Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 150004 AFDGYX Area Forecast Discussion National Weather Service Gray ME 704 PM EST Tue Nov 14 2017 .SYNOPSIS... High pressure builds in from the north through Wednesday and continues the cool weather. The next storm system will drag a cold front towards the area on Thursday. Mainly rain with some interior snowfall is expected with the system. However...it is possible that this system strengthens near the coast...which could bring colder temperatures and a little more in the way of frozen precipitation. Cold high pressure builds in again for Friday before the next system arrives this weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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7 pm Update: Adjusted sky grids to reflect cloudy conditions through the evening as per latest obs and satellite imagery inidicate. Temps will only very slowly fall due to cloud cover this evening. Input latest mesonet data with no other changes needed at this time. Previous Discussion: Surface ridging continues to build in while upper low passes overhead. These conflicting wx features complicate the forecast for tonight...mainly as it relates to cloud cover and temps. Drier air is trying to bleed into the region from the NE...but upper low aloft is pooling moisture and creating weak lift enough to continue overcast skies. Upper low is not forecast to pass E of the forecast area until after 06z. So I expect clouds to linger thru at least then. There is also not much impetus to mix out the cloud deck...so I have increased clouds thru about 12z when daytime heating and Sly flow should help. That will keep lows from tumbling overnight under the high pressure. That being said...any breaks in the clouds will allow temps to drop quickly...but these are not expected to be widespread.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... High pressure will be in control Wed...with remaining clouds scattering out. Still not expecting temps to warm all that much...despite return flow. Wed night ridging surface and aloft slides E...and allows the next trof to approach from the W. It is a well defined s/wv...but at this time ridging looks to hold off precip until closer to 12z. Sly flow will keep temp trend closer to non- diurnal...with temps possibly rising overnight. Despite that temps will initially be cold enough across much of the interior for precip to start as snow. The highest QPF and thus snowfall amounts will mainly be in the mtns...where upslope flow will enhance lift before the main trof arrives. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The deterministic models are now in decent agreement on the long wave pattern through the upcoming weekend. We begin the period with an upstream shortwave impulse approaching from the eastern Great Lakes on Thursday. The associated surface low will track northeast into eastern Canada while the trailing warm and cold front sweep east into New England along with an occluding warm sector. BUFKIt forecast soundings suggest a rain/snow mix across the interior with rain along the coast. A triple point low develops over the Gulf of Maine late Thursday. The frontal system and ocean low exit into the maritimes Thursday night with upslope snow showers across the higher terrain producing several inches of snow before ending Friday morning. Shortwave ridging follows for Friday along with more cool...dry weather and gusty northwest winds. Meanwhile...digging shortwave energy enters the Pacific northwest on Thursday and eventually carves out a deep trough over the central CONUS by the start of the upcoming weekend. At the surface...deepening low pressure will cross the Great Lakes and move into eastern Canada. The trailing warm and cold fronts will sweep into New England on Saturday. Of note...the models have backed off on the idea of a secondary low developing near the coast Saturday night. With more warm air now expected...there should be a brief mix to rain across the mountains with a rain event for the remainder of the forecast area. Gusty onshore winds remain possible Saturday night and early Sunday...especially along the coast east of Casco Bay as the cold front sweeps offshore. In the wake of this system...upslope snow showers are likely in the cyclonic flow Sunday and Monday. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Short Term...Surface high pressure continues to build into the region though abundant low level moisture remains trapped. CIGs are expected to be BKN to OVC most of the night...but CIGs should remain VFR. VFR conditions continue Wed into the first part of Wed night. Late in the period the next approaching system will spread MVFR conditions from W to E...with areas of IFR developing across the interior where -SN is possible. The best chance for IFR will be after 06z. Long Term... Thu...MVFR in -ra and MTN -ra/-sn with lcl IFR. Fri...NW Sfc wind gusting to 25 KT. Sat...MVFR with lcl IFR in rain and fog. S sfc wind gusting up to 30 kt psb at coastal TAF sites. Sun...VFR with lcl IFR in Mtn -shsn. && .MARINE... Short Term...NE flow continues on the waters...and will continue overnight into Wed. A few gusts near 20 kts and seas 3 to 5 ft are expected tonight. Winds seem to be just enough off shore to prevent seas from building higher than 5 ft...so no SCA anticipated. Flow becomes Sly Wed and will start to increase late ahead of the next system. Long Term... Thu...Small craft conditions are likely bays with gales possible on the open waters. Fri...Small craft conditions are likely. Sat PM - Sun AM...Small craft conditions are likely bays with gales possible on the open waters. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Marine

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