Area Forecast Discussion
Issued by NWS Portland, ME

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000 FXUS61 KGYX 191439 AAA AFDGYX Area Forecast Discussion...UPDATED National Weather Service Gray ME 939 AM EST Thu Jan 19 2017 .SYNOPSIS... High pressure will build in for the remainder of the week, with above normal temperatures expected into Monday. A storm system may affect the region beginning Sunday night and continuing into early next week. Gusty winds and mixed precipitation will be associated with this system, primarily Monday into Tuesday. An upper level trough may keep unsettled conditions over the region later next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Update...A few minor tweaks to bring forecast in line with latest observational trends. Some lingering snow continues over the Penobscot Bay region...but will quickly come to an end as s/wv trof passes E of the region. A few upslope snow showers are possible in NW flow behind it given the abundant low level moisture remaining. S/wv ridging quickly moves in late this afternoon and evening. Previous discussion...A short wave will move through the region this morning. As of 3 am widespread snow was falling across Maine with freezing drizzle in portions of New Hampshire. The snow will move through and out of the region in the next few hours with clouds lingering through the day time. Low level moisture will remain through the day. The short wave should be just enough to cut off the drizzle by mid morning but some isolated pockets may continue through the day.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... High pressure begins to build in from the southwest tonight. Warm air advection aloft will begin overnight. This will create a surface inversion trapping the residual moisture near the surface. Low clouds and fog will develop overnight especially in the mountain valleys. Have increased cloud cover and temperatures above the mostly clear guidance to account for this. Friday temperatures will begin to warm up but low clouds will remain especially in the mountains. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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Upcoming hazards: A complex weather system may affect the region early next week. Potential hazards include heavy rain, mixed precipitation and wind. A ridge of high pressure will remain just to our west, over New York State extending south through the Mid Atlantic region Friday night into Saturday morning. Nevertheless, warm air advection cloudiness will spill over the ridge and into Maine and New Hampshire. Colder air will then seep into the region in association with a backdoor cold front Saturday afternoon and Saturday night. There may be pockets of light snow, but any precipitation will likely be on the light side with little in the way of dynamics in the atmosphere and a limited moisture supply. This colder air will continue to advect southwards on Sunday, setting the stage for a mixed precipitation event next week. 00Z model runs have trended colder with the initial surge of precipitation on Monday. During this period, a large and anomalousarea of low pressure will track northeast to the Mid Atlantic region. With cold air in place and the wet bulbing effect, snow will break out across the region as a conveyor belt of strong easterly winds develops over the region. This pattern will allow warm air to overwhelm the coastline and portions of southern New Hampshire to change the precipitation over to rain. Although warming will continue aloft and limit the amount of snowfall Monday night, enough cold air will remain in the lower levels to allow for the whole gambit of mixed precipitation. Sleet and freezing rain will be possible over the interior with mainly rain falling along the coast. This mixed precipitation will retreat to the far north on Tuesday with rain falling in most other areas. There will be strong gusty winds Monday into Tuesday, especially along and near the coastline. Expect areas of heavy rain as well which may lead to rises on area rivers, potentially producing ice jam issues. Any precipitation will become light on Wednesday and change to snow as the system pulls into the Canadian Maritimes. Do not expect full time clearing as much weaker upper level low pressure systems will remain overhead and to our west during the mid/late week timeframe.
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&& .AVIATION /15Z THURSDAY THROUGH MONDAY/... Short Term...Low level moisture will remain trapped under a developing surface inversion as warm air tries to move in aloft. This will keep ceilings at or below MVFR through Friday night. Thursday evening IFR in FZFG is expected for the mountain valley locations including HIE and LEB. Expect an improvement to MVFR for the day Friday before IFR Fog returns again Friday night. Long Term...Mainly VFR conditions over the weekend. Widespread IFR conditions, with areas of LIFR developing early next week in association with the large area of low pressure along the Mid Atlantic coastline. There could be a period of LLWS as a low level northeasterly flow will dominate for a period on Monday across the interior. && .MARINE... Short Term...Winds have decreased by seas remain around 5-7ft so have continued the Small Craft for Hazardous Seas only. Seas will continue to subside as high pressure builds into the region through Friday. Long Term...An increasing east, northeast gradient will develop on Sunday. Gale force winds with possible storm force gusts are possible early next week. The persistent fetch from the east will allow for large waves to build. && .GYX WATCHES/WARNINGS/ADVISORIES...
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ME...None. NH...None. MARINE...Small Craft Advisory for hazardous seas until 3 PM EST this afternoon for ANZ150-152-154.
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&& $$ NEAR TERM...Legro

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