Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 011547
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1147 AM EDT SUN MAY 1 2016

.SYNOPSIS...
LOW PRESSURE OVER THE EASTERN GREAT LAKES WILL MOVE NORTHEAST
TOWARD NEW ENGLAND TODAY AND TONIGHT... SPREADING RAIN INTO THE
REGION. RAINY WEATHER PERSISTS INTO MONDAY WHEN LOW PRESSURE MOVES
EAST INTO THE CANADIAN MARITIMES. WEAK HIGH PRESSURE WILL MOVE OUT
OF CANADA AND THROUGH NORTHEAST NEW ENGLAND ON TUESDAY. LOW
PRESSURE DEVELOPING OFF THE CAROLINAS WILL TRACK NORTHWARD INTO
NEW ENGLAND WEDNESDAY NIGHT INTO THURSDAY BRINGING ANOTHER CHANCE
OF RAIN.

&&
15Z UPDATE...
LIGHT RAIN RAIN CURRENTLY PUSHING THROUGH SOUTHERN NEW HAMPSHIRE
AND THIS AREA WILL CONTINUE TO SPREAD NORTH AND EAST ACROSS THE
FORECAST AREA THROUGH MID AFTERNOON. HAVE ADJUSTED POP AND WX
GRIDS TO REFLECT LATEST RADAR TRENDS. ASIDE FROM A FEW TEMP/TD
TWEAKS NO FURTHER CHANGES TO THE FORECAST PLANNED ATTM.


PREVIOUS DISCUSSION...
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
655 AM...NO SIGNIF CHANGES TO THE FORECAST...JUST HELD BACK THE
CHC POPS IN WRN ZONES AND OVERCAST INN GENERAL BY AND HOUR OR TWO
THIS MORNING...GIVEN CURRENT LOOK AND SAT/RADAR AND SKY
CONDITIONS. AT 11Z...10SM VIS RAIN BEGAN AT KALB...BUT HAVE TO GO
WEST TO CENTRAL NY FOR STEADIER RAIN. ALSO...THE AREA OF RAIN OVER
NY THIS MORNING...WILL BE DIMINISHING SOMEWHAT AS IT MOVES EAST.

PREVIOUSLY...MODELS CONTINUE TO SHOW PRECIP STRUGGLING TO MOVE
EAST ACROSS THE CT VLY TODAY. MID LVL THERMAL ADVECTION IS THE
ONLY STRONG FORCING MECHANISM AS 500MB DYNAMIC ARE WEAK AS WAVE
ALOFT MOVES INTO RIDGING...AND LOW LEVEL DRY AIR MAKES IT HARD FOR
RAIN TO REACH THE GROUND. WILL LKLY SEE SOME SHRA IN NH MIDDAY AND
THROUGH THE AFTERNOON...BUT ANY PRECIP WILL TAKE TO AT LEAST LATE
AFTERNOON TO MAKE IT INTO ME. STILL WILL SEE BKN-OVC SKIES THRU
THE DAY...AND ONSHORE FLOW WILL LIMIT HIGHS TO THE LOW-MID 50S
WITH THE WARMEST SPOTS INTERIOR KENNEBEC AND PENOBSCOT VLY
REGIONS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
INITIAL 500MB WAVE SHEAR OUT OVERNIGHT AS IT MOVES THRU THE
RIDGE...AND COULD SEE SOME RESIDUAL SHRA FROM THIS SYSTEM THIS
EVENING...OVERALL PRECIP LOOKS LIMITED TO JUST SOME SHRA
OVERNIGHT. LOOK FOR FOG AND MAYBE SOME SPOTTY DZ TO DEVELOP AS
BOUNDARY LYR MOISTURE STARTS TO INCREASE. LOWS WILL DROP OFF A BIT
AS THERE IS A BIT OF CAA BEHIND THAT WEAKENING FIRST WAVE...BUT
SHOULD ONLY DROP TO UPPER 30S TO LOW 40S.

ON MONDAY...WILL SEE A BETTER SFC LOW DEVELOP S OF NEW ENGLAND
AND TRACK JUST S AND E OF THEN GULF OF ME. THERE WILL BE SOME WEAK
PHASING OF A 500MB WAVE TO THE N WITH THIS SYSTEM AS IT PASSES
BY...AND BEST CHC FOR RAIN WILL BE MON AFTERNOON. MAYBE A QUARTER
TO HALF INCH ON MONDAY. ONSHORE FLOW WILL CONTINUE AND IT WILL BE
COOL WITH HIGHS IN THE MID 40S N...TO AROUND 50 IN THE S.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
LOW PRESSURE MOVES EAST INTO THE MARITIMES WITH HIGH PRESSURE
BUILDING IN BRIEFLY BEHIND IT MONDAY NIGHT INTO TUESDAY. THIS WILL
BE THE BEST CHANCE IN THE LONG TERM PERIOD TO SEE FREEZING
TEMPERATURES... BUT PERSISTENT LOW LEVEL MOISTURE WILL LIKELY KEEP
NIGHTTIME TEMPERATURES ACROSS MUCH OF THE AREA ABOVE FREEZING.

