AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE TALLAHASSEE FL 1103 PM EST TUE DEC 19 2000 --BEGIN UPDATED SECTION-- HAVE UPDATED FL ZONES TO LOWER MIN TEMPERATURES AS DEWPOINTS HAVE DROPPED INTO THE LOW TEENS. THE PENN STATE SHORT RANGE ENSEMBLE STATISTICS SHOW HEIGHTS/THICKNESSES/TEMPERATURES AROUND 4 STANDARD DEVIATIONS BELOW NORMAL DIRECTLY OVER OUR CWFA. THIS HIGHLIGHTS THE EXTREMITY OF THIS EVENT AND SUGGESTS GUIDANCE TEMPERATURES MAY NOT BE DEPENDABLE. WINDS ALREADY BECOMING LIGHTER OVER WRN ZONES...BUT WILL KEEP WIND CHILL ADVISORY IN EFFECT FOR THE TIME BEING. --END UPDATED SECTION-- WE PLAN TO EXPAND THE WIND CHILL ADVISORY INTO OUR AL AND GA ZONES. 00Z UPPER DATA SHOW STRONG LOW-LEVEL CAA WITH -18C AT 850MB UPSTREAM AT BHM. THIS SUGGESTS THAT SURFACE WINDS MAY STAY SUFFICIENTLY STRONG OVER NEXT SEVERAL HOURS TO DROP WIND CHILLS BELOW ZERO OVER OUR AL/GA ZONES. 23Z RUC PROGS A SURFACE HIGH TO BECOME CENTERED JUST W OF OUR CWA BY 12Z WITH A LOOSER PRESSURE GRADIENT...SO WE EXPECT TO NO LONGER MEET WIND CHILL ADVISORY CRITERIA OVER AL/GA BEFORE SUNRISE WEDNESDAY. IR SATELLITE SHOWS LOW CLOUDS GRADUALLY ERODING OVER LAND WITH LOSS OF INSOLATION. WINDS AND CLOUDS REMAIN PERSISTENT OVER OUR COASTAL WATERS THANKS TO STRONG UPWARD SENSIBLE AND LATENT HEAT FLUXES. CONVECTIVE PRECIPITATION BANDS MOVING ONSHORE N OF KTBW RADAR...AND WE EXPECT OUR FAR SE ZONES NEAR CROSS CITY SHOULD SEE A FEW SPRINKLES CONTINUING OVER NEXT FEW HOURS. WILL HANDLE THIS WITH SHORT TERM FORECASTS. WILL BUMP WINDS UP AND INCLUDE WIND CHILL ADVISORY FOR AL/GA ZONES. WILL REMOVE MENTION OF FLURRIES. TEMPERATURES STILL LOOK ON TRACK. NO CHANGES PLANNED FOR COASTAL WATERS. WILL BE ISSUING UPDATED NPW SHORTLY. .TLH... AL...HARD FREEZE WARNING AND WIND CHILL ADVY TNGT ALZ065>069. GA...HARD FREEZE WARNING AND WIND CHILL ADVY TNGT. GAZ120>124-131-142>148-155>161. FL...SCA GMZ750-755-770-775. HARD FREEZE WARNING AND WIND CHILL ADVISORY TONIGHT. FLZ07>019-026>029-034. TJT fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE JACKSONVILLE FL 830 PM EST TUE DEC 19 2000 WHAT DIFFERENCE A DAY MAKES. SOUNDINGS FROM TLH AND JAX REVEAL THE COLD AIRMASS ACROSS THE REGION...WITH THE 24 HR TEMP CHANGE IN THE MID LAYERS OF ATM "OFF THE CHART" ON MY WORKSTATION (I.E. >15 DEG C). FREEZING LEVEL NOW ABOUT 2 KFT AT JAX. SFC ANALYSIS AND OBS INDICATED SECOND SURGE OF COLD AIR NOW ALMOST THRU THE FORECAST AREA. IR SATELLITE IMAGES SHOW STRATO CU CLOUDS TENDING TO BREAK UP A LITTLE IN SRN GA WITH ANOTHER BATCH OF CLOUDS S OF A CTY-SGJ LINE. ISOL -RA POSSIBLE IN THIS SRN AREA OF CLOUDS BUT LITTLE IF ANY MEASURABLE REMAINDER OF TONIGHT. RUC AND MESO-ETA MODEL INDICATE THE SCT-BKN LOW CLOUDS SHOULD BE DISSIPATING THRU 12Z WED. THIS IS REASONABLE BASED ON RAPID MOVEMENT OF UPPER LEVEL TROUGH TOWARD THE E. TEMPS AT OR BELOW FREEZING NOW IN THE NRN ZONES WITH OCF IN SRN ZONE A CHILLY 43 DEG. POSSIBILITY OF A FEW FLURRIES IN THE NRN ZONES AROUND AMG BUT WITH CLOUDS DISSIPATING AT THIS TIME WILL NOT ADD. FOR UPDATE...WILL REWORD SKY CONDITIONS BUT OTHERWISE FORECAST COLD TEMPS TONIGHT LOOKS ON TRACK AS WELL AS WIND CHILLS. HARD FREEZE FOR MOST OF CWA WITH WIND CHILL ADVISORY IN EFFECT AS WELL. JUST A FEW CHANGES ANTICIPATED TO NPW TO REFINE FREEZING TEMP DURATIONS. MARINE...R2 TOWER SHOWED NW 30 KT WITH SEAS BUILDING TO ONLY 6 FT THUS FAR. BUOY 41008 IN LINE WITH R2 AT W27G33KT LAST HOUR WITH SEA 6 FT. BASED ON WIND DURATIONS OF ABOUT 9-12 HRS AND MAX FETCH LENGTH (NEAR 60NM) WITH THESE WIND SPEEDS...WILL BUMP UP SEAS A LITTLE. MODELS IN REASONABLE AGREEMENT TOO THAT WINDS WILL SUBSIDE BY 12Z SO MAY LOWER WINDS LATE. .JAX... .GA...SCA TODAY ALTAMAHA SOUND TO FERNANDINA BEACH. HARD FREEZE WARNING TONIGHT ALL ZONES. WIND CHILL ADVISORY TONIGHT ALL ZONES. RED FLAG WARNING WEDNESDAY OKEFENOKEE NWR. .FL...SCA TODAY FERNANDINA BEACH TO FLAGLER BEACH. HARD FREEZE WARNING TONIGHT ALL ZONES EXCEPT FLAGLER. FREEZE WARNING TONIGHT FLAGLER. WIND CHILL ADVISORY TONIGHT ALL ZONES. RED FLAG WARNING WEDNESDAY ALL ZONES. ARS/RAM fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 823 PM EST TUE DEC 19 2000 WE PLAN TO EXPAND THE WIND CHILL ADVISORY INTO OUR AL AND GA ZONES. 00Z UPPER DATA SHOW STRONG LOW-LEVEL CAA WITH -18C AT 850MB UPSTREAM AT BHM. THIS SUGGESTS THAT SURFACE WINDS MAY STAY SUFFICIENTLY STRONG OVER NEXT SEVERAL HOURS TO DROP WIND CHILLS BELOW ZERO OVER OUR AL/GA ZONES. 23Z RUC PROGS A SURFACE HIGH TO BECOME CENTERED JUST W OF OUR CWA BY 12Z WITH A LOOSER PRESSURE GRADIENT...SO WE EXPECT TO NO LONGER MEET WIND CHILL ADVISORY CRITERIA OVER AL/GA BEFORE SUNRISE WEDNESDAY. IR SATELLITE SHOWS LOW CLOUDS GRADUALLY ERODING OVER LAND WITH LOSS OF INSOLATION. WINDS AND CLOUDS REMAIN PERSISTENT OVER OUR COASTAL WATERS THANKS TO STRONG UPWARD SENSIBLE AND LATENT HEAT FLUXES. CONVECTIVE PRECIPITATION BANDS MOVING ONSHORE N OF KTBW RADAR...AND WE EXPECT OUR FAR SE ZONES NEAR CROSS CITY SHOULD SEE A FEW SPRINKLES CONTINUING OVER NEXT FEW HOURS. WILL HANDLE THIS WITH SHORT TERM FORECASTS. WILL BUMP WINDS UP AND INCLUDE WIND CHILL ADVISORY FOR AL/GA ZONES. WILL REMOVE MENTION OF FLURRIES. TEMPERATURES STILL LOOK ON TRACK. NO CHANGES PLANNED FOR COASTAL WATERS. WILL BE ISSUING UPDATED NPW SHORTLY. .TLH... AL...HARD FREEZE WARNING AND WIND CHILL ADVY TNGT ALZ065>069. GA...HARD FREEZE WARNING AND WIND CHILL ADVY TNGT. GAZ120>124-131-142>148-155>161. FL...SCA GMZ750-755-770-775. HARD FREEZE WARNING AND WIND CHILL ADVISORY TONIGHT. FLZ07>019-026>029-034. TJT fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NORTHERN INDIANA 202 PM EST TUE DEC 19 2000 18Z SFC MAP AND SAT SHOWING DEEP POLAR TROF THRU MISSISSIPPI VALLEY AND CLOSED H5 LOW OVR N MI. NICE THERMAL TROF EXTNDG WWD FM SFC LOW OVR SE ONTARIO. OTHERWISE ENORMOUS SINGLE SNOWBAND OCCURRING RIGHT DOWN THE CNTR OF LK MI MAKING LANDFALL OVR PORTER AND LAPORTE COUNTIES. 