013>016- 028-029-041-042. NE...NONE. CO...SNOW AND BLOWING SNOW ADVISORY FROM 8 PM THIS EVENING TO 11 AM MST SATURDAY FOR COZ091. && $$ DDT/FOLTZ/BURTIS ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DODGE CITY KS 254 PM CST FRI DEC 21 2007 .DISCUSSION... DAYS 1-2... CONCERNS HAVE INCREASED THIS FORECAST PACKAGE REGARDING DANGEROUS SNOW AND BLOWING/DRIFTING SNOW THREAT...TO THE POINT THAT BLIZZARD WARNING IS NECESSARY ACROSS PORTIONS OF SOUTHWEST KANSAS. EARLY AFTERNOON WATER VAPOR LOOP WITH RUC ANALYSIS OVERLAY SHOWS CLUSTER OF MID LEVEL PV MAXIMA ACROSS FOUR CORNERS REGION. PRIMARY VORT MAX WAS JUST ENTERING WESTERN NEW MEXICO WITH PERSISTENT LIGHTNING STRIKES NOTED AS WELL. THE PRIMARY MID LEVEL VORT WILL CONTINUE TO ROUND THE BASE OF THE TROUGH AND EJECT NORTHEASTWARD DURING THE EVENING HOURS...SPAWNING SUBSTANTIAL LOWER TROPOSPHERIC DEVELOPMENT TO THE SOUTH OF DDC CWA ACROSS THE PANHANDLES. LATEST 12HR FORECAST OF RUC AND NAM SHOW FAIRLY STRONG CYCLOGENESIS IN THE H85-7 LAYER ALONG THE "GOLDEN PATH" FOR SOUTHWEST KANSAS HEAVY PRECIPITATION EVENT. AS A MATTER OF FACT...THE LATEST RUC AND NAM 18Z RUNS SUGGEST MORE LOWER TROPOSPHERIC DEVELOPMENT AND SUBSEQUENTLY STRONGER LIFT FOR HEAVIER PRECIPITATION. THE 18Z NAM SHOWS MORE QPF AS WELL AS A RESULT (ON THE ORDER OF 5 TO 8 INCHES OVER THE SOUTHWESTERN COUNTIES). THE GREATEST H7 FRONTOGENESIS ASSOCIATED WITH THE CYCLONE WILL BE FOCUSED MAINLY ALONG AND SOUTH OF THE ARKANSAS RIVER. IT STILL APPEARS THAT THE DURATION OF SNOWFALL AT ANY ONE LOCATION WILL BE AROUND 6 TO 8 HOURS ON AVERAGE. DURING THIS TIME FRAME...SUBSTANTIAL SURFACE WINDS WILL PREVAIL WITH SUSTAINED NORTH WINDS ON THE ORDER OF 25 TO 35 MPH. GUSTS ARE EXPECTED TO BE FREQUENTLY IN THE 35 TO 45 MPH RANGE...AND GIVEN THIS...HAVE DECIDED TO UPGRADE THE WINTER STORM WATCH TO A BLIZZARD WARNING FOR ROUGHLY SYRACUSE TO JETMORE TO KINSLEY...SOUTH TO THE OKLAHOMA BORDER. NORTH AND EAST OF THIS BLIZZARD WARNING WILL GO WITH A SNOW AND BLOWING SNOW ADVISORY. IN THE BLIZZARD WARNING AREA...AM EXPECTING WIDESPREAD 3 TO 5 INCHES WITH SOME LOCAL 6 OR 7 INCH AMOUNTS POSSIBLE...ALTHOUGH MEASURING THE SNOW WILL BE A DIFFICULT ENDEAVOR TO SAY THE LEAST. IN THE SNOW/BLOWING SNOW ADVISORY AREA...WILL GO WITH MAINLY 1 TO 3 INCHES WITH THE 3-HR WINDOW OF BELOW 1/4 MILE VISIBILITY LESS CERTAIN TO MEET BLIZZARD CRITERIA. TRAVEL IS EXPECTED TO BE NEARLY IMPOSSIBLE DURING THE OVERNIGHT HOURS AND EARLY SATURDAY MORNING ACROSS MUCH OF SOUTHWEST KANSAS...AND WILL EMPHASIZE THIS IN THE UPDATED WSW PRODUCT. IF THERE IS A SILVER LINING TO THIS STORM IT IS THE FACT THAT IT WILL BE AT ITS HEIGHT DURING THE OVERNIGHT AND EARLY MORNING HOURS SUCH THAT TRAVEL WILL LIKELY BE LIMITED AS IT IS -- THAT SAID...IF THE SYSTEM EVOLVES AND EJECTS JUST A FEW HOURS SLOWER...THIS WILL PUT THE BULK OF SATURDAY MORNING/THROUGH MIDDAY IN EXTREMELY HAZARDOUS CONDITIONS ACROSS MUCH OF THE AREA. THE WINDS WILL NOT DECREASE MUCH AT ALL THROUGH THE AFTERNOON...SO EVEN ONCE THE SNOW ENDS...LINGERING BLOWING AND DRIFTING WILL REMAIN A PROBLEM. THE LOW SHIFTS RAPIDLY EAST BY SAT AFTERNOON AND EVENING...WITH MUCH LIGHTER WESTERLY WINDS TAKING OVER. DOWNSLOPE FLOW SHOULD HELP