Area Forecast Discussion
Issued by NWS Portland, ME

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FXUS61 KGYX 310754
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
354 AM EDT FRI JUL 31 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD IN FROM THE WEST TODAY...PROVIDING A DAY
WITH VERY LITTLE CHANCE OF SHOWERS OR THUNDERSTORMS FOR A CHANGE.
IT WILL STILL BE WARM TODAY...BUT NOTICEABLY LESS HUMID THAN
PREVIOUS DAYS. A WEAK COLD FRONT WILL CROSS THE AREA
SATURDAY...BRINGING ANOTHER THREAT FOR SHOWERS AND THUNDERSTORMS.
BEHIND THIS FRONT WE WILL SEE ANOTHER DROP IN TEMPERATURES AND
HUMIDITY. WEAK LOW PRESSURE ALOFT...SITUATED OVER QUEBEC...WILL
BRING A THREAT FOR SHOWERS OR STORMS MONDAY AND TUESDAY. COOLER
AIR MOVES IN THE MIDDLE TO END OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

HIGH IMPACT WEATHER POTENTIAL: PATCHY DENSE FOG THROUGH EARLY
MORNING...THEN NIL.

CURRENT PATTERN: HUDSON BAY LOW HAS BECOME RE-ESTABLISHED AS OF THIS
WRITING AS POTENT SHORTWAVE AND ASSOCIATED SURFACE LOW HAVE BECOME
VERTICALLY-STACKED AND STATIONARY IN THIS REGION. SOUTH OF THIS
FEATURE A COLD FRONT IS DRAPED FROM QUEBEC SOUTHWEST ALONG THE EAST
COAST OF THE UNITED STATES.  BEHIND THIS FEATURE...EARLY MORNING
WATER VAPOR IMAGERY REVEALS SUBSTANTIAL MIDLEVEL DRYING IS TAKING
PLACE...WITH LLEVEL DRYING OCCURRING JUST A TAD SLOWER IN A BROAD
SUBSIDENT REGIME.  LOOKING UPSTREAM...ADDITIONAL LOW-MID LEVEL
MOISTURE CAN BE SEEN ASSOCIATED WITH A WEAK SHORTWAVE OVER THE
NORTHERN GREAT LAKES PINWHEELING EAST. IN THE POST-FRONTAL
AIRMASS...A GENERALLY QUIET DAY IS EXPECTED TODAY...WITH FORECAST
CONCERNS CENTERED AROUND THE AFOREMENTIONED UPSTREAM SHORTWAVE AND
IT/S IMPLICATIONS FOR CLOUD/SHOWER POTENTIAL THIS AFTERNOON.

FOG: A HANDFUL OF LOCATIONS HAVE SEEN VSBYS DROP BELOW A MILE EARLY
THIS MORNING.  EXPECT VSBYS TO IMPROVE TOWARDS DAYBREAK AS LLEVEL
DRY ADVECTION CONTINUES...WITH DEWPOINTS FALLING THROUGH THE 60S AND
INTO THE UPPER 50S.

CLOUDS/PRECIP: MID LEVEL SHORTWAVE NOW CROSSING FROM ONTARIO INTO
WESTERN QUEBEC WILL RACE RAPIDLY EAST-NORTHEAST TODAY WITH AN UPTICK
IN QG FORCING FOR ASCENT SPREADING ACROSS NORTHERN NH AND NW MAINE
EARLY...BUT THEN CONTINUING EAST WITH OUR REGION IN ANTICYCLONIC
DPVA FOR THE AFTERNOON. MODEL SOUNDINGS SHOW A NON-ZERO BUILDUP OF
CAPE DURING THE AFTERNOON WITH THE RELATIVELY COOL TEMPERATURES
ALOFT... HOWEVER...SUBSTANTIAL CAPPING WILL BE IN PLACE IN THE
H6-7 LAYER. THUS...HAVE A HARD TIME SEEING MUCH IF ANY SHRA
ACTIVITY DEVELOPING...WITH PERHAPS A SPRINKLE IN THE MOUNTAINS
DURING THE AFTERNOON. A MUCH BETTER BET IS SOME INCREASE IN
CLOUDINESS BY AFTERNOON. GIVEN THE LOWER DEWPOINTS...IT WILL BE
VERY PLEASANT DAY TO END JULY.

TEMPERATURES: H8 TEMPS ARE SLOWLY DROPPING IN THE POST-FRONTAL
AIRMASS...BUT WILL REMAIN IN THE MID TEENS...SUPPORTING HIGHS WELL
INTO THE 80S PARTICULARLY IN THE DOWNSLOPE REGIMES...WITH LESS
IMPACTS FROM ANY SEA-BREEZES GIVEN DECENT WESTERLY GRADIENT.


