Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 261441 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 941 AM EST WED NOV 26 2014 .SYNOPSIS... LOW PRESSURE WILL DEVELOP OFF THE MID ATLANTIC COAST TODAY AND TRACK NORTHEAST TO JUST SOUTH OF CAPE COD BY WEDNESDAY EVENING....BRINGING A SIGNIFICANT SNOWFALL TO NORTHERN NEW ENGLAND. THE COASTAL LOW WILL CONTINUE NORTHEAST INTO THE MARITIMES WEDNESDAY NIGHT. COLD HIGH PRESSURE WILL BUILD IN FROM THE WEST ON FRIDAY AND SATURDAY. THE FLOW SHIFTS TO THE SOUTHWEST SUNDAY WITH A WARM UP EXPECTED. ANOTHER COLD FRONT CROSSES THE REGION ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... 938 AM UPDATE... HAVE UPDATED THE GRIDS BASED ON CURRENT CONDITIONS. CYCLOGENESIS ON TRACK AND THE WESTWARD SHIFT OF THE MODELS HAS STABILIZED. DRY SLOT MAY REACH THE COASTLINE LATER TONIGHT...CAUSING THE SNOW TO END AS A PERIOD OF SLEET OR FREEZING DRIZZLE. 7AM UPDATE... JUST SOME TWEAKS TO THE TEMPERATURES... STILL RUNNING ON THE WARM SIDE IN THE MOUNTAIN VALLEYS, HOWEVER DEW POINTS CONTINUE TO DROP AND MORNING KGYX SOUNDING IN PROGRESS SHOWS VERY DRY AIR ALOFT. HAVE LEFT SNOW AMOUNTS AS IS. LOW IS DEEPENING WITH HEIGHT FALLS OFF CHESAPEAKE BAY. AS WE CLOSE IN ON THE STORM MORE AND MORE MESOSCALE DETAILS HAVE EMERGED, AND HAVE ENHANCED OUR EXISTING FORECAST WITH THESE DETAILS... HOWEVER THE BROAD PICTURE HAS NOT CHANGED. ** A MAJOR WINTER STORM WILL IMPACT NH AND ME THROUGH WEDNESDAY AFTERNOON SIGNIFICANTLY HAMPERING TRAVEL** AT 09Z THE LOW WAS CENTERED JUST OFF THE CAROLINA COAST AND WILL TRACK RAPIDLY NORTHEASTWARD THROUGH THE DAY TODAY. TRACK FORECASTS HAVE COME INTO GOOD AGREEMENT FOR THE LOW TO PASS JUST NORTHWEST OF THE 70W/40N BENCHMARK AROUND 03Z THURSDAY. THERE ARE TWO MAIN AREAS OF CHANGE FOR THIS FORECAST PACKAGE. THE FIRST IS THE NORTHERN EXTENT OF THE HEAVY SNOW. QPF AMOUNTS HAVE INCREASED IN PRETTY MUCH ALL FORMS OF GUIDANCE... COMBINED WITH COLD TEMPS AND IDEAL SNOW GROWTH THIS HAS RESULTED IN AN INCREASE OF SNOWFALL FOR THE NORTHERN MOST ZONES... AND HAVE UPGRADED TO A WINTER STORM WARNING FOR THE WHOLE CWA. SOME POCKETS OF THE UPPER CT VALLEY MAY REMAIN MARGINAL IN TERMS OF SNOW TOTALS... BUT FEEL THE MAJORITY OF THE ZONE WILL MEET CRITERIA. THE OTHER CHANGE... AND OF GREATER CONCERN IS THE POTENTIAL FOR BANDING... RESULTING IN VERY HEAVY SNOWFALL RATES. VERY STRONG BANDING SIGNATURE WITH 700MB FRONTOGENESIS CONCENTRATED IN A LINE EXTENDING FROM KEENE NH PARALLEL TO THE GULF OF MAINE UP THROUGH TO CALAIS ME. THIS PAIRS UP NICELY WITH A LAYER OF INSTABILITY EXTENDING FROM 700 TO 500MB... SETTING US UP FOR A CLASSIC NORTHWEST SECTOR BAND AS THE LOW PASSES FROM SOUTH OF LONG ISLAND NORTHEASTWARDS TOWARDS THE BENCHMARK FROM 00Z-06Z TOMORROW. AT THIS POINT THIS SAME SIGNATURE IS EVIDENT IN ALL THE MAJOR GUIDANCE GFS/NAM/ECMWF/CMC ... GIVING FAIRLY HIGH CONFIDENCE OF THE FORMATION OF THE BAND. THE NATURE OF THE BEAST IS THAT THE EXACT LOCATION MAY SHIFT SLIGHTLY NORTH OR SOUTH.. GIVING VERY DIFFERENT SNOWFALL TOTALS WITHIN A FEW MILES BUT FEEL THERE WILL BE PORTIONS OF THE COASTAL PLANE IMPACTED BY THIS FEATURE BETWEEN 00Z AND 06Z. SNOW TOTALS HAVE INCREASED SLIGHTLY THROUGH THIS AREA TO REFLECT THIS BANDING POTENTIAL. **THIS BANDING WILL RESULT IN SNOWFALL RATES OF 1-3"/HR THROUGH THE MOST INTENSE PARTS OF THE BAND.