Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 252204 AAA AFDGYX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE GRAY ME 604 PM EDT MON APR 25 2016 .SYNOPSIS... A WARM FRONT WILL LIFT NORTH INTO SOUTHERN NEW ENGLAND AND STALL THERE TONIGHT AND TUESDAY. THIS WILL BRING SOME PRECIPITATION TO THE SOUTHERN HALF OF NEW HAMPSHIRE AND COASTAL MAINE. SOME OF THIS WILL FALL AS SNOW. COOL HIGH PRESSURE THEN SETTLES IN THROUGH MIDWEEK. LOW PRESSURE WILL PASS SOUTH OF NEW ENGLAND ON FRIDAY. && .NEAR TERM /THROUGH TUESDAY/...
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--601PM UPDATE-- UPDATED THE FORECAST TO ALLOW THE RED FLAG WARNING TO EXPIRE ON SCHEDULE AT 6PM. EXPECT US TO REMAIN PRECIPITATION FREE /OUTSIDE OF A STRAY SPRINKLE/ THROUGH THE EVENING HOURS...AND HAVE BROUGHT POPS DOWN A BIT UNTIL AFTER MIDNIGHT. MATCHED T/DEWPOINT/WINDS TO CURRENT TRENDS WHICH BOOSTED WINDS SOMEWHAT...BUT RESULTED IN LITTLE OTHER SIGNIFICANT CHANGES. PREVIOUS BELOW... A CLIPPER WILL MOVE EAST FROM THE GREAT LAKES ALONG A BAROCLINIC ZONE SET UP ALONG CENTRAL NEW ENGLAND. VISIBLE SATELLITE IMAGERY SHOWS MID/HIGH CLOUDS STREAMING INTO THE AREA ALONG THIS BOUNDARY AND WILL OVERSPREAD THE AREA BY THIS EVENING. A WEAK WAVE OF LOW PRESSURE WILL DEVELOP ALONG THIS FRONT LATER TONIGHT THAT WILL ENHANCE QPF NORTH OF THE BAROCLINIC ZONE INTO THE SOUTHERN AREAS OF NEW HAMPSHIRE AND SOUTHERNMOST MAINE. THE STRATIFORM STEADY MIXED PRECIPITATION WILL BE CONFINED TO SOUTHERN AND CENTRAL NH AND SOUTHWEST MAINE AND WILL CONTINUE THROUGH THE MORNING INTO THE EARLY AFTERNOON. THIS BECOMES A VERY TRICKY FORECAST WITH PTYPE LATER TONIGHT INTO TUESDAY AND THE OUTCOME WILL HAVE AN AFFECT ON TOTAL SNOW ACCUMULATIONS. CURRENTLY BOUNDARY LAYER TEMPS ARE VERY WARM (50-60 DEGS) DUE TO CLEAR SKIES ALL DAY ALLOWING SOLAR HEATING WHILE ALOFT H85 TEMPS ARE RATHER COLD (-3 TO -6C). ALSO...ANOTHER FACTOR WILL BE SURFACE DEWPOINTS ARE VERY LOW IN THE SINGLE DIGITS TO TEENS. OVERUNNING PCPN WILL DEVELOP OVER SOUTHERN AREAS OF NH AND WILL BE IN THE FORM OF RAIN THIS EVENING. WITH THE VERY DRY AIR MASS IN PLACE IN THE LOW LEVELS IT MAY TAKE A WHILE FOR THE ATMOSPHERE TO SATURATE AND THE RAIN TO REACH THE GROUND. BY LATER TONIGHT AND TOWARD MORNING EVAPORATIONAL COOLING WILL AID IN LOWERING BOUNDARY LAYER TEMPS TO WHERE TEMPS BECOME CRITICAL FOR RAIN VS SNOW. DUE TO THE COLDER TEMPS ALOFT HIGHER TERRAIN WILL BE MORE FAVORABLE FOR ACCUMULATING SNOWFALL OVER SOUTHERN AREAS. MODELS SHOW...AND IS TYPICAL IN THESE SCENERIOS A SHARP DELINEATING LINE OF QPF WHICH CUTS OFF QUICKLY OVER NORTHERN NH AND CENTRAL MAINE