Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 271356 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 956 AM 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/... 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 /14Z 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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