ERODE COLD AIR FROM THE LOWER TROPOSPHERE...HOWEVER IF THERE IS SUBSTANTIAL NEW SNOW COVER...TEMPERATURES WILL BE DIFFICULT TO RECOVER SUNDAY (ABOVE THE LOWER 30S). -UMSCHEID DAYS 3-7... MAIN FORECAST CHALLENGES IN THIS EXTENDED PERIOD CONTINUE TO BE CHANCES OF SNOW WITH SEVERAL PROGRESSIVE SHORTWAVES INTO FRIDAY. AN UPPER SHORTWAVE TROUGH WILL BRING A CHANCE FOR SNOW ON MONDAY FOLLOWED BY A STRONGER WAVE ON TUESDAY NIGHT INTO WEDNESDAY, THEN ANOTHER ON THURSDAY INTO FRIDAY MORNING. IT IS MUCH TOO EARLY TO TELL HOW MUCH SNOW WITH ANY OF THESE SYSTEMS HOWEVER THE ONE ON MONDAY DOES NOT LOOK LIKE TOO MUCH ACCUMULATION. MODELS HAVE COME TO A GENERAL AGREEMENT ON THE POSITION OF THESE SHORTWAVES BUT THE EXACT STORM TRACK AND UPPER LIFT WITH EACH ARE STILL NOT IN THE REALM OF PREDICTION THEREFORE SNOW AMOUNTS WILL BE HARD TO GUESS. STILL SOME ACCUMULATIONS ARE PROBABLE WITH EACH SYSTEM ESPECIALLY THE LATTER ONES. AS FOR TEMPERATURES HIGHS SHOULD ONLY BE IN THE 30S WITH LOWS FROM THE UPPER TEENS TO LOW 20S. LOOKS LIKE A POSSIBLE WARMING TREND BY AROUND NEW YEARS. .AVIATION... VFR CONDITIONS WILL RAPIDLY DETERIORATE TO IFR BY AROUND 06Z TONIGHT AS SNOW AND BLOWING SNOW BEGINS WITH WINDS PICKING UP TO 25 TO 35KTS. THE SNOW COULD BECOME HEAVY ENOUGH BY 8Z TO 14Z WITH STRONG WIND GUSTS TO 45KTS WITH LIFR CONDITIONS. LOOK FOR RAPID IMPROVEMENT AROUND 18Z SATURDAY WITH WINDS GRADUALLY DECREASING WITH SNOW MOVING OFF TO THE EAST. VFR CONDITIONS SHOULD RETURN AFTER 20Z SATURDAY. && .PRELIMINARY POINT TEMPS/POPS... DDC 23 28 15 37 / 90 90 0 0 GCK 21 28 12 37 / 80 80 0 0 EHA 22 28 13 37 / 90 80 0 0 LBL 23 28 14 38 / 90 90 0 0 HYS 22 26 14 34 / 80 90 0 0 P28 27 30 16 36 / 80 90 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... SNOW AND BLOWING SNOW ADVISORY FROM MIDNIGHT TONIGHT TO 12 PM CST SATURDAY FOR KSZ030-031-043>046-065-066-081-090. BLIZZARD WARNING FROM MIDNIGHT CST /11 PM MST/ TONIGHT TO 12 PM CST /11 AM MST/ SATURDAY FOR KSZ061>064-074>080-084>089. && $$ FN25/06/06 ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 145 PM EST FRI DEC 21 2007 .AVIATION...A LARGE AREA OF HIGH PRESSURE CURRENTLY LOCATED OVER QUEBEC...WILL KEEP SOUTHEAST FLOW OVR THE GREAT LAKES REGION THIS AFTERNOON INTO SATURDAY. THE SOUTHEAST FLOW OVR LAKE HURON WILL KEEP AT LEAST A BKN LAKE INDUCED LOW CLOUD DECK...OVER THE APN TAF SITE INTO TONIGHT. THE REST OF NRN LWR WILL SEE MVFR/VFR CONDS INTO THIS EVENING. LATER TONIGHT WARMER AIR WILL BEGIN TO MOVE INTO THE GREAT LAKES REGION...FROM A STORM SYSTEM MOVING INTO THE WRN LAKES. THE WARMER AIR MOVING OVER THE SNOW PACK ACROSS NRN MICHIGAN...WILL GENERATE LOW CLOUDS/FOG AND DRIZZLE. THIS WILL GENERATE IFR CIG AND VSBY CONDS OVERNIGHT ACROSS THE NRN MI TAF SITES. LIFR CIGS AND VSBYS ARE EXPECTED OVER NRN MICHIGAN SATURDAY BTW 12Z AND 18Z...AS WARM AIR CONTS TO PUSH NORTH INTO THE REGION... GENERATING LOW CLOUDS/DRIZZLE/RAIN AND FOG. SWR && .UPDATE...ISSUED 1117 AM FRI DEC 21 LITTLE TO NONE OF THE RETURNS ON THE RADAR ARE MAKING IT TO THE GROUND. SO HAVE SLASHED THE POPS FOR THE REST OF THE DAYTIME AS MID LEVEL DRY AIR CONTINUES OVER THE REGION. SO FAR, THE NAM AND RUC HAVE THE BETTER HANDLE ON THE 850 MB MOISTURE MOVING