Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 221327 AFDGYX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAY ME 927 AM EDT WED OCT 22 2014 .SYNOPSIS... A COASTAL LOW WILL BRING A PROLONGED PERIOD OF RAIN THROUGH THE END OF THE WEEK. THE SYSTEM WILL FINALLY DRIFT OFF INTO THE MARITIMES FRIDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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910 AM...AT 13Z A 1006 MILLIBAR OCEAN LOW CENTERED EAST OF THE DELMARVA. EXPECT RAIN TO INCREASE IN COVERAGE TODAY AS NEXT IMPULSE ROTATES AROUND THE UPPER LOW SITUATED ALONG THE VIRGINIA COAST ON GOES WATER VAPOR IMAGERY. BOTH THE KGYX 12Z RAOB AND DOPPLER RADAR VAD WINDS SHOW NE AT 40 KT JUST ABOVE THE LOW LEVEL INVERSION NEAR 2000 FT. I MADE MINOR ADJUSTMENTS TO 1ST PERIOD GRIDS FOR THIS ESTF UPDATE TO REFLECT MESONET AND RADAR TREND. PREV DISC... 6AM UPDATE...SLIGHT LULL IN THE PRECIP AS THE SUN RISES. ADJUSTED TO CURRENT OBSERVATIONS. THE COASTAL LOW HAS BEGUN TO DEVELOP WITH DUELING LOW PRESSURE CENTERS OFF DELMARVA AND EAST OF THE BENCHMARK. AHEAD OF THE LOW... WATER VAPOR IMAGERY SHOWS A STREAM OF MOISTURE ORIGINATING IN FLORIDA. A LIGHT STEADY RAIN IS FALLING ACROSS MAINE AS ISENTROPIC UPLIFT AHEAD OF THE LOW TAKES ADVANTAGE OF THE TROPICAL MOISTURE SOURCE. RAIN WILL CONTINUE THROUGH THE DAY AS THE LOW DEEPENS OFF THE SOUTHERN NEW ENGLAND COAST. IN THE COASTAL PLAIN WINDS WILL INCREASE DURING THE MORNING AS THE GRADIENT TIGHTENS... WITH GUSTS TO NEAR WIND ADVISORY POSSIBLE.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... GUIDANCE IN GOOD AGREEMENT THAT THE STORM WILL CONTINUE TO INTENSIFY AND MOVE NORTHEASTWARDS INTO THE GULF OF MAINE THROUGH THE OVERNIGHT HOURS. EXPECT PERIODS OF HEAVY RAIN. HEAVY RAIN WILL BE FOCUSED IN THREE AREAS... ALONG THE COAST ASSOCIATED WITH THE COASTAL FRONT... IN THE EAST FACING PORTIONS OF THE WHITE MOUNTAINS IN UPSLOPE FLOW... AND IN CENTRAL MAINE WHERE FRONTOGENESIS AND DYNAMICS FAVOR HEAVIEST RAINFALL. TOTAL RAINFALL AMOUNTS REMAIN AT 2 TO 4 INCHES... WITH LOCALLY HIGHER AMOUNTS UP TO 6 INCHES. WHILE RAINFALL RATES ARE NOT EXPECTED TO BE EXTREME ENOUGH FOR FLASH FLOODING... THE PROLONGED PERIOD OF RAIN AND TOTAL AMOUNTS MAY BE ENOUGH TO CAUSE FLOODING ALONG STREAMS AND RIVERS. A FLOOD WATCH HAS BEEN ISSUED FOR THE AREAS MOST LIKELY TO SEE RIVER FLOODING... FROM EASTERN NEW HAMPSHIRE THROUGH ALL OF WESTERN MAINE. