Area Forecast Discussion
Issued by NWS Portland, ME

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000
FXUS61 KGYX 271617
AFDGYX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAY ME
1217 PM EDT MON JUL 27 2015

.SYNOPSIS...
WARM AND HUMID AIR WILL REMAIN OVER MAINE AND NEW HAMPSHIRE FOR
THE NEXT SEVERAL DAYS. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE
MAINLY IN THE AFTERNOONS. SOME STRONGER STORMS ARE POSSIBLE ON
TUESDAY. A COLD FRONT WILL CROSS THE REGION ON THURSDAY. A WEAK
DISTURBANCE MAY BRING A FEW SHOWERS TO THE MOUNTAINS FRIDAY. UPPER
LEVEL TROUGHING REMAINS IN PLACE THROUGH EARLY NEXT WEEK BRINGING
PERIODIC FRONTAL PASSAGES.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
1215 PM...MESOSCALE MODEL CONSENSUS IS TO FIRE UP CONVECTION OVER
THE SRN TIER OF COUNTIES IN NH THIS AFTERNOON...WHERE LEFTOVER
BOUNDARY FROM YESTERDAY IS PROBABLY LINGERING. THEREFORE, HAVE
HOT THIS A LITTLE HARDER ON POPS/QPF THIS AFTERNOON. ALSO..MAY SEE
SOME BACKBUILDING ALONG THAT BOUNDARY SO ADDED HEAVY RAIN HERE.
ALSO WATCHING CONVECTION MOVING THROUGH THE MONTREAL AREA
NOW...WHICH MAY WORK INTO NRN ZONES LATER THIS AFTERNOON...AND
THIS HAS ACCESS TO SOME BETTER DYNAMICS, AND COULD PRODUCE SOME
SMALL HAIL OR GUSTY WINDS. ELSEWHERE...AWAY FROM THE COAST COULD
SEE A FEW SCATTERED TSRA POP UP THIS AFTERNOON, BUT WEAK CAPPING
SHOULD PREVENT THEM FROM LASTING LONG.

950 AM...THIS UPDATE SCALES BACK THE FOG...ALTHOUGH IT WILL
LINGER JUST OFFSHORE AND PROBABLY COME AND GO AT THE BEACHES
THROUGHOUT THE DAY. HAVE ALL SCALED BACK POPS TO CLOSER TO ZERO
THRU NOON...AND THEN INCREASE THEM TO CHC POPS BY 18Z. LOTS OF
CAPE IN SOME SPOTS TODAY...ON THE ORDER OF 1-2K J/KG...BUT LIGHT
VERTICAL WIND PROFILES. STILL COULD SEE A PULSE STORM OR TWO
ROTATE TO HOLD UP A CORE AND PRODUCE SOME SMALL HAIL AND MAYBE
SOME WIND. WILL HAVE TO WATCH BOUNDARIES FOR CONVECTIVE
DEVELOPMENT TODAY...SEA BREEZE...DIFFERENTIAL HEATING DUE TO
CLOUDS...AND BOUNDARY FROM YESTERDAY THAT MAY BE LINGERING ACROSS
CHESHIRE/HILLSBOROUGH COUNTIES.

PREVIOUSLY...MOIST AIR MASS NOW FULLY IN PLACE ACROSS MAINE AND
NEW HAMPSHIRE. THIS IS NOTED BY LOW LEVEL CLOUDS AND FOG OVER MUCH
OF MAINE AND PARTS OF NEW HAMPSHIRE EARLY THIS MORNING. THIS
SHOULD BURN OFF AS THE MORNING WEARS ON AND ALLOW TEMPERATURES TO
WARM INTO THE 80S OVER MOST OF NEW HAMPSHIRE... WHILE STAYING A
LITTLE COOLER OVER MAINE WHERE AN ONSHORE WIND TEMPERS WARMING.

AS THE HEAT AND HUMIDITY BUILD AT THE SURFACE... A SHORTWAVE
TROUGH MOVING THROUGH QUEBEC AND INTO NORTHERN MAINE TODAY WILL
PROVIDE THE UPPER LEVEL SUPPORT FOR SHOWERS AND THUNDERSTORMS TO
DEVELOP. THE HIGHEST CHANCE OF RAIN WILL BE IN THE EAST CLOSER TO
THE UPPER TROUGH BUT THERE WILL BE A CHANCE OF THUNDERSTORMS
AREAWIDE THIS AFTERNOON. WIND SHEAR TODAY IS ONLY ON THE ORDER OF
20 KT... SO NOT SOMETHING THAT WOULD SUGGEST SUPERCELLS.
HOWEVER... THE NORTH NORTHWEST UPPER LEVEL WINDS COULD COUNTERACT
THE SOUTH SOUTHEAST SEA BREEZE ALONG THE MAINE COAST AND PROVIDE
SOME LOCALLY ENHANCED AREAS OF BETTER TOTAL WIND SHEAR. THESE
AREAS WILL BE LACKING IN SURFACE BASED INSTABILITY DUE TO THE
COOLER ONSHORE WIND... BUT ELEVATED CONVECTION WILL STILL BE
POSSIBLE AS INSTABILITY REMAINS ALOFT EVEN OVER THESE AREAS. WITH
A GOOD AMOUNT OF INSTABILITY AROUND... THERE WILL BE THE CHANCE
FOR SOME SMALL HAIL TODAY WITH THE STRONGER STORMS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
SHOWERS AND THUNDERSTORMS SHOULD BECOME LESS NUMEROUS OVERNIGHT
WITH THE LOSS OF SURFACE BASED INSTABILITY. HOWEVER... ELEVATED
INSTABILITY STILL EXISTS SO ANY ONGOING CONVECTION COULD MAINTAIN
ITSELF THROUGH THE NIGHT. COULD SEE FOG REFORMING ALONG THE MAINE
COASTLINE.

