Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 172032
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
332 PM EST WED DEC 17 2014

.SYNOPSIS...
A WEAK LOW PRESSURE SYSTEM WILL SLOWLY EXIT THE GULF OF MAINE
THIS EVENING. BY THURSDAY MORNING...THE LOW WILL BE OVER THE
CANADIAN MARITIMES AND WEAK HIGH PRESSURE WILL BUILD IN BEHIND IT.
THERE IS POTENTIAL FOR A WEAK COASTAL SYSTEM SUNDAY INTO MONDAY
THAT MAY SPREAD SOME LIGHT SNOW INTO THE REGION. ANOTHER SYSTEM
WILL LIKELY STRENGTHEN AND PASS BY TO OUR WEST DURING THE MID
WEEK PERIOD.

&&

.NEAR TERM /TONIGHT/...
ELONGATED AREA OF LOW PRES IN THE GULF OF ME ATTM...WITH SFC TROF
EXTENDING BACK INTO SRN QUEBEC AND ONTARIO. OVERNIGHT UPPER LOW
PRES WILL DRIFT UNDERNEATH THE MAJORITY OF THE CWFA. THIS SHOULD
HOLD TROF BACK ACROSS NRN ZONES...AND KEEP FOCUS OF MOISTURE
STREAM INTO THE WRN ME MTNS AND PARTS OF THE WHITES. HI-RES MODEL
FORECASTS INDICATE THAT MID LEVEL WARMTH WAS LIKELY MAXIMIZED A
COUPLE HOURS AGO...AND WE SHOULD SEE A STEADY COOLING TREND ALOFT.
THIS IS CONFIRMED BY PLYMOUTH STATE VERTICALLY POINTED RADAR
SHOWING SNOW LEVELS DECREASING OVER THE LAST HOUR. SPOTTER REPORTS
INDICATE MANY NRN MTNS AND VALLEYS ALIKE CHANGED OVER TO SN FOR
GOOD IN THE LAST COUPLE OF HOURS AS WELL. ELY UPSLOPE FLOW WILL
ALSO CONTINUE TO DYNAMICALLY COOL THE COLUMN AND KEEP THE MTNS
SN THRU THE NIGHT. FORECAST MODEL ALSO DEEPEN THE H7 LOW THRU
MIDNIGHT...CLOSING OFF CONTOURS AS IT CROSSES THE STATE OF ME.
THIS SHOULD PROVIDE ENHANCED LIFT TO THE NW OF THE MID LEVEL LOW
TRACK...AGAIN KEEPING SNWFL FOCUSED OVER NRN ZONES. A BLEND OF THE
RFC QPF AND HI-RES MODEL GUIDANCE WAS USED TO PROVIDE A
REASONABLE REPRESENTATION OF HIGHER TERRAIN ENHANCEMENT. SNWFL
WILL WAX AND WANE A BIT THIS EVENING AS THE DRY SLOT LIFTS THRU
THE AREA...BUT I EXPECT FORCING TO REFOCUS LATER TONIGHT INTO THU.
HAVE EXPANDED THE WINTER WX ADVISORIES INTO COOS COUNTY NH...AND
ALL OF OXFORD...FRANKLIN...AND CENTRAL/SRN SOMERSET IN ME. THIS
WILL BE A RELATIVELY LONG DURATION LIGHT SNWFL EVENT...WHICH
COMPLICATES THINGS A BIT. I COULD EASILY SEE 6+ INCHES OF SNWFL
FOR NRN ZONES...BUT IT MAY FALL IN 18 OR 24 HOURS...SHY OF THE 9
INCH CRITERIA BEYOND 12 HOURS. A HEAVIER BAND OF SNWFL THIS
EVENING ACROSS NRN FRANKLIN OR CENTRAL SOMERSET COULD WARRANT AN
UPGRADE TO A WARNING IN THOSE AREAS.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
UPPER LOW PULLS INTO THE MARITIMES THU...BUT COOL...MOIST...NWLY
FLOW CONTINUES OVER THE REGION. THE FORCED ASCENT OVER THE HIGHER
TERRAIN WILL KEEP SHSN GOING IN THE FAVORED NW UPSLOPE REGIONS.
THIS IS LIKELY WHEN THE BULK OF THE ACCUMULATIONS WILL COME FOR
NRN NH AND THE WHITE MTNS. NW WINDS WILL ALSO BE GUSTY ALONG THE
COAST AND INTERIOR.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
CLEARING SKIES EXPECTED THURSDAY NIGHT AS LOW PRESSURE EXITS INTO
THE CANADIAN MARITIMES. THIS WILL BE FOLLOWED BY HIGH PRESSURE
BUILDING SOUTH AND INTO NEW ENGLAND FROM CANADA.