ON TUESDAY A POTENT SHORTWAVE TROUGH WILL DIVE SOUTHWARD OUT OF
CANADA AND THROUGH THE WESTERN GREAT LAKES. IN PART BECAUSE OF
LINGERING TROUGHING OVER THE CENTRAL UNITED STATES... THIS
SHORTWAVE TROUGH WILL BE ABLE TO DIG SO FAR SOUTH THAT IT WILL
BEGIN TO CUT ITSELF OFF FROM THE WESTERLIES... LEAVING A SLOW
MOVING CUT OFF LOW OVER THE UPPER OHIO VALLEY AND CENTRAL
APPALACHIANS WEDNESDAY AND THURSDAY. THE PLACEMENT OF THIS TROUGH
WILL SET UP A DEEP SOUTHERLY FLOW FROM THE TROPICS. AN INITIAL
WAVE EMBEDDED WITHIN THE OVERALL TROUGH WILL CAUSE LOW PRESSURE TO
FORM AT THE SURFACE NEAR THE CAROLINA COAST ON WEDNESDAY...
TRACKING NORTHWARD TOWARD NEW ENGLAND THURSDAY. MODELS SEEM TO BE
COMING INTO BETTER AGREEMENT THAT WEDNESDAY NIGHT INTO THURSDAY
WILL BE THE BEST CHANCE OF RAIN DURING FOR NORTHERN NEW ENGLAND...
THOUGH WITH THE CUT OFF LOW VERY SLOW TO MOVE OUT WE WILL HAVE TO
MAINTAIN A CHANCE OF RAIN THROUGH THE WEEKEND. COULD SEE FOG AND
DRIZZLE BEGINNING NEAR THE COAST AS EARLY AS WEDNESDAY MORNING DUE
TO A MOIST ONSHORE WIND.

WITH PERSISTENT TROUGHING OVER THE AREA... TEMPERATURES WILL BE
NEAR OR BELOW NORMAL FOR DAYTIME HIGHS DUE TO PLENTY OF CLOUD
COVER... COOL TEMPERATURES ALOFT... AND A FREQUENT ONSHORE LOW
LEVEL FLOW. LOW TEMPERATURES APPEAR LIKELY TO REMAIN ABOVE
FREEZING THROUGH THE WEEKEND DUE TO THE INCREASED LOW LEVEL
MOISTURE.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
SHORT TERM...SHOULD HANG ONTO VFR...DESPITE A FEW SHRA...AT LEAST
INTO EARLY TO MID-AFTERNOON...WITH MVFR MOVING INTO NH TERMINALS
THIS AFTERNOON...AND EVENTUALLY INTO ME THIS EVENING. WILL
PROBABLY SEE IFR CIGS DEVELOP TONIGHT...ALTHOUGH TIMING REMAINS
UNCERTAIN...BUT PROBABLY BY MIDNIGHT AT COASTAL TERMINALS...MAYBE
A LITTLE LATER. IFR SHOULD HANG ON THROUGH THE DAY
MONDAY...ALTHOUGH SOME TEMPO IMPROVEMENT MAY BE POSSIBLE MON
MORNING.

LONG TERM...SHOULD SEE IMPROVEMENT TO VFR TUESDAY. BUT AN ONSHORE
FLOW WILL START TO BRING IN LOW CLOUDS AND DRIZZLE AS EARLY AS
WEDNESDAY MORNING. EXPECT GENERALLY IFR OR LOWER CONDITIONS
WEDNESDAY AND THURSDAY AS LOW PRESSURE MOVES TOWARD THE AREA AND
SPREADS RAIN INTO THE REGION.

&&

.MARINE...
SHORT TERM...WEAK FLOW HOLD INTO TONIGHT BEFORE A SFC LOW TRACKS
JUST OF THE GULF OF THE GULF OF ME ON MONDAY AND WINDS/SEAS WILL
LIKLY REACH BORDERLINE SCA CRITERIA.

LONG TERM...EXPECT A LIGHT EASTERLY OR NORTHEASTERLY BREEZE
THROUGH WEDNESDAY. WINDS COULD PICK UP A BIT WEDNESDAY NIGHT INTO
THURSDAY AS LOW PRESSURE TRACKS UP THE EAST COAST AND TOWARD NOVA
SCOTIA. WAVE HEIGHTS WILL ALSO BE INCREASING ON THE NORTHEASTERLY
FETCH.

&&

.FIRE WEATHER...
PERSISTENT ONSHORE FLOW BEGINNING TODAY THROUGH MONDAY WILL MEAN
MODERATE TO HIGH RH...AND SOME SHRA ARE POSSIBLE TODAY INTO
TONIGHT...WITH WETTING RAINS EXPECTED MONDAY.

&&

.TIDES/COASTAL FLOODING...
A PERIOD OF HIGH ASTRONOMICAL TIDES IS COMING UP FROM THURSDAY
THROUGH THE WEEKEND. THE HIGHEST TIDE IS FRIDAY NIGHT WHEN
PORTLAND REACHES 11.9 FEET AT 11:35 PM. WILL NEED TO WATCH THIS
TIME PERIOD FOR POSSIBLE COASTAL FLOODING AS WINDS WILL GENERALLY
BE EASTERLY TO NORTHEASTERLY. COULD CONCEIVABLY SEE SOME COASTAL
FLOODING ISSUES AS EARLY AS THE THURSDAY EVENING TIDE DEPENDING ON
HOW THE TRACK/STRENGTH OF THE LOW SHAKES OUT.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...NONE.

&&

$$



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