Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 070443 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1143 PM EST Tue Dec 6 2016 .SYNOPSIS... A weak weather system will bring another round of light snow tonight and Wednesday morning to the region. Light accumulations are expected, which will lead to some slippery travel conditions. Additional snow showers are in the forecast for Thursday into Friday as colder air begins to moves in to the region. Significant snow accumulations are possible in parts of northern New York. The weekend is expected to be seasonably cold with scattered snow showers each day. && .NEAR TERM /UNTIL 6 PM WEDNESDAY EVENING/...
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As of 1137 PM EST Tuesday...Forecast remains on track. Leading edge of light snow has reached southern St. Lawrence County, and will continue to develop newd across the region during the next 1-3hrs. Continue to anticipate a few icy spots for the AM commute, and advise allowing extra time for traveling during the early morning hours. Previous Discussion...Mid-upper clouds are rapidly overspreading the North Country this evening from SW to NE in advance of shortwave trough across the upper Ohio Valley. Won`t see much cooling overnight as a result, with low temperatures near current values in the upr 20s to near 30F. Primary weather maker for the next 24 hours will be a burst of light precipitation associated with warm advection and a weak upper level trough. Composite mosaic radar reflectivity shows the leading edge of this precipitation extending from near KROC to KBGM at 2345Z. Current trends suggest snow will reach the Northern Adirondacks of NY around 05-06Z, and into the Burlington area/Champlain Valley by 07-08Z...consistent with previous shift expectations. All the hi-res models agree that as the precipitation shield lifts towards us, the intensity will be decreasing and starting to fall apart. this is best seen in the various "forecast radar" outputs. Total liquid precipitation is not expected to be all that much. Roughly 0.05-0.15" (highest totals south). It`s a "high PoP, low QPF" event. Profiles all suggest temperatures aloft will be cold enough for snow. Snow-liquid ratios will be running 9-12:1 or so. That suggests total snowfall will be 1/2" to just under 2" or so. As the night goes on, a low level southerly jet develops. This should help to reduce the overall amount of precipitation across the Champlain Valley. Though accumulations will be on the light side, timing suggests some slick spots for the morning commute. Temps generally rise above freezing by mid-morning, so localized issues with snow/icy spots will abate later in the morning. Precipitation tapers off quickly in the morning. Some of the snow may end as a little bit of sprinkles of rain or drizzle as the moisture depth decreases and we start to lose the ice formation ability within the clouds. Generally cloudy skies will remain however. Highs tomorrow should be a few degrees above normal, topping out well into the 30s and perhaps even close to 40.
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&& .SHORT TERM /6 PM WEDNESDAY EVENING THROUGH THURSDAY NIGHT/... As of 338 PM EST Tuesday...Primary feature influencing the North Country`s weather for the short term period will a strong mid/upper level trough swinging through the Great Lakes Wednesday night, and the northeast states Thursday through Thursday night. While little widespread/synoptic precipitation is expected, cold air advection behind a departing surface front combined with increasing southwesterly flow and warm Lake Ontario waters will aid in the development of a lake effect snow band early Thursday morning across portions of southern St. Lawrence and southern Franklin counties of Vermont. In addition, snow is expected to reach further downwind into northern Vermont, specifically around the Jay Peak region as the 850mb flow should be strong enough to support the transport of moisture there and will be enhanced by upslope processes. As the base of the upper trough swings across the BTV CWA Thursday, snow showers will become more widespread outside of the deeper valleys and likely a bit more convective as guidance is showing a little bit of CAPE, upwards of 100 J/kg across the higher elevations. Overall QPF for the event over a 24hr period from midnight Thursday to midnight Friday is less than a tenth for the valleys, but upwards of close to a half inch in the heart of the lake effect band and the northern Greens around Jay Peak. First guess at snow ratios puts us around 15:1 on average, yielding around 6-9" across southeastern St. Lawrence County prompting the issuance of a Lake Effect Snow Watch there. Across the rest of the area a dusting to and inch in the valleys is possible where snow may briefly mix with rain due to warm boundary layer temps, while portions of north-central and northeast Vermont could see 2-4" and the highest summits from Mount Mansfield to Jay Peak upwards of 4-6". && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 338 PM EST Tuesday...Overall the outlook for the end of the week and through much the upcoming weekend is a fairly good one with snow showers becoming more scattered through the day on Friday, and high pressure building in over the eastern seaboard for Saturday and Sunday. Upper flow remains out of the west/northwest so unfortunately we`ll likely see more clouds than sun with temps seasonably cool in the 20s for highs and teens to single digits for lows. Next potential system rolls into the area Sunday night, but exactly where the low tracks is still very much in question with global models in disagreement on the depth and strength of an upper trough shifting out of the central CONUS. Currently offering a blended approach with high chances for mainly snow Sunday night through Monday night, but that will certainly change as we dial in the forecast over the next couple of days. Stay tuned. && .AVIATION /06Z Wednesday THROUGH Sunday/...
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Through 06Z Thursday...Light snow will overspread the TAF locations from SW-NE between 06-09Z with developing IFR vsby (1-2SM) and HIR TRRN OBSCD. Light snow accumulations (1-2") anticipated over a period of 3-4 hrs...some impact expected to airport ground ops for morning pushback due to light snow accumulations. Snow will start to break up into more showery conditions after 14z Wednesday, and temperatures will warm above freezing at all TAF locations. Generally went with "VCSH" in the TAFs, but will see lingering MVFR ceilings for most locations with HIR TRRN OBSCD. South winds may gust 15-20kts in the Champlain Valley after late morning thru afternoon/early evening. Outlook 06Z Thursday through Sunday... Entire period - frequent MVFR ceilings. Scattered snow showers each day, resulting in localized IFR visibility and ceilings. Maybe extended period of IFR for SLK Wednesday night into Thursday night with frequent snow showers in vcnty of the nrn Adirondacks.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...Lake Effect Snow Watch from late Wednesday night through Thursday evening for NYZ029. && $$ SYNOPSIS...Nash NEAR TERM...Banacos SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Banacos

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