Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 210000 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 700 PM EST SAT DEC 20 2014 .SYNOPSIS... HIGH PRESSURE BUILDS OVER NORTHERN MAINE SUNDAY...ALLOWING THE FLOW TO TURN ONSHORE. A WEAK WEATHER DISTURBANCE MAY TRIGGER SOME FLURRIES OR LIGHT SNOW OVER SOUTHERN REGIONS RIGHT THROUGH MONDAY. A WEAK AREA OF LOW PRESSURE WILL MOVE UP THE COAST TUESDAY...WITH A MORE SIGNIFICANT SYSTEM GRADUALLY ORGANIZING WEDNESDAY...BEFORE MOVING OVER THE GREAT LAKES. THIS COULD BRING WINDY CONDITIONS AND THE POTENTIAL FOR HEAVY RAIN AROUND CHRISTMAS EVE INTO EARLY CHRISTMAS MORNING. && .NEAR TERM /TONIGHT/...
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7PM UPDATE... HAVE UPDATED THE FORECAST TO BRING HOURLY TEMPERATURE TRENDS IN LINE WITH LATEST OBSERVATIONS. HAVE ALSO MADE SOME MINOR ADJUSTMENTS TO SKY COVER AND POP. TWO AREAS OF CLOUDS ARE IMPACTING PARTS OF THE FORECAST AREA THIS EVENING AS SURFACE HIGH PRESSURE SITS OVER NORTHERN NEW ENGLAND AND SOUTHERN QUEBEC. SOME LOW CLOUDS HAVE MOVED SOUTHWEST ACROSS MUCH OF MAINE AND ARE NOW IMPACTING AUGUSTA AND LEWISTON AND POINTS EAST. ANOTHER AREA OF CLOUDS HAS PUSHED WESTWARD OFF THE WATER OVER SOUTHERN NEW ENGLAND AND INTO THE SOUTHERN HALF OF NEW HAMPSHIRE. SOME LIGHT SNOW SHOWERS ALSO ARE DRIFTING IN ON THE ONSHORE FLOW OVER MASSACHUSETTS AND SOME OF THESE SNOW SHOWERS ARE EXPECTED TO MOVE NORTH INTO SOUTHERN NEW HAMPSHIRE OVERNIGHT. THESE SNOW SHOWERS ARE PRIMARILY BEING GENERATED FROM THE ONSHORE FLOW OFF THE OCEAN. ONLY LIGHT ACCUMULATIONS ARE EXPECTED... UP TO ABOUT AN INCH. ORIGINAL DISCUSSION... STRATOCUMULUS CONTINUES TO POUR IN OFF THE GULF OF MAINE LATE THIS AFTERNOON. SCATTERED SNOW SHOWERS WILL REMAIN OFFSHORE FOR A FEW MORE HOURS PER LATEST RADAR TRENDS. HOWEVER...SOME PRECIPITATION WILL BEGIN TO ENTER THE SEACOAST OF NH THIS EVENING. 12Z MESOSCALE MODEL SUITE CONTINUES TO SHOW THESE SNOW SHOWERS BECOMING PERSISTENT ENOUGH TO DROP A LIGHT COATING OF SNOW IN THE MANCHESTER THROUGH PORTSMOUTH CORRIDOR. WITH MAINLY CLEAR SKIES UP NORTH...EXPECT ANOTHER COLD NIGHT WITH LOWS IN THE SINGLE NUMBERS. SOME AREAS IN THE NORTH WERE BELOW ZERO THIS MORNING.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
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SNOW SHOWERS MAY BE PERSISTENT OVER SOUTHERN NEW HAMPSHIRE EARLY SUNDAY DUE TO OCEAN EFFECT...WITH DRYING OCCURRING DURING THE AFTERNOON. THE PASSAGE OF A WEAK UPPER LEVEL LOW OVER EASTERN AREAS MAY BRING A SNOW SHOWER OR TWO TO THE MIDCOAST AREA OF MAINE. SOME CLEARING WILL OCCUR SUNDAY NIGHT AS THE WEAK SYSTEM SHIFTS TO THE EAST. HOWEVER...A LOW LEVEL NORTHEAST FLOW WILL CONTINUE...WHICH WILL ALLOW FOR THE POSSIBILITY OF A LIGHT SNOW SHOWER ALONG THE COAST AND SOME LOW CLOUDINESS. THIS WILL KEEP MINIMUM TEMPERATURES ALONG THE COAST IN THE MID TO UPPER 20S...WHILE THE MOUNTAINS DROP OFF INTO THE LOWER TO MIDDLE TEENS.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/...
