FLORIDA KEYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KEY WEST FL 945 PM EST MON DEC 29 2003 .DISCUSSION... .CURRENTLY.... ATLANTIC SURFACE HIGH PRESSURE HAS FINALLY BEGUN TO WEAKEN SOME.. ALLOWING PRESSURE GRADIENT OVER THE KEYS A RELAX A LITTLE THE PAST 2-3 HOURS. SURFACE WINDS AT REEF C-MAN SITES ARE NOW NEAR 15 KT SUSTAINED INSTEAD TO IN THE 15-20 KT RANGE...WHILE GUSTS ARE 20 KT OR LESS. A WEAK SECONDARY HIGH PRESSURE RIDGE IN THE GULF HAS NOSED TOWARD THE LOWER KEYS...TURNING WINDS A KEY WEST TO DRY TORTUGAS TO THE NE THE PAST 2 HOURS. MEANWHILE ALOFT...WINDS HAVE VEERED TO SE AT LEVELS 4-9 THSD FT...AND MAY BE MORE SOUTHERLY ABOVE THAT. CLOUDS HAVE INCREASED GREATLY OVER THE KEYS AND WATERS SINCE SUNSET...WITH CEILINGS MEASURED AT 6-7 THSD FT OVER KEY WEST AND MARATHON. DOPPLER RADAR IS STILL IN CLEAR AIR MODE...BUT IS INDICATING NEWLY DEVELOPING RAIN SHOWERS IN A SE-NW ORIENTED BAND OVER THE STRAITS SOUTH OF THE LOWER KEYS. .SHORT TERM FORECAST...TONIGHT... 18Z MODEL RUNS MAINTAIN SOME SE TO S WIND FLOW AT LEVELS NEAR AND JUST ABOVE THE 850 MB LEVEL OVERNIGHT...THEN TURN WINDS BACK MORE TO THE EAST LATER TUE. SIMPLY BASED ON CURRENT CLOUD AND RADAR TRENDS... I MAY ADD MENTION OF SLIGHT CHANCE (10 PCT) OF SHOWERS FOR REMAINDER OF TONIGHT TO PUBLIC ZONES...ALONG WITH INDICATING VARIABLE CLOUDS. WILL WATCH THE TREND A WHILE LONGER. TEMPS ARE RIGHT ON FORECAST. && .MARINE... THE EXPECTED DOWN TREND IN WIND SPEEDS IS OCCURRING...SO 1030 PM COASTAL WATERS FORECAST WILL REMOVE "EXERCISE CAUTION" HEADLINE FOR GULF WATERS AND INSIDE THE REEF WATERS...AND DOWNGRADE THE SMALL CRAFT ADVISORY FOR WATERS BEYOND THE REEF TO AN "EXERCISE CAUTION UNTIL SEAS SUBSIDE" HEADLINE FOR THE STRAITS. THE ODD TURN OF WINDS TO NE OVER KEY WEST/DRY TORTUGAS IS VAGUELY INDICATED BY THE LATEST RUC...BUT NOT BY ETA NOR GFS. RUC SUGGESTS THESE NE COMPONENT WINDS MAY LAST THROUGH THE NIGHT. I WILL ADD MENTION OF ISOLATED SHOWERS TO GULF WATERS...MAYBE ALSO TO FLORIDA BAY. && .AVIATION... AMENDED TAFS THIS EVENING TO ACCOUNT FOR INCREASE IN CLOUD COVER IN THE 060 TO 070 LAYER. A FEW SPRINKLES AND LIGHT SHOWERS DETECTED SOUTH AND WEST OF KEYW SHOULD REMAIN AWAY FROM THE TERMINALS AND OUTSIDE THE KMIA TO KEYW ROUTE. WINDS WILL REMAIN EASTERLY AND LIGHT BUT MAY TIP TO NORTHEAST AT TIMES OVERNIGHT. EXPECT VFR CONDITIONS THROUGH TUESDAY EVENING WITH ONLY AN INCREASE IN HIGH CIRRUS CLOUDS. && .EYW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC/MARINE..........C.B. AVIATION/NOWCASTS.....JR fl FLORIDA KEYS AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KEY WEST FL 1015 AM EST MON DEC 29 2003 .DISCUSSION... OBSERVATIONS AND TRENDS... EARLY VISIBLE SATELLITE IMAGES INDICATE THE LOWER CU DECK NEAR THE LOWER KEYS AND EXTENDING WEST AND NORTH INTO THE GULF WATERS WILL BE THINNING OVER THE NEXT HOUR OR SO. CAP HAS RISEN JUST ABOVE 6 KFT WITH A STEADY EAST WIND AROUND 20 KNOTS THROUGH THAT DEPTH. CMAN OBSERVATIONS ARE STILL AVERAGING 20 KNOTS WITH SLIGHTLY HIGHER GUSTS ON THE ATLANTIC SIDE. ISLAND SENSORS ARE AT 10 MPH OR BELOW. REMAINDER OF TODAY... TEMPERATURES ALREADY IN THE LOWER 70S ON TRACK WITH GUIDANCE...AND WITH THINNING LOWER CLOUDS AND ONLY A SMALL AMOUNT OF THIN CI ...AFTERNOON HIGHS OF 74 TO 78 LOOK FINE. NO AFTERNOON ZONE UPDATE. && .MARINE... RUC AND MESOETA...AS WELL AS GFS GUIDANCE...INDICATE THAT THE EASTERLY WINDS WILL REMAIN CLOSE TO THEIR PRESENT SPEEDS THROUGH THE REMAINDER OF THE AFTERNOON. WITH THE FETCH AND DURATION ESTABLISHED...THE HEADLINES WILL REMAIN AS THEY ARE ON THIS UPDATE. NO OTHER ADJUSTMENTS. && .AVIATION... CLOUDS ARE THINNING A LITTLE AHEAD OF SCHEDULE ESPECIALLY OVER THE MAINLAND. WE HAVE ISSUED A RECENT AMENDMENT OF THE ROUTE FORECAST TO ACCOUNT FOR THIS. WE STILL ANTICIPATE VFR CONDITIONS ALONG THIS ROUTE AND AT THE TERMINALS. && .EYW WATCHES/WARNINGS/ADVISORIES...SCA ATLANTIC WATERS TODAY. $$ PUBLIC/MARINE/GRIDS......MR AVIATION/SHORT TERM......DM fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE INDIANAPOLIS IN 830 PM EST MON DEC 29 2003 .UPDATE...PRECIP IS ABOUT TO END ACROSS THE IND FORECAST AREA...THUS WILL REMOVE FROM FCST AROUND 930 PM. SATELLITE SHOWS THE CLEARING LINE RAPIDLY MOVING ACCROSS SOUTHERN IL AT 01Z. RUC40 AND MESO ETA SHOW STRONG MID-LEVEL DRYING AFTER 03Z BUT STILL PRETTY MOIST THRU 850H TIL MORNING. CURRENT CLEARING FORECAST LOOOKS PRETTY GOOD WITH SOME CLEARING IN THE WEST BUT NOT TIL AFTER 12Z IN THE EAST. A FEW FLURRIES ARE NOT OUT OF THE QUESTION...BUT ARE MORE LIKELY TO THE NORTHER AND WILL NOT MENTION AT THIS TIME. && .PREV DISCUSSION...UPPR PTN XPCTD TO DEAMPLIFY OVR THE NEXT FEW DAYS. SYS CURRENTLY OVR THE MIDWEST WL PASS THRU THE AREA TONIGHT...WHILE ANOTHER SHORT WV TROF WL CUT ACRS THE NRN GRTLKS AROUND WED. AT THE SFC...DIFFUSE FRONTAL SYS XPCTD TO MOV E OF THE AREA THIS EVENING. MODELS IN GOOD AGREEMENT WITH THE DETAILS. FCST FOCUS CENTERS ON POPS TONIGHT ALONG WITH TEMPS. IN THE NR TERM...STILL QUITE A BIT OF CLD ENHANCEMENT UPSTREAM...SO THINK PCPN IS NOT DONE YET...ALTHOUGH BACK EDGE OF ENHANCEMENT BEGINNING TO MAKE PROGRESS EWD. WL CONT THE POPS INTO THE EVEN HRS OVR THE SERN 2/3RDS OF CWA UNTIL PASSAGE OF UPPR TROF...WHICH LOOKS TO BE AROUND 04Z OR SO. THICKNESSES SUGGEST RAIN MAY MIX WITH SNOW AS PCPN IS ENDING...BUT DURATION OF ANY SNOW WL BE BRIEF AND NOT WORTH A MENTION IN ZONES. LO CLDS SHOULD CLR OUT OF THE AREA AFT MIDNIGHT AS 850MB THERMAL TROF LIFTS OFF TO THE NE FAIRLY QUICKLY. LTR PDS LOOK QUIET WITH HI PRES RDG BLDG IN. SHORT WV TROF MOVG ACRS THE NRN GRTLKS ON WED MAY DRAG A FNT INTO THE AREA...BUT MOISTURE/LIFT PROFILES SUGGEST LTL WX WITH FNT. LO LVL THICKNESSES SUGGEST NGM MOS HIGHS FOR TUES ARE TOO COOL. WL RAISE THEM ABOUT 5 DEGS. OTHERWISE...GUIDANCE LOOKS PRETTY GOOD. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ JAS/JEO in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1025 PM EST MON DEC 29 2003 .DISCUSSION... FCST CONCERN OVERNIGHT IS -SN AND LIGHT ACCUMULATIONS. WV IMAGERY SHOWS REMNANTS OF TROF THAT SHEARED NE LAST NIGHT LINGERING ACROSS ONTARIO TO NE MN/WRN LAKE SUPERIOR. SUBTLE TWIST/VORT MAX NOTED OVER NW LAKE SUPERIOR. THIS FEATURE RESPONSIBLE FOR -SN THAT BLOSSOMED FROM NE MN INTO UPPER MI THIS AFTN AND EVENING THOUGH THERE WAS PROBABLY SOME SUPPORT AS WELL FROM MORE SUBSTANTIAL TROF TRACKING E THRU MID MISSISSIPPI VALLEY. ANOTHER SHORTWAVE FROM DAKOTAS TO IA WAS MOVING STEADILY EWD TOWARD WRN LAKES WITH LITTLE OR NO ASSOCIATED PCPN. AT THE SFC...A TROF WAS SLOWLY DROPPING S ACROSS LAKE SUPERIOR AND CURRENTLY EXTENDS FROM NEAR WRN LAKE SUPERIOR BUOY LOCATION TO TIP OF KEWEENAW AND ENE FROM THERE. SPOTTER REPORTS INDICATE SNOW AMOUNTS SO FAR HAVE BEEN LIGHT WITH FLUFF FACTOR PUSHING AMOUNTS TO 0.5 TO 1 INCH IN A FEW SPOTS OVER THE W. IF A COLDER AIRMASS WAS OVER LAKE SUPERIOR...THIS WOULD HAVE BEEN A NICE LAKE ENHANCED SNOW EVENT THIS EVENING AS DEEPER/SHARPER LOW-LEVEL TROUGHING WOULD HAVE DEVELOPED OVER THE LAKE...CREATING STRONGER WINDS/BETTER CONVERGENCE. AS THE SITUATION CURRENTLY IS...IT DOESN'T APPEAR THERE IS MUCH LAKE ENHANCEMENT OCCURRING. A CHECK OF 00Z RAOBS SUGGESTS 850MB TEMP MAY BE AROUND -8C WHILE LATEST RUC ANALYSIS FILLS IN THE GAPS AND SHOWS 850MB TEMPS OVER LAKE SUPERIOR ARE -6 TO -7C...JUST SUFFICIENT FOR LAKE ENHANCEMENT. APPEARS THE OVERALL LIGHT/VRBL WIND REGIME (5-15KT) THRU 850MB AND LACK OF MORE SUBSTANTIAL OVERWATER INSTABILITY IS WORKING AGAINST ENHANCEMENT. WOULD BE AN ENTIRELY DIFFERENT STORY IF AIRMASS WAS COLDER. GOING FCST IS PROBABLY OKAY ON SNOW AMOUNTS SINCE FLUFF FACTOR IS FAIRLY HIGH AND SOME AREAS ARE NEARING AN INCH. BETTER CONVERGENCE SHOULD DEVELOP OVERNIGHT WITH SOME STRENGTHENING OF LOW-LEVEL WIND FIELDS OVER WRN FCST AREA. WILL GO WITH ANOTHER 1 TO 3 INCHES ADDITIONAL SNOW OVERNIGHT IN AREA OF BEST LOW-LEVEL CONVERGENCE WHICH SHOULD SETUP ACROSS ONTONAGON/SRN HOUGHTON COUNTIES AS WRLY FLOW AIDED BY LAND BREEZE COMPONENT ON S END OF WRN LAKE IS IMPINGED UPON BY NRLY FLOW FARTHER N (NOTE NRLY WINDS AT PILM4 AND ROAM4). OTHERWISE...PROBABLY ANOTHER INCH (MAYBE 2) ACROSS THE REST OF THE W AND LESS THAN AN INCH ACROSS REMAINDER OF FCST AREA AS TROF SLOWLY MOVES E AND LIGHT SYNOPTIC SNOW SLOWLY WINDS DOWN. TEMP FCST IN GOOD SHAPE. ROLFSON && .PREV DISCUSSION... DISCUSSION FOR TUE THRU MON ISSUED AT 430 PM EST. AS SURFACE RIDGE BUILDS OVER UPPER MI TUESDAY AFTERNOON...LOW PRES ASSOCIATED WITH