IN WHICH LOOKS THE BEST. SO HAVE SCT SPRINKLES IN THE FORECAST FOR THE AFTERNOON. BASED ON THE LOWER CLOUDS (AROUND 1500 FEET) AT ANJ, AS WELL AS BELOW FREEZING TEMPERATURES, PUT PATCHY ZL- IN FOR E UPPER WITH IT CHANGING TO SCT SPRINKLES FOR THE AFTERNOON AS THE TEMEPERATURES WARM AND THE DRY AIR PUSHES THE LOWER CLOUDS OUT. OTHERWISE, TEMPERATURES AND WINDS LOOK GOOD. LUTZ && .PREV DISCUSSION... /ISSUED 738 AM EST FRI DEC 21 2007/ AVIATION...BKN MVFR CIGS ANTICIPATED ACROSS PORTIONS OF NRN LOWER MICHIGAN THIS MORNING...PARTICULARLY AT PLN/APN WITH SE FLOW OFF LAKE HURON PUSHING LOW CLOUD COVER INTO THOSE AREAS. OTHERWISE... SPOTTY ELEVATED SHOWER ACTIVITY WILL BE FOUND ACROSS THE REGION TODAY ALONG ADVANCING NOSE OF WARM AIR AND MOISTURE ALOFT. LOWERING CIGS/VSBYS ALONG WITH AREAS OF DRIZZLE ANTICIPATED TONIGHT LEADING TO MVFR AND EVENTUALLY IFV CONDITIONS AT ALL THREE TAF LOCATIONS. ADAM && DISCUSSION...ISSUED AT 509 AM. LONGWAVE TROUGH PATTERN PREVALENT ACROSS NORTH AMERICA WITH A MYRIAD OF AMPLIFYING SHORTWAVES MOVING THROUGH THE FLOW. MOST SIGNIFICANT OF THESE WAVES...AND WHAT WILL BE THE MAIN FOCUS IN THE FORECAST FOR THE WEEKEND...BEGINNING TO TRAVERSE THE EXPANSE OF THE ROCKIES. ONE PIECE OF ENERGY NOW DIGGING INTO THE SW STATES WHILE ANOTHER WAVE IN WESTERN CANADA. OPERATIONAL NAM/GFS SOLUTIONS AS WELL AS THE GFS ENSEMBLES AND ECMWF SOLUTION ALL STILL DEPICTING A TROUGH MERGER BETWEEN THESE TWO SYSTEMS OVER THE UPPER MIDWEST... LATE SATURDAY THROUGH SUNDAY...AND ASSOCIATED RAPID SPIN-UP OF A DEEP SFC LOW OVER NRN MICHIGAN. IN THE MEANTIME...STILL PLENTY TO THINK ABOUT IN THE SHORT TERM. BUILDING MID LEVEL RIDGING DOWNSTREAM OF THIS SYSTEM AND INCREASING LOW LEVEL WARM/MOISTURE ADVECTION INTO THE WESTERN GREAT LAKES EXPECTED TO DOMINATE TODAY THROUGH MUCH OF SATURDAY...WITH CHANCES FOR LIGHT SHOWER AND DRIZZLE/FREEZING DRIZZLE ACTIVITY THE MAIN FORECAST ISSUES. TODAY AND TONIGHT...MID CLOUD COVER AND ELEVATED RADAR RETURNS ALONG ADVANCING MID LEVEL MOISTURE GRADIENT CONTINUE TO PRESS INTO THE REGION FROM THE WEST-SOUTHWEST. HOWEVER...MORE WIDESPREAD LOW CLOUD COVER AND DRIZZLE ACTIVITY STILL WAY BACK ACROSS CENTRAL WISCONSIN INTO WESTERN UPPER MICHIGAN...ALTHOUGH SOME STRATUS HAS DEVELOPED/ EXPANDED ACROSS THE HIGHER TERRAIN OF NE LOWER MICHIGAN OVERNIGHT. THUS FAR...RADAR RETURNS LOOK CONVECTIVE IN NATURE AS AXIS OF STEEPER MID LEVEL LAPSE RATES PRESSES OUT OF WISCONSIN. BUT OUTSIDE OF A COUPLE OBS IN SW LOWER MICHIGAN SHOWING PRECIP OVERNIGHT... NOTHING REALLY GETTING TO THE GROUND THUS FAR. HOWEVER...RADAR RETURNS HAVE INCREASED IN COVERAGE OVER THE LAST HOUR OR SO AND PROBABLY NEED TO CARRY SOME SORT OF PRECIP THIS MORNING AS THE MOISTURE AXIS AND STEEPER LAPSE RATES LIFT UP THROUGH THE REGION. QUESTION IS...WHAT WILL IT BE? FORECAST NAM SOUNDINGS FOR THIS MORNING DEPICT ABOVE FREEZING LAYER ALOFT NOSING INTO THE REGION. BUT GIVEN THE DRY LOW LEVEL AIR STILL IN PLACE AND CONVECTIVE NATURE TO THE PRECIP...THINK ANYTHING THAT DOES REACH THE GROUND WILL BE OF THE FROZEN VARIETY. TIME WILL TELL OF COURSE BUT FOR NOW WILL CARRY CHANCY SNOW SHOWER WORDING THROUGH MIDDAY. THEN BY LATER THIS AFTERNOON THROUGH SATURDAY...LOW LEVEL