Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 160227 CCA AFDGYX Area Forecast Discussion...CORRECTED National Weather Service Gray ME 927 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...Onshore flow continues. With moist low levels and convergence over land...weak low level lift is resulting in persistent snowfall. Much like the miserable mist we see in the spring time with cold...onshore flow. 00z GYX sounding shows a saturated layer only around 100 mb thick...1000 to 4000 ft agl. But just about all of it is colder than -10C. This layer also features unidirectional due E flow. Aside from NE winds at the surface...that is the only Ely component to wind in the entire sounding. Until we lose that Ely flow...the snow will likely continue. Forecast models are far to Nly with low level winds at the moment...which is why there is a lack of guidance supporting snowfall. Forecast soundings do show that after 06z...very low level winds above the surface try and become more Wly. I suspect that despite these winds being biased a little too Nly...they show the general trends of veering flow and a gradual weakening if not end of onshore snowfall. 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 /02Z 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... 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. && $$ NEAR TERM...Legro

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