12Z MODELS INITIALIZED THE CONUS WELL TDA. SOME DIFFERENCES IN STRENGTH OF NEXT UPSTREAM SYS SEEN AMPLIFYING ACRS SW CANADA ATTM. FCST CONCERN TONIGHT CNTRS ARND LES AND THAN NEXT SYS WED NIGHT AND THU. 15Z RUC2 ALG WITH 12Z ETA/MESOETA HANDLING SINGLE LES BAND VRY WELL. SNOWBAND MAKING SLW EWD PROGRESS AND LOOKS TO SIT IN ACRS LK EFFECT WARNING AREA FOR A GOOD WHILE THIS EVENING. STILL LOOKS TO BE QUITE A IMPRESSIVE EVENT YET GIVEN THE DEEP CYCLONIC FLW ALG THE ENTIRE LENGTH OF LK MI...INVERSION HGHTS AROUND 10 K/FT AND AT LEAST A CONDITIONAL DELTA T. MESOETA/RUC2 QPF FCSTS AND A WORKUP OF LES CHART BOTH SHOW A GOOD 6 INCHES WITH UP TO 10 OVR BERRIEN...NRN LAPORTE AND NW ST. JOE POSSIBLE. XPC SBN TO SEE HEAVIEST SNOWFALL FM IN 22Z-03Z TIMEFRAME. WILL EXTEND THE GOING WARNING THRU THE OVERNIGHT GIVEN THE SOMEWHAT SLWR PROGRESSION OF LES BAND AND UPR LOW. AS FOR THE REST OF THE AREA...LES BAND COULD DROP AN INCH... MAYBE TWO NR WARNING AREA TONIGHT AS BAND CONTS TO SHIFT EWD. HWVR GRADIENT WKNS THROUGH THE EVENING SO WILL LET BLWG SNOW ADVISORY EXPIRE WITH NEXT ZONE ISSUANCE. SUSPECT SW TO SRN THIRD OF FA WILL CLR TONIGHT AND REALLY LIKE ETA 2M TEMP DEPICTION FOR MINS AS MOS GUIDANCE CONTS ITS WARM BIAS. TEMPS ON THE RISE WED AS NEXT SYS KICKS OUT INTO THE PLAINS. INCREASING SW TO S FLW LOOKS TO WARM THINGS UP WITH INCREASING WAA SO FCST GUIDANCE MAXS IN THE BALLPARK. XPC SNOW FM THIS NEXT SYS TO HOLD OFF AND NOT REALLY GET GOING UNTIL EVENING. ETA/AVN SIMILAR WITH THIS SYS COMPARED TO LAST NIGHTS SYS. 285K SFC SHOWS STG ISENTROPIC LIFT WED NIGHT WITH 2 G/KG MIXR WITH QPFS USING SWE OF 20:1 BOTH POINTING TO 3 TO 6 INCH SNOWFALL POSSIBLE. MORE NRN TRACK OF THIS SYS ALLOWS FOR HEART OF NEXT REINFORCING SHOT OF ARCTIC AIR TO SWING ACRS CWA THU AFTERNOON AND THU NIGHT. STG CAA AND DEEPENING MIXING LYR COULD POSE SIG PROBLEMS THU NIGHT IN TERMS OF WIND. THIS WILL NEED TO BE MONITORED CLOSELY GIVEN INCREASING VERY DEEP SNOWPACK FOR THESE PARTS. AS THIS SYS DEPARTS...XPC LK EFFECT TO ONCE AGAIN KICK IN ALTHOUGH NOT AS ROBUST GIVEN PROGGED PROGRESSIVE NATURE THU NIGHT INTO EARLY FRIDAY. OTHERWISE ARCTIC AIRMASS COURTESY OF CONTD ANOMALOUS NW FLW WILL KEEP FA IN THE DEEP FREEZE THROUGH THE EXTNDD. GUIDANCE TEMPS CONT TO TREND COLDER AS THIS WAS FOLLOWED. D+7 AND BEYOND LOOKS QUITE INTERESTING BUT WILL KEEP TUE PD DRY FOR NOW. .IWX...LAKE EFFECT SNOW WARNING CONTINUED FOR TONIGHT INZ003-004-012- 013...MIZ077-078 TEH in AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAUNTON MA 149 PM EST TUE DEC 19 2000 ...WARNINGS AND ADVISORIES TO BE READJUSTED AT 4PM BASED ON 18Z ETA AND RUC AS WELL AS UPSTREAM REALITY AND AM 90 PCT CONFIDENT FOR MUCH BELOW NORMAL COLD (MORE THAN -10F BLO NORMAL) FOR AT LEAST SVRL DAYS WITHIN 12/25-1/1/01... LOOK FOR AN UPDATE OF THIS PRODUCT AROUND 3PM. HAVE SEEN 1814Z 12 HR WINDTER WX FCST GRAPHIC. FOLLOW NOWBOS...ZFPBOS...SWOMCD FOR EXPECTED DVLPTS AS BOMBOGENESIS HAS BEGUN. PPP FALLS AND LIGHTNING STARTED CRANKING AROUND 16Z NR THE CAROLINA COAST AND WE/RE ABOUT TO GO FULL TILT WITH 7MB 3HRLY FALLS OFF DELMARVA BY 21Z. LARGE FLAKES LIKELY NW ORH CTY INTO MONADNOCKS TNGT. RIVERS: SEE RVSBOS AND FLSBOS FOR DETAILS ON MINOR CT RVR FLOODING CREST AND SUBSEQUENT THURSDAY RECESSION. STAFFING: EXTRA FOR TNGT AND WED AM INCOMING REPORTS. FRI: AVN/MRF/EC/UK ALL SAY ANOTHER EVENT OF WINTRY MIX HERE...THAT PAVES THE WAY FOR SEVERAL INCREASINGLY STRONG CFPS THIS WKND AND EARLY NEXT WEEK THEN A VERY COLD OUTBREAK (XPCTG ABOUT 15F BLO NORMAL AROUND NEXT WEDNESDAY WITH BOSTON "NORMAL" 37/23). FRI SNOW EVENT MAY B COMPLICATED BY WARM BL ON SELY FLOW. LR: NAO FCST STRONGEST NEGATIVE HAVE SEEN IN PAST 5 MONTHS AND THIS COMBINED WITH MDT TO STG POSITIVE PNA SUGGESTS STRONGLY DEPRESSED JET AND HEAVY DUTY N ATLC/N CANADA BLOCKING. SIGNS IN MRF FOR MAX TEMPS IN "BOSTON" NO HIGHER THAN 20F BY MIDDLE OF NEXT WEEK...IE 12/27-29 TIME FRAME. I DO BELIEVE THIS WILL COME TO PASS FOR AT LEAST 2 DAYS...ESPECIALLY IF LEFTOVR SNOWCOVER IS AROUND. STORM TRACK WILL B ACROSS DIXIE WITH ALWAYS AN EYE FOR A LATE TURN TO THE NNE OFFSHORE AND LARGE DVLPT. WHETHER THE STORMINESS OCCURS NXT WEEK IS IN DOUBT ESPECIALLY SINCE OUR CURRENT SPATE OF STORMINESS (12/12,14,17,19 AND POSSIBLY 12/22) HAS TO ABATE SOMETIME. BLV STRONGLY ODDS FAVOR VERY COLD NEXT WK BUT IN DOUBT ABOUT HOW MUCH SNOWSTORM RISK HERE IN SNE. NWR: SOAPSTONE IS OTS ATTM. BOX 88D HAS BASICALLY RTS. .BOX...WINTER STORM WARNING MAZ02>4-08,10 NHZ11-12 LT TDY INTO WED WINTER WX ADV CT02>04 MAZ04>06-9,11>13 RI 1,2 RIVER FLOOD WARNING CT RVR HFD COUNTY. MARINE: GLW ALL (ONLY BRIEF FOR NARR BAY AND BOS HARB). DRAG ma AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 