&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

HIGH IMPACT WEATHER POTENTIAL: THREAT FOR AN ISOLATED SEVERE
STORM PARTICULARLY NORTHERN AREAS ON SATURDAY.

PATTERN/IMPLICATIONS: CYCLONIC FLOW ALOFT WILL DOMINATE THE PATTERN
THROUGHOUT MUCH OF THE COLUMN THROUGH THE SHORT TERM FORECAST PERIOD
WITH ONE PRIMARY DISTURBANCE IN THIS CYCLONIC FLOW PUSHING INTO THE
AREA ON SATURDAY.  FORECAST CHALLENGES PRIMARILY CENTER ON THIS
FEATURE...AND IT/S ABILITY TO BRING SHOWERS AND THUNDERSTORMS TO THE
REGION.

FRIDAY NIGHT:  GOOD FLOW OFF THE DECK AND A DRIER EVENING AIRMASS
SUGGESTS MUCH LESS FOG POTENTIAL OVERNIGHT...ESPECIALLY AFTER A DAY
THAT SHOULD BE FREE FROM RAIN.  EXPECT SOME INCREASING MID AND UPPER
LEVEL CLOUDINESS FROM UPSTREAM SHORTWAVE LATE...WITH A PARTLY CLOUDY
NIGHT ON TAP THROUGHOUT THE REGION.  WITH THE DRIER LLEVEL
AIRMASS...A COOLER NIGHT LOOKS TO BE IN STORE...WITH LOWS RANGING
FROM THE MID 50S NORTH TO THE LOWER 60S COASTAL AREAS AND SOUTHERN
NEW HAMPSHIRE.

SATURDAY: ROBUST SHORTWAVE ROTATES INTO THE REGION ON SATURDAY WITH
ASSOCIATED MID LEVEL HEIGHT FALLS OVERSPREADING THE REGION.  THIS QG
FORCING WILL BE WORKING WITH MODESTLY INCREASED MOISTURE AS COMPARED
TO FRIDAY AS PWATS MOVE BACK TO AROUND ONE INCH /RIGHT AROUND NORMAL
FOR THE FIRST DAY OF AUGUST/. LOW AND MID LEVEL LAPSE RATES ARE
DECENT...ASSISTED BY MID LEVEL COOL POOL TO THE NORTH OF THE REGION.
THUS...FULLY EXPECT SHOWERS TO EXPAND ACROSS THE REGION DURING THE
MORNING AS DAYTIME HEATING LEADS TO GROWING LLEVEL INSTABILITY.
AS FOR THE THUNDER THREAT...INSTABILITY IS MARGINAL AS SURFACE
DEWPOINTS STRUGGLE BACK TO THE 60 DEGREE MARK. IN ADDITION...THERE
IS PLENTY OF DRY AIR ALOFT...WHICH...WHEN COMBINED WITH STOUT DEEP
SHEAR /0-6KM BULK SHEAR 40-50 KTS/ COULD POTENTIALLY PORTEND A
HOSTILE ENVIRONMENT DUE TO ENTRAINMENT. THAT SAID...WITH ENOUGH
INSTABILITY...ANY STORMS THAT DEVELOP WOULD HAVE ACCESS TO AMPLE
SHEAR AND LOWER FREEZING LEVELS THAN OF LATE...AND THUS A
CONDITIONAL SEVERE THREAT. BEST MOISTURE RESIDES FURTHER
NORTH...WHICH AGREES WELL WITH SPC/S INTRODUCTION OF A MARGINAL
RISK OVER COOS COUNTY NH AND MUCH OF NORTHERN MAINE. WILL
INTRODUCE MENTION OF THIS POTENTIAL IN THE MORNING HAZARDOUS
WEATHER OUTLOOK. TEMPERATURES WILL LIKELY BE A TAD COOLER THAN ON
FRIDAY...PARTICULARLY FURTHER NORTH WHERE THE GREATEST CLOUD COVER
AND PRECIPITATION COVERAGE IS EXPECTED. EXPECT TEMPERATURES TO
RANGE FROM THE 70S IN THE MOUNTAINS THE LOWER/MIDDLE 80S OVER
SOUTHWEST MAINE AND SOUTHERN NEW HAMPSHIRE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
500 MB CONTINUES TO TEND BACK TOWARD A MORE +PNA
PATTERN...ALTHOUGH SKEWING MORE TOWARDS AN OMEGA BLOCK BY MID TO
LATE WEEK WITH TROUGHING FIRMLY ENSCONCED OVER JAMES BAY AND NRN
QUEBEC. THIS TREND WILL LEAD TO AN UNSETTLED PATTERN THROUGH THE
PERIOD...WITH THE THREAT FOR SHRA/TSRA...HIGHEST IN THE NORTHERN
ZONES. HOWEVER...FAST FLOW WILL KEEP THINGS MOVING AND PREVENT
ANY SIGNIFICANT RAIN EVENTS.

