Area Forecast Discussion
Issued by NWS Portland, ME

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453 FXUS61 KGYX 180145 AFDGYX Area Forecast Discussion National Weather Service Gray ME 845 PM EST Fri Nov 17 2017 .SYNOPSIS... Northwesterly winds will diminish this evening as high pressure continues to build in form the west. The high will crest across the area early Saturday before gradually sliding offshore. A warm front will lift northward on Saturday night with a mix of rain showers south and rain/snow in the north. A cold front will cross the region on Sunday bringing gusty winds and accumulating upslope snows to the mountains. High pressure builds in for the start of next week. && .NEAR TERM /THROUGH SATURDAY/... Update... Have updated the grids based on current conditions and latest set of mesoscale models. Upslope clouds continue to remain in place over the western mountains of Maine and northermost New Hampshire this evening. Elsewhere, downslope conditions will continue with clear skies and a gradual decrease in wind speeds. Have made minor adjustments to the overnight lows and dew points based on current trends. Prev Disc... At 19z...a 985 millibar low was over the Canadian maritimes while a 1024 millibar ridge was draped across the eastern Great Lakes. The pressure gradient between these two features will continue to relax over the next few hours with northwest winds gusty northwest winds diminishing. With the exception of some lingering upslope clouds across the mountains this evening...a clear and cold night is on the way with lows in the teens and lower 20s. && .SHORT TERM /SATURDAY NIGHT/... On Saturday...the high pressure ridge will crest across the forecast area during the morning before quickly retreating offshore by afternoon. A milder return southerly flow will develop by afternoon along with warm air advection clouds arriving from the west ahead of the next progressive shortwave impulse and associated low pressure system. Highs on Saturday will average a good five to seven degrees milder compared to today. Any precipitation that arrives will hold off until nearly dusk and be confined to northern and western sections...with any light wintry mix limited to areas near the international border. Saturday night...an intensifying surface low tracks just north of the eastern Great Lakes across Ontario province. That will push a warm front north across the area with any light mixed wintry precipitation across the mountains and international border area changing to plain rain. Expect any icing or wet snow/sleet accumulations to be quite light before the transition to all rain occurs and temperatures continue to rise overnight. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Sunday morning begins with low pressure moving along the Saint Lawrence river to our north. As it moves north and east, it will drag a rather robust cold front through the region. Strong southerly flow ahead of the front will allow temperatures Sunday morning to start off in the 40s to lower 50s. Right now it looks like the front should swing through during the late morning and early afternoon hours. Strong cold air advection sets up just behind the front. Temperatures will begin to fall sharply during the afternoon and evening hours. Expect winds of around 35kts to mix down to the surface at most locations. While this should be shy of high wind warning criteria, it may be enough to meet wind advisory criteria. Will hold off on headlines for now and let later shifts get a better look at things. The front moves quickly offshore and by Monday morning high pressure will dominate the eastern United States. Temperatures on Monday will be around 10 degrees cooler than normal. High pressure remains in place until Wednesday when another cold front is expected to move through. This one looks much weaker though and it almost completely washes out before passing through. It will likely only consist of a small drop in temperatures and a wind shift. High pressure remains in place through the end of the period. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... Short Term /through Saturday Night/...becoming VFR throughout this evening with gusty NW winds diminishing to under 10 KT this evening. VFR through Sat...with MVFR cigs developing Sat evening and lowering to IFR in RA and FG with areas of -fzra/sleet/snow possible across the mountains. Long Term...Expect mainly VFR throughout the period. There could be a short time of IFR/MVFR vsbys and cigs Sunday morning ahead of the cold front. However, once the front moves through VFR conditions will return quickly. Strong gusty winds behind the front could pose some LLWS concerns Sunday afternoon and evening. && .MARINE... Short Term /through Saturday Night/...SCAs will remain in place for the outer waters overnight. Gales have been dropped. Long Term...Cold front moving through on Sunday will produce strong gusty winds Sunday afternoon and evening. Winds will certainly be strong enough to meet Small Craft Advisory criteria and may approach Gale force. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EST Saturday for ANZ150-152- 154. && $$

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