1030 AM EST TUE DEC 19 2000 COMPLEX WX PATTERN LATE THIS MORNING...WITH LAKE ENHANCED EVENT IN PROGRESS. SFC LOW IS JUST OFF THE LAKE HURON COAST...WITH THE UPPER LOW CENTERED OVER LOWER MI ATTM...PROVIDING DEEP CYCLONIC FLOW AND LOW LEVEL CONVERGENCE TO NRN LOWER MI. LARGE LAKE ENHANCED BAND HAS SET UP FROM JUST S OF ROGERS CITY INTO MONTMORENCY COUNTY DRIVEN BY NE FLOW OFF OF LAKE HURON. ANOTHER LAKE ENHANCED BAND OFFSHORE OF NW LOWER MI IS GRADUALLY SHIFTING INLAND ACROSS LEELANAU AND BENZIE COUNTIES LATE THIS MORNING. LATEST RUC AND MESOETA...HAVE SLIGHTLY SLOWED THE DEPARTURE OF THE UPPER LOW...WHICH MAKES SENSE GIVEN THIS SYSTEM IS NEARLY VERTICALLY STACKED. SHORT TERM MODELS ALSO HOLD THE SFC LOW BACK OVER UNFROZEN LAKE HURON THRU 21Z...WHICH ALSO MAKES SENSE. THIS WILL MAINTAIN GOOD SYNOPTIC SUPPORT FOR LAKE ENHANCED BAND DEVELOPMENT INTO THE AFTERNOON...ESPECIALLY FOR NE LOWER MI COUNTIES WHERE CYCLONIC FLOW AND LOW LEVEL CONVERGENCE WILL BE MAXIMIZED. SPOTTER FROM ROGERS CITY HAS REPORTED NEARLY 8 INCHES IN PAST 14 HRS...WITH MORE ON THE WAY. WILL INCLUDE PRESQUE ISLE COUNTY IN WARNING AS LAKE ENHANCED BANDING WILL CONTINUE TO PUSH ONSHORE UNTIL LATE AFTERNOON AS WINDS SHIFT TO A MORE NORTHERLY COMPONENT. AN ADDITIONAL 3 TO 5 INCHES EXPECTED IN THE WARNED AREA...WITH LOCALLY HIGHER AMOUNTS POSSIBLE. WILL MAINTAIN ADVISORIES INTO THE AFTERNOON FOR AREAS JUST W OF THE WARNING...WITH AN ADDITIONAL 1 TO 3 INCHES EXPECTED. LAKE BAND JUST NOW ENTERING LEELANAU COUNTY WILL CONTINUE TO SLOWLY SHIFT FURTHER INLAND AS WINDS BECOME MORE NORTHERLY. THUS...WILL SLIGHTLY INCREASE AMOUNTS FOR LEELANAU... BENZIE AND MANISTEE TO 2 TO 3 INCHES FOR THE AFTERNOON. HOWEVER... WILL NOT ISSUE AN ADVISORY FOR THESE AREAS AS ONLY MINOR ACCUMULATIONS OCCURRED IN THESE AREAS OVERNIGHT. SPOTTERS ALONG LAKE HURON AND IN WHITEFISH BAY HAVE ALSO REPORTED WINDS GUSTING TO NEAR 30 MPH. WILL ACCOUNT FOR THESE HIGHER WINDS IN THESE LOCATIONS FOR THE AFTERNOON. .APX...WINTER STORM WARNING...THIS AFTERNOON... MIZ018-023-024-029-030-035-036-042. WINTER WEATHER ADVISORY...THIS AFTERNOON... MIZ017-022-027-028-033-034-041. EME mi MINNESOTA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHANHASSEN/TWIN CITIES MN 815 PM CST TUE DEC 19 2000 FORECAST CONCERN IS HOW FAR SOUTH SNOW WILL DEVELOP DURING NIGHT. RATHER IMPRESSIVE LOOKING VORT/MID LEVEL CIRC NEARING ND BORDER AND HEADING ESE. 00Z RUC TAKES MOST OF QG FORCING INTO N MN. WARM ADVECTION QUITE STRONG INTO CWA BUT...00Z RUC NOT SHOWING DECENT SATURATION ON THE 285 K SURFACE UNTIL EARLY MORNING TOWARD MSP AREA. ABOUT 2 G/KG TO WORK WITH FOR MOISTURE. MIGHT BE ENOUGH FOR A COUPLE INCHES...MAYBE 3 IN N OR NE PART OF CWA. CURRENT FORECAST HAS THE TREND FOR BEST POPS. THINK THERE WILL BE SOME RISING TEMPS IN WEST AND MORE STEADY IN EAST. .MSP...NONE. RICHARDSON mn SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GREAT FALLS MT 900 PM MST TUE DEC 19 2000 WILL UPDATE ZONES AND STATE FORECAST. DISTURBANCE SWINGING DOWN FROM NORTH SEEMED TO HANG UP ALONG NORTH SLOPES OF LITTLE BELT AND BIG SNOWY MOUNTAINS THIS EVENING. REPORTED SNOW ACCUMULATIONS UNDER BAND GENERALLY 2 TO 3 INCHES WITH ISOLATED REPORTS OF 4 TO 5 INCHES. RADAR AND SATELLITE IMAGERY INDICATE THIS BAND DISSIPATING SOME AND FINALLY STARTING TO PUSH OUT OF CWA. NEXT CONCERN IS DISTURBANCE CURRENTLY OVER ALBERTA AND SASKATCHEWAN. 00Z AVN...ETA AND NGM ALL DROP THIS DOWN OVER CWA JUST AFTER MIDNIGHT. RUC BRINGS ENERGY IN...THOUGH NOT A DISTINCTIVELY DIFFERENT WAVE. DISTURBANCE CURRENTLY IS CREATING LIGHT SNOW AND GUSTY NORTHERLY WIND RESULTING IN AREAS OF BLOWING AND DRIFTING SNOW ACROSS SOUTHERN ALBERTA AND SASKATCHEWAN. GRADIENTS TONIGHT ACROSS CWA FORECASTED TO RELAX SLIGHTLY THEN TIGHTEN UP WEDNESDAY...SO STILL BELIEVE WIND WILL BE DECREASING ACROSS CWA TONIGHT. WITH NORTHERLY FLOW AND UPSLOPING...EVEN WITH ONLY MODERATE RH...BELIEVE SNOW WILL FALL MOST AREAS OF CWA TONIGHT...WITH OROGRAPHICS CONTINUING TO PLAY A SIGNIFICANT ROLE IN ACCUMULATIONS FOR NORTH FACING SLOPES. DISTURBANCE TO PUSH OUT OF CWA BY MORNING WITH ENOUGH CLEARING TO ALLOW TEMPS TO DROP. REMAINDER OF FORECAST ON TRACK WITH COLDER TEMPS AND DECREASED PRECIP WEDNESDAY AND WEDNESDAY NIGHT THEN WARMING SOME THURSDAY. PLANNING MINOR ADJUSTMENTS OF POPS AND TEMPS TO ZONES AND WILL UPDATE SFP AS WELL. GL FOR EXTENDED...PERIOD TO BE UNSETTLED WITH ISOLATED TO SCATTERED SNOW SHOWERS EACH DAY AND COOLER TEMPERATURES MOVING IN OVER THE WEEKEND. MRF CONTINUES WITH GOOD RUN TO RUN CONSISTENCY WHILE ECMWF AND UKMET SOLUTIONS SHOWING ONLY MINOR DISCREPANCIES. HIGH PRESSURE RIDGE COVERING WESTERN MT THURSDAY WEAKENS FRIDAY AS A PACIFIC SYSTEM PUSHES INLAND. AS THE SYSTEM ERODES THE RIDGE...THE SYSTEM WILL WEAKEN SOME AS WELL. CURRENT FORECASTS SHOW REMNANT ENERGY WITH CHANNELED VORTICITY PUSHING IN FROM THE WEST FRIDAY AFTERNOON. WEAK DYNAMICS AND NORTHWEST FLOW PERSIST OVER CWA THROUGH SATURDAY AS RIDGE BEGINS REBUILDING OVER ERN WA/OR. MEANTIME...LARGE LOW PRESSURE SYSTEM NEAR HUDSON BAY HAS NUMEROUS EMBEDDED DISTURBANCES SWEEPING AROUND THE SYSTEM. BY SUNDAY...RIDGE WILL HAVE EDGED SLIGHTLY EASTWARD WHILE LOW EXPANDS TO WEST. THIS DEVELOPMENT WILL PUT THE CWA UNDER A NORTHERLY FLOW...STEERING ONE OF THE LOW/S DISTURBANCES