APPROACHING SHORTWAVE OVER MONTANA DEVELOPS OVER THE DAKOTAS. AS THE LOW APPROACHES THE UPPER GREAT LAKES TUESDAY NIGHT A SOUTHERLY FLOW OUT AHEAD OF IT USHERS IN DRIER AIR. WITH THIS DRIER AIR...EXPECTING CLOUD COVER TO DECREASE AND ALLOW OVERNIGHT LOWS IN THE MID TEENS TO LOWER 20S. WHILE ETA...GFS...AND UKMET IN GOOD AGREEMENT ABOUT TIMING...STRENGTH...AND PLACEMENT OF UPPER LEVEL AND SURFACE FEATURES WITH THIS NEXT SHORTWAVE...THE ETA APPEARS TO BE OVERTAPPING THE DRIER AIR AND DOES NOT GENERATE ANY QPF OVER THE CWA. ISENTROPIC LIFT AND LOW LEVEL CONVERGENCE ARE PRESENT TUESDAY NIGHT THROUGH EARLY WEDNESDAY AND GFS AND UKMET DO GENERATE PRECIP DURING THIS TIME...EXPECTING MOST OF CWA TO SEE SNOWFALL OVERNIGHT BUT ONLY MINIMAL AMOUNTS UNTIL AFTER THE LOW PASSES. COLD AIR ADVECTION BEHIND THE LOW FILTERS INTO WESTERN CWA WEDNESDAY MORNING AS 850MB TEMPS DROP FROM -6C TO -13C...WHICH MAY DESTABILIZE THE LOWER LEVELS ENOUGH TO GENERATE LIGHT LAKE EFFECT SNOW SHOWERS THROUGH WEDNESDAY NIGHT. SNOW SHOWERS WILL LIKELY BE MOST INTENSE EARLY WEDNESDAY OUT WEST AS INVERSIONS START OUT AROUND 5K TO 6K FEET...BUT QUICKLY PLUMMET TO AROUND 3K FEET BY THE AFTERNOON. FOR THE EASTERN ZONES...INVERSIONS NEVER REALLY START OUT MORE THAN 4K FEET AND QUICKLY FALL TO 3K FEET WHICH WILL LIMIT INTENSITY OF SNOW SHOWERS. INLAND AREAS WILL SEE A FEW FLURRIES FROM GUSTY NORTHWEST WINDS. ALSO WITH THE COLD ADVECTION AND SUBSIDENCE BEHIND THE SYSTEM...SURFACE WINDS OVER THE WESTERN CWA WHICH MAY SEE SPEEDS OF 30 TO 40 MPH. WILL MENTION HIGH WINDS INLAND IN THE HAZARDOUS WEATHER OUTLOOK UPDATE...AND ISSUANCE OF A WIND ADVISORY WILL NEED TO BE CONTEMPLATED FOR WEDNESDAY AFTERNOON AND EVENING WITH THE COMING FORECASTS. THE COLD AIR AND EXTENSIVE CLOUD COVER WILL KEEP OVERNIGHT LOWS IN THE TEENS TO AROUND 20...BUT WILL PREVENT HIGH TEMPS FROM WARMING MORE THAN LOWER 20S FOR THE WESTERN CWA AND MIDDLE 20S ACROSS THE EAST. NEARLY ZONAL FLOW AT 500MB ACROSS THE UPPER CONUS DEVELOPS WEDNESDAY WITH HIGH PRESSURE OVER THE OHIO RIVER VALLEY EXTENDING A RIDGE INTO THE UPPER GREAT LAKES BY THURSDAY MORNING. CLOUD COVER WILL DECREASE AS WINDS SUBSIDE AND BACK TO THE SOUTH ON THURSDAY...THOUGH SOME LIGHT LAKE EFFECT SNOW SHOWERS MAY LINGER NEAR LAKE SUPERIOR SHORELINE OVER THE FAR EASTERN CWA. LIGHT WINDS OVER THE INTERIOR CWA NEAR WI WILL ALLOW LOWS FOR THURSDAY TO FALL INTO THE LOWER TEENS...MAYBE EVEN AROUND 10 DEGREES. ISENTROPIC LIFT AND LOW LEVEL CONVERGENCE PRESENT OUT AHEAD OF THIS SYSTEM AS WELL...BUT SNOW MAY NOT DEVELOP UNTIL LATE THURSDAY AFTERNOON AND EVENING. ANOTHER SHORTWAVE THOUGH MUCH WEAKER THAN THE PREVIOUS PROGGED TO DEVELOPING OVER THE NORTHERN ROCKIES EARLY THURSDAY AND APPROACH THE UPPER GREAT LAKES THURSDAY NIGHT INTO EARLY FRIDAY MORNING. MRF AND ECMWF OPERATIONAL MODELS IN DECENT AGREEMENT WITH THIS SYSTEM AND PLACEMENT OF SURFACE LOW OVER ONTARIO AND RIDGE BUILDING INTO THE UPPER MIDWEST FOR FRIDAY. 850MB TEMPS ALSO CONSISTENT AROUND -4C TO -6C. ALTHOUGH 500MB FLOW IS FAIRLY ZONAL ACROSS UPPER CONUS...GFS IS STRONGER AND QUICKER WITH A TROUGH MOVING ONSHORE ON THE WEST COAST. BOTH MODELS DEPICT A SHORTWAVE FORMING OVER THE NORTHERN ROCKIES FRIDAY MORNING...HOWEVER THERE IS SOME DISCREPANCY BETWEEN THE TIMING AND PLACEMENT OF THE CORRESPONDING SURFACE LOW. THE CURRENT CONSENSUS TRACK FOR THE SYSTEM ON FRIDAY WOULD BE FROM MONTANA RIGHT ACROSS LAKE SUPERIOR AND UPPER MI...WITH 850MB TEMPS WARMING SLIGHTLY TO AROUND 0C TO -2C ACROSS THE CWA. CURRENT FORECAST HAS CHANCE OF LIGHT SNOW FOR THIS PERIOD...BUT WITH WARMER TEMPS EXPECTED NEAR THE SURFACE WILL CHANGE TO A RAIN AND SNOW MIX FOR SOUTHERN COUNTIES ESPECIALLY NEAR LAKE MICHIGAN. BY SATURDAY NIGHT EARLY SUNDAY A FAIRLY SHARP FRONTAL PASSAGE WILL USHER DOWN COLD AIR AND DROP 850MB TEMPS TO -14C TO -16C...WITH NO HINT OF WARMING THROUGH MONDAY. THE COLD AIR WILL LIKELY PRODUCE SOME LAKE EFFECT SNOW SHOWERS...THOUGH LOW LEVEL ANTICYCLONIC FLOW MAY HINDER DEVELOPMENT. GFS ENSEMBLES IN DECENT AGREEMENT WITH SLIGHTLY SOUTHWEST FLOW IN ADVANCE OF DEEPENING 500MB TROUGH OVER WESTERN CONUS...AND COLD AIR FILTERING DOWN BEHIND THE SURFACE RIDGE SLIDING DOWN FROM CANADA. RIDGE BECOMES ELONGATED TO OUR NORTH CREATING AN EASTERLY FLOW FROM AREAS OF LOW PRESSURE TO OUR SOUTH. AFOREMENTIONED SHORTWAVE DUE TO APPROACH CENTRAL PLAINS BY MONDAY WHICH MAY BE A DRY DAY DEPENDING ON STRENGTH OF RIDGE AXIS. LAROSA && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 430 PM EST MON DEC 29 2003 .DISCUSSION... FORECAST QUANDARY FOR THIS AFTERNOON IS SERIES OF SHORTWAVES AND THEIR IMPACTS TO CWA OVER THE NEXT FEW DAYS. DESPITE DYNAMICS TO SUPPORT SNOWFALL AND PRECIPITATION ACCUMULATIONS...THE RELATIVE QUICKNESS OF THESE SYSTEMS WILL INHIBIT SIGNIFICANT ACCUMULATIONS. A DEEP SOUTHERLY FLOW TO REPLENISH AIRMASS DOES NOT APPEAR LIKELY UNTIL NEXT WEEKEND. VISIBLE SATELLITE IMAGERY SHOWS WIDESPREAD LOW CLOUD COVER OVER MN...WI...AND UPPER MI WITH SURFACE OBS INDICATING TEMPERATURES IN THE MIDDLE TO UPPER 20S...WITH TEMPS IN THE 30S ACROSS CWA. RUC INDICATES SLIGHTLY COLDER AIR WILL BEGIN FILTERING ACROSS UPPER MI...THOUGH CLOUD COVER WILL PROHIBIT MUCH RADIATION KEEPING OVERNIGHT LOWS IN THE 20S. MAIN CONCERN TONIGHT IS LAKE EFFECT SNOW SETUP FROM NORTHERLY FLOW AS SURFACE TROUGH BEGINS TO SLIDE EASTWARD. DESPITE LOW LEVEL MOISTURE...SHEARING WIND PROFILES AND LIMITED INSTABILITY WITHIN THE MIXED LAYER WILL PREVENT MUCH IN THE WAY OF SNOWFALL ACCUMULATIONS ACROSS CWA. HOWEVER...DECENT AREA OF CONVERGENCE SHOULD ALLOW NUMEROUS SNOW SHOWERS TO DEVELOP AND DEPOSIT A FEW INCHES OF ACCUMULATION ACROSS ONTONAGON...HOUGHTON... AND KEWEENAW COUNTIES. GOGEBIC COUNTY IS UNDER A LESS FAVORABLE FLOW PATTERN AND WILL NOT SEE AS MUCH SNOWFALL AS PREVIOUSLY THOUGHT. AS SURFACE RIDGE BUILDS OVER UPPER MI TUESDAY AFTERNOON...LOW PRES ASSOCIATED WITH APPROACHING SHORTWAVE OVER MONTANA DEVELOPS OVER THE DAKOTAS. AS THE LOW APPROACHES THE UPPER GREAT LAKES TUESDAY NIGHT A SOUTHERLY FLOW OUT AHEAD OF IT USHERS IN DRIER AIR. WITH THIS DRIER AIR...EXPECTING CLOUD COVER TO DECREASE AND ALLOW OVERNIGHT LOWS IN THE MID TEENS TO LOWER 20S. WHILE ETA...GFS...AND UKMET IN GOOD AGREEMENT ABOUT TIMING...STRENGTH...AND PLACEMENT OF UPPER LEVEL AND SURFACE FEATURES WITH THIS NEXT SHORTWAVE...THE ETA APPEARS TO BE OVERTAPPING THE DRIER AIR AND DOES NOT GENERATE ANY QPF OVER THE CWA. ISENTROPIC LIFT AND LOW LEVEL CONVERGENCE ARE PRESENT TUESDAY NIGHT THROUGH EARLY WEDNESDAY AND GFS AND UKMET DO GENERATE PRECIP DURING THIS TIME...EXPECTING MOST OF CWA TO SEE SNOWFALL OVERNIGHT BUT ONLY MINIMAL AMOUNTS UNTIL AFTER THE LOW PASSES. COLD AIR ADVECTION BEHIND THE LOW FILTERS INTO WESTERN CWA WEDNESDAY MORNING AS 850MB TEMPS DROP FROM -6C TO -13C...WHICH MAY DESTABILIZE THE LOWER LEVELS ENOUGH TO GENERATE LIGHT LAKE EFFECT SNOW SHOWERS THROUGH WEDNESDAY NIGHT. SNOW SHOWERS WILL LIKELY BE MOST INTENSE EARLY WEDNESDAY OUT WEST AS INVERSIONS START OUT AROUND 5K TO 6K FEET...BUT QUICKLY PLUMMET TO AROUND 3K FEET BY THE AFTERNOON. FOR THE EASTERN ZONES...INVERSIONS NEVER REALLY START OUT MORE THAN 4K FEET AND QUICKLY FALL TO 3K FEET WHICH WILL LIMIT INTENSITY OF SNOW SHOWERS. INLAND AREAS WILL SEE A FEW FLURRIES FROM GUSTY NORTHWEST WINDS. ALSO WITH THE COLD ADVECTION AND SUBSIDENCE BEHIND THE SYSTEM...SURFACE WINDS OVER THE WESTERN CWA WHICH MAY SEE SPEEDS OF 30 TO 40 MPH. WILL MENTION HIGH WINDS INLAND IN THE HAZARDOUS WEATHER OUTLOOK UPDATE...AND ISSUANCE OF A WIND ADVISORY WILL NEED TO BE CONTEMPLATED FOR WEDNESDAY AFTERNOON AND EVENING WITH THE COMING FORECASTS. THE COLD AIR AND EXTENSIVE CLOUD COVER WILL KEEP OVERNIGHT LOWS IN THE TEENS TO AROUND 20...BUT WILL PREVENT HIGH TEMPS FROM WARMING MORE THAN LOWER 20S FOR THE WESTERN CWA AND MIDDLE 20S ACROSS THE EAST. NEARLY ZONAL FLOW AT 500MB ACROSS THE UPPER CONUS DEVELOPS WEDNESDAY WITH HIGH PRESSURE OVER THE OHIO RIVER VALLEY EXTENDING A RIDGE INTO THE UPPER GREAT LAKES BY THURSDAY MORNING. CLOUD COVER WILL DECREASE AS WINDS SUBSIDE AND BACK TO THE SOUTH ON THURSDAY...THOUGH SOME LIGHT LAKE EFFECT SNOW SHOWERS MAY LINGER NEAR LAKE SUPERIOR SHORELINE OVER THE FAR EASTERN CWA. LIGHT WINDS OVER THE INTERIOR CWA NEAR WI WILL ALLOW LOWS FOR THURSDAY TO FALL INTO THE LOWER TEENS...MAYBE EVEN AROUND 10 DEGREES. ISENTROPIC LIFT AND LOW LEVEL CONVERGENCE PRESENT OUT AHEAD OF THIS SYSTEM AS WELL...BUT SNOW MAY NOT DEVELOP UNTIL LATE THURSDAY AFTERNOON AND EVENING. ANOTHER SHORTWAVE THOUGH MUCH WEAKER THAN THE PREVIOUS PROGGED TO DEVELOPING OVER THE NORTHERN ROCKIES EARLY THURSDAY AND APPROACH THE UPPER GREAT LAKES THURSDAY NIGHT INTO EARLY FRIDAY MORNING. MRF AND ECMWF OPERATIONAL MODELS IN DECENT AGREEMENT WITH THIS SYSTEM AND PLACEMENT OF SURFACE LOW OVER ONTARIO AND RIDGE BUILDING INTO THE UPPER MIDWEST FOR FRIDAY. 