MODELS THEN BRING A WEAK AREA OF LOW PRESSURE UP THE COAST MONDAY
AND TUESDAY. THERE IS NOT MUCH CONSENSUS WITH THE 12Z PACKAGE WITH
THIS FEATURE. CURRENTLY THE EURO IS THE FURTHEST WEST WITH THE
POSITION OF THE SURFACE AND UPPER LEVEL FEATURES.

ALL EYES THEN SHIFT TO THE 24TH...AS LOW PRESSURE RAPIDLY
INTENSIFIES AND MOVES NORTH. QUESTION IS WHETHER THE SYSTEM
FOLLOWS THE COASTLINE OR CROSSES OVER THE GREAT LAKES. FOR
NOW...CONFIDENCE LEVEL IS LOW. IF THE GREAT LAKES TRACK
VERIFIES...EXPECT LOCALLY HEAVY RAIN AND HIGH WINDS OVER THE
REGION. SOUTHEASTERLY GRADIENT WILL LIKELY REACH STORM FORCE FOR A
SHORT PERIOD OVER THE WATERS WITH STRONG GUSTY WINDS OVER LAND.
STRONG WINDS WOULD LIKELY REACH THE COASTLINE LATE WEDNESDAY ALONG
THE COAST AND HIGHER TERRAIN.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
SHORT TERM...AREAS OF IFR CONDITIONS WILL CONTINUE TO LIFT NEWD UP
THE COAST THIS EVENING...WITH WIDESPREAD MVFR LINGERING IN ITS
WAKE. GRADUALLY SHRA WILL MIX WITH AND TRANSITION TO SHSN BY
THU. THIS WILL LEAD TO SCT IFR CONDITIONS AT TIMES NEAR THE COAST.
IN THE MTNS...IFR CONDITIONS WILL LINGER THRU THU. GUSTY NW WINDS
ARE POSSIBLE THU AS WELL...WITH GUSTS AOA 20 KTS.

LONG TERM...A FEW AREAS OF MVFR CONDITIONS DEVELOPING IN PATCHY
LIGHT SNOW MONDAY NIGHT THROUGH TUESDAY NIGHT. IFR CONDITIONS
DEVELOPING WITH A STRONG AREA OF LOW PRESSURE PASSING BY TO OUR
WEST WEDNESDAY.

&&

.MARINE...
SHORT TERM...HAVE EXTENDED THE SCA IN TIME AND IN AREA TO THE
BAYS...AS WINDS LOOK TO INCREASE IN NW FLOW THU. WINDS WILL RELAX
BRIEFLY TONIGHT...BUT STEADILY INCREASE BY MORNING AS CAA
COMMENCES.

LONG TERM...SCA CONDITIONS EXPECTED TUESDAY...WITH STORM FORCE
WINDS POSSIBLE ON WEDNESDAY AS A STRONG AREA OF LOW PRESSURE
BRINGS HIGH SOUTHEAST WINDS TO THE REGION.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...WINTER WEATHER ADVISORY UNTIL 1 PM EST THURSDAY FOR MEZ007>009-
     012>014.
NH...WINTER WEATHER ADVISORY UNTIL 1 PM EST THURSDAY FOR NHZ001-002.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST FRIDAY FOR ANZ150>154.

&&

$$

LEGRO/JC



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