AND SOME COOLER AIR DOWN INTO MT EAST OF THE DIVIDE. THIS DISTURBANCE SHOULD EXIT THE CWA MONDAY MORNING. ANOTHER SMALL DISTURBANCE RIDING OVER THE HIGH PRESSURE RIDGE WILL THEN DROP IN TUESDAY. GL CCF NUMBERS GTF JU 010/023 001/030 016 106300 CTB EU 008/021 903/027 013 107200 HLN EB 012/025 905/025 007 104200 BZN EB 010/022 906/024 007 104200 WEY JB 005/016 912/019 000 106400 DLN EB 010/023 906/025 007 103200 HVR BU 006/015 909/022 007 107200 LWT JU 008/017 904/025 010 107400 mt FORECAST DISCUSSION FOR EASTERN NORTH DAKOTA AND NORTHWEST MINNESOTA NATIONAL WEATHER SERVICE EASTERN ND/GRAND FORKS ND 914 PM CST TUE DEC 19 2000 MSAS DATA AND SFC ANALYSIS SHOWS LOW OVER SE SASKATCHEWAN THIS EVENING WITH BEST PRESSURE FALLS DEPICTED OVER NE ND. NEW ETA/MESOETA TAKES LOW ON SIMILAR TRACK WITH RESPECT TO PREVIOUS RUNS...WITH 0Z RUC MORE NORTH AND NEW NGM FURTHER SOUTH. CONSIDERING WHERE BEST PRESSURE FALLS CURRENTLY LOCATED...ETA/MESOETA PREFERRED AT THIS TIME. THESE MODELS SHOW SYSTEM IS VERTICALLY STACKED...WHICH SUPPORTS SLOWER MOVEMENT THAT ALL MODELS HAVE BEEN TRENDING TOWARD. BEST 850 TO 500 MB Q VECTOR FORCING MOVES ACROSS NRN RED RIVER VALLEY INTO NRN MN OVERNIGHT WHICH CORRELATES WELL WITH LOCATION OF SNOW ON LOCAL RADAR. HEAVIEST SNOW CURRENTLY OVER SRN SASKATCHEWAN AND SE MANITOBA JUST N OF SFC LOW POSITION. FOLLOWING ETA/MESOETA TRACK...BEST SNOWFALL TO OCCUR OVER EXTREME NRN RED RIVER VALLEY INTO FAR NW MN OVERNIGHT. CURRENT FORECASTS GENERALLY HANDLING THIS...SO WILL NOT MAKE ANY CHANGES TO POPS AND ONGOING WARNINGS/ADVISORIES. WINDS HAVE PIKED UP QUITE A BIT THIS EVENING ALONG AND WEST OF THE VALLEY. WILL BUMP UP WINDS TO REFLECT ONGOING CONDITIONS. WITH 1000 TO 850 MB THICKNESS RISING OVERNIGHT...TEMP TRENDS REASONABLE EXCEPT OVER DVL REGION WHERE SLOWER MOVEMENT SUPPORTS KEEPING THIS AREA WARMER THROUGH 12Z. .FGF...WINTER STORM WARNING WED/WED NGT NRN RRV AND POINTS NE/NW TO CANADIAN BORDER. WINTER WEATHER ADVISORY LATE TONIGHT THRU WED NGT DVL BASIN. WINTER WEATHER ADVISORY WED/WED NGT REST OF CWA. RJT nd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 210 PM EST TUE DEC 19 2000 VERY INTERESTING DAY TO WORK...WITH A POTPORRI OF LOW PRES SYSTEMS AFFECTING THE FA. THE LOW OVR ONT IS PUSHING A DRY SLOT UP AGAINST THE WEST FACE OF THE ALLEGHENIES INTO BFD. THE LOW OVR SOUTHERN VA IS HOLDING THE FRONT AND ASSOC DEFORMATION BAND OVR CENT PA. THIS IS DOING 2 THINGS. IT IS KEEPING THE SNOW FALLING AT THE RATE OF .5 INCHES PER HOUR OVR THE RIDGE/VAL SECTION OF PA AND IT IS HOLDING THE SNOW FROM OUR EXTREME SE. LNS HAS HAD A FEW FLURRIES WHILE MDT IS GETTING MOD SN AT 18Z. THE 15Z RUC SHOWS THE LOW LVL FRONTOGENESIS LINING UP PERFECTLY WITH THE HEAVIEST BANDS OF SN ON KCCX. THIS WILL TRANSLATE INTO MDT AND JUST NW OF LNS DURG THE AFTN. NW LANCASTER COUNTY WILL PROB GET CLOSE TO 5 INCHES WHILE THE SE CORNER OF THE COUNTY GETS 2 TO 3 SO THAT SHUD WORK. FURTHER N AND W THERE IS GOING TO BE A BIT MORE. WITH THE SOUTHERN VA DEVELOPMENT THERE IS A COASTAL FRONT THAT HAS PUSHED AS FAR WEST AS THE DEL RIVER. THIS COMBINED WITH THE COLD AIR PUSHING IN FROM THE WEST IS CREATING LO LVL FRONTOGENESIS OVR THE CENT PART OF PA. THIS WILL CONTINUE THRU AT LEAST 00Z. AT THE RATE OF A HALF INCH PER HR WE ARE GOING TO PICK UP ANOTHER 3 INCHES OF SNOW OVR THE CENTRAL THIRD. WITH 3 TO 4 INCHES DOWN THAT PUTS US INTO WARNING CRITERIA. IN ORDER TO AVOID THIS PROBLEM FOR A TYPICAL PENNSYLVANIA SNOWFALL WE WILL SAY AROUND 5 INCHES...RATHER THAN GIVING A RANGE WHICH WOULD REQUIRE A WARNING. THE NEW ETA IS SHOWING THE DEFORMATION BAND STAYING OVR THE MIDDLE THIRD OF THE STATE THRU 00Z. THERE IS STILL A REFLECTION OF THE LOW OVR S VA AT 00Z. THIS WILL ALLOW THE FRONTOGENESIS TO CONT UNTIL THAT TIME. BETWEEN 0 AND 6Z THE LOW FALLS APART AND THE STORM CENTER OFF SHORE TAKES OVER. THIS WILL WIPE OUT THE FRONTOGENESIS OVR PA AND THE SNOW WILL JUST TAPER TO FLURRIES. THERE PROB WILL NOT BE A DEFINITIVE MOVEMENT FROM W TO E AS IT ENDS...IT WILL JUST DSPT. THE NEXT FEW DAYS WILL FEATURE A COLD NW FLOW GRAD BACKING INTO THE SW. THE NEXT WX SYSTEM THU AFTN AND EVE IS DEPICTED DIFFERENTLY BY BOTH THE ETA AND AVN. THE AVN SHOWING JUST A FRONT WITH THE ETA SHOWING SOMETHING SIMILAR TO TDY. HAVE TO DEAL WITH THE PRESENT SYSTEM THO AND WILL NOT DELVE TOO MUCH INTO THE FARAWAY FUZZIES. .CTP...WINTER WX ADV THROUGH THIS EVENING E OF ALLEGHENY FRONT. HEAD pa AREA FORECAST DISCUSSION FOR CENTRAL/NORTHCENTRAL AND NORTHEAST SOUTH DAKOTA AND WEST CENTRAL MINNESOTA NATIONAL WEATHER SERVICE ABERDEEN SD 945 PM CST TUE DEC 19 2000 MADE SOME CHANGES TO THE FORECAST DUE TO THE NEW MDLS...ETA AND RUC. BELIEVE THAT ANY CHANCE OF SNOW THROUGH THE REST OF THE NIGHT IS OVER ...EXCEPT FOR SOME FLURRIES IN THE ATY/SIS AREA THROUGH MIDNIGHT. OTHERWISE...MDLS SHOW DRYING AND SUBSIDENCE MOVING IN THROUGH THE REST OF THE NIGHT. THEREFORE...SKIES SHOULD GO P/C ACROSS THE CWA. LL RH INCREASES LATE AND THERE MAY BE SOME LOW CLOUDS MOVING IN ACROSS THE NORTHERN PART OF THE CWA BY MRNG. STRONG WARM FRONT MAKING ITS WAY TO THE EAST ACROSS THE CWA TONIGHT IN RESPONSE TO THE SFC LOW PRES MOVING SE ACROSS ND. THE EASTERN PART OF THE ABR CWA WILL NOT SEE MUCH OF A WARM UP WITH THIS FRONT BUT SHOULD SEE THE TEENS BY MRNG WITH SOME 20S