850MB TEMPS ALSO CONSISTENT AROUND -4C TO -6C. ALTHOUGH 500MB FLOW IS FAIRLY ZONAL ACROSS UPPER CONUS...GFS IS STRONGER AND QUICKER WITH A TROUGH MOVING ONSHORE ON THE WEST COAST. BOTH MODELS DEPICT A SHORTWAVE FORMING OVER THE NORTHERN ROCKIES FRIDAY MORNING...HOWEVER THERE IS SOME DISCREPANCY BETWEEN THE TIMING AND PLACEMENT OF THE CORRESPONDING SURFACE LOW. THE CURRENT CONSENSUS TRACK FOR THE SYSTEM ON FRIDAY WOULD BE FROM MONTANA RIGHT ACROSS LAKE SUPERIOR AND UPPER MI...WITH 850MB TEMPS WARMING SLIGHTLY TO AROUND 0C TO -2C ACROSS THE CWA. CURRENT FORECAST HAS CHANCE OF LIGHT SNOW FOR THIS PERIOD...BUT WITH WARMER TEMPS EXPECTED NEAR THE SURFACE WILL CHANGE TO A RAIN AND SNOW MIX FOR SOUTHERN COUNTIES ESPECIALLY NEAR LAKE MICHIGAN. BY SATURDAY NIGHT EARLY SUNDAY A FAIRLY SHARP FRONTAL PASSAGE WILL USHER DOWN COLD AIR AND DROP 850MB TEMPS TO -14C TO -16C...WITH NO HINT OF WARMING THROUGH MONDAY. THE COLD AIR WILL LIKELY PRODUCE SOME LAKE EFFECT SNOW SHOWERS...THOUGH LOW LEVEL ANTICYCLONIC FLOW MAY HINDER DEVELOPMENT. GFS ENSEMBLES IN DECENT AGREEMENT WITH SLIGHTLY SOUTHWEST FLOW IN ADVANCE OF DEEPENING 500MB TROUGH OVER WESTERN CONUS...AND COLD AIR FILTERING DOWN BEHIND THE SURFACE RIDGE SLIDING DOWN FROM CANADA. RIDGE BECOMES ELONGATED TO OUR NORTH CREATING AN EASTERLY FLOW FROM AREAS OF LOW PRESSURE TO OUR SOUTH. AFOREMENTIONED SHORTWAVE DUE TO APPROACH CENTRAL PLAINS BY MONDAY WHICH MAY BE A DRY DAY DEPENDING ON STRENGTH OF RIDGE AXIS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ LAROSA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1213 PM EST MON DEC 29 2003 .UPDATE... THE WAVE OF LOW PRESSURE IS DEVELOPING OVER THE LOWER OHIO VALLEY. THE WATER VAPOR IMAGERY SHOWS PLENTIFUL MOISTURE IN PLACE. ALOFT THE UPPER JET WAS STRONGER THAN THE MODELS EXPECTED AND THE RUC PLACES MUCH OF SOUTH CENTRAL LOWER MICHIGAN IN THE DIFFLUENT RIGHT ENTRANCE REGION OF THE JET THIS AFTERNOON. SO AM EXPECTING A RATHER WET AFTERNOON FOR THE JACKSON AREA...TAPERING OFF AS YOU HEAD NORTHWEST TO SOME SPRINKLES FOR GRR. LDM CONTINUES TO SEE VARYING AMOUNTS OF CLOUDS AND PROBABLY SHOULD STAY THAT WAY FOR THE AFTERNOON. FORECAST SOUNDINGS FROM THE RUC SUPPORT MAINLY RAIN FOR THE AFTERNOON. NOTICED THE ETA THROUGH 18Z TODAY HAS NO PRECIPITATION FORECASTED WHERE IT IS ACTUALLY FALLING...MAINLY SOUTHEAST IL...TO CENTRAL INDIANA. && .GRR...WATCHES/WARNINGS/ADVISORIES...NONE. && $$ MJS mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1045 AM EST MON DEC 29 2003 .DISCUSSION... UPDATE FOCUS IS SNOW COVERAGE TODAY. SNOW AMOUNTS SHOULD REMAIN LESS THAN AN INCH THROUGH SUNSET AS MOISTURE AND FORCING ARE LIMITED. WV LOOP ALONG WITH 12Z RAOBS DEPICT SHORTWAVE TROUGH STRETCHING FM JAMES BAY TO WRN MN. ASSOCIATED SFC TROUGH SLIGHTLY E OF UPR WAVE AS IT NOW BEGINS TO MOVE INTO WRN LK SUPERIOR. ROABS FM MPX/INL MOIST THROUGH H7 (ALTHOUGH BARELY REACHING ABOVE CRITICAL -10C ISOTHERM) WHILE GRB ROAB ONLY HAS THIN LAYER OF MOISTURE AROUND H85. COLD AIR ADVECTION TAKING PLACE FM SW THIS MORNING WITH COLDEST POCKET OF H85 TEMPS OVR ERN SD/SW MN. ETA/RUC SHOW COOLER TEMPS PUSHING NE TOWARD UPR MI THROUGH AFTN. MQT RADAR/SFC OBS OVR UPR MI SHOW NO PCPN WHILE KDLH RADAR AND SFC OBS OVR CNTRL MN/NW WI PICKING UP SOME FLURRIES DUE TO THE INCREASING COLD ADVECTION AND UPR DIVERGENCE FM 130-140KT H3 JET STREAK RACING NNE ACROSS ERN WI/UPR MI. CURRENT FCST FOR TODAY NEEDS LITTLE CHANGING. DRY H9-H8 LAYER OVR MOST OF CWA ATTM SHOULD GRADUALLY MOISTEN THROUGH AFTN AS SHORTWAVE/SFC TROUGH AND COLD AIR ADVECTION CONJUR UP SUFFICIENT LIFT. BASED ON OBS FM A MUCH MORE MOIST UPSTREAM WOULD EXPECT RANDOM FLURRIES TO INCREASE TO MORE FORMIDABLE SNOW SHOWERS BY MID AFTN OVR WRN ZONES DUE TO INCREASING FLOW OFF LAKE AND OVER WATER INSTABILITY (DLT T/S AROUND 13C) AND OVR REST OF CWA BY EVENING DUE TO INCREASING UPR DIVERGENCE FM APPROACHING JET STREAK. CONCERNING LES TONIGHT 12Z GUIDANCE SUGGESTS THAT SHEAR WITHIN MIXED LAYER AND ONLY MARGINAL INSTABILITY WILL OFFSET DEEPER MOISTURE AND SOME TRANSIENT LOWER LEVEL CONVERGENCE TO PRODUCE SUB ADVY SNOW OVR WRN TIER. BEST CONVERGENCE LOOKS TO FORM FM KEWEENAW PENINSULA INTO PORCUPINE MTS OF ONTONAGON COUNTY. GOGEBIC COUNTY NOW LOOKING UNFAVORABLE AS WINDS SHIFT NW-W QUICKLY THROUGH H85 BY 06Z (WOULD PREFER MORE NRLY DIRECTION FOR THIS AREA TO SEE GREATER SNOW COVERAGE). UPDATED WX/POP/SNOW GRIDS FOR TONIGHT TO ADDRESS THIS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DULUTH MN 945 PM CST MON DEC 29 2003 .DISCUSSION...A VORT MAX HAS REMAINED OVER THE MN ARROWHEAD THIS EVENING AS DEPICTED BY THE RUC. SNOW SHOWERS HAVE BEEN SLOW TO DIE, BUT THEY ARE WEAKENING. A SMALL SINGLE CONTOUR CLOSED LOW FORMED JUST NORTHEAST OF THE ARROWHEAD AND THAT HAS HELPED MAINTAIN THE SNOW SHOWERS AS WELL. THAT LITTLE FEATURE IS FILLING ATTM. AN E-W COLD FRONT OVER EXTREME NRN MN IS DROPPING S, BUT IT IS PARALLEL TO THE UPPER FLOW SO PROGRESS WILL BE SLOW. SINGLE DIGITS LOW TEMPERATURES STILL APPEAR ON SCHEDULE FOR THAT AREA, BUT FARTHER S IN WISCONSIN ZONES, WE RAISED THE OVER NIGHT LOWS A BIT DUE TO CLOUDIENSS THAT WILL REMAIN. && .DLH...WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. $$ CS mn AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 215 PM CST MON DEC 29 2003 .DISCUSSION... SNOWFALL IN CURRENT AREA RADAR MOSAIC SHOWS A CLOSE CORRELATION WITH RUC 700 MB CLOSED HEIGHT CIRCULATION. THIS MID LEVEL LOW ALONG WITH IDEAL TEMPERATURE PROFILE AND LOW LEVEL INSTABILITY WAS ENOUGH TO BRING ACCUMULATIONS NEAR AN INCH. THE RUC MODEL FORECASTS THIS 700 MB LOW MOVING FROM NEAR HUDSON...WISCONSIN AT 18Z TO LADYSMITH BETWEEN 21Z AND 00Z. SNOW EXPECTED TO DISSIPATE BEHIND THIS FEATURE EARLY THIS EVENING. PARTIAL CLEARING OVERNIGHT SHOULD ALLOW MUCH COLDER TEMPERATURES UNDER WEAK SURFACE RIDGE BY DAYBREAK. WARM ADVECTION TUESDAY IS EXPECTED TO PRECEDE THE NEXT PACIFIC SYSTEM. PREFER THE MORE AGGRESSIVE GFS SOLUTION WITH THIS SYSTEM WHICH IS EXPECTED TO MOVE RAPIDLY ACROSS THE REGION. EXPECT A CHANCE OF PRECIPITATION IN THE NORTHWEST PORTION OF OUR COUNTY WARNING AREA LATE TUESDAY WITH THE BEST FORCING REMAINING JUST TO OUR NORTH. THE GFS MODEL HINTS AT A STRONG DRY SLOT SURGING TOWARD CENTRAL MINNESOTA BY MIDNIGHT TUESDAY NIGHT. SNOW OVER OUR COUNTY WARNING AREA SHOULD BE OVER BY WEDNESDAY MORNING. SUBSIDENCE EXPECTED TO CUT OFF THE CHANCE OF PRECIPITATION ABRUPTLY BEHIND THIS FEATURE. ANOTHER PACIFIC LOW PRESSURE SYSTEM FORECAST OVER THE NORTH CENTRAL PLAINS STATES ON THURSDAY AND CONTINUES THE TREND OF THE PAST FEW SYSTEMS BY TRACKING NORTH AND WEST OF MSP LEAVING US OUT OF THE MAIN PRECIPITATION SWATH. LOOKING AHEAD...CHALLENGE ON DEALING WITH SHOTS OF MOISTURE AND POTENTIAL LIGHT BOUTS OF PCPN AS WELL AS THE PENETRATION OF ARCTIC AIR. SMOOTHING WAS DONE THIS AFTN ON BORDERING TEMPS FOR DAY SIX THROUGH SEVEN. LIKE THE IDEA OF GOING TOWARD CLIMATE. CONCERN NOW IS OVER THE PCPN SHOWN ON NEW GFS CNTRL MN ON FRI. WILL NOT FLIP FLOP AT THIS TIME. THIS PCPN COULD WELL BE NORTH OF THE CWA. GENERAL THINKING IS THAT COLD AIR WILL SETTLE SOUTH AS IS TYPICAL OF NEW YEAR CLIMO BUT ARCTIC BLAST IS STILL SOMETHING TO MONITOR FOR DAY SEVEN. TROFS COMING INTO WEST COAST DAYS THREE THROUGH SEVEN HAVE STRENGTH YET TO BE DETERMINED WHEN THEY REACH UPR MS VLY. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. $$ mn AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BINGHAMTON NY 929 PM EST MON DEC 29 2003 .UPDATE...UPDATED GRIDS TO CHANGE OCCNL PRECIP TO SHOWERS...ADJUST TEMPS OVERNIGHT AND ON TUE...AND REMOVE PRECIP BEYOND EARLY AFT IN SERN ZONES. 