Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 231112 AAB
AFDGYX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAY ME
712 AM EDT WED JUL 23 2014

.SYNOPSIS...
HIGH PRESSURE CENTERED TO OUR SOUTH WILL KEEP HOT AND HUMID AIR
IN THE AREA TODAY. A COLD FRONT WILL APPROACH LATE TODAY AND
BRING SHOWERS AND STRONG TO POSSIBLY SEVERE THUNDERSTORMS. THE
FRONT MOVES ACROSS THE REGION TONIGHT AND EXITS OFFSHORE THURSDAY
MORNING. HIGH PRESSURE BUILDS IN FROM THE WEST FRIDAY AND
SATURDAY. WET WEATHER WILL ONCE AGAIN BE POSSIBLE LATE IN THE
WEEKEND AND EARLY NEXT WEEK AS THE NEXT UPPER TROUGH DIVES IN.

&&

.NEAR TERM /THROUGH TONIGHT/...
UPDATE...HAVE ADJUSTED SKY GRIDS BASED ON EARLY VISIBLE SATELLITE
IMAGES. ALSO TWEAKED TEMPS AND DEW POINTS BASED ON CURRENT
OBSERVATIONAL TRENDS.

PREVIOUS DISCUSSION...EARLY THIS MORNING THE BIGGEST WX CONCERN
REVOLVES AROUND FOG. A VERY MOIST AIR MASS IN PLACE...WITH DEW
POINTS CURRENTLY IN THE UPPER 60S ACROSS SRN ZONES...IS LEADING TO
SOME LIGHT FOG AND HAZE ACROSS MOIST OF THE AREA. IN
ADDITION...COASTAL FOG/STRATUS IS DEVELOPING ACROSS DOWNEAST ME.
AS FAR AS THE LATTER GOES...GENERALLY SW FLOW SHOULD KEEP THIS TO
PENOBSCOT BAY EWD FOR NOW.

ATTENTION THEN TURNS TOWARDS THIS AFTERNOON...WHERE WIDESPREAD
SHRA AND TSTMS ARE FORECAST TO AFFECT THE AREA. DEEP SWLY FLOW
WILL CONTINUE THE HOT AND HUMID CONDITIONS ACROSS THE CWFA AGAIN
TODAY. EXPECT HIGHS TO CLIMB AOA 90 FOR SRN NH AND INTERIOR ME. A
LARGE RESERVOIR OF MOIST AIR LAYS TO THE SW...UP THRU H9 AND
H8...SO DEW POINTS WILL LIKELY NOT MIX OUT MUCH THIS AFTERNOON. OF
NOTE ON IR SATELLITE THIS MORNING ARE SOME CLOUDS...WHICH REGIONAL
ASOS ARE ESTIMATING TO BE BETWEEN 6 AND 8.5 KFT. IF ACCAS IS
INDEED FORMING ALREADY...AIR MASS SHOULD BE PLENTY UNSTABLE ALOFT
FOR AFTERNOON CAPE VALUES TO CLIMB WELL ABOVE 1000 J/KG. STRONGEST
SHEAR WILL BE TIED TO THE FNT ITSELF...SO EXPECT A STEADY INCREASE
THRU THE DAY. DURING THE AFTERNOON A SEASONABLY STRONG WIND FIELD
AT H8 AND H7 IS FORECAST TO OVERSPREAD THE AREA. KMWN IS ALREADY
SUSTAINED WLY AT 40 KTS...SO THIS IS A GOOD SIGN THAT MODEL
FORECASTS ARE ON TRACK.

WITH PREDOMINANTLY WLY FLOW THRU THE COLUMN...HODOGRAPHS WILL
FAVOR MULTI-CELL CLUSTERS WITH OCNL SUPERCELLS. WITH FLOW ALSO
PARALLELING THE FORCING ALONG THE FNT...SHOULD SEE DEVELOPMENT
GROW INTO A LINEAR FASHION INTO THE EVENING. THAT PARALLEL FLOW
WILL ALSO MEAN TRAINING STORMS...SO HEAVY RNFL REMAINS IN THE
FORECAST. STEEP LLVL LAPSE RATES...HIGH PWAT AIR...AND SEASONABLY
STRONG MID LVL FLOW SUPPORT AT LEAST ISOLD DAMAGING WIND GUSTS.
AMPLE INSTABILITY WILL ALSO SUPPORT SOME HAIL THREAT...WITH PLENTY
OF CAPE IN THE -10 TO -30 C LAYER. HOWEVER...HIGH FREEZING LVL
WILL PRECLUDE THIS FROM BEING A GREATER THREAT. VEERED WINDS
WITHIN THE NEAR SURFACE LAYER WILL ALSO PRECLUDE AN ELEVATED
TORNADO THREAT. FINALLY...FREQUENT LIGHTNING WILL BE A THREAT WITH
THIS LINE OF STORMS...AS EVIDENCED BY ONGOING CONVECTION INVOF
LAKE ERIE. SREF AND SPC SSEO GUIDANCE SUGGEST TWO AREAS MORE
FAVORED FOR STRONG STORMS. ONE WOULD BE CENTRAL ME...WHERE GREATER
SHEAR SHOULD EXIST. THE OTHER BEING SRN NH...WHERE THE GREATEST
INSTABILITY WILL OCCUR. HOWEVER...WILL KEEP SEVERE WORDING GOING
FOR THE MAJORITY OF THE CWFA AND NOT GET TOO CUTE ATTM.