POSSIBLE. S TO SE WINDS WILL BECOME W TO NW BY MRNG ACROSS MUCH OF THE CWA. THEY SHOULD BECOME BREEZY ACROSS THE C AND NC. ON WED...MDLS SHOW STRONG WINDS DEVELOPING AS GOOD LL MIXING OCCURS WITH STEEP LAPSE RATES AND A GOOD PRES GRAD DEVELOPING. ARCTIC FRONT MOVES SOUTH ACROSS THE CWA WITH TEMPS FALLING THROUGH THE DAY AND BITTERLY COLD WIND CHILLS DEVELOPING ALONG WITH BLOWING SNOW. STRONG WINDS WILL CONTINUE INTO WED NIGHT WITH BITTERLY COLD WIND CHILLS ALONG WITH BLOWING SNOW. MAY NEED AN ADVISORY FOR WED AND WED NIGHT. .ABR...NONE MOHR sd AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 919 PM EST TUE DEC 19 2000 PREVIOUS FORECAST STILL LOOKS TO BE IN GOOD SHAPE. WILL ONLY UPDATE TO MAKE A FEW SMALL CHANGES AND KEEP THINGS CURRENT. WILL RIDE WITH ALL CURRENT HEADLINES AS IS. COASTAL STORM APPEARS TO BE ON TRACK FOR PASSING JUST BARELY TO THE EAST OF CAPE COD AND THE ISLANDS OF MA BY 09Z. THIS IS APPROXIMATELY WHERE THE BEST SFC PRESSURE FALLS ARE ATTM. SFC LOW ACRS THE ERN GREAT LKS REGION TO WEAKEN WITH TIME OVRNITE TONITE. SFC PRESS GRADIENT TO INCREASE ACRS THE FA REGARDLESS OF THIS OVRNITE TONITE. 12Z ETA LOOKS TO HAVE DONE THE BEST JOB WITH THE POSN OF THE COASTAL LOW AT 00Z (IT WAS A TAD TOO DEEP WITH IT THOUGH). 12Z ETA WAS ALSO A TAD TOO DEEP WITH THE SFC LOW ACRS THE ERN GREAT LKS REGION AT 00Z. COASTAL STORM TO TRACK ACRS THE GULF OF ME AND UP INTO THE CANADIAN MARITIMES ON WED. CYCLONIC SFC FLOW TO PERSIST ACRS THE FA ON WED. WK RIDGE OF HI PRESS TO MOVE ACRS THE GREAT LKS REGION ON WED AS WELL. UPR TROF TO MOVE ACRS THE ERN GREAT LKS REGION TONITE...THEN ACRS THE FA EARLY ON WED. S/W TO TRACK UP THE ERN SEABOARD OVRNITE TONITE AS WELL. STRONG NW FLOW ALOFT TO DEVELOP ACRS THE FA FOR WED. 21Z RUC SHOWS TEMPS ALOFT TO BE PLENTY COLD FOR SN ACRS THE FA OVRNITE TONITE. SFC TEMPS TO GET DOWN INTO THE MID TEENS (ST LAW VLY) TO THE U20S. T1MIN TEMPS ARE 15-25 DEG F. MESONET OBS SHOW THAT READINGS ARE BASICALLY ALREADY AT THESE VALUES. NOT EXPECTING MUCH MORE COOLING AT THE SFC OVRNITE...SO WILL JUST WIDEN UP MOST LOW TEMP FORECASTS FOR THE OVRNITE PERIOD. SFC FLOW TO BECOME NORTHERLY AT AROUND 5 KTS TONITE. BEST LOW-LVL (AND MID-LVL) MOISTURE TO BE LOCATED ACRS VT TONITE (LEAST ACRS NRN NY STATE). BEST LOW-LVL MOISTURE ADVECTION AND H85 THETA-E ADVECTION TO TAKE PLACE TO THE EAST AND SOUTH OF THE FA TONITE. PW VALUES OVRNITE APPEAR TO MAX OUT AT 0.25-0.5". RUC SHOWS BEST H85 FGEN TO BE LOCATED ACRS SRN/ERN VT AND NH BETWEEN 06Z-09Z TONITE. BEST H7 FGEN TO BE LOCATED ACRS VT BETWEEN 06Z-09Z TONITE. PCPN TO PICK UP IN INTENSITY BY AROUND 09Z TONITE. RUC SHOWS 0.1-0.4" OF QPF THRU 09Z TONITE (BEST ACRS ERN/SRN VT). SNOWFALL RATIOS HERE AT BTV SO FAR HAVE BEEN ABOUT 25-TO-1. STILL NOT EXPECTING A STRAIGHT 10-TO-1 RATIO FOR THE REST OF THE EVENT. 21Z RUC BASICALLY LOOKS VERY SIMILAR TO THE 12Z ETA FROM MY PERSPECTIVE. HPC MANUAL QPF GRAPHICS SHOW LESS THAN 0.6" OF QPF ACRS THE FA THRU 18Z WED (AVG VALUES APPEAR TO BE ABOUT 0.25"). 12Z ETA SHOWS BETWEEN 0.1" AND LESS THAN 0.85" OF QPF FOR THE SAME TIME PERIOD. AS WAS THOUGHT YESTERDAY...THESE UPR LIMITS MAY NOT VERIFY...BUT WITH HIGH SNOWFALL RATIOS STILL EXPECTING ANYWHERE FROM 2" TO AS MUCH 8" OR SO ACRS THE FA THROUGHOUT THE ENTIRE EVENT. LEAST AMTS WILL FALL ACRS THE FAR WRN ZONES. H85 WAA TO TAKE PLACE ACRS THE FA EARLY TONITE...THEN CAA LATER TONITE (STRENGTHENING WITH TIME ON WED). SOME AMT OF LOW-LVL MOISTURE TO LINGER ACRS THE FA ON WED AS MID-LVLS DRY OUT. PCPN TAPERING OFF TO -SHSN STILL LOOKS GOOD FOR WED (ESPECIALLY IN THE MTNS). FEW TWEAKS TO FIRST PERIOD WINDS BASED ON CURRENT OBS TRENDS AND RUC DATA. DROPPED POPS (TO LIKELY) AND SNOWFALL AMTS ACRS ST LAW CTY SINCE 88D MOSAIC/BUFCAN DATA INDICATES THAT THE PCPN APPEARS TO HAVE SUBSIDED IN THAT NECK OF THE WOODS. SOME MORE PCPN STILL POSSIBLE WITH UPR TROF PASSAGE THERE. BEST MOISTURE PLUME IN H2O VAP IMAGERY APPEARS TO HAVE PASSED THE FA BY AS OF LATE...BUT STORM SYS STILL HAS A WAY TO GO UP THE COAST AND IS STILL EXPECTED TO DEEPEN...SO WILL HOLD ONTO POPS AND SNOW AMTS ELSEWHERE. REST OF CHANGES TO GOING ZFP COSMETIC. WORK ZONES OUT AND ABOUT UNDER ALBWRKCWF. FINAL ZFP ISSUANCE BY AROUND 945 PM. .BTV...WINTER STORM WARNING INTO WED MORNING VTZ003-004-006>008- 010>012 WINTER WX ADVISORY INTO WED MORNING VTZ001-002-005-009-NYZ027- 028-030-031-034-035. MURRAY vt AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 925 AM EST WED DEC 20 2000 CURRENTLY: LATEST 500-MB RUC & WATER VAPOR IMAGERY SHOWED SHORTWAVE TROUGH EXITING THE MID-ATLANTIC/NE CONUS W/ ZONAL/SUBSIDENT FLOW OVER THE CWFA. MORE SHORTWAVE ENERGY DIVING SE THRU THE PLAINS WILL BE OUR NEXT WEATHER MAKER. AT THE SURFACE...HIGH PRESSURE RIDGE INFLUENCING MUCH OF THE SERN CONUS W/ CENTERS OVER AL & LA. CLEAR SKIES CWFA-WIDE PER VISIBLE SATELLITE & METARS W/ CAA SC EVIDENT OVER THE GULF WATERS. COLDEST TEMPS RECORDED THUS FAR THIS SEASON W/ MORNING LOWS IN THE UPPER TEENS & LOWER 20S. N-NW WINDS 5-10 MPH CONTRIBUTING TO VERY COLD WIND CHILL READINGS IN THE SINGLE DIGITS & TEENS. 12Z TLH SOUNDING SHOWED SHALLOW MOISTURE BELOW 950 MB & VERY DRY ABOVE (PWAT=0.14"). ZFP: WILL UPDATE TO REMOVE HARD FRREZE WARNING AS TEMPS WARM INTO UPPER 20S-LOWER 30S BY LATE MORNING. 