MOISTURE FINALLY GETS SHOVED INTO THE REGION LATER THIS AFTERNOON AND ESPECIALLY THIS EVENING...SETTING THE STAGE FOR AREAS OF FOG AND DRIZZLE TO DEVELOP. HAVE NOT CHANGED MUCH TO THE GOING FORECAST IN THIS REGARD OTHER THAN SLOWING DOWN THE DEVELOPMENT OF WIDESPREAD FOG AND DRIZZLE UNTIL LATER IN THE EVENING...AND ADDING FREEZING DRIZZLE TO SOME OF THE HIGHER TERRAIN AREAS WHERE TEMPS WILL LIKELY HOVER AROUND FREEZING. SOUPY CONDITIONS THEN EXPECTED TO PERSIST THROUGH SATURDAY ALTHOUGH CONTINUING WARM ADVECTION/MOISTENING ALOFT MAY BRING BETTER CHANCES FOR MEASURABLE PRECIP INTO THE REGION. IN ANY EVENT...A DREARY...DAMP COOL DAY LOOKS ON TAP FOR NRN MICHIGAN WITH TEMPS SLOWLY REACHING THE 35 TO 40 DEGREE MARK. SATURDAY NIGHT THROUGH SUNDAY...TROUGH MERGER SLATED TO TAKE SHAPE OVER THE UPPER MIDWEST BRINGING ABOUT A RAPID SPIN UP OF A DEEP SFC LOW NEARLY OVER THE STATE...TRACKING UP ACROSS EASTERN LAKE SUPERIOR ON SUNDAY. VERY STRONG DYNAMICS COME INTO PLAY IN THIS SCENARIO AND AT THIS POINT CATEGORICAL POPS ARE JUSTIFIED SATURDAY NIGHT INTO SUNDAY WITH A GOOD SWATH OF PRECIP RUNNING UP THROUGH THE REGION. ALSO AT THIS POINT...MAINLY RAIN ANTICIPATED SATURDAY NIGHT WITH THE LOW DEEPENING JUST WEST OF THE REGION AND +4C OR BETTER H8 AIR GETTING SHOVED UP THROUGH EASTERN UPPER MICHIGAN. A RAPID CHANGEOVER TO SNOW AS WELL AS SOUTHWEST-WEST LAKE EFFECT/ENHANCED SNOW SHOWERS EXPECTED TO FOLLOW SUNDAY AS CORE OF -14C OR COLDER H8 AIR ROTATES AROUND INTO LOWER MICHIGAN. A LOT OF WIND AND THE POTENTIAL FOR HEAVY SNOW/NEAR BLIZZARD CONDITIONS WITH THIS SYSTEM SUNDAY AND SUNDAY NIGHT WILL LIKELY WARRANT HEADLINES IN THE NEXT 1 TO 2 FORECAST CYCLES. TBA CHRISTMAS EVE AND CHRISTMAS...LAKE AGGREGATE TROUGHING WILL CONTINUE ACROSS THE GREAT LAKES THROUGH THE DAY ON MONDAY...BEFORE 850MB TEMPERATURES WARM TO AROUND -5C BY 00Z MONDAY. WITH SURFACE TROUGH ROTATING ACROSS NORTHERN MICHIGAN EARLY MONDAY MORNING...EXPECT TO SEE FAIRLY WIDESPREAD SNOW SHOWERS AND BLOWING SNOW. DURING THE DAY ON MONDAY...DEEPER MOISTURE STARTS TO PULL OUT AND PRECIPITATION SLOWLY BECOMES PURELY LAKE EFFECT. FINALLY...AS THE BOUNDARY LAYER WARMS...LAKE EFFECT WILL END MONDAY EVENING. HIGH PRESSURE WILL BECOME ESTABLISHED OVER THE GREAT LAKES BY CHRISTMAS DAY...PROVIDING A FAIRLY PLEASANT DAY WITH HIGHS WARMING INTO THE LOWER 30S UNDER PARTLY SUNNY SKIES AFTER STARTING THE DAY IN THE TEENS. KAS && .APX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LMZ341. LH...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LHZ346. LS...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS AFTERNOON FOR LSZ321. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BISMARCK ND 337 PM CST FRI DEC 21 2007 .SHORT TERM... THE FCST IS CERTAINLY COMPLICATED TODAY...BUT ONCE AGAIN SPLIT FLOW ALOFT HAS SHOWN ITSELF NOT TO BE A MAJOR SNOW PRODUCER IN THIS AREA. THE 12Z GFS GETS OUR NOD PER ITS INITIALIZATION OF THE UPPER LOW IN ALBERTA AT 12Z AND ITS HANDLING OF THE PRECIP BAND WORKING INTO CENTRAL ND AS OF 21Z. HOWEVER...ITS QPF AMOUNTS ARE MUCH TOO HIGH WITH LACK OF MORE FOCUSED DEEP LAYERED ASCENT...AND HENCE WE HAVE CUT THIS BACK. WINTER WEATHER HEADLINES REMAIN THE CONCERN INTO THE EVE