SUNDAY WILL SEE PARTLY SUNNY SKIES AND CHANCE FOR SHRA/TSRA IN THE
MTNS. MON AFTERNOON INTO TUE LOOK LIKE THE BEST CHC FOR CWA WIDE
SHRA/TSRA AS TROUGHING SAGS S...AND PULLS A COLD FRONT THROUGH NRN
NEW ENGLAND. WED /THU WILL KEEP US ON THE COOLER SIDE OF THE
FRONT...AS IT STALLS ACROSS THE MID ATLANTIC. SOME MTNS SHOWERS
WILL BE POSSIBLE AS UPPR LVL TROUGH AND ASSOCIATED COLD POOL WILL
BE JUST TO THE N OF THE CWA.

TEMPERATURE WILL SUNDAY WILL BE NEAR NORMAL WITH HIGHS IN THE MID
70S TO MID 80...BUT WILL CLIMB BACK ABOVE NORMAL ON MONDAY WITH
HIGHS IN THE 80S...AND APPROACHING 90 AGAIN IN INTERIOR SRN NH.
OVERNIGHT LOWS SAT AND SUN NIGHT WILL RANGE FROM THE UPPER 50S TO
MID 60S...AND MONDAY NIGHT WILL BE MORE MUGGY WITH LOWS IN THE 60S
TO AROUND 70. TEMPS MAY FALL TO SLIGHTLY BELOW NORMAL BY MID TO
LATE WEEK. STAYED CLOSER TO THE EURO THOUGH AS THE GFS IS PROBABLY
OVERDOING THE COOL AIR INCURSION LATE IN THE WEEK.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
SHORT TERM...OUTSIDE OF EARLY MORNING IFR/LIFR FOG...EXPECT VFR
CONDITIONS TO DOMINATE THE COMING TAF PERIOD AS DRIER AIR PUSHES
INTO THE REGION BEHIND A DEPARTING COLD FRONT.

THROUGH DAYBREAK...IT/S A BATTLE BETWEEN ONGOING DRY ADVECTION AND
RESIDUAL LLEVEL MOISTURE /ENHANCED BY YESTERDAY/S RAINFALL/.  FEEL
THAT THE WORST CONDITIONS WILL OCCUR DURING THE NEXT FEW
HOURS...BEFORE IMPROVING TOWARDS DAYBREAK AS DRY ADVECTION SLOWLY
WINS OUT.  LEB/HIE LIKELY TO SEE THE MOST SIGNIFICANT FOG...BUT EVEN
HERE...EXPECT ONLY BRIEF DIPS TO LIFR/VLIFR.  FOG SHOULD DISSIPATE
SHORTLY AFTER SUNRISE.

FOR THE DAY TODAY...EXPECT FEW-SCT CU TO DEVELOP BY AFTERNOON...
PARTICULARLY OVER LEB/HIE.  CAN/T RULE OUT A STRAY SPRINKLE IN THESE
SPOTS...BUT NO RESTRICTIONS ARE ANTICIPATED.  SKIES SHOULD PARTIALLY
CLEAR THIS EVENING.

WESTERLY WINDS WILL STRENGTHEN TO 10G18KTS FOR THE DAY TODAY BEFORE
DIMINISHING TO 5KTS OR LESS THIS EVENING.

LONG TERM...MAINLY VFR SAT NIGHT THROUGH TUESDAY... WITH VLY FOG
POSSIBLE EACH NIGHT. SCT SHRA/TSRA WILL IMPACT MOST OF THE
TERMINALS LATE MON AND MON NIGHT.

&&

.MARINE...
SHORT TERM /THROUGH SATURDAY/...WINDS/WAVES LOOK TO REMAIN BELOW
SMALL CRAFT LEVELS THROUGH THE SHORT TERM FORECAST PERIOD UNDER
GENERALLY LIGHT SOUTHWESTERLY WINDS.

LONG TERM....PERSISTENT SW FLOW SUNDAY AND MONDAY COULD BRING
SWELL TO 5 FT OR SO BY SUNDAY NIGHT....WHICH WOULD LINGER THROUGH
MON NIGHT.

&&

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

&&

$$
SYNOPSIS...CEMPA
NEAR TERM...ARNOTT
SHORT TERM...ARNOTT
LONG TERM...CEMPA
AVIATION...ARNOTT/CEMPA
MARINE...ARNOTT/CEMPA



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