12Z TEMPS AT OR A FEW DEGS ABOVE MOS...SO INHERITED MAX TEMP FCSTS ON TRACK. MARINE: BOTH OFFSHORE BUOYS HAVE WINDS JUST BELOW SCEC CRITERIA...HOWEVER SEAS STILL AT SCA LEVELS (7-9 FT). EXPECT GRADUAL DIMINISHING TREND TO LAST THRU THE AFTN. SCA WILL BE LOWERED FOR THE NEAR SHORE LEGS AS C-MANS HAVE WINDS IN 5-10 KT RANGE. WILL KEEP SCA GOING FOR THE OFFSHORE LEGS THRU EARLY AFTN W/ SEAS BELOW 7 FT THEREAFTER. FIRE WEATHER: RED FLAG WARNING FOR ALL FL COUNTIES WHERE AFTN MIN RH VALUES WILL DROP BELOW 35% FOR AT LEAST 4 HRS...EXCEPT ALONG THE IMMEDIATE COAST. .TLH... AL...HARD FREEZE WARNING TONIGHT ALZ065>069. GA...HARD FREEZE WARNING TONIGHT GAZ120>124-131-142>148-155>161. FL...SCA THRU EARLY AFTN OFFSHORE WATERS (GMZ770-775). HARD FREEZE WARNING TONIGHT FOR FLZ007-009>011-013-016>019-026>029-034. FREEZE WARNING TONIGHT FLZ08-012-014-015. RED FLAG WARNING ALL ZONES THIS AFTN TIL SUNSET. MAJ fl AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE GOODLAND KS 746 AM MST WED DEC 20 2000 BASED ON WHAT IS GOING ON JUST UPSTREAM OF CWFA AND LATEST RUC...AM GOING TO INTRODUCE PCPN INTO THE FCST. BASED ON A COOP OBSERVER REPORT IN YUMA COUNTY OF SNOW ACCUMULATING ON THE GROUND JUST RECEIVED...GLD WSR-88D SHOWG REFLECTIVITIES INCREASING IN INTENSITY AND COVERAGE...AND LATEST RUC...DECIDED TO MENTION LIGHT SNOW INSTEAD OF FLURRIES IN ALL ZONES. .GLD...WIND ADVISORY FOR COUNTIES ALONG AND EAST OF A MCCOOK TO GOVE LINE. BULLER ks AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE GOODLAND KS 739 AM MST WED DEC 20 2000 BASED ON WHAT IS GOING ON JUST UPSTREAM OF CWFA AND LATEST RUC...AM GOING TO ADD FLURRIES AND SPRINKLES TO ALL ZONES. .GLD...WIND ADVISORY FOR COUNTIES ALONG AND EAST OF A MCCOOK TO GOVE LINE. BULLER ks AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 950 AM CST WED DEC 20 2000 MID AND HIGH LEVEL CLOUDINESS SPREADING RAPIDLY EAST ACROSS MY NORTHERN THIRD THIS MORNING BUT ENOUGH SUN MAKING IT THROUGH SO THAT PC WILL WORK ACROSS THE NORTH. VIS SATELLITE IMAGERY SHOWING LOW LEVEL CLOUDS JUST NOW COMING ON SHORE ACROSS SE TX. MESOETA WAS A LITTLE FAST WITH THIS MOISTURE RETURN YESTERDAY BUT NOW IS MORE IN LINE WITH 12HR RUC FCST. CLOUDS COULD BE RATHER WIDESPREAD ACROSS MY WESTERN HALF NEAR OR SHORTLY AFTER 21Z. SHOULD NOT TAKE LOW CLOUDS LONG TO MAKE IT THIS WAY AS 65KT LOW LEVEL JET DEVELOPS ACROSS E TX THIS AFTN. WOULD PREFER TO SEE INCREASING CLOUDINESS OR BECOMING MOSTLY CLOUDY ACROSS THE WEST HALF THIS AFTERNOON AND WILL PROBABLY NEED TO UPDATE FOR THIS REASONING. TEMPS MAY NEED TO BE LOWERED A CATEGORY IN A FEW PLACES BUT WILL WAIT AND TAKE A LOOK AT 17Z OBSERVATIONS BEFORE MAKING THIS CALL. UPDATE OUT SHORTLY AFTER 17Z. 13 .SHV...NONE. la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TALLAHASSEE FL 320 PM EST WED DEC 20 2000 CURRENTLY: LATEST 500-MB RUC & WATER VAPOR IMAGERY SHOWS AMPLIFYING TROUGH OVER THE PLAINS STATES. LEAD SHORTWAVE ENERGY TO AFFECT OUR CWFA NOW MOVING INTO SRN PLAINS. AT THE SURFACE...HIGH PRESSURE RIDGE CENTERED OVER AL/GA/FL. CLEAR SKIES CONTINUE PER VISIBLE SATELLITE & METARS. CAA SC PULLING AWAY FROM OUR COASTAL WATERS. MID AFTERNOON READINGS FAST APPROACHING FCST MAXIMA W/ MID 30S NW AREAS...UPPER 30S TO LOWER 40S ELSEWHERE. VARIABLE TO NLY WINDS LESS THAN 10 KTS STILL PRODUCING WIND CHILLS IN THE UPPER 20S & 30S. MODELS/ZFP: SHORT-RANGE MODELS SHOW MID/UPPER TROUGH OVER PLAINS AMPLIFYING AS IT MOVES TO ERN CONUS BY 12Z FRI. ZONAL FLOW ALOFT BECOMES SWLY THU/THU NIGHT...THEN NWLY LATE FRI. AT THE SURFACE... HIGH PRESSURE RIDGE OVER ERN CONUS YIELDS TO A ANOTHER COLD FRONT. MODELS DIFFER IN TIMING OF FROPA W/ FASTER ETA INTO S GA/FL BIG BEND ...SLOWEST NGM INTO WRN FL PNHDL...AND MIDDLE-OF-ROAD AVN OVER SW GA/ERN FL PNHDLBY 00Z FRI. MODEL QPFS ALSO DIFFER W/ NGM DRIEST... ETA WETTEST...AND AVN IN BETWEEN THE TWO EXTREMA. THINK ETA IS TOO AGRESSIVE W/ POPS & LIFT...AND HAVE LEANED TOWARD DRIER NGM/AVN SOLUTION W/ LOW CHANCE POPS WRN ZONES & SLIGHT CHANCE POPS SW GA THU AFTN. SHOULD BE RAIN EVENT AS TEMPS WILL BE ABOVE FREEZING AT SURFACE & BOUNDARY LAYER. ONLY SLIGHT CHANCE POPS ELSEWHERE THU NIGHT AS FRONT PASSES & PUSHES EAST OF CWFA AROUND 06Z FRI. DECREASING CLOUDS & INCREASING NW-N WINDS IN WAKE OF FROPA GIVING WAY TO A BRISK FRI W/ TEMPS ABOUT 5-10 DEGS COOLER. CLEAR SKIES & DIMINISHING WINDS FRI NIGHT IDEAL SCENARIO FOR ANOTHER HARD FREEZE FOR ALL BUT IMMEDIATE COASTAL ZONES. EXTENDED: LATEST LONG-RANGE GUIDANCE MAINTAINS HIGH PRESSURE AS THE DOMINANT FEATURE FOR OUR CWFA THRU CHRISTMAS DAY ALONG W/ A SLOW MODERATION IN TEMPS TO CLIMO LEVELS. THE NEXT CHANCE FOR RAIN WILL BE LATE TUE INTO WED. MARINE: NELY WINDS THIS EVENING BECOME ELY OVERNIGHT...THEN VEER TO S-SWLY THU AFTN AS FRONT APPROACHES. WINDS QUICKLY SHIFT TO NLY & INCREASE TO SCEC/SCA LEVELS LATE THU THRU FRI NIGHT. FIRE WEATHER: RETURN FLOW AHEAD OF NEXT COLD FRONT THU WILL KEEP MIN RH VALUES JUST ABOVE THE CRITICAL THRESHOLD. DEWPOINTS FALL INTO THE TEENS FRI W/ DRIER AIRMASS FILTERING IN BEHIND FRONT...SO WATCH/WARNING WILL LIKELY BE REQUIRED. PRELIM CCF... TLH 021/058 036/052 0120 PFN 032/059 040/053 1320 DHN 026/055 034/048 1320 ABY 022/055 035/048 0220 VLD 022/058 038/050 0120 .TLH... AL...FREEZE WARNING TONIGHT ALZ065>069. GA...HARD FREEZE WARNING TONIGHT GAZ120>124-131-142>148-155>161. FL...HARD