WITH TRAVEL IMPACTS...BUT TEMPS BECOME THE MAIN ISSUE OVER THE WEEKEND. LOOKING THROUGH MODEL DIAGNOSTICS TELLS US WHY SNOW HAS NOT BEEN AS INTENSE AS QPF WOULD SHOW...WITH THE PRIMARY QG FORCING ACROSS THE FA RATHER DISJOINTED...AND FOCUSED IN WSTRN SD WHERE CLOUD TOPS HAVE COOLED MOST TODAY. WE ALSO LACKED JET DYNAMICS WITH A DOMINANT SRN STREAM...AND ISENTROPIC LIFT WAS ALSO MINIMIZED. MOST UPWARD VERTICAL MOTION HAS COME VIA DIFFERENTIAL PVA ALOFT COURTESY THE SE-MOVING UPPER LOW NOW IN CENTRAL SASKATCHEWAN. THERMAL FORCING IS NOT FAVORABLE...HENCE THE POOR DEEP LAYER Q-VECTOR RESPONSE. THE 12Z GFS AND MORE RECENT RUC RUNS HAVE HOWEVER CAUGHT THE BAND OF SNOW SPREADING JUST AHEAD OF THE PRIMARY CAA INTO CENTRAL ND. WE GOT 1-3 INCHES OF SNOW IN THIS BAND AND SINCE IT IS PROGRESSIVE DO NOT EXPECT MUCH MORE THAN THAT. SNOW RATIOS WILL WILL DROP AS STRONG 925-850MB CAA CONTINUES INTO THE EVE...BUT PWATS ALSO DROP TO 0.25 INCHES IN THE 50-75NM ZONE BEHIND THE PRIMARY LOW LEVEL BAROCLINIC ZONE. THE MAIN ISSUE IS GOING TO BE BLSN...WITH 30KT GUSTS COMMON ACROSS SW ND ALREADY. GFS BUFR SOUNDINGS SHOW 30-35KTS AT THE TOP OF THE MIXED LAYER INTO THIS EVE SO WE WILL CONTINUE TO GET THESE GUSTS AT THE SFC...BUT THE PRIMARY ISALLOBARIC COMPONENT /3-HOUR PRESSURE RISE CENTER OF ONLY 3MB AS OF 21Z/ HAS WEAKENED THE PAST 6 HOURS. WITH FALLING SFC TEMPS AND BLOWING/DRIFTING...ROADS WILL BE SLICK AND HENCE WE WILL CONTINUE WITH THE SN/BS ADVZY. WE DID HOWEVER UTILIZE THE 12Z GFS TIMING OF THE SNOW BAND TO DROP THE ADVZY IN THE WEST AT 02Z...THE CENTRAL AT 06Z...AND HUNG ON TO THE HEADLINE IN THE JMS AREA UNTIL 12Z. KDIK HAS OCCASIONALLY BEEN DOWN 1SM THE PAST FEW HOURS SO EVEN BEHIND THE PRIMARY SN BAND SOME TRAVEL PROBLEMS WILL CONTINUE. DRY AIR AHEAD OF THE SFC HIGH HAS WORKED INTO NW ND THOUGH SO WE WILL DROP THE ADVZY FROM NW ND. THE UPPER VORT DROPS INTO CENTRAL ND SAT AND THE COLUMN COOLS DRASTICALLY WITH 850MB TEMPS DOWN TO -20 C. THERE WILL STILL BE SOME MIXING WITH PROG SOUNDINGS SHOWING 25KTS TO BRING TO THE SFC...BUT THIS WILL DO NOTHING FOR THE TEMP RISE. WE UNDERCUT GUIDANCE CONSIDERABLY GIVEN THE STRENGTH OF COOLING AND APPROACH OF THE SFC HIGH...AND ADDITION OF SOME SNOW PACK...ALBEIT MINOR IN MOST SPOTS. THE SAME GOES FOR SUNDAY...WHEN MIXING WILL BE EVEN MORE LIMITED WITH THE SFC RIDGE AXIS SITTING ON TOP OF US. WIND CHILLS WILL BE A PROBLEM...PERHAPS AS EARLY AS LATE TONIGHT...AND MORE LIKELY LATER ON SATURDAY. HOWEVER...WE WILL STOP SHORT OF ISSUING THOSE HEADLINES FOR NOW IN ORDER TO AVOID CONFUSION WITH THE PRESENT EVENT. S/W RIDGING PROGRESSES ACROSS THE NRN PLAINS ON MON AHEAD OF THE NEXT TROUGH STILL SET TO APPROACH BY 12Z TUE. THE 12Z GFS IS A BIT MORE AGGRESSIVE WITH HEIGHT FALLS WITH THIS NEXT SYSTEM...SO A CHANCE OF SNOW IS IN THE CARDS IN WSTRN ND. AGAIN THOUGH THE ENERGY WILL BE SPLIT AND HENCE CONFIDENCE IN GETTING MUCH OUT OF THE SYSTEM IS LOW. .LONG TERM... FEW CHANGES IN THE LONG TERM PERIOD TODAY. THE ECMWF AND GFS ARE IN FAIR AGREEMENT AND HPC WENT MAINLY WITH THE ECMWF FOR DETAILS. KEPT MENTION OF LIGHT SNOW TUESDAY WITH LONGWAVE TROUGH EXTENDING FROM THE MAIN LOW IN NORTH CENTRAL CANADA AND ANOTHER LOW IN THE