** IN NEW HAMPSHIRE... THE CORRIDOR FROM CONCORD TO MANCHESTER WILL SEE HEAVY SNOW STARTING AROUND 21Z AS THE BAND PUSHES NORTHWARDS. BETWEEN 00Z AND 03Z IT SETS UP NICELY PARALLEL TO THE COAST THROUGH THE ENTIRE COASTAL PLANE... IMPACTING ALL NORTH SOUTH TRAVEL ROUTES IN THE CWA. OVERALL THE QUICK MOVING NATURE OF THE SYSTEM WILL HELP AS MOST AREAS WILL SEE THE MOST INTENSE SNOWFALL RATES LIMITED TO AROUND 3HRS. AN EXCEPTION TO THIS IS THE LEWISTON TO AUGUSTA REGION... WHERE THE BAND MAY PIVOT AS THE LOW TURNS MORE NORTHWARD KEEPING THE I-95 CORRIDOR OF SOUTHWEST MAINE UNDER THE HEAVY SNOW A BIT LONGER. ONCE AGAIN...THE CONDITIONS WILL BE QUICKLY DETERIORATING AND EXPECTED TO BE THE WORST WED AFTERNOON AND EVENING...COINCIDING WITH THE BUSIEST TRAVEL TIMES. TRAVELERS SHOULD BE AT THEIR DESTINATIONS BY WED AFTERNOON IF AT ALL POSSIBLE. && .SHORT TERM /THURSDAY/... THE STORM WILL RAPIDLY EXIT THE AREA ON THANKSGIVING DAY.. WITH SNOW CLEARING FROM WEST TO EAST IN THE MORNING AND MINIMAL ADDITIONAL ACCUMULATION AFTER DAY BREAK. HIGH TEMPERATURES WILL BE NEAR FREEZING AND DROP OFF THROUGH THE DAY AS COLD AIR ALOFT PUSHES INTO THE REGION. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HEMISPHERIC 500MB PATTERN REMAINS ON THE UNSTABLE SIDE AS SMALL SCALE BLOCKS SET UP AND BREAK DOWN EVERY COUPLE OF DAYS...ALTHOUGH OVERALL TREND IS STILL TOWARD A +PNA PATTERN...BUT WITHOUT SIGNIFICANT AMPLIFICATION...WHICH MEANS MORE IN THE WAY OF A TROUGH ACROSS ACROSS CENTRAL AND ERN NOAM. SO...ALTHOUGH IT WILL BE SOMEWHAT UNSETTLED WITH FLUCTUATING TEMPS THRU THE PERIOD...NO SIGNIFICANT SYSTEMS ARE EXPECTED. IT STARTS OUT COLD THU NIGHT INTO FRIDAY AS SFC RIDGE BUILDS IN FROM THE SW. MODELS SUGGESTING POSSIBLE INVERTED TROUGH THU NIGHT...ALTHOUGH STRENGTH AND LOCATION VARY FROM MODEL TO MODEL. WILL HAVE TO WATCH FUTURE MODELS RUNS TO SEE IF THIS SYSTEM WILL SPREAD ANY LIGHT SNOW INTO COASTAL SECTIONS. THE HIGHS SHOULD BUILD IN FOR FRI AND FRI NIGHT...WITH MAXES FRI AND SAT GENERALLY IN THE UPPER 20S TO AROUND 30 IN THE N AND 30S ELSEWHERE. SW FLOW SETS UP FOR SAT NIGHT INTO MON WITH BROAD WAA PATTERN ALOFT...WHICH WILL WARM THINGS UP A BIT...BUT SHOULD ALSO PRODUCE A FAIR AMT OF MID-HIGH CLOUDS...WITH HIGHS IN THE UPPER 30S AND 40S BOTH SUN AND MON. ANOTHER WEAK WAVE AT 500MB TRACKS THRU LATE MONDAY AND DRAGS A COLD FRONT ACROSS THE REGION...WITH A THREAT FOR SHRA/SHSN. IT COOL DOWN AGAIN FOR TUE...BUT WARMER AIR RETURNS BY THE MIDDLE OF NEXT WEEK. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... SHORT TERM...VFR CONDITIONS PREVAIL THRU EARLY WED. CONDITIONS RAPIDLY DETERIORATE FROM S TO N THRU WED AFTERNOON. CONDITIONS WILL QUICKLY DROP TO IFR AND LOWER BY EVENING. COULD SEE SOME BRIEF MIXING WITH RA AT KPSM AND KPWM...BEFORE A TRANSITION TO ALL SNWFL. WINDS ALONG THE COAST WILL BE GUSTY FROM THE NNE...AROUND 25-30 KTS. CONDITIONS QUICKLY IMPROVE TO MVFR OR VFR THU AS LOW PRES PULLS AWAY. LONG TERM...MAINLY VFR THU NIGHT THROUGH SUNDAY. COASTAL TERMINALS...ESPECIALLY KPWM/KPSM...HAVE A SLIGHT CHC FOR SOME IFR IN LIGHT SNOW THU NIGHT. && .MARINE... SHORT TERM...GALE WARNINGS IN EFFECT STARTING WED AFTERNOON. COASTAL STORM WILL QUICKLY MOVE ACROSS THE GULF OF ME...WITH A BRIEF PERIOD OF GALE FORCE GUSTS. SCA WILL LIKELY BE NEEDED FOLLOWING THE LOW PRES. LONG TERM...GENERALLY QUIET WITH SUB-SCA CONDS ON THE WATERS THU NIGHT INTO SAT. SCA MAY BE NEEDED FOR INCREASING SW FLOW ON SUNDAY. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR MEZ012>014- 018>028. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST THURSDAY FOR MEZ007>009. NH...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NHZ002>010- 013-014. WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST THURSDAY FOR NHZ001. MARINE...GALE WARNING FROM 5 PM THIS AFTERNOON TO 7 AM EST THURSDAY FOR ANZ150>154. && $$ JC

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