Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 271022 AAA
AFDGYX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAY ME
622 AM EDT MON APR 27 2015

.SYNOPSIS...
PERSISTENT UPPER LEVEL LOW PRESSURE OVER THE CANADIAN MARITIMES
WILL SHIFT SW INTO THE GULF MAINE TODAY SUPPORTING SHOWER
ACTIVITY. THE LOW WILL SHIFT SLOWLY EAST TUESDAY ALLOWING HIGH
PRESSURE TO BUILD IN WEDNESDAY AND THURSDAY. LOW PRESSURE PASSES
SOUTH OF THE AREA FRIDAY... WITH HIGH PRESSURE BUILDING BACK IN
BEHIND IT NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
.UPDATE...
A FEW SHOWERS NOW ENTERING SOMERSET AND FRANKLIN COUNTIES THIS
MORNING WITH A FEW RETURNS OVER SOUTHERN NH. THERE IS LIKELY
NOTHING REACHING THE GROUND ESPECIALLY OVER SOUTHERN NH. HAVE
ADJUSTED POPS BASED ON LATEST MODELS... OTHERWISE FORECAST IS IN
FOOD SHAPE.

&&

PREVIOUS DISCUSSION...
STACKED LOW PRESSURE MOVES FROM NOVA SCOTIA TODAY TOWARDS THE
GULF OF MAINE. THIS WILL HELP TRIGGER WIDESPREAD SHOWERS
THROUGHOUT THE DAY AND PUSH A BACKDOOR BOUNDARY THROUGH THE REGION
THIS EVENING. RAINFALL AMOUNTS WILL BE LIGHT. HIGHS WILL ONLY WARM
INTO THE MID 40S TO MID 50S THANKS TO CLOUD COVER. THE WARMER
TEMPERATURES WILL BE IN SOUTHERN NH WHERE CLEARING MAY OCCUR THIS
AFTERNOON. GUSTY NORTH WINDS WILL MAKE IT SEEM COOLER HOWEVER.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
LOW PRESSURE WILL BECOME MORE COMPACT AND PULL AWAY TO THE EAST
TONIGHT. MOST SHOWERS OVER NH AND WESTERN MAINE SHOULD BE OVER
BY THE EVENING WITH SOME LINGERING RAIN OVER THE MIDCOAST AND IN
THE HIGHER TERRAIN WHERE FLURRIES MAY FALL. TEMPERATURES DROP AS
THE BACKDOOR COLD FRONT MOVES THROUGH FROM NE TO SW. MOST
LOCATIONS SHOULD DROP INTO THE MID TO UPPER 30S WITH SOME LOWER
40S ALONG THE COAST.

ON TUESDAY SHOWERS STILL LINGER... AS ALTHOUGH THE UPPER LOW WILL
BE TO OUR EAST WE WILL STILL BE DOMINATED BY CYCLONIC FLOW.
PRECIPITATION WILL MAINLY BE CONFINED TO THE HIGHER TERRAIN AND
DOWNEAST. WIDESPREAD UPPER 50S AND LOWER 60S ARE EXPECTED TUESDAY
EXCEPT PERHAPS FOR NORTHERN SECTIONS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
LINGERING EFFECTS OF UPPER LOW PRES WILL REMAIN OVER THE REGION
WED. SHOWER ACTIVITY LOOKS LESS LIKELY...THOUGH AFTERNOON INCREASE
IN CLOUD COVER WILL STAY IN THE FORECAST.

FORECAST BECOMES LOW CONFIDENCE BEYOND THU...AS UPPER LOW PRES
FROM THE SERN CONUS LOOKS TO DRIFT UNDERNEATH RIDGING OVER THE
NORTHEAST. IT WILL BE A COMPLEX PATTERN...WITH INTERACTION BETWEEN
THE DEPARTING UPPER LOW PRES...HIGH PRES TO THE N...AND DIGGING
S/WV TROF ON THE BACKSIDE OF APPROACHING UPPER LOW. THE 27.00Z GFS
IS MOST AGGRESSIVE WITH DIGGING S/WV...ALLOWING SERN UPPER LOW
PRES TO LIFT AND PHASE MUCH FARTHER NWD. THIS IS THE MOST
PESSIMISTIC OUTCOME...BUT ALSO AN OUTLIER. THE 27.00Z CMC FORECAST
KEEPS OUR CURRENT UPPER LOW CLOSER THRU LATE WEEK...LEAVING LITTLE
ROOM FOR THE NEXT UPPER LOW TO MOVE NWD. FINALLY THE 27.00Z ECWMF
PLAYS THINGS BETWEEN THOSE UPRIGHTS. WEAKER WITH THE BACKSIDE S/WV
AND ALSO QUICKER WITH THE DEPARTING UPPER LOW...THIS ALLOWS A
COASTAL LOW TO DEVELOP...BUT ALSO REMAIN WELL S OF OUR AREA.
FAVORED A 40/40/20 ECMWF/CMC/GFS BLEND FOR POP...WHICH GENERALLY
KEEPS CHANCE SHOWERS CONFINED TO SRN THIRD OF THE FORECAST AREA
LATE WEEK. THOUGH NE FLOW OVER THE AREA WILL LIMIT THE AMOUNT OF
WARMTH WE SEE THRU THE WEEKEND...SO TEMPS REMAIN NEAR NORMAL FOR
NOW.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
SHORT TERM...CONDITIONS WILL RANGE FROM VFR TO MVFR TODAY IN
LIGHT SHOWERS WITH GUSTY NW WINDS. CEILINGS SHOULD IMPROVE TONIGHT
WITH VFR FOR TUESDAY.

LONG TERM...VFR CONDITIONS ARE EXPECTED TO PREVAIL IN THE
EXTENDED. UPPER LEVEL LOW PRES WILL BEGIN TO DEPART WED...SO ANY
MVFR SHOWER CHANCES WILL DIMINISH IN KIND. THE GFS FORECAST OF
COASTAL LOW PRES COMING THIS FAR N IS VERY LOW CONFIDENCE AT THIS
POINT...SO WILL FAVOR JUST AN INCREASE IN CLOUDS ACROSS SRN ZONES
FOR NOW.

&&

.MARINE...
SHORT TERM...A BACKDOOR FRONT MOVES ACROSS THE WATERS MONDAY
NIGHT WITH GUSTY NORTH WINDS TO FOLLOW. A SCA WILL BE NEEDED FOR
LATE MONDAY NIGHT INTO TUESDAY.

LONG TERM...CANNOT RULE OUT A PERIOD OF SCA CONDITIONS LATE IN THE
WEEK AS A COASTAL LOW PASSES WELL S OF THE WATERS. SUSTAINED NELY
FLOW SHOULD AT LEAST BUILD SEAS TO AROUND 5 FT FOR A TIME BEFORE
THEY DIMINISH.

&&

.FIRE WEATHER...
RECENT WIDESPREAD RAINS AS WELL AS GOOD RH RECOVERY EACH NIGHT
WILL HELP KEEP FIRE CONCERNS LOW.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING TO 11 AM EDT
     TUESDAY FOR ANZ150>152-154.

&&

$$

HANES/LEGRO



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