SOUTHERN PLAINS. THE ECMWF CUTS OFF THE SOUTHERN LOW FROM THE WESTERLIES...WHILE THE GFS KEEPS THE LONGWAVE TROUGH MAINTAINED AS THE SYSTEMS MOVE EAST ACROSS CENTRAL NORTH AMERICA. AFTER THIS...THE STATE REMAINS BETWEEN LOWS THAT TRACK ACROSS CANADA AND LOWS TRACKING ACROSS THE SOUTHERN PART OF THE CONUS. THIS WILL KEEP THE FORECAST DRY WITH NO BIG ARCTIC OUTBREAKS BUT ALSO NO WARM-UPS FROM THE SOUTHWEST. EXPECTING HIGHS IN THE TEENS AND 20S WITH LOWS 5 TO 15 ABOVE - CLOSE TO AVERAGE FOR THIS TIME OF YEAR. && .AVIATION... SURFACE LOW PRESSURE OVER EASTERN NEBRASKA WITH AN INVERTED TROUGH EXTENDING FROM THE LOW INTO THE RED RIVER VALLEY OF NORTH DAKOTA. GUSTY NORTHWEST WINDS OVER WESTERN AND CENTRAL NORTH DAKOTA WITH AREAS OF SNOW AND BLOWING SNOW CENTRAL. THIS SNOW EXPECTED TO PERSIST THROUGH 02Z TO 05Z. THE BACK EDGE OF THE CLOUDS WITH DRY AIR IS MOVING INTO NORTHWESTERN NORTH DAKOTA AT THIS TIME. EXPECT FALLING SNOW TO END OVER CENTRAL NORTH DAKOTA BY AROUND 03Z. MVFR AND IFR CEILINGS AND VSBYS TO IMPROVE TO VFR OVER WESTERN ROUTES BY 02Z AND OVER CENTRAL NORTH DAKOTA BY 06Z...BUT PERSIST UNTIL 12Z IN THE RED RIVER VALLEY. ANOTHER MVFR/IFR CLOUD SHIELD EXPECTED TO MOVE INTO NORTHWESTERN NORTH DAKOTA AFTER 06Z AND SPREAD TO CENTRAL NORTH DAKOTA BY 12Z. && .BIS WATCHES/WARNINGS/ADVISORIES... SNOW AND BLOWING SNOW ADVISORY UNTIL MIDNIGHT CST /11 PM MST/ TONIGHT FOR NDZ003>005-011>013-019>022-034-035-042-045-046. SNOW AND BLOWING SNOW ADVISORY UNTIL 8 PM CST /7 PM MST/ THIS EVENING FOR NDZ018-031>033-040-041-043-044. SNOW AND BLOWING SNOW ADVISORY UNTIL 6 AM CST SATURDAY FOR NDZ023-025-036-037-047-048-050-051. && $$ CJS/HW/JV nd AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA NATIONAL WEATHER SERVICE SIOUX FALLS SD ..UPDATED AVN DISCUSSION 1157 AM CDT FRI DEC 21 2007 .DISCUSSION... UPDATED THE GRIDS AND ZFP. MAIN CONCERN WAS OVR THE ERN AND WRN SECTIONS OF THE FSD FA FOR THIS AFTERNOON. FIRST FOR OUR WEST...12Z RAOBS CAME IN AND SHOW A HUGE WARM LYR ABOVE THE SFC AT KABR AND KLBF. THIS WAS PICKED UP BY THE NAM/RUC MODEL SNDGS SO DECIDED TO CHANGE THE PCPN TYPE TO PURE RAIN GIVEN CURRENT SFC TEMP READINGS. EXCEPT FOR A POSSIBILITY MIX OF -RA/-FZRA IN KINGSBURY AND BROOKINGS COUNTIES FOR LATER THIS AFTERNOON WHERE SFC TEMPS ARE A BIT COOLER. ALSO BROUGHT IN A MIX OF -RA/-FZRA IN THE LATE AFTERNOON HRS TOWARD EVENING IN THE HURON AND CHAMBERLAIN VICINITIES AS SFC TEMPS COOL JUST BEHIND THE FROPA. HOWEVER FOR THE BULK OF THE AFTERNOON...WITH THEIR RISING DEWPT TEMPS...THEY SHOULD JUST GO OVER TO PURE RAIN IN OUR FAR WEST. IN OUR FAR EAST...DECIDED TO JUST GO AREAS OF FOG ALL AFTERNOON. THE WALL OF STRATUS CONTINUES TO HUG RIGHT ALONG THE CWA BORDER BETWEEN US AND DMX. BUT THERE ARE INDICATIONS ON SATELLITE THAT THIS SHOULD BEGIN TO BACK INTO OUR FA AS THE AFTERNOON PROGRESSES...AND ALSO THE H925 WINDS SHIFT FM THE S TO THE SE. AM HOPEFUL THOUGH...THAT THERE WILL BE ENUF THICKER HIGH CLOUDS OVR THE STRATUS TO KEEP DENSE FOG FM FORMING FM THE WINDOM MN TO STORM LAKE IA STRETCH. TONIGHT MAY BE A DIFFERENT STORY THOUGH...RIGHT AHEAD OF THE FROPA WHEN THE SFC WINDS GO DEAD. WL RE EVALUATE THAT A BIT LATER. && .AVIATION... LOW CIGS AND VIS