Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 171143 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 643 AM EST Fri Nov 17 2017 .SYNOPSIS...
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Colder air will is moving into the region today with mountain snow showers ending this morning. Sunshine and dry weather will return as the day progresses as a weak area of high pressure moves in. The next low pressure system brings another round of mainly rain possibly mixed with snow Saturday afternoon and evening and then back to snow showers at the back end of the storm. Also expect gusty winds for Saturday night and Sunday.
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&& .NEAR TERM /THROUGH SATURDAY/...
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As of 643 AM EST Friday...Forecast on track. Snow is ending in all but the mountains as drier air moves in on unstable NW flow so not expecting any additional accumulation except maybe an inch at the summits. Some icy spots possible on roads for the morning commute, especially across the wrn slopes of the Green Mtns where orographic enhancement and cooling temps will combine the most favorably. Sunshine should break out this afternoon as high pressure builds in across the mid-Atlantic and Northeast states. Winds remain brisk from the northwest, and this combined with air temps topping out in the 30s will create some wind chills through the day in the teens and 20s. The high crests over the region tonight with clearing skies for the first half of the night, and some high clouds moving in from the west ahead of our next system. Low temps a bit tricky with some scattered high clouds and developing southerly flow by morning but still expecting temps dropping into the teens and 20s area-wide while warm air advection riding in aloft will keep the highest peaks in the 20s warming into the lower 30s. On Saturday a bit of a complex warm advection pattern begins as low pressure tracks from IL to near DTW by evening. Increasing probabilities of precipitation from SE to NE. Could be a couple bands of warm frontal precip moving in by afternoon or early evening but should be very light until evening. Typical ENE St. Lawrence river valley channeling will develop with a bit cooler temps there but it`s looking like the delayed arrival will pretty much ensure most of us see light rain with high temperatures in the upper 30s to lower 40s, but can`t quite rule out a few patches of light rain/snow mix at the higher elevations if it cools to the wet bulb and starts earlier rather than later.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 400 AM EST Friday...Global 00Z models remain consistent in showing deep ~ 980 mb low pressure tracking into the St. Lawrence Valley Saturday night into Sunday with a variety of weather for the forecast area. This morning`s 00Z NAM deterministic run showing a more pronounced southerly surface low track remains a clear outlier and has been discounted once again. With the anticipated low track temperatures will hold steady in the lower 40s or slowly rise into the mid and upper 30s depending on locale into the overnight hours under increasing southerly flow. The only exception will be the far northern St. Lawrence Valley where pressure-driven channeling effects will likely keep stubborn northeasterly flow locked in much of the night as the low approaches. These trends are in close agreement with the latest GFS and ECMWF MOS-based guidance with a bit of our prior forecast thrown in for good measure. This supports widespread, mainly light to moderate precipitation mainly in the form of rain overspreading the forecast area Saturday evening into Saturday night. Any light snow or sleet would be very early on and at the highest elevations of the northern mountains. By 12Z Sunday the surface low should be situated near Montreal and will exit quickly northeast during the day pushing a very sharp cold front across the area during the morning hours. Impressive 3-hourly pressure rises from 3-9 mb immediately behind the front support persistence in showing winds trending quite gusty from west/northwesterly in the 25 to 40 mph range by late morning into the afternoon hours. Additionally, given the tight baroclinicity along the boundary a band of briefly heavy showers will be possible with this feature. Highs to range in the 37 to 42 range during mid- morning across the Adirondacks/St. Lawrence Valley before falling by late morning into the afternoon, and the lower to mid 40s across VT before falling as well by afternoon. As colder air pushes into the area some minor light snow accumulations will be possible across the Adirondacks and northern Greens to the order of a dusting to an inch or so. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 400 AM EST Friday...Sensible weather conditions then gradually quiet down Sunday night as parent upper trough pulls east and surface high pressure builds in from the upper Midwest and Great Lakes. Any lingering snow showers or flurries will end through the evening hours as skies gradually trend partly cloudy and gusty winds slowly abate overnight. Low temperatures by sunrise Monday seasonably chilly in the teens to lower 20s. After a tranquil though chilly day on Monday the typical up and down temperature roller coaster cycle of November re-asserts itself into the mid-week time frame. The mildest day should occur on Tuesday as high pressure slides off the east allowing southerly flow to boost readings into the 40s for most spots. A cold front will then cross the area Tuesday night into early Wednesday with a renewed threat of light rain/snow shower activity. Behind this front conditions trend mainly dry from Wednesday night onward into late week under a seasonably cold late Autumn airmass. An early look at the Thanksgiving holiday suggests partly cloudy skies and dry weather, though on the chilly side with temperatures mainly in the lower and mid 30s. No large scale travel concerns are expected. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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Through 12Z Saturday...Mainly MVFR with LCL IFR at SLK until 13-15Z then VFR as high pressure builds in. NW Winds will gust 20-25kts until late afternoon then winds go light/calm after sunset with SKC. A warm front aloft will bring high clouds perhaps as low at BKN100 at KMSS by 12z Sat. Outlook... Saturday: Mainly VFR, with local MVFR possible late. Chance RA. Saturday Night: Mainly MVFR, with local IFR possible. Definite RA, Likely SN. Sunday: Mainly MVFR, with local IFR possible. Windy with gusts to 35 kt. Likely RA, Chance SHRA, Chance SHSN. Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Monday: Mainly VFR, with local MVFR possible. NO SIG WX. Monday Night: Mainly VFR, with areas MVFR possible. NO SIG WX. Tuesday: Mainly VFR, with areas MVFR possible. Slight chance SHRA. Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Chance SHSN.
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&& .MARINE...
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As of 640 AM EST Friday...A Lake Wind Advisory remains in effect for today. Northwest winds at Colchester reef continue at 25 gusting to 30 knots and will continue through midday as cold air pours over the 50 degree lake waters leading to a very unstable boundary layer hence the gustiness. Winds will gradually simmer down this afternoon. Anyone out boating will need to be aware of the rough conditions that will result from the strong winds.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Sisson SHORT TERM...JMG LONG TERM...JMG AVIATION...Sisson MARINE...Sisson

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