Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 180035 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 735 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 /UNTIL 6 AM THURSDAY MORNING/...
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730 PM...PRECIPITATION WAS GRADUALLY CHANGING TO SNOW AND SLEET ACROSS THE AREA. I MADE MINOR ADJUSTMENTS TO 1ST PERIOD GRIDS TO REFLECT THE CURRENT MESONET FOR THIS ESTF UPDATE. PREV DISC... 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.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... 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 /THURSDAY NIGHT 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 /00Z THURSDAY 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. && $$ ES

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