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... STEADY RNFL WILL COME TO AN END THU NIGHT INTO FRI...TAPERING TO SHOWERS DURING THE DAY FRI. AS LOW PRES LIFTS NEWD WINDS WILL TURN NWLY AND DOWNSLOPING SHOULD DRY OUT AREAS DOWNWIND OF THE MTNS. ANY SIGNIFICANT PCPN IS NOT EXPECTED...AS THE BULK WILL HAVE ALREADY FALLEN. TROF REMAINS IN PLACE OVER THE ERN CONUS SAT...AND NRN STREAM S/WV WILL RACE OUT OF CENTRAL CANADA LATE SAT INTO SUN. THIS WILL BRING A RENEWED CHANCE FOR SHOWERS...ESPECIALLY IN THE HIGH TERRAIN WHERE A MIX IS POSSIBLE. SFC COLD FNT WILL PUSH THRU THE REGION SUN...WITH GUSTY WINDS BUT THE BULK OF PCPN REMAINING IN THE MTNS. CANNOT RULE OUT A STRAY SHOWER MAKING IT TO THE COASTAL PLAIN...BUT POP WILL ONLY REFLECT SLIGHT CHANCE ATTM. RIDGING SFC AND ALOFT TAKES HOLD FOR EARLY NEXT WEEK. FOR THOSE SICK OF THE RAINY...RAW WX THIS WILL BE A WELCOME CHANGE...AS SEASONABLY WARM TEMPS RETURN TO THE AREA. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... SHORT TERM...PERSISTENT IFR CONDITIONS EXPECTED IN RAIN WITH PERIODS OF LIFR CONDITIONS POSSIBLE THROUGH THURSDAY. TO THE NORTH AND WEST OF THE MOUNTAINS CONDITIONS WILL NOT BE AS BAD DUE TO DOWNSLOPING. LONG TERM...IFR TO MVFR CONDITIONS WILL LIKELY LINGER THRU THE DAY ON FRIDAY AND THEN PERIODS OF MVFR CONDITIONS INTO THE WEEKEND WITH SCATTERED SHOWERS POSSIBLE SATURDAY AND SUNDAY ESPECIALLY IN THE NRN ZONES. && .MARINE... SHORT TERM...NORTHEAST WINDS WILL INCREASE WITH SEAS BUILDING TO 10 TO 15FT ON THE OUTER WATERS AS THE LOW INTENSIFIES AND MOVES THROUGH THE GULF OF MAINE. LONG TERM...SEAS WILL REMAIN HIGH FRI...GRADUALLY SUBSIDING INTO SAT. WINDS WILL BE NEAR MARGINAL SCA THRESHOLDS FOR PART OF FRI...HOWEVER SCA WILL LIKELY STILL BE NEEDED FOR SEAS OVER 5 FT. && .HYDROLOGY... TOTAL RAINFALL AMOUNTS OF 2 TO 4 INCHES ARE EXPECTED WITH SOME LOCATIONS POSSIBLY EXCEEDING 6 INCHES. WHILE THIS RAIN WILL NOT FALL QUICKLY ENOUGH TO CAUSE FLASH FLOODING... THE CUMULATIVE EFFECT OF THIS MUCH RAIN OVER THE NEXT SEVERAL DAYS MAY BE ENOUGH TO BRING SOME STREAMS AND RIVERS INTO FLOOD. A FLOOD WATCH HAS BEEN ISSUED FOR WEDNESDAY AND THURSDAY WHEN THE HEAVIEST RAIN IS LIKELY TO OCCUR. ANY FLOODING WHICH DOES OCCUR MAY LINGER BEYOND THURSDAY AS WATERS SLOWLY DRAIN TOWARD THE SEA. && .TIDES/COASTAL FLOODING... TIDES ARE ONLY EXPECTED TO RISE TO AROUND 9.5 FEET OR SO DURING THE HEIGHT OF THE STORM. WITH A HIGHEST SURGE OF AROUND 1 FOOT... OCCURRING AT LOW TIDE ... COASTAL FLOODING IS NOT EXPECTED. HOWEVER... THE PERSISTENT NORTHEAST FLOW MAY CAUSE A SURGE OF MORE THAN 1 FOOT AND WILL COMBINE WITH 10 TO 15 FT WAVES TO CREATE THE POTENTIAL FOR SPLASH OVER AND BEACH EROSION. THE MOST LIKELY AREAS TO BE IMPACTED WILL BE THE SEACOAST OF NEW HAMPSHIRE AND YORK COUNTY MAINE. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...FLOOD WATCH THROUGH THURSDAY EVENING FOR MEZ007>009-012>014- 018>028. NH...FLOOD WATCH THROUGH THURSDAY EVENING FOR NHZ004-006-008>010- 013-014. MARINE...GALE WARNING UNTIL 8 AM EDT THURSDAY FOR ANZ150>154. && $$ ES

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