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THE WEAK ONSHORE FLOW CONTINUES MONDAY INTO TUESDAY WITH LOW LEVEL MOISTURE DEEPEST ALONG THE COAST. SOME PERIODS OF LIGHT SNOW OR DRIZZLE OR EVEN SOME FREEZING DRIZZLE ARE POSSIBLE MONDAY AND MONDAY NIGHT. ON TUESDAY THE WARMER ONSHORE FLOW DEEPENS AS THE HIGH MOVES FURTHER OFFSHORE ALLOWING A SOUTHEAST FLOW TO INCREASE...SO CANNOT RULE OUT SOME LIGHT INTERMITTENT PRECIPITATION. THE MAIN EVENT WILL BE THE ONSET OF THE HEAVIER PRECIPITATION LATE CHRISTMAS EVE AND ESPECIALLY CHRISTMAS DAY AND NIGHT WHERE THE RAIN WILL BECOME HEAVY AT TIMES AS A STRONG WARM ADVECTION PATTERN DEVELOPS BEING ACCOMPANIED BY A STRONG LOW/MID LEVEL JET. THE MAIN UPPER LOW PASSES WELL TO OUR WEST AS IT MOVES THROUGH THE GREAT LAKES. QPF TOTALS FOR LATE TUESDAY INTO THURSDAY COULD BE IN THE 2-4 INCH RANGE. DUE TO VERY WARM AIR THIS WILL BE IN THE FORM OF RAIN EVEN IN THE MOUNTAINS. SOME FLOODING PROBLEMS MAY ARISE IN THE HEADWATERS BY WEDNESDAY NIGHT OR THURSDAY DUE TO THE COMBINATION OF SNOWMELT AND THE HEAVY RAINS. ALL MODELS AGREE ON MILD TEMPERATURES...USED A BLEND OF THE MODELS. SYSTEM FINALLY WINDS DOWN BY THURSDAY AFTERNOON AS A DRY SLOT MOVES ACROSS THE AREA. ANOTHER SYSTEM WHICH WILL BE WEAKER APPROACHES FOR THE WEEKEND WHICH ALSO LOOKS WARM AND WET.
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&& .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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SHORT TERM...IFR CLOUD DECK IS ADVANCING SOUTHWEST ACROSS MUCH OF MAINE THIS EVENING. THIS WILL PRIMARILY IMPACT AUGUSTA AND ROCKLAND BUT COULD IMPACT PORTLAND AS WELL. ANOTHER AREA OF MVFR/VFR CLOUDS ARE IMPACTING SOUTHERN NEW HAMPSHIRE AND MAY LOWER A BIT INTO THE MVFR TO IFR RANGE OVERNIGHT. SOME LIGHT SNOW SHOWERS ARE ALSO POSSIBLE ACROSS SOUTHERN NEW HAMPSHIRE INCLUDING AT PORTSMOUTH AND MANCHESTER OVERNIGHT INTO SUNDAY MORNING. LONG TERM...POSSIBLE PERIODS OF MVFR TO IFR AT COASTAL TERMINALS MONDAY AS INVERTED TROUGH DEVELOPS ACROSS THE GULF OF MAINE. MVFR LIKELY TO HOLD TUESDAY INTO TUESDAY NIGHT...LOWERING TO IFR LATE TUESDAY NIGHT INTO THURSDAY IN RAIN...WITH INCREASING E-SE WINDS WEDNESDAY.
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&& .MARINE...
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SHORT TERM...A FEW WIND GUSTS CONTINUE JUST BELOW 25 KTS THIS AFTERNOON...WITH WAVES 4` OR LOWER...THEREFORE NO FLAGS IN THE NEAR TERM. WINDS SHOULD CONTINUE TO SLOWLY DECREASE TONIGHT INTO TOMORROW FROM THE NORTHEAST. LONG TERM...STRONG LOW PRESSURE WILL MOVE WELL TO THE WEST AND WILL CAUSE WINDS TO INCREASE TO GALES TUESDAY NIGHT THROUGH WEDNESDAY WITH BORDERLINE STORM FORCE WINDS POSSIBLE WEDNESDAY NIGHT. SEAS COULD BUILD IN EXCESS OF 15 FT OVER THE OUTER WATERS BY WEDNESDAY NIGHT. GUIDANCE LOOKS LOW ON BOTH WINDS AND SEAS WHICH IS TYPICAL FOR THESE TYPE OF EVENTS.
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&& .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...NONE. MARINE...NONE. && $$ NEAR TERM UPDATE... KIMBLE

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