18Z META AND 00Z RUC IN FAIR AGREEMENT THAT FRONT WILL PASS THRU WITH LIMITED AND WEAKENING DYNAMICS. WHAT IS LEFT OF THE DYNAMICS WILL ALSO LIFT NEWD QUICKLY DURING THE DAY ON TUE...THUS THOSE AREAS NOT AFFECTED BY THE LAKES WILL SEE PRECIP END AROUND EARLY AFTERNOON. BUMPED UP MINS A BIT TONIGHT...AS MOS TEMPS ARE NOT DROPPING AS EXPECTED. ALSO...LOOKS LIKES HIGHS IN MOST PLACES WILL OCCUR ~12Z...THEREFORE HAVE ADJUSTED GRIDS/ZONES TO REFLECT THAT TREND. MJC && .PREV DISCUSSION.... TONIGHT...CLOUDS WILL CONTINUE TO INCREASE THIS EVENING AHEAD OF A TROUGH THAT WILL LIFT OUT OF THE MIDWEST AND APPROACH WRN NY/PA TUESDAY MORNING. MODELS SHOW STRONG UPPER JET DYNAMICS 06Z-12Z WITH AREA OF RAIN SPREADING ACROSS THE FORECAST AREA FROM WEST TO EAST TONIGHT. TIMING IS SLOWER THAN PREVIOUS RUNS, WITH THE PRECIP NOT REACHING THE EASTERN AREAS UNTIL NEAR DAYBREAK. TUESDAY...WILL CONTINUE THE STEADIER SHOWERS ACROSS THE EAST IN THE MORNING AS THE COLD FRONT PASSES THROUGH AND COLDER 850 TEMPS PUSH INTO THE REGION FROM THE WEST. WILL TAPER THE RAIN TO SCATTERED SNOW SHOWERS FOR THE WESTERN ZONES IN THE MORNING AND ACROSS THE EAST FOR THE AFTN. TUESDAY NIGHT...BUFKIT SOUNDINGS INDICATE THAT THERE MAY BE A LITTLE LAKE EFFECT SHSN ACTIVITY UP NORTH, BUT INVERSION REMAINS FAIRLY LOW WITH NOT MUCH IN THE WAY OF INSTABILITY. ANY LAKE EFFECT WILL DIMINISH DURING THE OVERNIGHT WITH SOME 850 WAA AND SFC RIDGING BUILDING INTO THE AREA OVERNIGHT. THEREFORE, ONLY LIGHT ACCUMS EXPECTED. WILL KEEP JUST CHC POPS TO COVER IT FOR NOW. WEDNESDAY...CLIPPER SYSTEM SKIRTING ACROSS NORTHERN GREAT LAKES WILL SPREAD SOME CLDS INTO MAINLY NORTHERN HALF OF THE CWA. SOME UPWARD MOTION ASSOCIATED WITH THIS FEATURE NOTED ACROSS THE NORTHWEST PART OF THE FA IN THE AFTN. ATTM, WILL PUT IN LOW CHC POPS. LONG TERM (WED NGT THROUGH MON)... FAIRLY QUIET WITH NO SIG WX IN THE OFFING. WENT WITH 00Z GFS FOR THE MOST PART. A FEW WEAK SYSTEMS MAY PRODUCE SOME SPOTTY LGT PCPN, WITH GFS PROFILES INDICATING THE PSBLTY OF SOME -SN/-FZRA LATE THU NGT/FRI MRNG. GNRLY PARTLY TO MOSTLY CLOUDY SKIES WITH ABV NORMAL TEMPS. STRONGER SYS MAY GET ORGANIZED FOR EARLY NXT WEEK. && .AVIATION... VFR CONDITIONS UNTIL 09-12Z, THEN RAPIDLY FALLING CIGS/VSBY'S AS RAIN MOVS IN FROM W-E. WINDS PICKING UP BRHIND THE FNT, WITH G25-30. && .BGM WATCHES/WARNINGS/ADVISORIES... NY...NONE. PA...NONE. $$ JML/BRADY ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 250 PM EST MON DEC 29 2003 .ANOTHER SPRING-LIKE DAY ACROSS THE CWA WITH ABUNDANT SUNSHINE AND TEMPERATURES GENERALLY IN THE 40S AND 50S...RETURN TO SEASONABLE WEATHER LATE TOMORROW THROUGH FRIDAY. .DISC...AT 1 PM...COLD FRONT EXTENDED FROM ABOUT CHICAGO TO NEW ORLEANS. UPPER FLOW NEARLY PARALLEL TO FRONT SO EASTWARD PROGRESS IS SLOW. RUC ANALYSIS SHOWING 160 KT JET MAX OVER UPPER GREAT LAKES. COLD FRONT PROGGED THROUGH AREA DURING MORNING TOMORROW. AHEAD OF FRONT RAIN AND RAIN SHOWERS EXPECTED. THERE MAY BE A FEW ISOLATED POCKETS OF FREEZING RAIN TOMORROW MORNING IN SHELTERED VALLEYS. DEWPOINTS STILL BELOW FREEZING ACROSS CWA AND MODELS SHOWING GOOD RADIATIONAL COOLING CONDITIONS UNTIL JUST BEFORE SUNRISE WHEN CLOUDS RAPIDLY INCREASE AND PRECIPITATION MOVES IN. SIMILAR SITUATIONS HAVE OCCURRED AT LEAST TWICE IN LAST 10 DAYS WITH MANY TRAFFIC ACCIDENTS. WILL ISSUE SPS TO HIGHLIGHT POSSIBLE HAZARDOUS DRIVING CONDITIONS FOR MORNING COMMUTE. BY 18Z TOMORROW...FRONT THROUGH ALL BUT FAR EASTERN COUNTIES. ETA THERMAL PROFILES SHOW RAPID COOLING AND DESTABILIZATION OF ATMOSPHERE BEHIND FRONT BETWEEN 15Z AND 18Z. ETA/AVN CRANK OUT A TENTH OR TWO OF LIQUID AS SNOW OVER NORTHWESTERN AREAS TOMORROW AFTERNOON AND EVENING SO A FEW INCHES OF LAKE EFFECT SNOW POSSIBLE IN FAVORED AREAS. ANOTHER WEAK FRONT PUSHES THROUGH ON WEDNESDAY. WENT CHANCE SNOW FOR NORTHERN AREAS AND HIGHER TERRAIN SOUTH. SEASONABLE WEATHER CONTINUES INTO FRIDAY WITH SCT LAKE EFFECT SNOW SHOWERS THURSDAY AND OVERRUNNING/WARM ADVECTION SNOW POSSIBLE FOR FRIDAY. LOOKS TO BE LIGHT AT THIS TIME. EXTENDED...12Z ENSEMBLES MUCH SLOWER THAN 12Z OPERATIONAL GFS WITH VERY COLD AIR NOW OVER WEST. WET SYSTEM PROGGED IN FOR WEEKEND AND WAVY FRONT WILL LINGER THROUGH MONDAY...WITH PERIODS OF RAIN...ALTHO SOME SNOW POSSIBLE FOR NORTHERN HERKIMER/HAMILTON COUNTIES. COLD ARCTIC AIR WILL GRADUALLY WORK ITS WAY EAST BY NEXT TUESDAY. IF GFS ENSEMBLES ARE CORRECT...TEMPERATURES MAY BE BELOW NORMAL MIDDLE OF NEXT WEEK. .AVIATION...VFR CONDS WILL PERSIST UNTIL 12Z. -SHRA WILL PUSH INTO RGN ARND 12Z AND THERE MAY BE ISOLD AREAS WITH -FZRA UNTIL ARND 15Z TUE. .HYDROLOGICAL DISCUSSION...NO HYDRO PROBLEMS AT LEAST THROUGH FRIDAY. RAINFALL TUESDAY SHOULD BE UNDER A HALF INCH AND NOT BE ENOUGH TO PRODUCE MUCH OF A RESPONSE FROM AREA STREAMS AND RIVERS. .ALY...SPS FOR ISOLATED POCKETS OF FREEZING RAIN TUESDAY MORNING. FINAL GRIDS DONE. $$ SND ny AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY NATIONAL WEATHER SERVICE RAPID CITY SD 713 PM MST MON DEC 29 2003 .DISCUSSION...THE MAIN FORECAST CONCERN OVERNIGHT IS TEMPERATURES. BOTH ADVECTIVE AND PHYSICAL PROCESSES WILL COME INTO PLAY. IN TERMS OF ADVECTION...SURFACE OBSERVATIONS SHOWED A WARM FRONT OVER THE SWRN CWFA...FROM JUST NORTH OF KGCC AND KCUT TO JUST SOUTH OF KSFD. THE 00Z UPPER-AIR OBSERVATIONS ALSO INDICATED WARM ADVECTION OVER AND TO THE SOUTH OF THIS REGION...AND 24-HR TEMPERATURE CHANGES SHOWED WARMING FROM THE SURFACE THROUGH THE MID-TROPOSPHERE. GIVEN RELATIVELY WEAK SURFACE PRESSURE FALLS ACROSS THE CWFA...DO NOT EXPECT THE FRONT TO MAKE MUCH PROGRESS. NEVERTHELESS...THE RUC DOES FORECAST WARM ADVECTION TO PERSIST OVER THE SWRN CWFA OVERNIGHT. IN TERMS OF PHYSICAL PROCESSES...SNOW COVER EXISTS OVER THE NRN HALF OF THE CWFA...AS WELL AS PARTS OF WCNTRL AND SCNTRL SD. GIVEN ONLY THIN CLOUD COVER AND LIGHT WINDS OVER MUCH OF WRN AND SCNTRL SD...THIS WILL LEAD TO STRONG RADIATIONAL COOLING. RELATIVELY MORE CLOUD COVER EXISTS OVER NERN WY AND FAR SWRN SD...SO THE COOLING WILL NOT BE AS DRAMATIC THERE. AS A RESULT OF THIS...WILL ADJUST THE PREVIOUS FORECAST OVER NERN WY...THE BLKHLS...AND SWRN SD...TO RAISE THE MIN TEMPERATURES BY SEVERAL DEGREES...WHERE WARM ADVECTION WILL BE STRONGEST. OTHER- WISE...THE REST OF THE FORECAST LOOKS GOOD. && .UNR WATCHES/WARNINGS/ADVISORIES... .SD...NONE. .WY...NONE. && $$ BUNKERS sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 957 AM CST MON DEC 29 2003 .DISCUSSION... THE MID AND UPPER LEVEL LOW PRESSURE TROUGH WAS MOVING OVER EASTERN TEXAS THIS MORNING. CLOUDS ASSOCIATED WITH THE JET STREAK AHEAD OF THE TROUGH WERE STILL AFFECTING MOST OF SE TX. FORECAST ITEMS OF NOTE FOR TODAY INCLUDE SKY COVER AND POPS...TEMPERATURES...AND COASTAL WINDS AND SEAS. THE CURRENT VISIBLE SATELLITE TRENDS INDICATE THE 12Z RUC HAS A GOOD HANDLE ON CLEARING OUT THE AREA TODAY. CURRENTLY THERE WAS A SOLID MID AND HIGH LEVEL DECK MOVING OVER MOST OF THE FORECAST AREA WITH SOME CLEARING BEHIND THIS TO THE SOUTHWEST. THERE WILL BE ENOUGH HIGH CLOUDS AROUND TO NOT WARRANT CLEARING OUT EVERYTHING UNTIL MID AFTERNOON. TEMPERATURES WILL BE AFFECTED BY THE CLEARING SKIES AND SHOULD REACH AROUND 60 TO 62 OVER MOST OF THE INLAND AREAS. WILL UPDATE TO LOWER THE POPS...CLEAR OUT THE SKY COVER A BIT FASTER...AND UP THE DAYTIME HIGH TEMPERATURES A COUPLE OF DEGREES OR SO. THE WIND HAS DIMINISHED OVER THE BAYS AND NEARSHORE WATERS...ENOUGH TO DROP THE SCEC OVER THE BAYS AND LOWER THE SCA TO SCEC WITHIN 20 NM. WILL KEEP THE SCA UP FROM 20 TO 60 NM DUE TO WINDS AND SEAS. PL-40 41 && .HGX WATCHES/WARNINGS/ADVISORIES... SCEC 00 TO 20 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL. SCA 20 TO 60 NM HIGH ISLAND TO THE MATAGORDA SHIP CHANNEL. && $$ tx AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DES MOINES IA 355 PM CST TUE DEC 30 2003 .DISCUSSION... CDFNT SWINGING THRU TNGT AS UPR TROF OVR THE DKTAS MOTORS EWD. NEG PCPN OVRNGT WITH A DECENT COOLDOWN FOR TMR. HIGHS IN THE 30S/40S VS 40S/50S TDA. SPLIT FLOW READILY VISIBLE IN WV IMAGERY OVR THE W CST AS PAC JET SPLITS EWD AND SWD. CDR TMPS TMR WL BEGIN TO MODERATE WED NGT AND THU AS SLY FLOW DVLPS. THERE IS ONE FLY IN THE OINTMENT THAT WL LIKELY HOLD OFF SGFNT WRMG THU...THAT WL LIKELY BE LOW ST MOVG NWD. THE 48HR RUC HAS WDSPRD LIFR CIGS BY 12Z THU WHICH IS SUPPORTED BY THE 925 SFC IN THE ETA. THUS...MORE CLDS FOR THU AND NOT QUITE AS ROBUST ON THE WRMUP...DESPITE 1000-850 THICKNESSES SOME 20-30M HIGHER(THICKER?) THAN TDA. THINKING IS THAT A MORE WLY FLOW WL SHOVE THE LWR CLDS EWD LTR IN THE DAY...BUT MOST LIKELY PAST MAX HEATING. WL STILL HOLD ON TO SML POPS IN THE SERN CRNR IN RESPECT TO CONTG FCST OF LGT PCPN BY THE AVN AND SOME EXTENT THE ETA NOW AS WELL. AS THE BROAD UP TROF FORMS OVR THE WRN TWO-THIRDS OF THE COUNTRY...PAC JET ENERGY LOOKING TO FORCE MORE MID LVL MOISTURE EWD INT THE CNTRL US WITH LGT SNOW THREAT DVLPG LATE FRI NGT AND SAT. AT THE MOMENT...HAVE NOT JUMPED ON THIS...BUT CONTD THE PREV THINKING FOR SML POPS IN SRN IA. WL BE LOOKING AT THIS MORE CLOSELY IN LTR RUNS AS ARCTIC AMS OOZES GRDLY SWD. TMPS IN THE OUTPDS ARE THE BEST ESTIMATE SINCE WE COULD JUST AS EASILY BE MUCH WRMR OR MUCH COLDER! && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ MYERS ia AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1030 AM EST TUE DEC 30 2003 .UPDATE...8-BIT RADAR RESOLUTION SHOWS A RAPID DECREASE IN SNOW SHOWERS/FLURRIES WITH EXTENSIVE STRATUS DECK REMAINING. 