Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 261658
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1158 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/...
1158 AM UPDATE...
ANY RAIN OVER SOUTHERN AREAS CONTINUES TO QUICKLY CHANGE TO
SLEET...THEN SNOW. EXPECT THIS TREND TO CONTINUE AS DEW POINTS
REMAIN IN THE MID 20S TO NEAR 30. -SN SWITCHES TO +SN OVER A SHORT
PERIOD OF TIME. TRAVEL SHOULD BE COMPLETED SOON.

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 /18Z WEDNESDAY THROUGH MONDAY/...
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 UNTIL 7 AM EST THURSDAY FOR MEZ007>009.
NH...WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NHZ002>010-
     013-014.
     WINTER STORM WARNING UNTIL 7 AM EST THURSDAY FOR NHZ001.
MARINE...GALE WARNING FROM 5 PM THIS AFTERNOON TO 7 AM EST THURSDAY FOR
     ANZ150>154.

&&

$$



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