ABOUND FOR THE TAF SITES THRU THE NEXT 24 HRS. FIRST FOR KSUX...THE LOW LEVEL WINDS WILL BACK TO AN ESE DIRECTION AS THE AFTERNOON PROGRESSES...LASTING INTO THIS EVENING. THEREFORE AM CONCERNED THAT THE LOW STRATUS AND FOG CURRENTLY TO THE E OF THIS AREA WILL BACK IN TOWARD EVENING...INTO THE IFR AND LIFR RANGE. WL HAVE TO MONITOR TO SEE IF THE FOG GOES 1/4SM DURING THE EVENING HRS BEFORE THE FROPA. AFTER THE FROPA...VIS WL GO UP...BUT WL STILL BE REDUCED IN ANY AREAS OF SN/BLSN WITH LOW CIGS STAYING PUT THRU SAT MORNING. SAME PROBLEM AT KFSD...WITH SOME POSSIBLE IFR CIGS BACKING IN FM THE EAST THIS EVENING. SNOW SHOWERS AFT MIDNIGHT WITH TEMPO IFR CIGS/VIS WARRANTED. AT KHON...NOT EXPECTING THE LOW VIS/CIGS TO THE EAST TO BACK INTO THIS AREA. BUT KHON WL LIKELY SEE MVFR/IFR CIGS/VIS AFTER THE FROPA IN SNOW/BLSN. && .PREV DISCUSSION... NEXT PBLM IS TIMIMG OF FNT. MODELS NOW SLOWER AND REALLY DO NOT PUSH FNT INTO WRN CWA UNTIL AFTN. S/W WAVE IN NRN FLOW WL SKIM BY THE NRN CWA THIS AFTN AND WL KEEP CHC OF S THERE WITH REST OF CWA DRY TODAY. FOCUS SHIFTS TO THE S WITH SRN STREAM WAVE FOR TONIGHT. BULK OF PRECIP TONIGHT WL OCCUR BEHIND FNT AND CLOSER TO SRN STREAM WAVE. AM CONCERNED THAT BULK OF PRECIP WL REMAIN. HAVE TRIMMED BACK POPS TO LIKELY OVR NW IA LATER TONIGHT AS FEEL PRECIP WL LIKELY HOLD OFF THERE UNTIL AAFTER 06Z WHEN SRN STREAM WAVE PUSHES ENE. AHEAD OF FNT TONIGHT...WL LIKELY SEE AREAS OF OFG ALONG WITH PATCHY DRIZZLE OR FREEZING DRIZZLE IN THE EVE SO PUT THAT IN FCST ACRS NW IA. ACRS REST OF CWA TONIGHT...WL SEE A CHC OF LIGHT SNOW WITH NRN TROF AND WNDS SHUD PICK UP BEHIND FNT AS CAA KICKS IN. WL BE CLOSE TO WND ADVY WRN CWA BUT FOR NOW WL NOT ISSUE HEADLINE. SAT LOOKS WINDY AND COLD WITH TEMPS NOT CLIMBING MUCH AT ALL. WUD EXPECT PLENTY OF STRATUS ERN CWA DURING THE DAY WITH CHC OF S- ACRS ERN CWA IN THE MORN. SUN LOOKS WINDS OND COLD AS UPPER LOW SITS OVR MN. EXPECT PLENTY OF SC OVR ERN CWA WITH A PSBLTY OF FLURRIES OVR SW MN. MOST PLACES WILL NOT GET OUT OF TEENS FOR HIGHS. HOLIDAY LOOKS DRY WITH NO MAJOR STORMS THRU NEXT WEEK. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ MJF sd AREA FORECAST DISCUSSION...AMENDED FOR WIND ADVISORY NATIONAL WEATHER SERVICE EL PASO TX/SANTA TERESA NM 213 PM MST FRI DEC 21 2007 .SYNOPSIS... A STRONG UPPER LEVEL TROUGH WILL CONTINUE TO SUPPLY THE BORDERLAND WITH BREEZY TO WINDY WESTERLY WINDS INTO THE OVERNIGHT HOURS TONIGHT...ESPECIALLY ALONG EAST-FACING SLOPES. IN ADDITION...THIS SYSTEM BRINGS WITH IT A GOOD SHOT FOR SIGNIFICANT SNOWFALL ACROSS THE MOUNTAINS OF SOUTHERN NEW MEXICO...BUT ONLY A SLIGHT CHANCE FOR PRECIPITATION NEARER THE INTERNATIONAL BORDER. MUCH COOLER TEMPERATURES CAN BE EXPECTED TOMORROW...AND OUR READINGS WILL HAVE A TOUGH TIME RECOVERING TO NORMAL LEVELS THROUGH THE REMAINDER OF THE WEEK. && .DISCUSSION... AS A STRONG BERING STRAIGHTS 500MB CYCLONE CONTINUES TO EJECT ENERGY INTO THE JET...EACH BURST STRENGTHENS AND PULLS SOUTH- SOUTHEAST AS THEY ENTER THE PACIFIC NW. MORE SPECIFICALLY...4 SUCH SYSTEMS WILL SKIRT THE CWA THROUGH THE 7-DAY PERIOD. THE FIRST TROUGH...ALREADY STRETCHING THROUGH UTAH AND ARIZONA AS OF 18Z TODAY...LOOKS TO BE OUR BEST SHOT FOR PRECIPITATION