Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 202131 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 431 PM EST Mon Nov 20 2017 .SYNOPSIS...
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Light snow will gradually diminish as the night wears on tonight. Milder but breezy weather is expected for Tuesday. A cold front will come through the region late Tuesday night and Wednesday, bringing a few rain and snow showers. Thanksgiving Day is expected to be dry with temperatures in the 30s.
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&& .NEAR TERM /THROUGH TUESDAY NIGHT/...
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As of 431 PM EST Monday...Quick update to keep more light snow around through the evening hours with an inch or less most areas...but another 1 to 2 inches in the mountains...especially over parts of the northern and central Green Mountains. Previous Discussion... Well, still trying to play some catchup with the combo Lakes Superior/Huron snow band that has moved across northern NY and now into northern VT. The snowfall intensity and coverage has ended up being more than even the hi-res models indicated, at least here locally in the Champlain Valley and along the western slopes. Given that it`s snow, radar doesn`t detect it very well, so it wasn`t until it started snowing here in the Champlain Valley that we could "see" it on radar. Appears that there was some blocked flow that developed as well. That said, it appears that using the GOES-16 IR channel has been working well by using the -25C cloud top temperatures to show where the best snows are occurring. Over the last hour, the overall trend has been for cloud tops to start to warm. Although the hi-res models were doing fairly well earlier this morning, they have totally missed the snow here in the Champlain Valley and across the Green Mountains. Have tried to enhance coverage of the snow above what the models give, but even then, I`m still too low. Will probably continue to forecast chase the snow band over the next few hours. However, by this evening, wind flow will turn more southwest and be disruptive to the bands that are out there. So as we go on toward midnight, we will only be left with clouds and a few flurries, especially across northern NY. Southerly flow strengthens on Tuesday as the pressure gradient tightens due to high pressure moving off the coast, and our next weather system moving into the Great Lakes. Model soundings indicate 35-40 knots of wind between 925-850mb, especially in the Champlain Valley as topographically forced winds develop. Won`t mix down all of that to the surface, but it will result in a breezy day -- likely gusts to 30-35 mph. Southerly winds will bring in a warmer airmass, with highs well into the 40s across the region, even around 50F in the Champlain and St Lawrence Valleys. Precipitation ahead of a cold front will start moving into northern NY Tuesday evening, reaching the Champlain Valley by midnight. Boundary layer temperatures will be warm enough that it will be all rain, with snow only above 2500-3000 feet. The actual cold front will be a few hours behind the precipitation. So in the pre-dawn hours on Wednesday, expecting the rain to turn into snow showers across most of northern NY, with snow levels decreasing across Vermont.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 259 PM EST Monday...A weak cold front from a clipper system will be tracking through the North Country Wednesday morning. That front should bring light showers through the morning hours on Wednesday. With 925mb and 850mb temps warmer than 0C by 12z Wednesday, anticipate generally rain showers with some snow mixing in generally above 2000 ft. Behind the front, weak cold air advection will bring colder temps back to the North Country. Temps should gradually fall through the day with morning highs mainly in the mid/upper 30s, dropping to the upper 20s to mid 30s by sunset. As we move into the evening hours high pressure should start to build in, and the precip should come to an end. Total snow accumulations should be minor with an inch or less anticipated. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 334 PM EST Monday...Expect an active pattern heading into the weekend with fast flow aloft and several clipper-type systems tracking to our north bringing warm fronts and cold fronts through the North Country. The Thanksgiving holiday should be relatively quiet as high pressure moves to our south but but the evening hours another upper level trough and surface clipper will slide through bringing a brief shot at precip generally in the higher elevations. We see a quick break in the action on Friday before another system starts to deepen and track over the Great Lakes. Guidance is trending towards this clipper tracking a good bit north of the Saint Lawrence valley and with that low pressure track, anticipate much of the same with warm air advection bringing a widespread rain followed by a sharp cold front. With the cold front rain showers will become snow showers, and freezing temperatures surge in behind causing the potential for icy travel conditions Saturday night into Sunday. && .AVIATION /22Z MONDAY THROUGH SATURDAY/... Through 18Z Tuesday...Flight conditions are all over the place thanks to a couple of bands of light snow. As an example, it`s IFR with 1/2sm in snow at BTV, while across the lake it`s P6SM BKN049 at PBG. These bands of snow will tend to slowly diminish over the next 6 hours as they stretch west to east and waver slightly north and south. Eventually, generally after 03z, conditions will transition to VFR most everywhere. May take until 06-08z for SLK and MSS for VFR. For Tuesday, primary weather item will be developing gusty south winds. Expecting 25-30kt gusts, especially in the Champlain Valley. Outlook... Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Chance SHSN. Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA, Chance SHSN. Wednesday Night: Mainly VFR, with local MVFR possible. NO SIG WX. Thanksgiving Day: Mainly VFR, with local MVFR possible. NO SIG WX. Thursday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Friday: Mainly VFR, with areas MVFR possible. Slight chance SHSN. Friday Night: Mainly VFR, with local MVFR possible. Chance SHRA, Slight chance SHSN. Saturday: Mainly VFR, with areas MVFR possible. Likely SHRA, Likely SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Nash NEAR TERM...Evenson/Nash SHORT TERM...Deal LONG TERM...Deal AVIATION...Nash

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