Area Forecast Discussion
Issued by NWS Portland, ME

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419 FXUS61 KGYX 152244 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 544 PM EST Mon Jan 15 2018 .SYNOPSIS... Low pressure will develop off the mid atlantic coast Tuesday and then intensify as it moves northeast through the Gulf of Maine Wednesday. High pressure builds eastward into the region late in the week and into the weekend with a return southwest flow bringing warmer temperatures by the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
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Update...Shallow moisture in onshore flow is producing some very light snow across parts of Wrn ME and will eventually move into SErn NH. AMDAR soundings in the vicinity of BOS are showing the stratus layer to be only around 1000 to 1500 ft thick...so very little snowfall is expected from this deck. But I have added very light snow wording to the forecast...with slightly higher PoP over the foothills where some orographic lift may help increase the depth of the moist layer. Previous discussion...Arctic high pres anchored well to the north will continue to produce a light northeast flow through tonight helping to continue spreading some low clouds from the Bay of Fundy and off the coastal waters into southern and central areas of ME/NH. There may be some flurries or very light snow with this cloud deck as well, but accumulations are not expected at this time. Also, high clouds will be spreading east into the western areas of the region later this evening from the approaching upper trof to the west. Due to the arctic dome anchored to the north and nosing south into the area tonight, another cold night expected. But, temps will not be as cold as last night due to the clouds. A blend of guidance temps seemed reasonable with overnight lows ranging from about 5 below in the mountains to around 10 above along the coastal plain.
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&& .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... On Tuesday skies will be generally mostly cloudy as a southwest flow aloft develops ahead of the digging positively tilted, progressive, long wave trof over the Great Lakes. With weak WAA overunning developing in the afternoon, some light snow may begin to develop across NH. Temps will be warmer with highs in the 20s. Tuesday night the upper trof approaches the mid atlantic coast spawning low press off the DELMARVA peninsula. This low will deepen as it moves northeast toward Cape Cod by Wed morning. Snow will overspread the forecast area from south to north Tuesday night and may become heavy at times after midnight through Wednesday morning. Of note: Models that have been further east the last few days have generally come in line today with the EURO solution of keeping the track of low pres closer to the coast and also deeper. Latest 12z Euro run is even further north thus the increased confidence for the Winter Storm Watch issuance at this time. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Snow, possibly heavy at times is expected for the Wednesday morning commute in the watch area, with light to moderate snows to the NW. In general, 4 to 8 inches of snow is expected across our forecast area, with locally higher amounts possible in the Monadnocks. This system will be a pretty fast mover so most of the accumulating snow will end by mid-late Wednesday afternoon - sooner across western and southern zones. Thereafter, a long stretch of dry (or mainly dry) weather is expected through the weekend along with a warming trend. The next system of interest continues to be advertised on a good portion of the 12z model suite in the Mon-Tue timeframe. This could be a mix to rain type event, but changes at this time range are pretty certain. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... Short Term...Some MVFR cigs expected at times tonight into Tue over southern and central areas of ME/NH while further north VFR conditions will prevail. By late Tue and Tue night conditions will deteriorate to IFR as snow overspreads the area from S-N. Long Term...IFR or lower expected Wednesday morning in snow before improving to VFR from sw to ne Wed afternoon and evening. VFR expected Wed night through the weekend. && .MARINE... Short Term...Outer waters - SCA winds from the north will continue into this evening and then diminish but seas will be slow to subside until Tue morning. Tue and Tue night winds and seas will be light. In the bays - Winds will be light and seas below 5 ft. Long Term...SCA conditions are possible Wed through Thurs in the wake of low pressure moving into the maritimes. && .HYDROLOGY... All rivers but the Kennebec at AUG have fallen below flood stage, but ice jams have frozen into place in some areas, and rivers need to need to monitored as these jams could move without notice. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...Winter Storm Watch from Tuesday evening through Wednesday afternoon for MEZ012-018>028. NH...Winter Storm Watch from Tuesday evening through Wednesday afternoon for NHZ004>015. MARINE...Small Craft Advisory until 6 AM EST Tuesday for ANZ150-152-154.
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&& $$ NEAR TERM...Legro

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