OF ANY OF THESE SYSTEMS. RUC-ANALYZED NEGATIVE LI`S JUST AHEAD OF THE 500 MB TROUGH AXIS HAVE BEEN HOST TO AN AREA OF CONVECTION ALL MORNING...AND HAVE PUSHED INTO WESTERN NEW MEXICO AS OF 20Z THIS AFTERNOON. THIS ACTIVITY WILL BE MAINLY RAIN EXCEPT ABOVE AROUND 7500 FEET AS IT MOVES INTO THE GILA ZONE THIS AFTERNOON. SNOW LEVELS WILL DROP QUICKLY TO BELOW 5000 FEET NORTH OF LAS CRUCES BY MIDNIGHT TONIGHT AS COLD AIR FILTERS IN FROM THE NORTH AT THE SURFACE BEHIND A SIDE-DOOR FRONT. BY THIS TIME OUR MAIN TROUGH AXIS WILL HAVE PUSHED FAR ENOUGH EAST TO LIMIT THE RISK FOR SIGNIFICANT SNOWS IN THE LOWLANDS. WITH THE MAIN BAND OF ENERGY HOLDING OFF UNTIL LATER TO EFFECT THE SACRAMENTO MOUNTAIN AREA...MORE SIGNIFICANT SNOWS LOOK TO BE MORE LIKELY THERE. AMOUNTS APPEAR TO BE WELL-HANDLED WITH THE CURRENT ADVISORIES. A STRONG SURFACE PRESSURE GRADIENT WILL REMAIN ESTABLISHED OVERNIGHT TONIGHT AS A STRENGTHENING LEE-SIDE LOW SLIDES ACROSS NORTHERN TX. THIS WILL SUPPORT BREEZY TO WINDY CONDITIONS - ESPECIALLY ACROSS THE EAST-SLOPES OF AREA MOUNTAINS - THROUGH THE NIGHT. MUCH COOLER TEMPERATURES FOR TOMORROW WILL BE HARD TO BRING UP AS DISTURBANCE AFTER DISTURBANCE CROSSES THE AREA BRINGING WITH THEM REINFORCING SHOTS OR COOL AIR. OUR SECOND DISTURBANCE...SLATED FOR SUNDAY NIGHT/MONDAY CONTINUES TO LOOK DRIER. AS SUCH...HAVE REMOVED MENTIONABLE POPS FOR THE SYSTEM. THE THIRD DISTURBANCE IS SLATED FOR CHRISTMAS DAY. AS READINGS FINALLY RETURN TO LATE-DECEMBER NORMS...A STRONG UPPER LEVEL TROUGH IS PROGGED TO DIG INTO THE SOUTHWEST. CURRENT MODEL SOLUTIONS INDICATE WINDY CONDITIONS WITH THE POTENTIAL FOR MAINLY THE NORTHERN PORTIONS OF THE CWA TO SEE AND PRECIPITATION. THIS WOULD BE FOLLOWED AGAIN BY A COLD AIR INTRUSION FROM THE NORTH FOR THE 26TH. OUR FOURTH AND FINAL DISTURBANCE OF THE PERIOD LOOKS MUCH LIKE THE 3RD...AND WOULD MAKE FOR BREEZY TO WINDY CONDITIONS AND A SLIGHT CHANCE OF PRECIPITATION MAINLY NORTH OF LAS CRUSES THURSDAY AFTERNOON/EVENING. && .AVIATION...VALID 22/00Z-23/00Z MOSTLY VFR CONDITIONS EXPECTED THROUGH THE PERIOD. HOWEVER...THERE WILL BE AREAS OF MVFR AND IFR TONIGHT INTO SATURDAY MORNING FOR CIGS AND VSBY IN RAIN/SNOW SHOWERS THAT WILL OBSCURE MTN TOPS. WINDS OF 20 TO 25 KTS GUSTING TO 35 KTS THIS EVENING INTO TONIGHT WILL LIKELY CAUSE MODERATE MECHANICAL TURBULENCE...ESPECIALLY ACROSS EASTERN SLOPES OF AREA MOUNTAINS. WINDS DIMINISHING DURING THE NIGHT AND VFR CONDITIONS RETURNING FROM WEST TO EAST SATURDAY MORNING. && .PRELIMINARY POINT TEMPS/POPS... EL PASO 36 50 25 53 30 / 10 0 0 0 0 SIERRA BLANCA TX 35 48 23 53 26 / 10 0 0 0 0 LAS CRUCES 33 50 24 52 29 / 10 0 0 0 0 ALAMOGORDO 32 50 21 50 25 / 20 10 0 0 0 CLOUDCROFT 25 33 10 37 16 / 60 20 0 0 0 TRUTH OR CONSEQUENCES 31 47 21 50 26 / 20 0 0 0 0 SILVER CITY 28 43 19 45 22 / 30 0 0 0 0 DEMING 32 49 22 51 28 / 10 0 0 0 0 LORDSBURG 31 49 21 51 27 / 20 0 0 0 0 && .EPZ WATCHES/WARNINGS/ADVISORIES... NM...WIND ADVISORY UNTIL 6 PM MST THIS AFTERNOON FOR NMZ022>025- 030>032. SNOW ADVISORY UNTIL 6 AM MST SATURDAY FOR NMZ022. SNOW ADVISORY FROM 6 PM THIS EVENING TO 12 PM MST SATURDAY FOR NMZ025. TX...WIND ADVISORY UNTIL 6 PM MST THIS AFTERNOON FOR TXZ055-056. && $$ PIEPER tx