12Z RAOBS UPSTREAM SHOWING WARMING 850MB TEMPS AND DRIER AIR ADVECTING ACROSS LAKE MICHIGAN. SOME WAA INDUCED CLOUDS, AC DECK, WAS EVIDENT ACROSS SOUTHERN WISCONSIN BUT THESE WILL LIKELY THIN WITH TIME AS CLOUDS OUTPACED THE UPSTREAM WAA REGIME UNDERWAY. SO THE QUESTION IS CLOUD COVER TODAY AND RUC/ETA SOUNDINGS ARE NOT MUCH HELP AS THEY ARE ON TOTAL OPPOSITE ENDS... WITH APPROACH OF RIDGE AXIS AND DRIER AIR THAT COMES WITH THIS...WOULD HAVE TO FAVOR CLOSER TO THE RUC WHICH WOULD SUPPORT CURRENT THOUGHTS OF SOME BREAKS IN THE CLOUD COVER THIS AFTERNOON FROM WEST TO EAST. EXPERIMENTAL NEW LAMP GUIDANCE ALSO HINTS AT THIS WITH SOMEWHAT COOLER TEMPS UNDER THE CLOUD COVER THROUGH THE "MAX HEATING" TIME FRAME. WE WILL DROP OUR HIGHS A COUPLE OF DEGREES IN THE GRIDS AND BACK OFF THE TIMING SOMEWHAT WHEN WE WILL SEE THE SUN. BGM && .PREV DISCUSSION...ISSUED AT 325 AM EST THE CURRENT SURFACE MAP SHOWS THE COLD FRONT THAT PASSED TROUGH SE MICHIGAN LAST EVENING ALREADY MOVING INTO THE APPALACHIANS WITH COLDER AIR NOW FILTERING ACROSS LOWER MICHIGAN. THE WATER VAPOR LOOP INDICATES AN UPPER TROUGH AXIS LOCATED OVER WESTERN LOWER MI...WITH SOME WRAP AROUND MOISTURE LOCATED OVER EASTERN WI/WESTERN LOWER MI. THE 00Z UPPER AIR SOUNDING OUT OF KMPX INDICATED AMPLE MOISTURE EXTENDING ALL THE WAY TO 600MB. THE 00Z UPPER AIR PLOTS ALSO INDICATED 850MB TEMPS OF -10 TO -11C UPSTREAM OF LAKE MICHIGAN...WHICH IS NOW ADVANCING ACROSS THE LAKE. SOME WEAK DIFFERENTIAL VORTICITY ADVECTION COUPLED WITH THE DEEP MOISTURE AND MARGINAL INSTABILITY OFF LAKE MICHIGAN WILL PROVIDE SOME LIGHT LAKE ENHANCED SNOW SHOWERS AND FLURRIES DOWNWIND OF LAKE MICHIGAN THIS MORNING...WITH NO ACCUMULATIONS EXPECTED. THE CURRENT KGRR RADAR IS ALREADY SHOWING AN INCREASE IN RETURNS OFF THE LAKE. GIVEN THE DEGREE OF LIFT...MOISTURE AND ENHANCEMENT OFF LAKE MICHIGAN...WILL MAINTAIN SCATTERED LIGHT SNOW SHOWERS THIS MORNING. MOISTURE IS MORE LIMITED TOWARD THE OHIO BORDER...SO WILL ONLY MENTION FLURRIES ACROSS LENAWEE/MONROE COUNTIES. THE MOISTURE QUICKLY PUSHES OFF TO THE NORTHEAST THIS AFTERNOON...WITH CONSIDERABLE DRYING IN THE LOW LEVELS ADVANCING ACROSS LOWER MI FROM SW TO NE. ETA SOUNDINGS ON BUFKIT TRY TO HOLD ONTO LOW LEVEL MOISTURE THROUGH 00Z THIS EVENING. GIVEN THE DEGREE OF DRYING AT 850MB AND WITH SURFACE FLOW BECOMING STRONGLY ANTICYCLONIC BY LATE AFTERNOON...WILL OP TO HAVE SKIES BECOMING PARTLY SUNNY THIS AFTERNOON. THE CURRENT MID LEVEL TROUGH NOW EVIDENT OVER WESTERN MONTANA WILL QUICKLY MOVE EAST AND AMPLIFY TODAY AND TONIGHT. THE 00Z MODEL SUITE ARE IN VERY GOOD AGREEMENT WITH THIS SYSTEM. MODEL SOLUTIONS INDICATE THE SHORT WAVE WILL REACH THE UPPER MISSISSIPPI VALLEY BY 06Z TONIGHT...THEN LIFT INTO THE NORTHERN GREAT LAKES BY 12Z WEDNESDAY. QG FORCING AHEAD OF THIS WAVE IS QUITE STRONG OVERNIGHT TONIGHT INTO WEDNESDAY MORNING ACROSS THE NORTHERN HALF OF THE FORECAST AREA. A BIG LIMITING FACTOR FOR PRECIP THOUGH WILL BE A SEVERE LACK OF MOISTURE. ETA SOUNDINGS INDICATE THE MID LEVELS NEVER MOISTEN UP ENOUGH TO SUPPORT PRECIP. THE GFS SOLUTION SHOWS A LITTLE MORE AVAILABLE MOISTURE...AND INDICATES A COUPLE HUNDREDTHS OF PRECIP GENERALLY NORTH OF M-59. GIVEN THIS IS OFTEN A BIAS OF THE GFS...WILL LEAN TOWARD THE DRYER ETA SOLUTION AND ONLY MENTION FLURRIES LATE TONIGHT INTO WEDNESDAY MORNING ACROSS THE SAGINAW VALLEY AND THUMB. THE DYNAMICS WITH THIS SYSTEM WILL SPIN UP A RELATIVELY DEEP SURFACE LOW OVER SOUTHERN LAKE SUPERIOR BY WEDNESDAY MORNING. THIS WILL DEVELOP A STRONG PRESSURE GRADIENT OVER LOWER MI. ETA SOUNDINGS INDICATE MIXING WILL TAP INTO SOME 35KTS ON WEDNESDAY IN THE COLD AIR ADVECTION AROUND THE LOW. SO WILL MENTION WIND GUSTS UP TO 40 MPH ON WEDNESDAY. THIS SYSTEM WILL VERY QUICKLY PUSH OFF TO THE EAST OF THE REGION BY WEDNESDAY EVENING AS A FAST ZONAL FLOW ALOFT PERSISTS ACROSS THE CONUS. MODEL SOLUTIONS BEGIN TO DIVERGE TOWARD THE END OF THE WEEK IN THEIR HANDLING OF NUMEROUS SHORT WAVE ENERGY ACROSS THE NORTHERN TIER OF THE US. THE ETA/GFS/CANADIAN/UKMET DO AGREE HOWEVER THAT REMNANTS OF A CUT OFF LOW OFF OF THE SOUTHERN CALIFORNIA COAST WILL MOVE INTO THE MISSISSIPPI VALLEY BY THURSDAY NIGHT...SENDING A WAVE OF MOISTURE AND WARM AIR ADVECTION INTO THE GREAT LAKES. THIS WILL SPELL A CHANCE FOR PRECIPITATION THURSDAY NIGHT INTO FRIDAY. THE ETA IS THE MOST AGGRESSIVE WITH THE WARM AIR WITH THIS SYSTEM. AT THIS STAGE IN THE FORECAST...WILL NOT GET TOO AGGRESSIVE WITH WARMING UP TEMPS THURSDAY INTO FRIDAY. WILL HOWEVER MENTION PRECIP TYPE AS ALL RAIN THURSDAY NIGHT SOUTH OF I-69 AS EVEN THE GFS SOLUTION HAS 1000-850MB THICKNESS VALUES GREATER THAN 1300M IN THESE LOCALS. WILL FORECAST TEMPS A COUPLE DEGREES ABOVE GUIDANCE TONIGHT SINCE THE GRADIENT WILL RAPIDLY STRENGTHEN WITH THE APPROACH OF THE NEXT SYSTEM. LOW TEMPS SHOULD ACTUALLY OCCUR DURING THE EVENING WHILE SOME SURFACE RIDGING LINGERS OVER SE LOWER MI. WEDNESDAY NIGHT WILL FORECAST TEMPS A COUPLE DEGREES BELOW GUIDANCE GIVEN ANOTHER SURFACE RIDGE AXIS MOVING OVERHEAD AND MOSTLY CLEAR SKIES. I WILL NOT STRAY MUCH FROM MAV GUIDANCE THROUGH THE REST OF THE FORECAST PERIODS. && .DTX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ CONSIDINE EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT HTTP://WWW.CRH.NOAA.GOV/DTX (ALL LOWER CASE) mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 1020 AM EST TUE DEC 30 2003 .DISCUSSION... SFC TROUGH IS ORIENTED ACROSS SRN HALF OF LK SUPERIOR AT 15Z BUT OBS ACROSS SUPERIOR AND UPR MI INTO NRN WI SHOWING PRESSURES HAVE ROSE AROUND 2-3MB IN LAST COUPLE HOURS. THIS SUGGESTS THAT TROUGH IS LOSING WHATEVER PUNCH IT HAD AND THIS MAKES SENSE AS PRIMARY SHORTWAVE LOBE IS OVR LK SUPERIOR AND SHIFTING NE AWAY FM TROUGH. OTHER THAN ISOLD BAND OF SNOW FM BIG BAY INTO DEERTON...CLOUDY SKIES OVR UPR MI PRODUCING NO PCPN. RUC HAS EXCELLENT HANDLE ON SFC WINDS AND PRESSURES AND HAVE FOLLOWED FOR UPDATE. SOUTH OF TROUGH...WHICH IS MOST OF CWA EXCEPT KEWEENAW PENINSULA INTO PICTURED ROCKS LAKESHORE...WILL SEE LITTLE MECHANISMS FOR ADDITIONAL PCPN AS HT RISES SPREAD INTO AREA. CONSIDERING UPSTREAM OBS ARE TURNING UP ONLY CLOUDY SKIES ACROSS NRN WI INTO ERN MN...WILL GO THAT ROUTE AND GO WITH DRY FCST FOR AFTN. NORTH OF TROUGH...CKC (GRAND MARAIS, MN) REPORTING LGT SNOW AND WITH WEAK COLD AIR ADVECTION (H85 TEMPS DROP TO -10C OVR NW LK SUPERIOR BY LATE AFTN) AND ONSHORE FLOW OPTED TO KEEP FLURRIES/-SHSN OVR KEWEENAW ENTIRE DAY. ANY SNOW ENDS BY LATE AFTN WITH ATTN TURNING TO STORM SYSTEM OVR PLAINS ATTM. SNOW WITH THAT LOW DOES NOT LOOK TO START UNTIL LATE EVENING-OVERNIGHT. AS SHORTWAVE PRESSES FARTHER NE MAY SEE SOME BREAKS OF SUN DEVELOP LATE DAY ALONG WI BORDER...BUT OVERALL MVFR CLOUDS (1000-3000FT) WILL LINGER. TEMPS GOING NOWHERE FAST WITH CLOUDS AND NEUTRAL TEMP ADVECTION. GRIDS ONLY SHOW FEW DEGREE RISE OFF CURRENT TEMPS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ JLA mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MARQUETTE MI 345 AM EST TUE DEC 30 2003 .DISCUSSION... MAIN FCST CONCERN IS SYSTEM FOR LATE TONIGHT/WED 08Z WV LOOP AND 500MB HEIGHT ANALYSIS OFF THE RUC SHOWED A RIDGE ALONG THE EAST COAST...A TROUGH OVER THE MISSISSIPPI VALLEY... ANOTHER RIDGE BUILDING OVER THE ROCKIES AND A TROUGH OVER THE W COAST. BOTH TROUGHS CONTAIN NORTHERN AND SOUTHERN STREAM FEATURES. THE ONE OVER THE MISSISSIPPI VALLEY HAS A SHRTWV OVER NORTHERN LAKE SUPERIOR WITH ANOTHER SHRTWV OVER KENTUCKY. THE TROUGH ALONG THE W COAST HAS A SHRTWV OVER NW MONTANA/SOUTHERN ALBERTA AND ANOTHER OVER CENTRAL CALIFORNIA. ANOTHER STRUNG OUT SHRTWV NOTED ALONG THE EASTERN SIDE OF THE RIDGE OVER THE ROCKIES...EXTENDING FROM SOUTHERN MANITOBA TO SOUTHERN ILLINOIS. THIS RIDGE MOVING TOWARDS UPPER MI NOT NEARLY AS WARM AS THE PREVIOUS ONE...WITH 500MB HEIGHTS NEARLY 300 METERS LOWER AT 40 N LATITUDE. HOWEVER...850MB TEMPS AT 00Z WERE -5C AT RAP AND +1C AT LBF. OVER UPPER MICHIGAN... TEMPS WERE AROUND -8C...PROVIDING LAKE ENHANCEMENT TO THE CURRENT CLOUDY SKIES AS SEEN ON 11-3.9 UM SATELLITE IMAGERY...AND AIDING IN THE CURRENT SCATTERED -SHSN ON KMQT RADAR. CLOUDS ALSO HELPING IN KEEPING TEMPS UP WITH READINGS IN THE MID TO UPPER 20S AT 08Z. SATELLITE IMAGERY ALSO SHOWED CLEAR SKIES ON THE WEST SIDE OF THE SHRTWV OVER THE PLAINS. AT THE SFC...A WEAK TROUGH WAS ALONG THE SOUTH SHORE OF LAKE SUPERIOR AND A RIDGE OF HIGH PRESSURE EXTENDED FROM MISSOURI TO MANTIOBA. WITH WESTERLY WINDS COMING DOWN THE ROCKIES...PRESSURES ARE FALLING WITH A LOW OVER NORTH CENTRAL WYOMING AND A WARM FRONT EXTENDING EASTWARD TO FSD. TODAY...SHRTWV TROUGH OVER NORTHERN LAKE SUPERIOR MOVES SE WHILE THE RIDGING OVER THE PLAINS BUILDS IN. ORIGINAL THOUGHT WOULD HAVE THE SFC TROUGH MOVE S...BUT WITH THE SHRTWV ALONG THE EASTERN SIDE OF THE RIDGE MOVING ACROSS UPPER MICHIGAN AROUND NOON...THE TROUGH DOES NOT GO ANYWHERE. DURING THE AFTERNOON...WINDS TURN TO THE SW AS THE SFC HIGH PRES RIDGE MOVES TO THE EAST OF UPPER MI...SO THE TROUGH PRETTY MUCH FALLS APART. 