Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 182239 AFDGYX Area Forecast Discussion National Weather Service Gray ME 639 PM EDT Tue Apr 18 2017 .SYNOPSIS... High pressure will crest over the coastal plain tonight. The circulation around this high will bring a cool onshore flow to the area. Weak low pressure passes to our north Wednesday night and will bring some showers to the region, especially across the north. Another low will bring steadier precipitation Thursday night into Friday. The precipitation could fall as some snow in the highest elevations. The low may hang around allowing for an unsettled weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Surface high pressure will continue to build southwestward across the region this evening. The leading edge of the SFC high in the form of a back door cold front/seabreeze can be seen on radar on the coastal plain at this time and will work inland going forward early this evening. This will turn the winds to east and cool off the temps. A few showers are occurring on and near the mid coast this afternoon and these may continue through the evening hours, but be quite light. Getting low temperatures right will be a challenge. Normally with 1030+ high pressure cresting overhead lows would bottom out pretty cold. However, moisture trapped beneath subsidence inversion should allow stratocu to hang on overnight, at least in patches. This will hamper temp drops in places, so went the middle of the road with respect to the guidance lows. However, areas that stay clear and calm will likely get into the 20s without much trouble. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
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635 pm Update: Quick ESTF update to input latest obs data. Quiet evening with some of the clouds over southern Maine slowly eroding away. Previous forecast looks good. Minor tweaks to temps and sky grids based on latest data. Previous Discussion: The SFC high moves off the the east on Wednesday setting up more of a southeasterly flow, but still off the water for many. Therefore we are expecting another cool-ish day. Clouds increase as the day wears on, with showers entering northern and western sections of the forecast area during the afternoon hours as a short wave trough approaches from the west. These will move across the rest of the region Wednesday night. However, QPF amounts are expected to be pretty light...generally a tenth of an inch or less. Some wet snow will be possible at the highest elevations of the western ME mountains Wednesday evening.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/... The models are in decent agreement on the longwave pattern through early next week. Temperatures will average below normal with a semi permanent vortex over Hudson Bay and as series of impulses rotating around it delivering fresh rounds of cold air to the region. will We begin the period with a frontal system extending from northern New England through the Great Lakes. A digging shortwave impulse over the northern plains states will slide eastward into New England before exiting the coastline on Saturday. At the surface...an associated surface low will travel eastward along the quasi- stationary frontal boundary before exiting the coast Friday night. Showers and patchy drizzle on Thursday will transition to a steadier rain Thursday night as overrunning increases in advance of the approaching surface wave. The rain should taper off from west to east Friday evening as the low and frontal boundary slide offshore. We`ll see lingering clouds and a few rain or snow showers across northern and mountains sections Friday night into Saturday with cold air aloft...upslope flow...and lingering troffiness. Shortwave ridging will offer a bit of a respite Saturday night into Sunday with a weak surface ridge traversing the area. A northern stream impulse will drive a cold front across the area Sunday night into Monday marked by clouds and a few showers along with a fresh shot of cold air to begin the new work week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Short Term...Mostly VFR cigs are expected tonight, but a period of MVFR is possible after midnight, especially at southern NH terminals. A cold front with showers will move through Wednesday night, and this will likely bring cigs down into the IFR range later Wednesday night. Long Term... Thu...Areas of MVFR in -shra. Thu night - Fri...IFR with areas of LIFR in RA and FG. Sfc wind gusts to 25 kt. Sat...Areas of MVFR in -shra with mtn -shra/-shsn. Sfc wind gusts to 25 kt. && .MARINE... Short Term...A few gusts of up to 25 kt will be possible this evening as high pressure builds in but will not be widespread of frequent enough to warrant a SCA. However, a SCA has been issued for all waters for Wednesday afternoon and night as strong winds and higher seas are expected in advance of a cold front. Long Term... Thu...Small Craft conditions are possible. Fri - Sat...Small Craft conditions are possible...will gales outside the bays. && .FIRE WEATHER... Cool, moist onshore flow overspreads the entire area tonight into Wednesday. There will be a chance of showers Wednesday afternoon and night more widespread rain expected Thursday night into the weekend. && .HYDROLOGY... Flood warnings continue for the Kennebec, Androscoggin, and Connecticut rivers, but colder air should allow snow melt to wane and rivers levels to recede below flood stage tonight. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 3 PM Wednesday to 6 AM EDT Thursday for ANZ150>154. && $$

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