Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 120324 AAC AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 1124 PM EDT Wed Oct 11 2017 .SYNOPSIS... Low pressure will pass well south of New England tonight as high pressure continues to build over the region. High pressure will crest over the region Thursday and will drift off to the east on Friday. A cold front will approach from the northwest Friday night and will sag south into northern New England on Saturday stalling over the region Saturday night. Low pressure approaching from the west will lift the front north on Sunday. Low pressure will track east along this boundary through southern Canada Sunday night and will drive a trailing cold front through the region on Monday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Update...As Nrn frontogenesis band weakens...dry air is winning out now. Rain is turning to showers and becoming much more scattered. The last area of showers back across NY will swing towards the region after midnight...and so some low chance PoP will remain in SWrn NH for a few hours. Otherwise cool...dry Canadian air is bleeding into the region from the N and will continue to allow temps to fall into the 30s for large parts of the forecast area. Previous discussion...Showers over New York State will continue to press eastward tonight. The light precipitation will be triggered by a weak and shearing upper level trough as it quickly moves east through a fast flow. However, the precipitation will be limited overnight as Canadian high pressure continues to drain in very dry air from the north and into Maine and New Hampshire. Much of the precipitation will evaporate up as falls through a very dry layer. Nevertheless, will expand the chance and slight chance pops northward into portions of central New Hampshire overnight. Patchy fog will develop over the interior sheltered valleys overnight. This may not be overly widespread however as cloud cover is expected over southern and central areas. There will be areas of frost in the mountains, foothills and portions of the interior. The growing seas has already ended in the mountains and foothills. This leaves northern Carroll, norther Grafton and interior Cumberland counties for a frost advisory overnight with widespread frost expected. Southern interior sections may see some patchy frost.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... The upper level trough shears east of our region and exits New England Thursday morning. This will leave the region with mainly sunny conditions as a large dome of high pressure crests over the region. It will be cooler than the last few days with most areas struggling to peak out much warmer than 60 degrees. Patchy frost and patchy fog will repeat themselves Thursday night as the ridge remains over the forecast area. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... High pres moves off the coast Fri allowing a return warmer south to southwest flow to develop. The warmer south to southwest flow will continue through Sunday. This will lead to warmer temps with increasing humidity over the weekend. The GFS model is trying to indicate a weak wave moving across southern New England Sat possibly spreading some rain into extreme southern areas while other models ignore it and keep the area dry. Also, it appears scattered showers may be focused along a weak boundary across the mountains Sat which make more sense. Will have to see this resolves so will probably hedge some in the mountains and extreme southern areas. Models generally agree on timing of the strong upper trof and associated strong cold front moving across the region late Sunday night into early Mon. Scattered showers can be expected along and ahead of this front. Winds will be strong and gusty behind the front Monday ushering much colder air for Mon night through Tue. Downsloping areas Mon-Tue will become mostly clear while clouds and a few showers will linger in the mountains. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions this evening followed by patchy IFR late tonight in the sheltered valleys. VFR conditions on Thursday, followed by more patchy inland valley fog Thursday night. Long Term...Valley fog Fri morning may produce some IFR/LIFR conditions across the area...otherwise VFR Fri into Sat. Extreme southwest areas of ME and southern NH may see MVFR/IFR conditions develop Sat into Sat night as a wave of low pressure moves across southern New England spreading rain and low clouds. Sun conditions remain mainly VFR. A strong cold front will move southeast across the region Sun night with MVFR conditions in scattered showers. A strong gusty northwest flow develops behind the cold front Mon. && .MARINE... Short Term...A northeast flow will continue over the coastal waters. A few locations gusts may peak out around 20 kt as the surface ridge builds in from the north, while low pressure passes south of New England. Long Term...SCAs possible with a south to southwest flow Sunday and Sunday night ahead of an approaching front...and then Monday as winds become northwest behind the strong cold frontal passage. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Frost Advisory until 8 AM EDT Thursday for MEZ019. NH...Frost Advisory until 8 AM EDT Thursday for NHZ003-004. MARINE...None.
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