Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 222110 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 410 PM EST MON DEC 22 2014 .SYNOPSIS... AN WEAK ONSHORE FLOW WILL CONTINUE THROUGH TUESDAY. A SIGNIFICANT LOW PRESSURE SYSTEM WILL MOVE ACROSS THE GREAT LAKES WEDNESDAY INTO THURSDAY. THIS COULD BRING WINDY CONDITIONS AND THE POTENTIAL FOR HEAVY RAIN AROUND CHRISTMAS EVE INTO EARLY CHRISTMAS MORNING. ANOTHER LOW PRESSURE SYSTEM WILL APPROACH THE REGION LATE IN THE WEEKEND POTENTIALLY BRINGING SOME WINTRY WEATHER. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A PERSISTENT LIGHT ONSHORE FLOW FROM THE EAST COMBINE WITH SOME WEAK WAA OVERRUNNING ALOFT FROM THE SOUTHWEST WILL COMBINE TO BRING PERIODS OF LIGHT PCPN TONIGHT. A WINTER WX ADVISORY HAS BEEN ISSUED FOR SOUTHWEST NH FOR SOME VERY LIGHT SNOW OR MIXED PCPN TONIGHT INTO EARLY TUE BEFORE CHANGING TO RAIN TOWARD MORNING AS THE BOUNDARY LAYER TEMPS WARM BACK ABOVE FREEZING. ELSEWHERE ACROSS CENTRAL AND NORTHERN NH AND WESTERN MAINE ANY LIGHT PCPN WILL BE IN THE FORM OF SNOW. TOWARD AND ALONG THE COASTAL AREAS BOUNDARY LAYER TEMPS WILL BE MARGINAL DUE TO THE ONSHORE FLOW SO THE PCPN MAY BE IN THE FORM OF LIGHT RAIN. USED A BLEND OF THE MODELS FOR POPS AND OVERNIGHT TEMPS. STAYED WITH RFCQPF VALUES WHICH CONFIRMED ONLY VERY LIGHT AMOUNTS OF QPF EXPECTED OVERNIGHT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... OVER SOUTHERN AREAS OF NH AND ME, LOW LEVEL TEMPS WILL SLOWLY WARM ABOVE FREEZING SO ANY AREAS OF LGT SNOW OR MIXED PCPN SHOULD CONVERT TO RAIN AS THE DAY PROGRESSES. OVER NORTHERN AREAS, SOME LIGHT SNOW WILL CONTINUE BUT NO ACCUMULATIONS EXPECTED. OF NOTE: BUFKIT SHOWS NICELY THE VERY SHALLOW INVERSIONS ACROSS NH AND SRN ME TUE MORNING BUT WITH TIME THEY GET WIPED OUT DURING THE DAY. ALL AREAS CHANGE TO RAIN TUE NIGHT AS THE WAA ALOFT FROM THE SOUTH AND SOUTHWEST CONTINUES WHILE AT THE SAME TIME THE LOW LEVEL ONSHORE FLOW STRENGTHENS. QPF AMOUNTS WILL REMAIN LIGHT THROUGH TUE NIGHT AS PER RFCQPF. STAYED CLOSE TO A SUPERBLEND OF MODELS FOR TEMPS WHICH SEEMED TO APPEAR RATHER REPRESENTATIVE FOR THE SCENARIO. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... THE WEDNESDAY THROUGH THURSDAY MORNING PERIOD CONTINUES TO LOOK LIKE A WET ONE. COLD AIR DAMMING WILL LIKELY HOLD TOUGH AT THE SFC ON WEDNESDAY...HOLDING TEMPERATURES IN THE 30S. HAVE LOWERED HIGHS FOR WEDNESDAY IN STEP WITH MESOSCALE GUIDANCE BUT THEY MAY NEED TO BE LOWERED A LITTLE MORE MOVING FORWARD. IN A NUTSHELL...A COLD RAIN IS EXPECTED WEDNESDAY WITH SOME ICING POSSIBLE IN THE MORNING ACROSS THE NORTHERN MOUNTAINS. THE WARM FRONT TO OUT SOUTH LOOKS TO PUSH NORTHWARD WEDNESDAY NIGHT AS A STRONG SHORT WAVE TROUGH APPROACHES FROM THE SOUTHWEST. THE COLD SFC AIR WILL BE TOUGH TO DISLODGE BUT IT LOOKS LIKE THE WARM FRONT SHOULD MAKE IT INTO SOUTHERN NH WEDNESDAY NIGHT...THEN CONTINUE TO PUSH NORTH THURSDAY BEFORE COLD FRONT/OCCLUSION MOVES THROUGH. IT/S POSSIBLE THAT MANCHESTER/NASHUA NH CORRIDOR COULD BE 55-60 DEGREES LATER WED NIGHT WHILE AT THE SAME TIME CONCORD IS IN THE 30S. SHOULD