FREEZE WARNING TONIGHT FLZ016>019-026>029-034. FREEZE WARNING TONIGHT FLZ008-012-014-015. RED FLAG WARNING ALL ZONES TIL SUNSET. MAJ fl AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SHREVEPORT LA 140 PM CST WED DEC 20 2000 LATEST VIS IMAGERY SHOWING LOW CLOUDS SPREADING RAPIDLY NORTHWARD ACROSS EAST TEXAS AND THEY SHOULD ENGULF ALL OF THE REGION THIS EVENING AHEAD OF A COLD FRONT CURRENTLY MOVING ACROSS NORTH CENTRAL TEXAS. RUC MODEL GUIDANCE HAS HANDLED THE FRONT WELL ALL MORNING AND HAS IT APPROACHING NE TX/SE OK BY 900 PM THIS EVENING. WEAK DIVERGENCE ALOFT AND RELATIVELY WEAK Q-VECTOR CONVERGENCE IN THE 700-300MB LAYER WILL SUPPORT SMALL POPS ACROSS THE WEST OVERNIGHT TRENDING HIGHER AS YOU GO EAST INTO NORTH CENTRAL LOUISIANA. MODEL FCST SOUNDINGS CONTINUE TO SUPPORT A SLIGHT CHANCE OF SLEET MIXING WITH THE RAIN BEFORE ENDING TONIGHT ACROSS THE NORTH BUT AS YESTERDAYS DISCUSSION READ...SLIGHT IS REALLY PUSHING IT. CAN FIND NO REASON TO KEEP MIXED PRECIPITATION FROM THE INTERSTATE 20 CORRIDOR - SOUTH SO HAVE REMOVED THIS MENTION. WHILE GRADIENT APPEARS TO RELAX SOMEWHAT JUST AHEAD OF THE FRONT TONIGHT...WILL KEEP THE CAUTION UP THROUGH THE NIGHT BECAUSE WHILE WINDS MAY RELAX...GRADIENT TIGHTENS UP ONCE AGAIN BEHIND THE FRONT WITH THE WIND SHIFT. SLIGHT WARMUP FOR THURSDAY AS 1035 SFC HIGH SETTLES INTO THE CENTRAL PLAINS WITH MODERATE COLD AIR ADVECTION PATTERN AND FULL SUN. BRISK NORTHWEST WINDS WILL MAKE IT FEEL COLDER SO WILL NEED TO CONTINUE CAUTION WORDING INTO THE DAY THURSDAY. HIGH PRESSURE SETTLING INTO THE SOUTHERN PLAINS THURSDAY NIGHT WILL MEAN A RELAXING PRESSURE GRADIENT AND VERY COLD TEMPERATURES WITH POSSIBLE RECORDS ACROSS SOME LOCATIONS. EXTENDED...AVN/MRF/NOGAPS CONTINUES TO LOOK MORE AND MORE INTERESTING FOR THE WEEKEND INTO THE FIRST OF NEXT WEEK AS MOISTURE SLATED TO RETURN AS EARLY AS SATURDAY MORNING ACROSS THE WEST. DEEPENING UPPER TROUGH ACROSS THE PACIFIC NORTHWEST DROPS INTO THE FOUR CORNERS REGION BY CHRISTMAS DAY WITH OUR FLOW BACKING AROUND TO THE SOUTHWEST. ANOTHER SHOT OF COLD AIR PROGD TO DROP INTO THE LOWER MISS VALLEY LATE SUNDAY WITH A POSSIBLE OVERRUNNING PRECIP EVENT UPCOMING. WILL INTRODUCE SLIGHT CHANCES OF RAIN ACROSS THE WEST HALF SUNDAY ONLY. A MIXTURE OF RAIN/ SLEET ACROSS THE NORTH WITH JUST RAIN FURTHER SOUTH ON CHRISTMAS DAY AND TUESDAY. IT MUST BE NOTED THAT CONSIDERABLE UNCERTAINTY EXITS WITH THIS EXTENDED PACKAGE BUT TO KEEP WITH THE CONTINUITY OF SURROUNDING OFFICES...NEED TO INCLUDE THE POSSIBILITY OF A WINTERY MIX AT THIS TIME. PRELIMINARY NUMBERS TO FOLLOW...13 SHV 34/48/18/37 3100 MLU 36/48/18/37 5200 TXK 30/47/17/37 3100 TYR 30/48/18/40 2000 LFK 35/50/19/43 3000 .SHV...NONE. la AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GAYLORD MI 405 AM EST WED DEC 20 2000 SHORT RANGE DISCUSSION...12Z UPPER AIR PLOTS SHOW STRONG MID TROPOSPHERIC WAVE OVER THE NORTH CENTRAL U.S. WHICH IS POISED TO DROP INTO THE WESTERN GREAT LAKES REGION AND AMPLIFY TONIGHT AND THURSDAY. WITH PLENTY 850 MB COLD AIR STILL IN PLACE ACROSS THE REGION...THE POTENTIAL FOR SIGNIFICANT LAKE ENHANCEMENT REPRESENTS PRIMARY FORECAST CONCERN. TONIGHT...HAVE OPTED TO FOLLOW ETA MODEL SOLUTION...WHICH IS A COMPROMISE BETWEEN THE STRONGER AVN AND THE WEAKER NGM. LATEST RUN OF THE RUC SEEMS TO SUPPORT THIS SOLUTION...KEEPING THE SURFACE LOW ON A MORE EASTERLY TRACK. BY 12Z THURSDAY...EXPECT SURFACE LOW TO BE NEAR GRB. AS 500 MB WAVE DEEPENS...ETA 850/500 MB RH VALUES ARE FORECAST TO INCREASE TO ABOVE 80 PERCENT...AS STRONG 850/500 MB Q-VECTOR CONVERGENCE OVERSPREADS THE REGION. MODEL QPF FIELDS... TOGETHER WITH 700 MB MIXING RATIOS UNDER 2 G/KG SUPPORT A GENERAL 2-3 INCH SNOWFALL IN AREAS NOT RECEIVING A LAKE CONTRIBUTION. NOW FOR THE LAKE CONTRIBUTION. IT WILL BE VERY CLOSE WHETHER OR NOT COASTAL SECTIONS OF LAKE MICHIGAN FROM GRAND HAVEN TO MANISTEE...AND COASTAL SECTIONS OF LAKE HURON FROM ALCONA TO ROGERS CITY RECEIVE FAVORABLE WINDS FOR LAKE CONTRIBUTIONS TONIGHT. A WIND SHIFT OF ONLY 10-20 DEGREES WILL MAKE A TREMENDOUS DIFFERENCE. FEEL THAT WITH SURFACE TO 850 MB MEAN WINDS GENERALLY FROM THE SOUTH...THE LAKE MICHIGAN SHORELINE HAS A BETTER CHANCE TO RECEIVE HEAVY SNOWFALL -- ESPECIALLY AS WAA AND A SLIGHT VEERING LOW LEVEL WIND PROFILE EVOLVES OVERNIGHT. WILL UPGRADE LEELANAU...BENZIE...AND MANISTEE COUNTIES TO A WARNING FOR LATE TONIGHT AND THURSDAY. THE HEAVIEST SNOW IN THIS AREA WILL LIKELY OCCUR BETWEEN 12Z AND 18Z THURSDAY AS WINDS TURN TO THE SW WITH THE PASSAGE OF THE SURFACE TROUGH. BY LATE THURSDAY...6 TO 10 INCHES OF SNOW IS EXPECTED...ESPECIALLY ALONG THE IMMEDIATE LAKE SHORE. JUST THE OPPOSITE SCENARIO ALONG THE LAKE HURON SHORELINE...WHERE SOUTHERLY WINDS AND POTENTIAL FOR A LAND BREEZE COMPONENT SHOULD KEEP HEAVIEST SNOW **JUST** OFFSHORE. HAVE THEREFORE NOT UPGRADED TO A WARNING FOR PRESQUE ISLE...ALPENA...AND ALCONA COUNTIES. IT WILL BE A CLOSE CALL. FOR EASTERN UPPER...ETA MODEL SHOWS WARM FRONTAL BOUNDARY SETTING UP ALONG THE SOUTH SHORE OF EASTERN UPPER. LOW LEVEL CONVERGENCE IS FORECAST TO BE STRONG...WITH A STRONGER SE LOW LEVEL WIND COMPONENT PROVIDING FOR A LONG FETCH OVER NORTHERN LAKE HURON. SYNOPTIC SCALE MOISTURE/ASCENT...TOGETHER WITH LAKE TO 850 MB DELTA T/S OF NEAR 18C SHOULD PROVIDE NECESSARY