Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 291636
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1236 PM EDT WED JUL 29 2015

.SYNOPSIS...
WARMER THAN NORMAL TEMPERATURES AND HUMID CONDITIONS WILL CONTINUE
ACROSS MAINE AND NEW HAMPSHIRE THROUGH THURSDAY. A COLD FRONT
MOVING INTO THE REGION WILL BRING THE THREAT FOR STRONG TO SEVERE
THUNDERSTORMS TO THE REGION THURSDAY AFTERNOON AND EVENING. BEHIND
THIS FRONT...SOMEWHAT DRIER AIR WILL FILTER INTO THE REGION FOR
FRIDAY. THIS WEEKEND...A SERIES OF WEAK DISTURBANCES MAY BRING A
FEW SHOWERS AND THUNDERSTORMS PRIMARILY TO THE MOUNTAINS...WITH
TEMPERATURES NEAR OR SLIGHTLY ABOVE SEASONAL NORMALS.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...

1235 PM...MINOR ESTF UPDATE TO INGEST THE CURRENT MESONET VALUES
INTO 1ST PERIOD GRIDS.

PREV DISC...
940 AM...MINOR ESTF UPDATE TO REFLECT CURRENT MESONET IN 1ST
PERIOD GRIDS. I ALSO ADJUSTED MAXIMUM TEMPERATURES UP A DEGREE OR
TWO IN SOME AREAS BASED ON THE 12Z KGYX RAOB. THE WEAK SURFACE BOUNDARY
REMAINS ORIENTED FROM NORTHWEST TO SOUTHEAST AND IS SITUATED FROM
NORTHERN NEW HAMPSHIRE THROUGH CENTRAL MAINE. THAT SHOULD PROVIDE
A FOCUS FOR WIDELY SCATTERED CONVECTION. REWORKING THE 12Z KGYX
RAOB YIELDS CAPES NEAR 1500 J/KG WITH POTENTIAL FOR GUSTY WINDS IN
ANY CELLS THAT DO DEVELOP.

PREV DISC...
.UPDATE...
EARLY MORNING SHOWERS HAVE DRIED UP AND HAVE LOWERED POPS FOR THE
NEXT COUPLE OF HOURS. SOME PATCHY FOG STILL AROUND WITH MORE
CLOUDS MOVING IN FROM THE NORTH.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM THURSDAY/...
CONVECTION DIES DOWN AFTER SUNSET AND TEMPERATURES COOL OFF
SOMEWHAT BUT NOT AS MUCH AS PREVIOUS NIGHTS AS WARM AIR ADVECTION
ARRIVES AHEAD OF DECENT SHORT WAVE TROUGHING. ONCE AGAIN THURSDAY
WILL BE QUITE WARM AND ONLY A COUPLE DEGREES COOLER THAN WEDNESDAY
DUE TO INCREASED MOISTURE.

THE SET UP FOR THURSDAY`S THUNDERSTORMS LOOKS MORE POTENT WITH
BETTER KINEMATICS AND OVERALL FORCING THAN TODAY. THE STRONGEST
STORMS WILL BE AHEAD OF THE COLD FRONT. WE COULD HAVE EARLY
INITIATION AND STORM MODE WILL BE SUPERCELLULAR. BESIDES HAIL...
DAMAGING WINDS...AND FLASH FLOODING... EHI VALUES AND OTHER SPC
INDICES ARE HIGH FOR ROTATION AND SUSTAINED SUPERCELLS IN PARTS
OF MAINE... INDICATING PLENTY OF SHEAR FOR ROTATION. THIS IS
CONCERNING AND WOULD NOT BE SURPRISED IF WE HAD A TORNADO
SOMEWHERE IN FRANKLIN OR SOMERSET COUNTIES.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
HIGH IMPACT WEATHER POTENTIAL: ISOLATED SEVERE THUNDERSTORM
POTENTIAL BEGINNING SATURDAY AND CONTINUING INTO EARLY NEXT WEEK.
THE GREATEST THUNDERSTORM COVERAGE FOR THE FRIDAY-SUNDAY PERIOD
APPEARS TO BE ON SATURDAY AFTERNOON.

PATTERN SUMMARY: EARLY MORNING WATER VAPOR IMAGERY SHOWS IMPRESSIVE
SHORTWAVE ENERGY MOVING EAST ALONG THE US/CANADIAN BOARDER WEST OF
THE GREAT LAKES.  THERE IS GOOD DETERMINISTIC/ENSEMBLE GUIDANCE
AGREEMENT THAT THIS FEATURE WILL CONTINUE TO MOVE EAST AND
REINVIGORATE LONGWAVE TROUGHING NEAR HUDSON BAY.  THIS PATTERN IS
NOT ALL THAT ABNORMAL FOR THIS TIME OF YEAR AND WHILE 500 HPA
HEIGHTS WILL BE A TAD BELOW NORMAL...T8S WILL REMAIN NEAR NORMAL.
GIVEN OUR LOCATION ON THE SOUTHERN PERIPHERY OF THIS DEVELOPING
LONGWAVE TROUGHING...WE WILL HAVE ACCESS TO ROBUST WINDS ALOFT
WITH THE CORE OF THE JET ALOFT NEARBY...WITH NUMEROUS WEAK
SHORTWAVES IN THE BROADLY CYCLONIC FLOW ALOFT MOVING ACROSS NEW
ENGLAND. OVERALL...THIS PORTENDS TEMPERATURES NEAR OR SLIGHTLY
ABOVE SEASONAL NORMS THROUGH THE FORECAST PERIOD...WITH OCCASIONAL
BOUTS OF ISOLATED/SCATTERED SHOWERS/STORMS ASSOCIATED WITH THE
AFOREMENTIONED MID LEVEL SHORTWAVES IN THE BROADLY CYCLONIC FLOW
ALOFT. CERTAINLY NO WASHOUTS EXPECTED GIVEN THIS PATTERN...BUT
WITH DECENT WINDS ALOFT IN PLAY...CAN/T RULE OUT A FEW ISOLATED
SEVERE STORMS DURING THIS PERIOD.