BE A TIGHT GRADIENT. THE RAINFALL FROM THIS SYSTEM DOES NOT LOOK LIKE IT WILL BE AS HEAVY AS WAS ADVERTISED BY THE MODELS THE PREVIOUS SEVERAL DAYS. THIS LIKELY DUE TO THE ABSENCE OF A STRONG SOUTHEASTERLY INFLOW BELT JUST ABOVE THE SFC. INSTEAD...IT/S MAINLY DEEP LAYER SOUTHERLY/SOUTHWESTERLY FLOW JUST ABOVE THE BOUNDARY LAYER WHICH SHOULD KEEP STORM TOTAL RAINFALL AMOUNTS IN THE 1-2.25 INCH RANGE. THIS SHOULD KEEP ANY FLOODING PROBLEMS TO THE URBAN/POOR DRAINAGE KIND...WITH THE RIVERS REMAINING OK. THE HEAVIEST RAINFALL IS EXPECTED WED AFTERNOON INTO THU MORNING. A RUMBLE OF THUNDER CANNOT BE RULED OUT AS MARGINAL INSTABILITY DEVELOPS ABOVE THE COOL BOUNDARY LAYER. WILL ALSO HAVE TO WATCH OUT FOR GUSTY WINDS LATE WED NIGHT AND THU MORNING WHERE WE WARM SECTOR...AS THE LOW LEVEL JET COULD MIX DOWN. THIS WOULD BE ESPECIALLY POSSIBLE IN CONVECTION. OTHERWISE...FAIR WEATHER RETURNS THU AFTERNOON AND NIGHT. ECMWF HAS BEEN ADVERTISING A SNOWSTORM LATE IN THE WEEKEND OVER THE LAST FEW RUNS...SO WE/LL HAVE TO CONTINUE TO MONITOR THAT POTENTIAL. && .AVIATION /20Z MONDAY THROUGH SATURDAY/... SHORT TERM...MVFR CONDS EXPECTED TONIGHT THROUGH TUE AND MAY BECOME IFR AT TIMES IN ANY LIGHT PCPN. CONDS TO BECOME WIDESPREAD IFR CONDS TUE NIGHT. LONG TERM...EXTENDED PERIOD OF FLIGHT RESTRICTIONS WED INTO THU MORNING. LOOK FOR IFR OR LOWER DURING THIS TIME. EXPECT IMPROVEMENT TO VFR THU AFTERNOON...WHICH SHOULD HOLD THRU SATURDAY. && .MARINE... SHORT TERM...WINDS WILL REMAIN BELOW SCA CRITERIA TONIGHT THROUGH TUE NIGHT BUT THE CONTINUE EASTERLY FETCH WILL ALLOW SEAS TO BUILD ABOVE 5 FT OVER THE OUTER WATERS BEGINNING THIS EVENING AND CONTINUING THROUGH TUE NIGHT AS PER THE SWAN NAMSWAN GUID SUGGESTS. LONG TERM...MODELS CONTINUE TO BACK OFF THE STRONG WINDS WED INTO THU...BUT STILL A PERIOD OF GALES POSSIBLE IN THE S FLOW LATE WED AND WED NIGHT...BUT MORE LKLY IN STRONG W FLOW THU INTO THU NIGHT. && .HYDROLOGY... MODELS CONTINUE TO BACK OFF ON RAINFALL TOTALS FOR THE CHRISTMAS EVE/EARLY CHRISTMAS MORNING EVENT...BUT ARE STILL AROUND 2 INCHES. IN ANY CASE...WHILE THE THREAT OF FLOODING IS LOWER...IT STILL REMAINS A POSSIBILITY WED NIGHT INTO THU...MAINLY THE URBAN AND POOR DRAINAGE VARIETY. RIVER FLOODING DOESN/T LOOK LIKE A BIG THREAT AT THIS TIME SINCE IT LOOKS LIKE TEMPERATURES WON/T GET UP HIGH ENOUGH IN THE MOUNTAINS TO ALLOW FOR SUBSTANTIAL MELTING OF SNOW. && .TIDES/COASTAL FLOODING... ASTRONOMICAL TIDES ARE AT THEIR PEAK FOR THE MONTH. THIS...IN COMBINATION WITH STRONG SOUTHERLY WINDS LATE WED INTO EARLY THU WILL LIKELY ALLOW FOR SOME STORM SURGE. THERE IS SOME POTENTIAL FOR MINOR COASTAL FLOODING OR SPLASH OVER AND BEACH EROSION AROUND THE TIMES OF HIGH TIDE WED NIGHT INTO EARLY THU AFTERNOON. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...NONE. NH...WINTER WEATHER ADVISORY FROM 9 PM THIS EVENING TO 8 AM EST TUESDAY FOR NHZ007-008-011-015. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 8 PM THIS EVENING TO 6 AM EST WEDNESDAY FOR ANZ150-152-154. && $$ LONG TERM...MLE

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