850MB TEMPS WARM ABOVE -7C DURING THE AFTERNOON WHICH COMBINED WITH ANTICYCLONIC FLOW WILL DISSIPATE ANY LAKE EFFECT THAT MIGHT BE GOING ON UNDERNEATH THE CURRENT CLOUDY SKIES. THUS ANY SNOW SHOWERS OR FLURRIES SHOULD DISSIPATE THIS MORNING. ALSO...EXPECTING THE LOW CLOUDS TO CLEAR OUT DURING THE AFTERNOON WITH THE PASSAGE OF THE SECOND SHRTWV...BUT BE FOLLOWED UP QUICKLY BY MID/HIGH CLOUDS (ALREADY PRESENT IN WESTERN SOUTH DAKOTA). WITH LITTLE SUNSHINE TODAY...TEMPS WILL ONLY A RISE A FEW DEGREES OFF OF CURRENT READINGS. TONIGHT...SHRTWV OVER NW MONTANA MOVES TO CENTRAL LAKE SUPERIOR BY 12Z WED...PULLING THE SFC LOW UP TO STANNARD ROCK. WARM ADVECTION/ISENTROPIC LIFT FROM A 40 KT LOW LEVEL JET AT 850MB AHEAD OF THE LOW...COMBINED WITH RAPIDLY FALLING HEIGHTS AFTER MIDNIGHT... WILL HELP INCREASE VERTICAL MOTION ACROSS THE U.P.. SOURCE REGION OF AIR FOR THIS EVENING...OVER OMAHA AND RAPID CITY...SHOW DEWPOINT DEPRESSION OF NEARLY 10C FROM THE SFC TO 600MB. FIGURE MUCH OF THE VERTICAL MOTION OCCURRING DURING THE EVENING WILL BE USED IN MOISTENING THE AIR...THEN IT SHOULD BEGIN SNOWING AROUND MIDNIGHT. AFTER THE COLD FRONT PASSES THE WESTERN U.P. DURING THE OVERNIGHT HOURS...WINDS WILL KICK UP AS PRESSURES RISE ABOUT 2 MB/HR ALONG WITH THE 15 TO 25 KT SFC WINDS. ALSO...WITH 850MB TEMPS FALLING TO -10C BEHIND THE FRONT AND INVERSIONS RISING TO 6-7 KFT...EXPECT LAKE EFFECT SNOW SHOWERS TO FORM OVER WESTERN LAKE SUPERIOR...SPREADING INTO WESTERN UPPER MICHIGAN AROUND 09Z. SNOWFALL RATES WILL HAVE TO BE WATCHED AS BEST OMEGA OCCURS IN A NEAR SATURATED LAYER IN BETWEEN THE -12C AND -17C ISOTHERM. FOR NOW HAVE PUT UP TO 5 INCHES WITH THIS SYSTEM AND A LAKE EFFECT SNOW AND BLOWING SNOW ADVISORY MAY BE NEEDED ON THE NEXT SHIFT FOR THE FOUR WESTERN COUNTIES. MIN TEMPS STAYING ABOVE NORMAL WITH CLOUDS AND BREEZY CONDITIONS...FORECASTING AROUND 18 INTERIOR TO 23 OVER THE EAST. NEW YEARS EVE...SFC LOW AND SHRTWV QUICKLY MOVE E...WITH THE SFC LOW REACHING SW QUEBEC BY 00Z THU AND ANOTHER HIGH PRES RIDGE MOVING TO DLH AT THE SAME TIME. WINDY CONDITIONS WITH LAKE EFFECT SNOW WILL CONTINUE DURING THE MORNING...BUT THEN AS FLOW TURNS ANTICYCLONIC OVER WESTERN LAKE SUPERIOR...DRY AIR ADVECTS IN (RH'S OF LESS THAN 30 PERCENT ABOVE 5000 FT) AND INVERSIONS FALL TO 2500 FT...EXPECT THE SNOW TO DIMINISH IN THE AFTERNOON. WITH COLD ADVECTION AND LAKE CLOUDS...TEMPS WILL HAVE A HARD TIME RISING. LOW TO MID 20S SHOULD HOLD WEST AND CENTRAL AND NEAR 30 EAST. NEW YEARS EVE NIGHT...SFC HIGH PRES RIDGE CROSSES UPPER MI DURING THE NIGHT WITH RETURN FLOW SETTING UP LATE IN THE WESTERN AND CENTRAL U.P.. EXPECTING LAKE EFFECT CLOUDS TO FALL APART IN THE EVENING...WITH SOME HIGH CLOUDS PASSING ACROSS UPPER MICHIGAN DURING THE NIGHT AS A 110 KT JET SETS UP ALONG THE U.S. - CANADIAN BORDER. SHOULD BE A GOOD RADIATIONAL COOLING NIGHT WITH WINDS BECOMING LIGHT...FRESH SNOW COVER AND ONLY A FEW CLOUDS DURING THE OVERNIGHT. MAV GUIDANCE SHOWS LOWS AROUND 10 ABOVE AND THIS LOOKS REASONABLE. WOULD NOT BE SURPRISED TO SEE TRADITIONAL COLD SPOTS SUCH AS AMASA AND CLARKSBURG TO DROP INTO THE SINGLE DIGITS BEFORE THE WIND PICKS UP LATE. NEW YEARS DAY AND NIGHT...UNCERTAINITY HERE REGARDING NEXT SHRTWV COMING OUT OF THE PACIFIC NW. ETA/CANADIAN MUCH FASTER...BRINGING A SFC LOW AND COLD FRONT TO MN BY 00Z FRI...WHEREAS THE GFS/UKMET HAVE IT OVER THE CENTRAL PLAINS AT THE SAME TIME. HPC PREFERENCE IS FOR A COMPROMISE GIVEN THE UNCERTAINITY. WARM ADVECTION AHEAD OF THE SYSTEM WILL HELP BRING 850MB TEMPS UP TO -4C BY 18Z THU. ALONG WITH THE WARM ADVECTION...ISENTROPIC LIFT WILL INCREASE...WHICH MAY BE ENOUGH TO PRODUCE SOME PRECIP IN THE AFTERNOON. IF THE GFS PANS OUT...THE PRECIPITATION WOULD BE IN THE FORM OF SNOW...BUT IF THE ETA/CANADIAN PAN OUT...PRECIP WILL BE IN THE FORM OF FREEZING RAIN. THUS WILL ADD A POTENTIAL FOR FREEZING RAIN TO THE CHANCE OF SNOW IN THE FORECAST. TEMPS WARMER THAN WED DUE TO THE WARM ADVECTION AND SOUTHERLY WINDS. WILL BUMP UP HIGHS TO AROUND 30. REST OF FORECAST REMAINS THE SAME. UNCERTAINITY STILL REMAINS FOR FRI THROUGH SUN SYSTEM. GFS RUNS HAVE BEEN CONSISTENT...SHOWING RAIN HERE FOR FRI NIGHT FOLLOWED BY COLDER AIR MOVING IN ON SAT. HOWEVER...00Z UKMET/CANADIAN AND 12Z ECMWF ALL POINT TO HAVING SNOW...POTENTIALLY SIGNIFICANT. WILL PASS ALONG TO DAY SHIFT THESE CONCERNS. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ AJ mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBANY NY 220 PM EST TUE DEC 30 2003 .DISC...COLD FRONT BLEW THROUGH PRETTY MUCH ON SCHEDULE THIS MORNING. AHEAD OF FRONT A FEW POCKETS OF FREEZING RAIN REPORTED...AS WELL AS SOME TRAFFIC ACCIDENTS DUE TO ICE. LATEST RUC ANALYSIS SHOWS STRONG SURFACE PRESSURE GRADIENT AND 3HR PRESSURE RISES OF 6 TO 7 MB PRODUCING GUSTY WINDS. RADAR SHOWING UPSLOPE/LAKE EFFECT SHOWERS OVER WESTERN AREAS. TEMPS/OBS INDICATE RW-/SW- IN THE VALLEYS AND SW- OVER MOUNTAINS. NEXT COUPLE OF DAYS LOOK DRY OVER MOST OF AREA. WEAK CLIPPER GOES BY TO NORTH OF AREA TOMORROW. SYSTEM HAS DYNAMICS BUT LITTLE MOISTURE. KEPT SCATTERED SNOW SHOWERS OVER ADIRONDACKS. PARTLY CLOUDY ELSEWHERE. AFTER SYSTEM PASSES WINDS GO NORTHWEST FOR A TIME AND TEMP AND SHEAR PROFILES SHOW SOME LIGHT LAKE EFFECT SNOW POSSIBLE THURSDAY OVER ADIRONDACKS. DRY ELSEWHERE. THURSDAY NIGHT AND FRIDAY...WARM ADVECTION SNOW INDICATED BY MODELS. VERY LIGHT ACCUMULATIONS EXPECTED. A LITTLE BREAK EXPECTED FRIDAY NIGHT BEFORE COLD FRONT APPROACHES THE AREA ON SATURDAY. .EXTENDED...FORECASTING WILL GET DICEY (AND POSSIBLY ICY) LATER IN THE WEEKEND. THINGS SHOULD BE WARM ENOUGH FOR ALL RAIN ON SATURDAY. BY SATURDAY NIGHT...A SHALLOW SLOPED ARCTIC COLD FRONT IS FORECAST BY THE GFS TO UNDERCUT THE WARMER AIR ALOFT AS IT SLOWLY OOZES SOUTH ACROSS THE REGION. THIS COULD SPELL PROBLEMS AS THE FLOW ALOFT REMAINS SOUTHWEST. I CONTINUED TREND OF PREVIOUS CREW WITH FREEZING/FROZEN PRECIPITATION SUNDAY INTO MONDAY. FOLLOWED 00/12Z GFS ENSEMBLE GUIDANCE AND LOWERED TEMPS ENOUGH FOR ALL SNOW ON MONDAY AS WAVE MOVES ALONG THE FRONT. .AVIATION...CURRENT ALBANY RADAR VAD WIND PROFILE SHOWS 35-45 KNOTS OF WIND FROM THE WEST NORTHWEST BETWEEN 3 AND 5 THOUSAND FEET. SFC WIND GUSTS TO 40 MPH POSSIBLE THIS AFTERNOON AND EVENING AS WINDS MIX DOWN UNTIL AFTER SUNSET. GENERALLY...VFR CONDITIONS EXPECTED THROUGH TOMORROW. LOCALLY MVFR IN SNOW SHOWERS...ESPECIALLY OVER HIGHER TERRAIN. .HYDROLOGY...DRY CONDITIONS OR FROZEN PRECIPITATION EXPECTED THROUGH FRIDAY. STAGES EXPECTED TO RISE SLIGHTLY THIS EVENING FROM TODAYS RAIN...THEN FALL SLOWLY OVER NEXT FEW DAYS. .ALY...NONE. $$ SND ny AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE ALBANY NY 1210 AM EST TUE DEC 30 2003 .DISC...FORCED TO DO AN EARLY MORNING UPDATE DUE TO TEMPERATURES WELL BELOW ADVERTISED LOWS AT KGFL. BELIEVE THE REAL THREAT FOR FREEZING RAIN IS IN THE PART OF THE UPPER HUDSON VALLEY...SOUTH TO ABOUT SARATOGA SPRINGS FOR THE EARLY MORNING. HAVE MAD MINOR ADJUSTMENTS THE TIMING OF ONSET OF PRECIPITATION. NO CHANGES TO LATER PERIODS. .ALY...NONE. _____________________________________________________________________ **********PREVIOUS AREA FORECAST DISCUSSION***************** .ANOTHER SPRING-LIKE DAY ACROSS THE CWA WITH ABUNDANT SUNSHINE AND TEMPERATURES GENERALLY IN THE 40S AND 50S...RETURN TO SEASONABLE WEATHER LATE TOMORROW THROUGH FRIDAY. .DISC...AT 