DETAILS:

DRIER AIR WORKS INTO THE REGION BEHIND DEPARTING COLD FRONT THURSDAY
NIGHT...THUS ANY SHOWER/THUNDERSTORM ACTIVITY TO START THE PERIOD
WILL SHIFT SOUTH AND EAST OF THE REGION WITH DRIER AIR ARRIVING FROM
THE NORTH AND WEST.  THIS DRIER REGIME SHOULD ALLOW MOST LOCATIONS
TO REMAIN DRY FOR THE DAY FRIDAY...WITH PERHAPS ONE OR TWO SHOWERS
OVER THE MOUNTAINS GIVEN CLOSER PROXIMITY TO THE COLD POOL AT H5.

SOMEWHAT MORE ROBUST SHORTWAVE ENERGY ARRIVES ON SATURDAY...WITH AN
INCREASED CHANCE FOR SHOWERS AND THUNDERSTORMS...AGAIN GREATEST IN
THE MOUNTAINS...BUT SPREADING SOUTH AND EAST SOMEWHAT WITH THE
IMPROVED FORCING.  BEHIND THIS SHORTWAVE...THERE IS MODEST AGREEMENT
ON QUIETER CONDITIONS FOR THE DAY SUNDAY IN A BROADLY SUBSIDENT
REGIME WITH SOMEWHAT DRIER AIR OVERHEAD. THUS...MUCH LIKE
FRIDAY...WILL RESTRICT ANY LOW POPS TO THE MOUNTAINS.

MORE OF THE SAME AS WE REACH MONDAY-TUESDAY OF NEXT WEEK...WITH
DECREASING AGREEMENT ON SHORTWAVE TIMING AMONG DETERMINISTIC AND
ENSEMBLE GUIDANCE MEMBERS.  THE RESULT...UNFORTUNATELY...IS THAT
ISOLATED/CHANCE POPS WILL BE WARRANTED THROUGH THE END OF THE
FORECAST...PARTICULARLY EACH AFTERNOON...ESPECIALLY FURTHER NORTH
AND WEST /BOTH DUE TO TERRAIN ENHANCEMENT AND PROXIMITY TO MID-UPPER
LEVEL FORCING/.

TEMPERATURES:  TEMPERATURES LOOK TO BEGIN THE PERIOD ABOVE SEASONAL
NORMS FRIDAY...WITH SOME DOWNSLOPE ASSISTANCE UNDER WESTERLY WINDS.
FOR THE REMAINDER OF THE PERIOD...TEMPERATURES LOOK TO BE CLOSE
TO...OR JUST A BIT ABOVE SEASONAL NORMS...WITH T8S NEARLY STEADY IN
THE LOW TO MID TEENS.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
SHORT TERM /THROUGH 00Z FRI/...AREAS OF MVFR OVERNIGHT IN STRATUS
AND FOG WITH LCL IFR PSBL BTWN 09 AND 12Z TODAY IN PLACES WHICH
RECEIVED RAINFALL EARLIER. VFR PREVAILING TODAY WITH LCL MVFR
PSBL AFT 18Z IN WIDELY SCT SHRA AND TSRA VCNTY OF KAUG AND KRKD.
AREAS MVFR AFT 00Z THU IN STRATUS AND FOG WITH LCL IFR PSBL BTWN
08 AND 12Z THU.

LONG TERM...SHOWER AND THUNDERSTORM ACTIVITY THURSDAY AFTERNOON
MAY LINGER THROUGH THE EVENING...WITH CONTINUED ISOLATED-SCATTERED
MVFR-IFR RESTRICTIONS GIVING WAY VFR CONDITIONS THROUGH FRIDAY.
ADDITIONAL ISOLATED-SCATTERED SHOWER AND THUNDERSTORM ACTIVITY
POSSIBLE SATURDAY /MOST LIKELY TO IMPACT LEB/HIE/ WITH VFR
CONDITIONS DOMINATING ELSEWHERE...AND FOR ALL LOCATIONS ON SUNDAY.

&&

.MARINE...
SHORT TERM...WAVES AND WIND GUSTS WILL APPROACH SCA CONDITIONS IN
THE FAR OUTER WATERS LATE THURSDAY NIGHT.

LONG TERM...MARGINAL SCA WINDS/WAVES THURSDAY EVENING WILL SUBSIDE
AND REMAIN BELOW SCA LEVELS THROUGH THE WEEKEND.

&&

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

&&

$$
ES


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