Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 210352 AFDGYX Area Forecast Discussion National Weather Service Gray ME 1052 PM EST Mon Nov 20 2017 .SYNOPSIS... Axis of cold high pressure slides east across New England tonight, with a warm up expected on Tuesday. The next cold front will arrive on Wednesday with a chance of mixed precipitation in the mountains and rain along the coast. This front will bring a return to cold conditions which will last through the upcoming weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Update... The scattered snow showers and flurries over the higher terrain will continue to shrink in coverage over the next several hours. Relatively dry conditions remain in the lowest levels of the atmosphere with surface dew points mainly in the single numbers and teens across northern and central portions of the region. Lowered temperatures in the mountains as they are already near or at their forecast lows. Added some additional cloud cover to the forecast for the rest of this evening based on latest satellite imagery. Also, raised min temperature forecast over southern New Hampshire. This area remains under a low level cloud deck in association with the warm air advection that is beginning over western portions of the forecast area. This band of clouds will allow for large fluctuations in temperatures overnight from west to the cooler readings east. Will continue to raise the wind forecast for the higher terrain. Mount Washington continues to report wind gusts in excess of 100 mph. While winds will diminish somewhat overnight, high winds will continue over terrain above 2500 feet. Prev Disc... Winds have been a bit gustier than anticipated earlier today, however the gusts are beginning to lessen as the pressure gradient relaxes. One final round of light snow coming from a mid level cloud deck will move east and out of the forecast area this evening. Ridge axis slides by tonight allowing winds to go nearly calm before returning southerly in the morning. A warm front will move through aloft bringing some clouds and warmer temperatures. For tonight`s lows we had to consider the very dry starting conditions and the likelihood of calm winds leading to at least a few hours of good radiational cooling particularly in the northeast part of the forecast area. But cloud cover arriving overnight will halt the cooling at least for half of the area, with temperatures holding steady or slowly rising by morning. Expecting mostly 20s tonight, but some teens are expected in the valleys of northwest Maine.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
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Much warmer temperatures can be expected on Tuesday as a warm front lifts north of the area, putting us fully within the warm sector of the approaching wave. Fairly strong southwesterly low level flow will also aid in downslope warming to the east of the mountains. We are going with high temperatures in the 50s tomorrow, which represents mixing up to about 925 MB. Even warmer air exists above that, and if we were to mix to 850 MB temperatures in the 60s would be observed. However, mixing to 850 MB is tough to do this time of year only one month away from the winter solstice. Thus low to mid 50s seem the most reasonable for tomorrow. Southwest winds will be breezy again, but not as windy as the past few days. A few gusts to 30 MPH are not out of the question. With the cold front approaching from the west the pressure gradient will remain tight enough and clouds will increase enough to prevent strong cooling overnight. Lows will drop only into the 30s for most areas, though a few upper 20s are also possible in the colder north. The front will be knocking on the doorstep of New Hampshire and the Canadian border of Maine around dawn with a line of showers possibly forming along the front. This may take the form of a brief squall, but overall precipitation amounts would be light considering the lack of a good moisture connection with this system...yet.
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&& .LONG TERM /WEDNESDAY THROUGH MONDAY/... The long term period is dominated by fast flow across the region with fairly dry conditions for much of the period. A cold front will cross the region Wednesday. Although the models agree that the front will cross the region, models differ on the timing of the front and the effect of Atlantic moisture streaming northward ahead of the front. GFS and NAM keep this moisture off the coast while ECMWF brings it inland. Have used a blend of models across coastal areas with the likelihood of some morning showers across coastal areas. In the mountains, precip type is a bit questionable early Wednesday with temperatures near freezing but any precip should turn to snow showers as colder air moves into the region during the morning hours. Any snowfall accumulations in the mountains should be light. The front moves east Wednesday afternoon with any remaining showers ending early afternoon across the midcoast. High pressure builds across the area Thursday with another weak front crossing the area Thursday night or Friday morning. High pressure slips south of the region during the day Friday with another weak front crossing the area Saturday. The generally dry northwest flow is expected to continue into early next week. After Wednesday morning, the greatest chances for any precipitation will be in the mountains with the passages of cold fronts. && .AVIATION /04Z TUESDAY THROUGH SATURDAY/...
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Short Term...Gusty west northwest winds will diminish this evening with VFR conditions continuing. A southwest breeze will commence tomorrow morning. Where there is an inversion, mainly over New Hampshire, LLWS can be expected with strong gusty winds above the surface switching to the southwest. A cold front approaches from the northwest by Wednesday morning. Long Term...MVFR to IFR conditions possible Wednesday morning across coastal areas. MVFR to IFR conditions possible in mountain snow showers Wednesday. Otherwise...mainly VFR conditions expected.
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&& .MARINE... Short Term...The pressure gradient will continue to relax enough to allow gusts to fall off. Have therefore, discontinued the gales. With the offshore flow, wave heights will be greatest further from shore. Winds become southwesterly on Tuesday and will likely reach solid Small Craft Advisory criteria. Long Term...SCA conditions will persist in the offshore zones for much of the period in mainly northwest flow. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 5 AM EST Tuesday for ANZ150>152-154. && $$ JC

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