INGREDIENTS FOR HEAVIER SNOW. WIND TRAJECTORIES SHOULD FAVOR AREAS EAST OF I-75 FOR THE HEAVIEST SNOW. THURSDAY...SURFACE BOUNDARY -- AND ASSOCIATED CONVERGENCE -- WILL SWING ACROSS THE AREA THURSDAY MORNING TURNING WINDS MORE S/SW. WITH 500 MB WAVE STILL WEST OF LAKE MICHIGAN...EXPECT LAKE ENHANCEMENT TO INCREASE WEST OF A LINE FROM ELK RAPIDS TO CADILLAC. ACROSS REST OF NORTHERN LOWER...SYNOPTIC SNOW WILL CONTINUE...THOUGH MODELS SUGGEST SOME DRY SLOTTING DURING THE AFTERNOON...WHICH SHOULD LESSEN SNOWFALL S OF A CAD TO APN LINE. ACROSS EASTERN UPPER...SYNOPTIC SUPPORT WILL LINGER THROUGH THE DAY...AS WINDS REMAIN FROM THE SE AND 850 MB TEMPERATURES HOLD NEAR -13C. DEPENDING ON HOW PERSISTENT THESE SE WINDS ARE...SOME AREAS COULD RECEIVE SUBSTANTIAL SNOWFALL BY LATE THURSDAY. THURSDAY NIGHT AND FRIDAY...SURFACE LOW IS FORECAST TO MOVE EAST ACROSS EXTREME SOUTHERN UPPER MICHIGAN THURSDAY NIGHT. WITH OPTIMAL 850 MB TEMPERATURES NEAR -13C...REMAINING 850/500 MB Q-VECTOR FORCING AND MOISTURE...AND SURFACE CONVERGENCE ASSOCIATED WITH SURFACE LOW/TROUGH...AREAS WEST OF A LINE FROM CHEBOYGAN TO GAYLORD TO KALKASKA COULD SEE HEAVY ACCUMULATIONS AS LOW LEVEL WINDS TURN TO THE WEST. ON FRIDAY...TRADITIONAL NW FLOW LAKE EFFECT GETS ESTABLISHED...THOUGH THERE IS STILL SOME UNCERTAINTY ON LOCATION AND INTENSITY. LARGE SCALE SUPPORT WILL BE DIMINISHING...AND MESO-ETA SUGGESTS LAKE AGGREGATE TROUGH PASSING TO THE SOUTH...WHICH WILL TURN WINDS TO THE NORTH. EXTENDED FORECAST DISCUSSION...THE NEWEST MRF IS EXHIBITING REASONABLY GOOD RUN TO RUN CONSISTENCY...WITH COLD 500 MB MEAN TROUGH STILL FORECAST TO REMAIN IN PLACE OVER SE CANADA AND NE U.S.. FLOW ALOFT BECOMES ZONAL FOR A BRIEF TIME EARLY SATURDAY IN THE WAKE OF THURSDAY/FRIDAY SYSTEM...BEFORE NEXT WAVE DROPS SE OUT OF CANADA INTO THE N CENTRAL STATES SUNDAY. 850 MB TEMPERATURES REMAIN COLD ENOUGH FOR A CONTINUED CHANCE OF LIGHT LAKE EFFECT SNOW (MAINLY FLURRIES) ON SATURDAY...IN SPITE OF LIMITED LARGE-SCALE SUPPORT. 500 MB TROUGH ARRIVES ON SUNDAY...WHICH WITH CONTINUED OVER-WATER INSTABILITY...WILL PROVIDE A CHANCE OF SNOW SUNDAY. THE MRF HAS BACKED OFF JUST A BIT ON THE MAGNITUDE OF THE COLD AIR BEHIND THIS SYSTEM ON MONDAY...THOUGH BELOW NORMAL TEMPERATURES STILL APPEAR LIKELY. LAKE EFFECT IS EXPECTED TO LINGER INTO TUESDAY...AS 850 MB TEMPERATURES SLOWLY MODERATE IN ADVANCE OF YET ANOTHER 500 MB WAVE DROPPING SE OUT OF CANADA. WILL TENTATIVELY KEEP WEDNESDAY DRY WITH SLIGHTLY WARMER TEMPERATURES. LONGER RANGE MRF INTENSIFIES PREVIOUSLY MENTIONED 500 MB WAVE OVER THE GREAT LAKES WHICH...IF IT VERIFIES...WILL BRING ANOTHER BOUGHT OF SNOW AND COLD JUST PRIOR TO THE NEW YEAR. .APX...WINTER STORM WARNING...LATE TONIGHT AND THURSDAY... MIZ008-015-020-025-031. SMITH mi AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 358 PM EST WED DEC 20 2000 ...WARNINGS AND ADVISORIES IN EFFECT FOR NW GRR CWA.. FORECAST PROBLEMS FIRST FOUR PERIODS ARE FOR SNOW AMOUNTS WITH THE MULTIPLE THREATS OF ACCUMULATING SNOW COURTESY OF THE LATEST IN PARADE OF CLIPPER TYPE STORMS TO AFFECT GRR FA. SNOW ENCROACHING ACROSS SOUTHWEST LAKE MICHIGAN ATTM. GOOD INSENTROPIC UPGLIDE CAPTURED BY LATEST RUC WHICH CORRESPONDS WELL WITH HEAVIER SNOW SEEN ACROSS NORTHERN ILLINOIS. THIS BATCH SHOULD BE AFFECTING THE WESTERN FA EARLY THIS EVENING...WITH SECOND AREA OF ENHANCED MESOSCALE BANDING BACK OVER IA-MI-NB AREA ASSOC/W UPPER LEVEL DIVERGENCE FROM COUPLED JET. SHORTWAVE DIGS SOUTH OVERNIGHT AND AREA OF UPR DIVERGENCE IS OVER GRR FA AROUND 06Z. BULK OF SNOW SHOULD OCCUR BETWEEN 06 AND 12Z...WITH LAKE ENHANCEMENT ACROSS THE WARNING AND ADV AREA EXPECTED TO BOOST TOTALS. FLUFF FACTOR MAY ALSO BE IMPORTANT THIS TIME AROUND AS SNOW/LIQUID RATIOS EXPECTED TO BE IN THE 15 TO 20/1 RANGE. SW FLOW LES EVENT FOR THU FROM 12 TO 18Z WITH MESOETA INDICATING BAND COMES ON SHORE FROM MKG NORTH AROUND 16Z. WILL WORD THE WARNING AS SNOW BEING CLOSE TO THE LAKE SHORE...AS POSITION OF THE BAND WILL OF COURSE BE CRITICAL HERE. SOME LOCALIZED AMOUNTS NEAR 10 INCHES NOT OUT OF THE QUESTION IF BAND PERSISTS FOR ANY LENGTH OF TIME OVER ONE AREA. NO REST FOR THE WEARY...AS WRAP AROUND MOISTURE AND SHARP SFC TROF BRING THE POSSIBILITY OF A NW FLOW EVENT THUR NIGHT. WORDED THIS AS ACCUM LIKELY/POSSIBLE FOR NOW...BUT A WATCH MAY BE REQUIRED FOR THE FAVORED NW FLOW LES COUNTIES BY LATER SHIFTS. SLOW IMPROVEMENT FRI MORN AFT...BUT SHSN AND FLURRIES LOOK TO PERSIST RIGHT INTO FRI NIGHT. OSTUNO EXTENDED FORECAST DISCUSSION... MODELS CONTINUE TO ADVERTISE A LARGE CANADIAN HIGH PRESSURE SYSTEM DROPPING SOUTHWARD OUT OF CENTRAL CANADA THIS WEEKEND. BEING ON THE EAST SIDE OF THIS FEATURE...WE WILL EXPERIENCE PERSISTENT COLD AIR ADVECTION...GENERATING LOTS OF LAKE EFFECT SNOW SHOWERS. I LIKE THE AVN SOLUTION...SHOWING THE PASSAGE OF A WEAK SURFACE LOW ON SATURDAY...THEN COLD AIR ADVECTION RIGHT INTO CHRISTMAS DAY. PERHAPS A LULL IN THE ACTIVITY FOR TUESDAY AND WEDNESDAY WITH THE MRF SHOWING SOME SLIGHT WARMING AND DIVERGENT LOW LEVEL FLOW. HOWEVER...ANOTHER MAJOR UPPER LOW IS SEEN DROPPING DOWN FROM CENTRAL CANADA ON THURSDAY. .GRR...WINTER STORM WARNING FOR MASON...OCEANA...AND MUSKEGON COUNTIES FOR TONIGHT AND THURSDAY. SNOW ADVISORY FOR LAKE...NEWYAGO AND OTTAWA COUNTIES FOR TONIGHT AND THURSDAY. mi