1 PM...COLD FRONT EXTENDED FROM ABOUT CHICAGO TO NEW ORLEANS. UPPER FLOW NEARLY PARALLEL TO FRONT SO EASTWARD PROGRESS IS SLOW. RUC ANALYSIS SHOWING 160 KT JET MAX OVER UPPER GREAT LAKES. COLD FRONT PROGGED THROUGH AREA DURING MORNING TOMORROW. AHEAD OF FRONT RAIN AND RAIN SHOWERS EXPECTED. THERE MAY BE A FEW ISOLATED POCKETS OF FREEZING RAIN TOMORROW MORNING IN SHELTERED VALLEYS. DEWPOINTS STILL BELOW FREEZING ACROSS CWA AND MODELS SHOWING GOOD RADIATIONAL COOLING CONDITIONS UNTIL JUST BEFORE SUNRISE WHEN CLOUDS RAPIDLY INCREASE AND PRECIPITATION MOVES IN. SIMILAR SITUATIONS HAVE OCCURRED AT LEAST TWICE IN LAST 10 DAYS WITH MANY TRAFFIC ACCIDENTS. WILL ISSUE SPS TO HIGHLIGHT POSSIBLE HAZARDOUS DRIVING CONDITIONS FOR MORNING COMMUTE. BY 18Z TOMORROW...FRONT THROUGH ALL BUT FAR EASTERN COUNTIES. ETA THERMAL PROFILES SHOW RAPID COOLING AND DESTABILIZATION OF ATMOSPHERE BEHIND FRONT BETWEEN 15Z AND 18Z. ETA/AVN CRANK OUT A TENTH OR TWO OF LIQUID AS SNOW OVER NORTHWESTERN AREAS TOMORROW AFTERNOON AND EVENING SO A FEW INCHES OF LAKE EFFECT SNOW POSSIBLE IN FAVORED AREAS. ANOTHER WEAK FRONT PUSHES THROUGH ON WEDNESDAY. WENT CHANCE SNOW FOR NORTHERN AREAS AND HIGHER TERRAIN SOUTH. SEASONABLE WEATHER CONTINUES INTO FRIDAY WITH SCT LAKE EFFECT SNOW SHOWERS THURSDAY AND OVERRUNNING/WARM ADVECTION SNOW POSSIBLE FOR FRIDAY. LOOKS TO BE LIGHT AT THIS TIME. EXTENDED...12Z ENSEMBLES MUCH SLOWER THAN 12Z OPERATIONAL GFS WITH VERY COLD AIR NOW OVER WEST. WET SYSTEM PROGGED IN FOR WEEKEND AND WAVY FRONT WILL LINGER THROUGH MONDAY...WITH PERIODS OF RAIN...ALTHO SOME SNOW POSSIBLE FOR NORTHERN HERKIMER/HAMILTON COUNTIES. COLD ARCTIC AIR WILL GRADUALLY WORK ITS WAY EAST BY NEXT TUESDAY. IF GFS ENSEMBLES ARE CORRECT...TEMPERATURES MAY BE BELOW NORMAL MIDDLE OF NEXT WEEK. .AVIATION...VFR CONDS WILL PERSIST UNTIL 12Z. -SHRA WILL PUSH INTO RGN ARND 12Z AND THERE MAY BE ISOLD AREAS WITH -FZRA UNTIL ARND 15Z TUE. .HYDROLOGICAL DISCUSSION...NO HYDRO PROBLEMS AT LEAST THROUGH FRIDAY. RAINFALL TUESDAY SHOULD BE UNDER A HALF INCH AND NOT BE ENOUGH TO PRODUCE MUCH OF A RESPONSE FROM AREA STREAMS AND RIVERS. .ALY...SPS FOR ISOLATED POCKETS OF FREEZING RAIN TUESDAY MORNING. FINAL GRIDS DONE. $$ SND ny AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 230 PM CST TUE DEC 30 2003 FCST CONCERNS...SNOW THIS EVENING...THEN TEMPS...THEN STORM TRACK FRI NIGHT. MODELS HANDLING CURRENT SYSTEM FINE...WITH RUC/ETA VERIFYING QUITE WELL WITH MAX QPF PLACEMENT. AS FOR LATER PDS...AS DISCUSSED ON COORD CHAT 12Z GFS AN OUTLIER WITH SFC LOW FROM WRN MT INTO NE MT ON FRIDAY...VERSUS ETA/NOGAPS/CANADIAN/UKMET VERSION WITH SFC LOW THRU SD. PREFER THIS SD TRACK FOR NOW. WILL UPDATE HWO FOR SNOW THREAT FRI NIGHT AND FOR LOW WIND CHILLS AND COLD THIS WEEKEND. .SHORT TERM... RUC 295K OMEGA NAILING WHERE COLDEST CLOUDS ARE WITH HEAVIEST SNOW ON SRN EDGE OF THIS. MOVEMENT OF THIS IS SLIGHTLY DUE NORTH OF EAST...WHICH WOULD TAKE HEAVIEST SNOWS JUST NORTH OF A VALLEY CITY TO PARK RAPIDS LINE...AND JUST SOUTH OF A GRAND FORKS TO THIEF RIVER FALLS LINE. IN GRIDDS...HAD MAX OF AROUND 3 INCHES IN THIS AREA TAPPERING TO AN INCH OR LESS FAR SOUTH AND NORTHWEST PARTS OF THE FCST AREA. TIMING WISE...WENT CATGEORICAL SNOW THIS EVENING MOST AREAS...ENDING IN THE ERN ZONES (BJI-BDE-PKD) BY 09Z. .LONGER TERM... WK SFC RIDGE WORKS IN ON WEDNESDAY WITH WINDS TURNING TO THE SOUTH IN THE AFTN. WEAK SHORT WAVE ENERGY DOES SOUTHEAST OUT OF MANITOBA WITH SOME FLURRY POTENTIAL ACROSS NW MN IN THE AFTN AND EVENING. PROBLEM WED NIGHT AND THURSDAY ARE TEMPS. SOUTH WINDS TO HOLD UP WED NIGHT SO HAD TEMP FALL IN THE EVENING THEN RISING TEMPS OVERNIGHT WITH 20S PSBL ON THURSDAY...THOUGH FRESH SNOW COVER AND LIGHT WIND REGIME AT THE SFC MAY PLAY HAVOC ON THIS. AS FOR FRIDAY SYSTEM...EXCEPT FOR 12Z GFS...MODELS IN GOOD AGREEMENT IN TAKING STORM THAT MOVES ONSHORE NRN CALIFORNIA AND SRN OREGON INTO WYOMING ON FRIDAY WITH SFC LOW DEVELOPING AND MOVING ACROSS SD INTO CNTRL/SRN MN BY EARLY SATURDAY. ETA REALLY BULLISH WITH QPF AT 12Z WITH NEARLY .40 LIQUID IN SE ND/WCNTRL MN FRI AFTN. ENOUGH CAUTION STILL SO KEPT 50 POPS WITH THIS SYSTEM. .EXTENDED (SAT-TUE)... QUITE A BIT OF UNCERTAINTLY REMAINS WITH SFC LOW TRACK INTO SAT (SEE PMDEPD) SO WILL BASICALLY STICK WITH THE STATUS QUO FOR NOW WITH PCPN ON SAT. 12Z GFS TRACK IS NORTH OF THE BORDER WHILE THE ETA WEAKER AND ACROSS SOUTHERN MN. GFS TRYING TO SHOW ANOTHER WEAK SYSTEM MON (CLIPPING SOUTHEAST FA) WHICH THE CANADIAN ALSO SHOWS. WITH THE POLAR VORTEX DROPPING SOUTH SHIFTING THE UPPER JET SOUTH AS WELL...AM HESITANT TO ADD PCPN FOR NOW. TREND OF BRINGING COLDEST AIR OF THE SEASON SOUTH EARLY NEXT WEEK STILL LOOKS ON TRACK. GFS AND ECMWF BOTH AGREE IN SHOWING 1000-500MB THICKNESSES BEGINNING THEIR PLUNGE SUN...SO NO MAJOR CHANGES TO PREVIOUS GRIDS. WILL UPDATE HWO TO MENTION CHC SNOW LATE FRIDAY-EARLY SATURDAY AND TO HIGHLIGHT COLD THIS WEEKEND. GRIDDED WINDCHILLS HIT BELOW -40F IN THE NORTH SUN NIGHT. TOO FAR AWAY FOR ANY WATCH. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ RIDDLE/GODON nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 1010 AM CST TUE DEC 30 2003 GOING FCST ON TRACK AND NO CHANGES ATTM TO SNOW AMOUNTS WITH UPCOMING SYSTEM. AFTER A COLD START HOW WARM CAN IT GET WILL BE THE MAIN CHALLENGE THIS AFTN. 15Z SATELLITE AND RUC ANALYSIS SHOWS NICE VORT OVER SE MT...MOVING JUST SOUTH OF DUE EAST. VORT PROGGED TO MOVE THRU EXTREME SRN ND TO NR SISSETON SD BY 03Z. SFC LOW IN ECNTRL WYOMING AND SW SD WILL MOVE EAST ALONG WARM FRONT CURRENTLY IN SRN SD AND BE LOCATED NR BROOKINGS SD AT 00Z AND INTO WCNTRL/SW MN AT 03Z. ATTM...OBSERVATIONS AND RUC PROG INDICATE HEAVIEST AREA OF SNOW JUST ON TIP OF VORT WHICH WOULD PUT MAX SNOW BAND THRU CNTRL ND...ROUGHTLY BETWEEN HIGHWAY TWO AND INTERSTATE 94 IN ND...AND TOWARD BJI/PKD IN MN THIS EVENING. TIMING WISE...LOOKS LIKE SPREADING INTO THE VALLEY LATE AFTN AND INTO MN EARLY EVENING...LASTING ABT 6 HOURS. WILL SLIGHTLY ADJUST TIMING IN VALLEY ZONES TO PUT SNOW ACCUM INTO TONIGHT ZFP GROUP AND UP WORDING TO -SN LIKELY THIS EVENING. THOUGHT ABOUT SPLITTING FAR NORTH AND FAR SOUTH FOR LESSER AMTS...BUT WILL MAINTAIN 1-3 RANGE OVER THE AREA UNTIL MORE CERTAIN OF EXACT TRACK. WINDS NOT A BIG DEAL WITH THIS SYSTEM SO BLOWING SNOW WITH THIS ARCTIC FLUFF NOT A MAJOR PROBLEM...THUS NO HEADLINES NEEDED. AFTN TEMPS WILL HAVE A HARD TIME RISING MUCH ABV ZERO IN THE DVL BASIN WHERE LOWS LAST NIGHT DROPPED TO NEAR 20 BELOW AT LANGDON AND RUGBY. WILL ADJUST SOME HIGHS DOWNWARD AS CLOUDS INCREASE AND WINDS NOT ALL THAT STRONG. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...NONE. MN...NONE. && $$ RIDDLE nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORMAN OK 1123 AM CST TUE DEC 30 2003 WILL UPDATE TO NUDGE AFTERNOON HIGHS UP A TAD. USING 15Z RUC FOR 3-HR DEWPOINT AND WIND GRIDS...WHICH BRINGS AFTERNOON RH DOWN TO 5-10 PCT OUT W. RED FLAG WARNING CONTINUES W OF I-35. SKIES CHANGED TO MOSTLY SUNNY E AS CIRRUS IS THIN...AND THICKER STUFF NOW MOVING INTO NW TX WILL ONLY REACH W ZONES THIS AFTERNOON. CONTINUING TO LOOK CLOSELY AT A VERY TOUGH FCST REGARDING ARRIVAL OF COLD AIR THIS WEEKEND. INITIAL THINKING IS THAT FASTER/COLDER WILL BE THE BETTER FORECAST BASED ON CLIMO AND TYPICAL MODEL BIASES...BUT A LOT WILL DEPEND ON MESOSCALE/SHORTWAVE DETAILS WITHIN THE FAST FLOW THRU THE LONGWAVE TROF. MODELS WILL STRUGGLE WITH THESE AS WELL. FCSTID = 24 OKC 58 34 60 42 / 00 00 00 30 HBR 60 34 59 41 / 00 00 00 30 SPS 62 35 61 46 / 00 00 00 30 GAG 61 27 52 37 / 00 00 00 30 PNC 58 33 51 40 / 00 00 00 10 DUA 60 37 61 49 / 00 00 00 20 359 AM CST TUE DEC 30 2003 A TIGHTENING PRESSURE GRADIENT IS ALREADY BEGINNING TO CRANK UP THE WIND SPEEDS ACROSS THE AREA. IT SHOULD BE OUTRIGHT WINDY BY AFTERNOON OVER MOST OF OUR FORECAST AREA. COMBINING THAT WITH THE VERY DRY AIR IN PLACE... MOST OF OUR FORECAST AREA WILL REACH RED FLAG CRITERIA. WE WILL HAVE A RED FLAG WARNING FOR THIS AFTERNOON GENERALLY FROM I-35 WEST TO THE PANHANDLES. EAST OF I-35... RELATIVE HUMIDITIES WILL BE SOMEWHAT HIGHER... AND DROUGHT INDICES ARE MUCH LESS FAVORABLE FOR WILDFIRES. A MINOR COLD FRONT WILL DROOP INTO NORTHERN OKLAHOMA WEDNESDAY... LOWERING TEMPERATURES A BIT... THEN RECEDE NORTH AS STRONGER LOW PRESSURE STRENGTHENS TO OUR WEST. THE NEXT MAJOR SYSTEM WILL CROSS THE REGION THURSDAY... NEW YEARS DAY... BRINGING WIDESPREAD RAIN TO MOST OF OUR FORECAST AREA... ESPECIALLY