Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 031035
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
635 AM EDT WED JUN 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL CREST OVER THE REGION TODAY. THE HIGH WILL
SHIFT OFFSHORE TONIGHT AND THURSDAY. A COLD FRONT WILL APPROACH
FROM THE NORTH THURSDAY NIGHT AND WILL DROP SOUTH THROUGH THE
REGION ON FRIDAY. HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST
FRIDAY NIGHT THROUGH SATURDAY AND WILL CREST OVER THE REGION ON
SUNDAY. LOW PRESSURE WILL APPROACH FROM THE WEST EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
635 AM UPDATE...LITTLE CHANGE TO THE GOING FORECAST. JUST A FEW
MINOR ADJUTMENTS BASED ON LATEST TRENDS IN OBSERVATIONAL DATA.
DRYING IS CURRENTLY TAKING PLACE ACROSS SWRN NH AND CLOUDS ARE
THINNING THERE. THIS TREND SHOULD CONTINUE FURTHER NORTH AND EAST
AS THE MORNING PROGRESSES.

PREVIOUSLY...

LOW CLOUDS...SPOTTY DRIZZLE...AND PATCHY FOG WILL LINGER EARLY
ON THIS MORNING. HOWEVER...BUILDING HIGH PRESSURE AND HEATING WILL
AID IN THE EROSION OF THIS STUFF DURING THE EARLY MORNING HOURS.
SOME DIURNAL STRATO-CU MAY DEVELOP AND BECOME BKN AT TIMES THIS
AFTERNOON AS MOISTURE REMAINS IN THE 4-6 KFT LAYER. TEMPERATURES
WILL BE WARMER THAN THE LAST FEW DAYS...WITH HIGHS GENERALLY IN
THE 60S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
HIGH PRESSURE CRESTS OVERHEAD TONIGHT. THIS SHOULD MEAN CLEAR
SKIES AND CALM WINDS WHICH SHOULD RESULT IN RADIATIONAL COOLING.
WITH MOIST GROUND IN PLACE FROM RECENT RAINS...PATCHY GROUND FOG
IS EXPECTED WITH SOME OF IT LOCALLY DENSE ESPECIALLY IN RIVER
VALLEYS.

WARMER DAY ON THURSDAY WITH HIGH PRESSURE SHIFTING OFFSHORE AND
SOUTHERLY RETURN FLOW DEVELOPING UNDER MOSTLY SUNNY SKIES. THE
COASTAL PLAIN WILL BE COOLER WITH DEVELOPING ONSHORE FLOW DURING
THE AFTERNOON.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE PULLS OUT TO THE EAST THURSDAY NIGHT WITH AN UPPER
LEVEL TROUGH AND SURFACE COLD FRONT HEADED SOUTHEAST OUT OF THE
HUDSON BAY REGION OF CANADA AND TOWARD NORTHERN NEW ENGLAND. AT
THE SURFACE... SOUTHERLY FLOW WILL TRANSPORT WARMER AND MORE HUMID
AIR INTO THE REGION... SETTING THE STAGE FOR SHOWER AND
THUNDERSTORM ACTIVITY AS THE TROUGH AND FRONT ARRIVE.

ON FRIDAY... THE COMBINATION OF INCREASING LOW LEVEL MOISTURE...
COOLING TEMPERATURES ALOFT WITH THE APPROACHING TROUGH... AND LIFT
FROM SHORTWAVE TROUGHS EMBEDDED IN THE FLOW WILL PROVIDE THE SPARK
FOR SHOWERS AND THUNDERSTORMS DURING THE AFTERNOON AND EVENING
HOURS. TIMING OF THE SHORTWAVE TROUGHS IS UNCERTAIN AT THIS
POINT... BUT IT APPEARS THERE COULD BE A LEADING TROUGH MOVING
THROUGH THE AREA IN THE LATE MORNING... WHILE THE PRIMARY TROUGH
AXIS AND ASSOCIATED COLD FRONT MOVE THROUGH LATE IN THE DAY. EACH
OF THESE WAVES WOULD BE CAPABLE OF TRIGGERING SHOWERS AND
THUNDERSTORMS... THE EXTENT OF WHICH WOULD DEPEND ON WHETHER THE
TIMING CAN LINE UP WITH PEAK HEATING.