HI-RES MODEL GUIDANCE IS IN GOOD AGREEMENT THIS MORNING ON
TIMING...WITH AN EARLY START TO CONVECTION EXPECTED. WITHIN AN
HOUR OR SO OF NOON TSTMS SHOULD BE DEVELOPING ACROSS NRN VT AND
ADJACENT SRN CANADA. THIS WILL AFFECT NRN PARTS OF THE CWFA BEFORE
18Z. THE LINE OF STORMS SHOULD PROGRESS TO THE COAST BY 00Z.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
LOSS OF DAYTIME HEATING WILL ALLOW THE SEVERE THREAT TO DIMINISH
IN THE LATE EVENING...THOUGH SHEAR WILL CONTINUE TO INCREASE FOR A
TIME AND MAY OFFSET A RAPID DECLINE IN TSTMS.

OTHERWISE THERE WAS LITTLE CHANGE FROM PREVIOUS FORECAST. NW
ATLANTIC RIDGING WILL SLOW THE FROPA NEAR THE COAST. THE RESULT
WILL BE LINGERING CLOUDS AND PERHAPS AN ISOLD SHRA INTO THU.
EXPECT A GRADUAL CLEARING TREND THROUGHOUT THE DAY HOWEVER...WITH
TEMPS SOME 10 TO 15 DEGREES COOLER AND NOTICEABLY DRIER AIR.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
FAIR WX TO START THE LONG TERM FCST PERIOD...THEN A PROLONGED PERIOD
OF UNSETTLED WX.

THE SLOW MOVING SFC LOW AND FRONTAL SYSTEM CONT TO MOVE OUT TO SEA
THURSDAY NGT AS HIGH PRESSURE BUILDS IN FROM THE W. THE HIGH SHIFTS
OFFSHORE TO OUR S FRIDAY THRU SATURDAY AS FAIR WX DOMINATED WITH
MODIFYING TEMPS AS FLOW BECOMES SW AROUND THE OFFSHORE HIGH ON
SATURDAY. LOW PRESSURE MOVING TO THE E NE SATURDAY NGT AND SUNDAY
PUSHES A WARM FNT N TOWARD THE FCST AREA AS A STRONG UPPER LVL TROF
DRIVES EASTWARD THRU THE GREAT LAKES. THIS WILL BRING WARM HUMID AND
UNSTABLE AIR AND SHRA/TSTMS TO THE FCST AREA. THE UPPER LVL SYSTEM
STALLS AND CUTOFFS OFF OVER THE GREAT LAKES REGION SUNDAY NGT AND
MONDAY THEN SLOWLY SHIFTS TO THE E ON TUESDAY. THIS KEEPS A
SOUTHERLY FLOW SFC AND ALOFT CONTINUING WARM...HUMID AND UNSTABLE
AIR WITH SHRA/TSTMS ACROSS THE REGION.

USED A BLEND OF VARIOUS MODELS...HPC GUIDANCE...PREVIOUS FCST FOR
PERSISTENCE AND CLIMATOLOGY FOR THE LONG TERM FCST.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
SHORT TERM /THROUGH WEDNESDAY NIGHT/...IN INCREASINGLY MOIST AIR
MASS SOME MVFR VALLEY FOG IS POSSIBLE THIS MORNING BEFORE SUNRISE.
GENERALLY SW FLOW SHOULD KEEP ANY COASTAL FOG/STRATUS
DOWNEAST...POSSIBLY SNEAKING INTO KRKD FOR A COUPLE HOURS. OUTSIDE
OF THE MTNS VFR CONDITIONS WILL DOMINATE MOST OF THE DAY.
APPROACHING COLD FNT WILL BRING A ROUND OF SHRA AND TSTMS AROUND
NOON IN THE N...AND CLOSER TO 00Z ALONG THE COAST. THESE TSTMS MAY
BE STRONG TO SEVERE...WITH ISOLD GUSTS GREATER THAN 50 KTS AND
LARGE HAIL POSSIBLE...ESPECIALLY INLAND.

LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...IFR CONDITIONS WITH
SCT SHRA/TSTMS LIKELY TO DEVELOP SATURDAY NGT AND SUNDAY.

&&

.MARINE...
SHORT TERM /THROUGH WEDNESDAY NIGHT/...INCREASING SLY FLOW AHEAD
OF COLD FNT WITH BUILDING SEAS AND OCNL GUSTS OUTSIDE THE BAYS
REACHING MARGINAL SMALL CRAFT INTO THURSDAY NIGHT. OCNL VSBY
RESTRICTIONS IN FOG/HAZE LIKELY WITH A ROUND OF STRONG TO SEVERE
THUNDERSTORMS LIKELY ON THE NEAR SHORE WATERS WEDNESDAY EVENING.

LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...WINDS AND SEAS BELOW
SCA LEVELS THURSDAY NGT THRU SATURDAY MORNING THEN SOUTHERLY FLOW
INCREASES POSSIBLY PUSHING WINDS AND SEAS TO SCA LEVELS OVER THE
OPEN WATERS LATE SATURDAY THRU SUNDAY.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...NONE.
NH...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ150-152-
     154.

&&

$$

NEAR TERM...LEGRO







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