THE SOUTHEAST. A FEW THUNDERSTORMS WILL BE LIKELY ALONG WITH THE RAIN IN OUR SOUTHEASTERN COUNTIES ON THURSDAY. INSTABILITY LOOKS TOO WEAK TO SUPPORT THUNDER ELSEWHERE. ANOTHER COLD FRONT IS SCHEDULED TO ARRIVE SATURDAY... BRINGING A NOTICEABLE COOL-DOWN. SOME PRECIPITATION MIGHT OCCUR WITH THIS SYSTEM... BUT THE CHANCES ARE TOO LOW RIGHT NOW TO ADD TO THE FORECAST. THINGS GO DOWNHILL FROM THERE. IF THE GFS IS ANYWHERE CLOSE TO RIGHT WITH THE PATTERN ON MONDAY... THE VERY COLD AIRMASS TO OUR NORTH SHOULD CONTINUE OOZING SOUTH... CONTRARY TO THE GFS PLAN OF SPINNING UP A STRONG LOW OVER SOUTHWEST KANSAS ON TUESDAY. AS A RESULT... WE HAVE ASSUMED A MORE SOUTHWESTERLY POSITION OF THAT LOW AND PLAN ON CONTINUED NORTHERLY SURFACE FLOW AND CHILLY TEMPERATURES OVER OKLAHOMA AND NORTH TEXAS. EVEN COLDER AIR COULD ARRIVE LATER IN THE WEEK... BUT TIMING AND MAGNITUDE ARE VERY UNCERTAIN AT THIS POINT. IN THE WORST CASE SCENARIO... TEMPERATURES COULD REMAIN WELL BELOW FREEZING DURING THE DAYTIME ONCE THE CORE OF THE COLD AIR ARRIVES. FCSTID = 23 = CMS .OUN... OK...RED FLAG WARNING THIS AFTERNOON...APPROXIMATELY FROM I-35 WEST TX...RED FLAG WARNING THIS AFTERNOON...ALL ZONES ok AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ABERDEEN SD 325 PM CST TUE DEC 30 2003 .SHORT TERM...TONIGHT THROUGH FRIDAY NIGHT FORECAST ISSUES FOR SHORT TERM WILL BE PRECIP CHANCES FOR THIS EVENING AND FRIDAY ALONG WITH TEMPERATURES. SHORT WAVE TROUGH AXIS JUST APPROACHING WESTERN DAKOTAS WITH SMALL SCALE VORT LOBE PUSHING THROUGH SOUTHERN NORTH DAKOTA AT THIS TIME. ENHANCED SNOWFALL HAS REMAINED NORTH OF CWA ACROSS SOUTH CENTRAL NORTH DAKOTA. AREA OF ENHANCED REFLECTIVITY MATCHING UP NICELY JUST ON WARM SIDE OF MID LEVEL FRONTOGENESIS AXIS DRAPED ACROSS CENTRAL NORTH DAKOTA. RUC FORECASTING THIS MID LEVEL FRONTOGENESIS AXIS TO DRIFT EAST/NORTHEAST INTO EASTERN NORTH DAKOTA TONIGHT AS VORT LOBE ACROSS SOUTHERN NORTH DAKOTA SWINGS THROUGH BASE OF SHORT WAVE. WITH FORCING REMAINING NORTH OF CWA TONIGHT DO NOT SEE A NEED FOR ANYTHING MORE THAN A CONTINUATION OF LOW CHANCE POPS MAINLY JUST ACROSS FAR NORTHERN CWA. WINDS ALSO A CONCERN THIS EVENING. MSAS DATA SHOWING SURFACE PRESSURE RISES STRENGTHENING ACROSS SOUTHWEST SOUTH DAKOTA AND RUC/MESOETA PROGS TAKE THESE PRESSURE RISES AND STRONGEST LOW LEVEL CAA INTO SOUTHEAST SOUTH DAKOTA/EASTERN NEBRASKA TONIGHT. WILL HAVE TO CONTEND WITH FEW HOURS OF BREEZY/WINDY CONDITIONS ACROSS WESTERN CWA THIS EVENING BEFORE PRESSURE RISES DRIFT SOUTHEAST AND DECOUPLING BEGINS TO OCCUR. WITH SPEED OF SYSTEM SHOULD SEE GOOD DECOUPLING ACROSS ALL BUT MAYBE EXTREME EASTERN CWA. THUS...WILL SEE ANOTHER NIGHT OF GOOD RADIATIONAL COOLING...ESPECIALLY ACROSS NORTHWEST CWA WHERE 2-3 INCH SNOW COVER REMAINS. DID NOT ALTER TEMPS MUCH FROM PREVIOUS FORECASTER IN THIS AREA WITH LOWS FROM 0 TO 5 ABOVE. FOR WEDNESDAY AFTERNOON LEE TYPE TROUGH/WARM FRONT LIFTS INTO CWA WITH GOOD DOSE OF LOW/MID LEVEL WAA. ONCE AGAIN LITTLE CHANGE NEEDED IN TERMS OF MAX TEMP GRIDS FOR WED AFTERNOON. WILL STILL HAVE SOME MIXING ISSUES TO DEAL WITH ACROSS NORTHEAST CWA WITH WEAKER BL WINDS. TEMPS RANGING FROM MID 30S SOUTHWEST TO LOWER 20S FAR NORTHEAST STILL LOOK IN THE BALLPARK. ON WEDNESDAY NIGHT SHOULD SEE MINIMAL DIURNAL TEMP DROPOFF WITH SOUTH WINDS AND CONTINUATION OF GOOD LOW LEVEL WAA. WEAK TROUGH PASSAGE ANTICIPATED ON THURSDAY BUT NOT MUCH COLD AIR ASSOCIATED WITH THIS WEAK WAVE IN MID LEVEL ZONAL FLOW...SO STILL LOOKING LIKE WARMEST DAY OF SHORT TERM WITH TEMPS RUNNING A GOOD 15 DEGREES ABOVE NORMAL. FORECAST GETS A BIT MORE MUDDLED FOR THURSDAY NIGHT FRIDAY. BROAD UPPER TROUGH CURRENTLY ACROSS GULF OF ALASKA IS PROGGED BY ETA/GFS TO DROP INTO PACIFIC NORTHWEST BUT DISAGREEMENT ARISES IN SMALLER SCALE WAVES EJECTING INTO NORTHER TIER OF CONUS FOR FRIDAY. GFS TAKES A MORE AMPLIFIED WAVE EAST INTO THE GREAT BASIN REGION WHILE ETA IS FURTHER SOUTH AND WEAKER. GFS SOLUTION IS AN OUTLIER WITH ETA LINING UP BETTER WITH NOGAPS/CANADIAN. WENT WITH MODEL CONSENSUS AS GFS HAS NOT BEEN SHOWING MUCH CONSISTENCY WITH THIS PATTERN. DID INSERT CHANCE POPS FOR SOME LIGHT SNOW ACROSS NORTHERN TIER OF CWA FOR FRIDAY AFTERNOON IN GOING MORE WITH AN ETA TYPE SOLUTION. DID LOWER TEMPS A BIT ON FRIDAY NIGHT WITH GOOD CAA EXPECTED BEHIND THIS WAVE. MARSILI .LONG TERM...SATURDAY THROUGH TUESDAY MEDIUM RANGE MODELS COMING INTO LINE WITH STRONG COLD AIR ADVECTION AND ARCTIC SURFACE HIGH DROPPING INTO THE CENTRAL PLAINS DAY 6 AND BEYOND. OVERALL PATTERN APPEARS STABLE SO EXPECT LITTLE FLIP-FLOP OR RUN-TO-RUN VARIATION FOR THE NEXT FEW DAYS. ARCTIC DOME SETTLES IN BY END OF PERIOD AND MODIFIES SLOWLY IN THE OUT PERIODS. TUESDAY MARKS THE BEGINNING OF THE ARCTIC DEEP FREEZE FOR CWA WITH THE NORTH AND EASTERN ZONES AFFECTED THE MOST. SHORTWAVES EMBEDDED IN DOMINANT FLOW WILL INDUCE AMPLIFIED PATTERN. MOISTURE APPEARS LIMITED BUT MAY SEE SOME PRECIP FROM CHILLED ATMOSPHERE AND ACCOMPANYING WRING OUT. EXPECT LITTLE WARMING UNTIL A STRONGER PACIFIC MARITIME SYSTEM CAN MANEUVER ACROSS THE ROCKIES AND SCOUR THE PLAINS. THIS PROBABLY WILL NOT OCCUR UNTIL WELL BEYOND THE FORECAST PERIOD. MCNULTY && .ABR WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. && $$ sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LA CROSSE WI 218 PM CST TUE DEC 30 2003 .SYNOPSIS... WATER VAPOR IMAGERY SHOWING A VIGOROUS SHORTWAVE CENTERED NEAR KISN AT 1845Z. LOOP OF THIS DATA SHOWS THIS FEATURE MOVING DUE EAST. STRONG FORCING AHEAD OF THIS SHORTWAVE HAS BEEN PRODUCING SOME SNOW ACROSS THE DAKOTAS NORTH OF INTERSTATE 90. SURFACE ANALYSIS AT 18Z DEPICTS LOW PRESSURE CENTERED JUST EAST OF KPIR. A WARM FRONT EXTENDS FROM THIS LOW TO THE EAST ACROSS THE SOUTHERN PORTION OF THE FORECAST AREA ALONG THE IOWA/MINNESOTA BORDER. IN THE WARM SECTOR... CLOUDS ARE RATHER MINIMAL...SOUTHERLY WINDS ARE 20G30 KNOTS... DEWPOINT RECOVERY IS MINIMAL /MID 20S AT BEST/ AND TEMPERATURES ARE IN THE 35-45 DEGREE RANGE. && .SHORT TERM...TONIGHT AND WEDNESDAY MAIN FORECAST FOCUS IS THE IMPACT THE ABOVE MENTIONED SHORTWAVE WILL HAVE ON THE FORECAST AREA AS IT MOVES THROUGH. FORECASTER CONFIDENCE IS MEDIUM. 30/12Z ETA/GFS/RUC ARE IN GOOD AGREEMENT WITH THE TIMING AND AMPLITUDE OF THE FEATURE OVER THE PLAINS THIS MORNING. THEY ARE ALSO IN GOOD AGREEMENT AS IT MOVES THROUGH TONIGHT. THE MAIN DIFFERENCE IS THE AMOUNT OF MOISTURE PRESENT IN THE LOWER LEVELS OF THE ATMOSPHERE. THIS WILL DIRECTLY AFFECT THE PROBABILITY OF PRECIPITATION. FORECAST OF ETA/GFS/RUC FORCING IN THE MID LEVELS IS VERY SIMILAR. BOTH ARE QUITE STRONG. HOWEVER...THE ETA/RUC ARE MUCH DRIER THAN THE GFS. THIS MEANS THAT MUCH OF THE FORCING WOULD BE NEEDED TO SATURATE THE COLUMN BEFORE SNOW COULD BE PRODUCED IF YOU AGREE WITH THE ETA/RUC SOLUTIONS. LOOKING OVER THE CURRENT DATA...LAPS SOUNDINGS DO SHOW A PRONOUNCED DRY AREA IN THE LOWER LEVELS. SURFACE DEWPOINT DEPRESSIONS ARE 15-20 DEGREES. AND THE DISTURBANCE IS MOVING DUE EAST. GIVEN THESE 3 FACTORS...ACCEPT THE MODELS SOLUTIONS OF PUSHING THE BULK OF THE SNOW TO THE NORTH. HAVE MADE GRID ADJUSTMENTS ACCORDINGLY. .LONG TERM...THURSDAY THROUGH TUESDAY THE ECMWF/MRF 500 MB MEANS CONTINUE TO FORECAST A NEGATIVE HEIGHT ANOMALY DEVELOPING OVER CENTRAL CANADA. EVENTUALLY...A MEAN TROUGH WILL DEVELOP OVER THE UNITED STATES. THERE WILL BE 2 PROGRESSIONS DURING THIS TIME FRAME. THE FIRST...AS THE NEGATIVE ANOMALY DEVELOPS...THE FLOW ACROSS THE STATES WILL FLATTEN OUT INTO MORE OF A ZONAL TYPE PATTERN. THIS WILL KEEP TEMPERATURES ABOVE NORMAL WITH MINIMAL SENSIBLE WEATHER IMPACTS. THE SECOND WILL BE TROUGHING DEVELOPING OVER THE STATES AS THE NEGATIVE ANOMALY STRENGTHENS. THIS WILL PRODUCE A DOWNWARD TREND IN TEMPERATURES AND CAUSE A SERIES OF SYSTEMS TO MOVE THROUGH THE REGION. THIS COULD BE A VERY COLD PERIOD...BUT JUST HOW COLD IS CONTINGENT ON SNOW COVER. THE MODELS ARE SHOWING SOME VERY COLD AIR MOVING INTO THE REGION /-35C AT 850MB/. HOWEVER...IF THERE IS A LACK OF SNOW COVER...DON'T SEE TEMPERATURES DROPPING WELL BELOW ZERO AS WOULD BE THE CASE WITH A REASONABLE SNOW PACK. AS A RESULT...WENT ABOVE GUIDANCE UNTIL CONFIDENCE IN SNOW COVER CAN BE OBTAINED. WITH THAT SAID...AN INCREASE IN WEATHER ACTIVITY...WHICH IS ANTICIPATED... COULD PRODUCE A REASONABLE SNOW COVER. HOWEVER...THE CLOUDS WITH THESE SYSTEM WOULD THEN KEEP TEMPERATURES UP A BIT. && .ARX...WATCHES/WARNINGS/ADVISORIES... IA...NONE. MN...NONE. WI...NONE. && $$ KRC wi