Area Forecast Discussion
Issued by NWS Portland, ME

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158 FXUS61 KGYX 222139 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 539 PM EDT Sat Oct 22 2016 .SYNOPSIS... Low pressure will gradually lift north into Canada tonight. On the backside of this system...colder air will arrive on gusty west to northwest winds for the latter part of the weekend and early next week. Some accumulating snow will be possible in the mountains Saturday night into Sunday night. A large Canadian high pressure system will then dominate the region through midweek next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Update...I have adjusted the forecast to better match latest radar trends. Upper trof axis is crossing the Wrn portions of the forecast area at this time. Forcing ahead of it is leading to a couple bands of showers/rnfl. I updated PoP to walk that banded inflow rnfl out of the area. Behind the trof axis...dynamic cooling will start to drop freezing levels. MWN has already fallen 11 degrees in the last hour to 34. Colder air will work in from the SW...kind of an odd angle of approach...but precip at elevation will gradually change to snwfl. Already seeing observations report PSF and SLK...and expect that trend continues into the night. I have also updated snwfl grids for the mtns hour by hour to capture the cooling trends. I also would not be surprised if subsequent updates require a little more snwfl in the grids for higher terrain around EEN. Previous discussion...Showers will continue to rotate through all portions of Maine and New Hampshire through this evening. Surface dew points will remain in the 50s into this evening over eastern portions. Have included a slight chance of a thunderstorm as the dynamic upper low crosses our area. The axis of precipitation will then shift to northern and western areas as moisture raps around the surface low as it continues to gradually strengthen and exit through northern Maine. Sufficient cold air advection and wet bulb effect to trigger a changeover from rain showers to snow showers across the high terrain. There will be accumulating snow over the highest peaks. Followed a blend of match mos guidance for overnight mins which will be much above normal for this time of the year.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Hazard potential: Gusty winds up to 40 to 45 mph, especially over the high terrain. Rivers will begin to recede from the recent heavy rains. Gradient aligns through a deep layer on Sunday as the surface and upper level features will be to our northeast. Increased mixing will allow for winds to increase after sunrise with cold air advection continuing. This will allow for wind gusts in the 40 to 45 mph, very close to wind advisory criteria. However, wind fields are not quite as impressive as they appeared a couple days ago. Coordinated with BTV and CAR, and do to uncertainty, will not be issuing a wind advisory at this time, however we will not rule out isolated to possibly scattered power outages. Precip will be mainly confined to the upslope portion of the mountains in a gusty west to northwest flow. Expected some accumulating snows in the mountains to continue as H8 temperatures drop to -6C in the mountains by sunrise Monday. && .LONG TERM /MONDAY THROUGH SATURDAY/... The models are in decent agreement on the longwave pattern through late next week. The upper trough initially over the northeast CONUS will gradually lift out into the maritimes for the second half of the new work week. An upper ridge will briefly traverse the region Thursday. By early Friday...shortwave energy will approach from the Great Lakes and eventually carve out another upper trough over the eastern CONUS for next weekend. Overall...the upper pattern will support temperatures near or slightly below average for the period. In the dailies...low pressure surface and aloft over eastern Canada will provide cool unsettled weather in cyclonic flow...with the most persistent clouds and precipitation across the higher terrain. By Wednesday night...clearing and cold as heights begin to rise with arrival of high pressure. Thursday looks to be the pick of the week with a sunny start as the ridge crests across the area. Clouds will be on the increase during the afternoon from west-to-east ahead of our next disturbance approaching from the Great Lakes. We`ll see light overrunning precipitation arrive Thursday night. The forecast thermal properties across the higher terrain suggest it could begin as some wet snow and sleet before transitioning to plain rain. Onshore flow and a slow- moving frontal system promise a damp cool day to round out the workweek. Whiles the numericals diverge on shortwave timing and strength for the upcoming weekend...proximity of the longwave trough supports a cool and unsettled weekend for the forecast area. && .AVIATION /22Z SATURDAY THROUGH THURSDAY/... Short Term...IFR conditions gradually improving this evening over southern and central areas to VFR. Low ceiling and visibilities in -shrasn will allow for IFR and even periods of LIFR conditions in the north and perhaps far western areas. Long Term... Mon - Wed...Areas of MVFR psb mainly in mtn -shra/-shsn. Mon - Tues...Daytime NW sfc wnd gusting to 25 kt. && .MARINE... Short Term...Persistent W flow will keep an extended period Gales which will persist into Sun night. Gales over the coastal bays through Sunday with cold air advection and an increased gradient over the waters. Long Term... Mon - Wed...Small Craft conditions are likely. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...Gale Warning until 6 PM EDT Sunday for ANZ151-153. Gale Warning until 7 AM EDT Monday for ANZ150-152-154.
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&& $$ NEAR TERM...Legro is the U.S. government's official web portal to all federal, state and local government web resources and services.