WIND SHEAR SEEMS ADEQUATE FOR STORM ORGANIZATION AND ROTATING
SUPERCELLS WITH SOUTHERLY SURFACE WINDS AND WESTERLY WINDS
INCREASING WITH HEIGHT ALOFT. HOWEVER... THE BIGGEST UNCERTAINTY
IS INSTABILITY. MOISTURE RETURN MAY NOT BE SUFFICIENT TO PRODUCE
ENOUGH INSTABILITY FOR STRONG UPDRAFTS. CURRENT FORECASTS ONLY
PRODUCE AROUND 500 CAPE DURING THE AFTERNOON AHEAD OF THE COLD
FRONT. IF THIS INSTABILITY IS GREATER THAN FORECAST... THEN THERE
WILL BE A BETTER CHANCE FOR SEVERE THUNDERSTORMS. ANY THUNDERSTORM
ACTIVITY... SEVERE OR OTHERWISE... WOULD BE MOST LIKELY OVER THE
NORTHERN HALF OF NEW HAMPSHIRE AND THE NORTHWEST MAINE MOUNTAINS.
COASTAL AREAS WILL LACK INSTABILITY DUE TO ONSHORE SOUTHERLY FLOW.
ANY SHOWERS OR THUNDERSTORMS FRIDAY EVENING WILL DISSIPATE AS THE
TROUGH AND SURFACE COLD FRONT MOVE TOWARD THE COAST.

COOL HIGH PRESSURE BUILDS INTO THE AREA ON SATURDAY AND SHIFTS
EAST INTO THE CANADIAN MARITIMES ON SUNDAY. BY EARLY NEXT WEEK A
LONGWAVE TROUGH BEGINS TO SET UP OVER THE CENTRAL PORTION OF THE
CONTINENT FROM HUDSON BAY SOUTH THROUGH THE PLAINS. SHOULD SEE
INCREASING WARMTH AND MOISTURE WITH TIME. THE FIRST IN A SERIES OF
EMBEDDED WAVES WILL TRACK EAST/NORTHEAST THROUGH NEW ENGLAND
BEGINNING ON MONDAY WITH A GOOD CHANCE FOR SHOWERS. SEVERAL MORE
WAVES FOLLOW BEHIND IT UNTIL THE LONGWAVE TROUGH FINALLY MOVES
THROUGH AROUND MIDWEEK... KEEPING THE RAIN CHANCES IN THE FORECAST
UNTIL THEN.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
SHORT TERM...MVFR/IFR CEILINGS EARLY ON THIS MORNING...WILL
IMPROVE TO VFR BETWEEN 11Z AND 13Z. SPOTTY IFR CONDITIONS IN
GROUND FOG POSSIBLE TONIGHT...OTHERWISE VFR CONDITIONS ARE
EXPECTED TONIGHT AND THURSDAY.

LONG TERM...COULD SEE SOME LOW MARINE CLOUDS FRIDAY MORNING IN AN
ONSHORE FLOW. OTHERWISE VFR CONDITIONS ARE EXPECTED. SHOWERS AND
THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON AND EVENING MAINLY IN
THE MOUNTAINS.

&&

.MARINE...
SHORT TERM...A FEW 5 FOOTERS EARLY THIS MORNING WILL SUBSIDE INTO
THE 3 TO 4 FT RANGE EARLY ON. OTHERWISE...SUB-SCA CONDITIONS ARE
EXPECTED TODAY THROUGH THURSDAY.

LONG TERM...HIGH PRESSURE OVER THE GULF OF MAINE KEEPS WINDS
FAIRLY CALM THROUGH FRIDAY. A COLD FRONT CROSSES THE AREA FRIDAY
NIGHT AND SHIFTS THE WINDS TO THE NORTH BEHIND IT BUT WIND SPEEDS
WILL REMAIN BELOW ADVISORY LEVELS. HIGH PRESSURE BUILDS IN THROUGH
THE WEEKEND.

&&

.FIRE WEATHER...
EXPECT NO ISSUES NEXT FEW DAYS GIVEN RECENT WET PERIOD AND COOL
TEMPERATURES.

&&

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

&&

$$

NEAR TERM...EKSTER
SHORT TERM...EKSTER
LONG TERM...KIMBLE



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