Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 202306 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 706 PM EDT SAT SEP 20 2014 .SYNOPSIS... A WARM FRONT TRACKS NORTHEAST ACROSS THE AREA TONIGHT. A COLD FRONT WILL QUICKLY FOLLOW FROM THE WEST LATE SUNDAY INTO MONDAY...AND WILL PROVIDE A ROUND OF SHOWERS AND MAYBE EVEN AN ISOLATED THUNDERSTORM. A SECOND COLD FRONT WILL CROSS THE AREA TUESDAY FOLLOWED BY HIGH PRESSURE FOR THE REMAINDER OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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7 PM UPDATE...HAVE UPDATED THE FORECAST FOR MINOR ADJUSTMENTS BASED ON LATEST TRENDS IN OBSERVATIONAL DATA. THIS EVENING SHOULD CONTINUE TO BE MOSTLY CLOUDY BUT DRY. WELL AFTER MIDNIGHT...POSITIVE THETA-E ADVECTION IN THE LOW LEVELS STRENGTHENS AS K-INDICES RISE AND SHOWALTER INDICES DROP TO AROUND ZERO. SHOWERS ARE THEREFORE EXPECTED TO DEVELOP LATE AT NIGHT...WITH AN ISOLD RUMBLE NOT OUT OF THE QUESTION. PREVIOUSLY... 12Z SOUNDING NOTED SW FLOW AND A SATURATED LAYER FROM ABOUT 925 TO 800MB THIS MORNING. FORECAST SOUNDING SHOW THIS LAYER CONTINUING TONIGHT AS WAA CONTINUES AND MOIST TROPICAL AIR PUSHES INTO THE REGION. EXPECTING CLOUD COVER AND MUCH WARMER TEMPERATURES TONIGHT...WITH ALMOST ALL AREAS STAYING IN THE 50S OVERNIGHT. MOISTURE ADVECTION SHOULD ALSO HELP IN THE FORMATION OF FOG OVER THE WATERS AND ALONG COASTAL ZONES.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... MODELS ARE HAVING A TOUGH TIME HANDLING THE WAVE/LOW PRESSURE DEVELOPING OFF THE CAROLINAS. THE WAVE/LOW WILL MOVE NORTHWARD TOMORROW AND PASS VERY CLOSE TO THE 40/70 BENCHMARK. MODELS ALL AGREE THAT THIS SYSTEM WILL NOT SUPPLY MUCH IN THE WAY OF RAINFALL TO THE AREA BUT THE TROPICAL AIRMASS WILL BE NOTED AS PWAT VALUES WILL INCREASE TO THE 1.7 RANGE TOMORROW...WHICH IS ABOUT 2 STANDARD DEVIATIONS ABOVE NORMAL VALUES. THIS MOISTURE COMBINING WITH A WEAK LEADING SHORT WAVE WILL BE ENOUGH TO MAYBE BRING SOME LIGHT RAIN AND DRIZZLE TO THE SOUTHERN FORECAST AREA BY TOMORROW MORNING. A COLD FRONT WILL APPROACH THE AREA TOMORROW AFTERNOON INTO TOMORROW EVENING. THIS FRONT WILL KICK OFF SCT SHOWERS AND POSSIBLY A THUNDERSTORM...HOWEVER...EVEN WITH THE INCREASE IN LOW LEVEL MOISTURE THE INSTABILITY IS LOOKING MODEST AT BEST. THE BEST CHANCE FOR A STORM WILL BE IN THE WESTERN FORECAST AREA...WHERE BREAKS OF SUN AND HEATING IS MOST LIKELY TO OCCUR. && .LONG TERM /MONDAY THROUGH SATURDAY/... A COLD FRONT WILL BE MOVING OFFSHORE AND INTO EASTERN MAINE MONDAY MORNING. SKIES WILL CLEAR OUT OVER THE INTERIOR AND ALONG THE COAST AS DOWNSLOPING WESTERLY WINDS DEVELOP BEHIND THE BOUNDARY. CLOUDS AND SHOWERS WILL DIMINISH AND EVENTUALLY JUST REMAIN OVER THE HIGHER TERRAIN BY EARLY AFTERNOON. WE SHOULD SEE A DECENT TEMPERATURE GRADIENT FROM NORTH TO SOUTH DUE TO THIS WITH UPPER 50S NORTH TO LOWER 70S ALONG THE COAST. THE COLDER AIR BEGINS TO DIP DOWN MONDAY NIGHT INTO TUESDAY MORNING AND IS ENTRENCHED ALONG THE GREEN AND WHITE MOUNTAIN BASINS. THERE WILL BE A FEW LOCATIONS IN THE LOWER 30S BUT THE MAJORITY OF SITES SHOULD HOVER IN THE MID 30S. THIS IS PARTLY DUE TO THE PROXIMITY OF THE JETSTREAK AND SOME LINGERING MID AND HIGH LEVEL CLOUDINESS. ELSEWHERE TEMPERATURES WILL BE IN THE LOWER TO MID 40S. ANOTHER REINFORCING COOL FRONT MOVES THROUGH DURING THE DAY TUESDAY...BUT THE SOURCE IS WELL NORTH AND WILL RESULT IN LITTLE MORE THAN A WIND SHIFT. THE REMAINDER OF THE WEEK LOOKS PLEASANT AND PRECIPITATION FREE AS HIGH PRESSURE DOMINATES THE WEATHER AT THE SURFACE AND ALOFT. HIGH TEMPERATURES WILL TRANSITION INTO THE 60S AND 70S BY WEDNESDAY AND REMAIN THERE THROUGH AT LEAST SATURDAY. HIGH PRESSURE WILL PROMOTE CLEAR SKIES...LIGHT WINDS...AND QUICKLY DROPPING TEMPERATURES IN THE 30S AND 40S EACH NIGHT. && .AVIATION /23Z SATURDAY THROUGH THURSDAY/... SHORT TERM...INCREASE IN LOW LEVEL TROPICAL MOISTURE WILL ADVECT FOG AND LOW STRATUS INTO THE AREA TONIGHT. THIS WILL CAUSE IFR CONDITIONS FROM MIDNIGHT THROUGH TOMORROW MORNING. CEILINGS AND VIS SHOULD THEN INCREASE TO MVFR AND VFR CONDITIONS BEFORE A COLD FRONT DROPS THROUGH THE REGION LATE TOMORROW AFTERNOON AND INTO TOMORROW NIGHT. LONG TERM...MVFR OR BRIEFLY LOWER CONDITIONS MONDAY MORNING..MAINLY IN MOUNTAIN TERMINALS IN SHOWERS AND FOG. FOG WILL AGAIN BE POSSIBLE IN MOUNTAIN TERMINALS TUESDAY MORNING. VFR WILL PREVAIL THEREAFTER. && .MARINE...
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SHORT TERM...MARGINAL SCA CONDITIONS WITH GUSTS AROUND TO 25 KNOTS AND SEAS AROUND 5 FT ARE EXPECTED OVERNIGHT ON THE OCEAN WATERS. HAVE THEREFORE ISSUED A SCA FOR TONIGHT INTO SUNDAY. LONG TERM...A SMALL CRAFT ADVISORY MAY BE NEEDED MONDAY INTO TUESDAY MORNING AS A COLD FRONT CROSSES THE WATERS.
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&& .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...NONE. NH...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 3 PM EDT SUNDAY FOR ANZ150-152-154.
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&& $$ NEAR TERM UPDATE...MLE

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