SO LITTLE OR NO PRECIPITATION IS EXPECTED DEEPER INTO THE DRY AIR MASS TO THE NORTH. EXPECTING THIS TO BE A SNOWFALL FOR HIGHER TERRAIN ABOVE ABOUT 1000 FEET WHERE 2-5 INCHES MAY OCCUR ACROSS THE SOUTHERN HALF OF NH WHERE HIGHER QPF AMOUNTS OCCUR AND ALSO INTO PARTS OF EXTREME SOUTHWEST INTERIOR MAINE. IN THE LOWER ELEVATIONS SOME LIGHT ACCUMULATIONS OF AN INCH OR LESS MAY OCCUR ON GRASSY AREAS. THE ONSHOIRE FLOW ALONG THE COAST WILL KEEP MOST OF THE PCPN AS RAIN ALTHOUGH CAN`T RULE OUT A FEW PERIODS OF SNOW AT TIMES. THE SYSTEM EXITS BY TUE NIGHT FOLLOWED BY CLEARING AND ANOTHER COLD NIGHT. USED A BLEND OF MODELS FOR TEMP FORECAST AND POPS.
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&& .SHORT TERM /TUESDAY NIGHT/... && .LONG TERM /WEDNESDAY THROUGH MONDAY/... STRONG UPPER LOW WILL REMAIN OVER SOUTHEASTERN CANADA ON WEDNESDAY. THIS WILL ALLOW A SHORT WAVE TO ROUND THE BASE OF THE TROUGH DURING THE DAY. THE ATMOSPHERE WILL REMAIN VERY DRY DURING THIS PERIOD...HOWEVER THERE MAY BE A FLURRY OVER THE NORTHERN MOUNTAINS WHEN THE MOISTURE STARVED SURFACE TROUGH CROSSES THE REGION. A RIDGE OF CANADIAN HIGH PRESSURE WILL THEN NOSE INTO THE REGION...KEEPING DRY AIR OVER THE REGION. HOWEVER...YET ANOTHER AREA OF LOW PRESSURE WILL PASS SOUTH OF NEW ENGLAND LATE THURSDAY INTO FRIDAY. TEMPERATURE PROFILES SUGGEST THIS PRECIPITATION WILL BE MAINLY IN THE FORM OF RAIN. THEREAFTER...MORE COLD...CANADIAN HIGH PRESSURE BUILDS INTO THE REGION FROM CANADA. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... SHORT TERM...VFR CONDITIONS WILL LOWER TO MVFR LATER THIS EVENING OVER SOUTHERN NH AS LIGHT RAIN SPREADS INTO THE AREA THIS EVENING AND THEN NORTH LATER TONIGHT AS IT BECOMES MIXED WITH OR CHANGES TO SNOW. MVFR TO IFR CONDS WILL DEVELOP TOWARD MORNING ACROSS ALL OF SOUTHERN AND CENTRAL NH AND SOUTHERN MAINE IN MIXED RAIN AND SNOW. LONG TERM...LOW PRESSURE WILL PASS SOUTH OF NEW ENGLAND ON FRIDAY. THIS MAY BRING A PERIOD OF MVFR CONDITIONS BRIEFLY TO SOUTHERN PORTIONS OF THE REGION. OTHERWISE...EXPECT MAINLY VFR CONDITIONS THROUGH THE PERIOD. && .MARINE... SHORT TERM...WINDS AND SEAS WILL REMAIN BELOW SCA CRTGERIA THROUGH TUE NIGHT. LONG TERM...SEAS AND WINDS WILL REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS FOR THE MOST PART THIS WEEK. A PERIOD OF GUSTY NORTHERLY WINDS MAY OCCUR EARLY NEXT WEEK WITH THE PASSAGE OF AN OFFSHORE LOW. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...NONE. NH...NONE. MARINE...NONE.
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&& $$ NEAR TERM UPDATE...ARNOTT

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