ON TUESDAY A MORE PRONOUNCED SHORTWAVE TROUGH WILL MOVE THROUGH
THE AREA... ALONG WITH EVEN GREATER SURFACE BASED INSTABILITY.
CAPE VALUES GREATER THAN 2000 HAVE BEEN NOTED IN SOME MODEL
FORECASTS. OVERALL WIND SHEAR WILL BE A LITTLE BIT GREATER...
RANGING FROM 20 TO 30 KT. THIS IS GETTING ON THE BORDER LINE OF
WHAT MIGHT BE FAVORABLE FOR SOME STRONGER STORMS AND POSSIBLY A
FEW SUPERCELLS. AS A RESULT... HAVE MENTIONED SMALL HAIL AND GUSTY
WINDS IN THE FORECAST TO REFLECT THE THREAT FOR MORE SIGNIFICANT
THUNDERSTORMS. STORM PREDICTION CENTER HAS OUTLOOKED THE AREA IN A
MARGINAL RISK FOR SEVERE THUNDERSTORMS AND THIS SEEMS
APPROPRIATE. THERE IS SOME UNCERTAINTY ABOUT WHEN THE BEST UPPER
LEVEL FORCING WILL MOVE THROUGH... AS THE MODELS STILL DISAGREE ON
WHETHER IT WILL COINCIDE WITH PEAK HEATING OR COME THROUGH
EARLIER... LEAVING OUR AREA IN SUBSIDENT FLOW WHICH WOULD TEND TO
SUPPRESS CONVECTION.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
UPPER LEVEL LOW PRESSURE NEAR THE SAINT LAWRENCE RIVER VALLEY
WILL SHIFT SE AS RIDGING PUSHES EAST WEDNESDAY. AT THE SAME TIME
ANOTHER CUTOFF LOW WILL DEEPEN AND MOVE INTO CENTRAL CANADA. THIS
WILL KEEP THE RIDGING OVER THE NORTHEAST SHORT LIVED AND THE
RIDGING MOVES OFFSHORE LATE THURSDAY. THEREAFTER TROUGHING REMAINS
OVERHEAD INTO EARLY NEXT WEEK. INDIVIDUAL SHORT WAVE RIPPLES WILL
CAUSE INCREASED PRECIPITATION CHANCES AS IT LINGERS ALOFT EVERY
18-24 HRS OR SO.

THE RESULT HOWEVER BRIEF WILL BE 850MB TEMPERATURES OF 18 DEGREES
C OVER SOUTHERN NH WEDNESDAY. THIS WILL TRANSLATE TO LOWER TO MID
90S WITH MID 80S FOR MUCH OF THE REST OF THE AREA UNDER MOSTLY
SUNNY SKIES. IT WILL BE COOLER THURSDAY BUT SHOULD REACH THE 70S
AND 80S STILL AHEAD OF A FAST MOVING COLD FRONT. THUNDERSTORM
POTENTIAL LOOKS GOOD AND WE COULD HAVE STRONG STORMS WITH PLENTY
OF INSTABILITY AND DECENT SHEAR... ESPECIALLY OVER SOUTHERN
SECTIONS. NOT EXPECTING FLOODING TO BE AN ISSUE WITH A FAST MOVING
BOUNDARY ALTHOUGH PW VALUES DO INCREASE TO 1.75 INCHES OR SO WHICH
IS CLOSE TO THE 99TH PERCENTILE FOR THIS TIME OF YEAR.

FRIDAY SHOULD BE MOSTLY DRY BUT THE CARRABASSETT VALLEY MAY SEE A
FEW SHOWERS AS A WEAK DISTURBANCE BRUSHES THE AREA. A MORE POTENT
SHORT WAVE ARRIVES SATURDAY INTO SUNDAY BRINGING SHOWERS AND
THUNDERSTORMS FOR THE WEEKEND.

&&

.AVIATION /16Z MONDAY THROUGH FRIDAY/...
SHORT TERM...EARLY MORNING FOG AND LOW CLOUDS SHOULD BURN OFF
FAIRLY QUICKLY OVER NEW HAMPSHIRE AND FAR WESTERN MAINE. COULD
LINGER A LITTLE LONGER EAST OF PORTLAND THOUGH. AFTERNOON SHOWERS
AND THUNDERSTORMS ARE EXPECTED FOR MOST OF THE AREA... WITH THE
GREATEST THREAT BEING IN THE EAST. THUNDERSTORM CHANCES DECREASE
OVERNIGHT BUT WILL NOT GO AWAY ENTIRELY. MORE THUNDERSTORMS ARE
EXPECTED ON TUESDAY.

LONG TERM...PREVAILING VFR WITH PERIODS OF NOCTURNAL FOG IN MOIST
LOW LEVEL CONDITIONS. MVFR OR LOWER CONDITIONS IN SHOWERS
THURSDAY.

&&

.MARINE...
SHORT TERM...WEAK PRESSURE GRADIENT KEEPS WIND FLOW LIGHT AND SEAS
FAIRLY CALM.

LONG TERM...A COLD FRONT CROSSES THE WATERS WEDNESDAY MORNING
FOLLOWED BRIEFLY BY HIGH PRESSURE. ANOTHER FRONT CROSSES THE
WATERS LATE THURSDAY NIGHT. SEAS AND WINDS REMAIN BELOW SCA
CRITERIA.

&&

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

&&

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


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