Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 220139 AFDGYX Area Forecast Discussion National Weather Service Gray ME 939 PM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure will gradually shift off to the east tonight and and Monday. A slow moving cold front will approach from the west Monday night and Tuesday and will stall over the region Tuesday night. Several waves of low pressure will ride north along this boundary through Thursday as the front pushes east. High pressure will build in from the southwest on Friday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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940 pm Update: No changes needed to forecast. High clouds continue to spill across the region. Input latest mesonet data. 7 pm Update: High level moisture spilling through the large upper ridge axis. Have made adjustments to sky grid forecast for a partly cloudy night due to the high clouds. Input latest obs data with no discernable changes to temps at this time. Previous Discussion: High pressure center will remain off shore tonight...but plenty of surface ridging in place for radiational cooling. Started with low temps from this morning and blended in MOS guidance and bias corrected MOS guidance. This raised temps a few degrees from this morning...which makes sense given dew points are higher this afternoon and suggest mainly upper 30s at the coolest spots. Those increased dew points may also help valley fog form...especially across Wrn zones.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... With high center off shore flow will be more Ely Sun...keeping temps a little cooler especially on the Wrn ME coast and Seacoast NH. Mixed down H9 temps and then blended in the MET guidance to show the cooler onshore temps. Sun night increasing dew points and deeper return flow will keep temps more mild than previous nights. This may also allow for some more widespread radiation fog. && .LONG TERM /MONDAY THROUGH SATURDAY/... High pressure will continue to slide off to the east on Monday. After a sunny start to the day increasing onshore flow will bring scattered to broken ocean stratus into southern New Hampshire and Maine in the afternoon. Temperatures on Monday will again top out well above normal ranging from the mid 60s in the north and mid coast to the lower 70s in southern New Hampshire and southwest Maine. Slow moving cold front approaching from the west will increase onshore flow Monday night spreading ocean stratus into most of the forecast area. Showers ahead of this boundary may edge into the Connecticut Valley by daybreak but expect most of the area to see a dry night. Clouds will keep temps from falling off much with lows overnight ranging through the 50s. Cold front will gradually stall over the Hudson Valley on Tuesday with showers ahead of the front shifting east into New Hampshire and western Maine over the course of the day. Will see another warm day with highs ranging through the 60s. Frontal boundary will continue its slow eastward progress Tuesday night and Wednesday as several waves of low pressure ride north along it. Tropical connection will provide plenty moisture in advance of this system so several inches of much needed rain will fall across the region. Jackpot for rainfall still appears focused in eastern Maine but 2 to 3 inches across New Hampshire and western Maine looking more likely with both the ECMWF and GFS both showing these amounts if not slightly more. Lows Tuesday night will be almost summer-like with readings only dropping into the upper 50s to lower 60s. Highs on Wednesday will range through the 60s. Focus of heavy rainfall will shift east Wednesday night as the front pushes into western Maine. Looking for rain in the evening to taper to showers with areas of drizzle. Lows overnight will range through the 40s to near 50 in coast and midcoast areas. Deep upper trough will swing in from the west on Thursday keeping conditions unsettled through the day. Looking for mostly cloudy skies with scattered showers and much cooler temps. Expect highs ranging through the 50s. Upper trough will lift out to the northeast Thursday night as shallow ridging builds in from the west. Expect evening showers to give way to partial clearing after midnight. Fair weather will return on Friday as high pressure builds south of New England. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Short Term...Widespread VFR conditions will continue thru Sun. Higher dew points and high pressure tonight will likely help valley fog form in the CT River Valley. LIFR after 06z for LEB and HIE...lifting at HIE first and LEB around 13z. Onshore flow Sun night may allow more widespread IFR fog to develop...though confidence is low at this time. Long Term...VFR Monday with areas of MVFR ceilings developing in the south during the afternoon. IFR/LIFR ceilings Monday night through Wednesday. MVFR ceilings Thursday. && .MARINE... Short Term...Wind and seas will remain below SCA thresholds with high pressure in place thru Sun night. Long Term...SCA`s may be needed Monday night. Gales possible on Tuesday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Marine is the U.S. government's official web portal to all federal, state and local government web resources and services.