Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 250812 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 412 AM EDT Tue Oct 25 2016 .SYNOPSIS... A trough of low pressure will continue to produce brisk winds and chilly temperatures through midweek with scattered mainly mountains snow showers. Temperatures will be in the 30s mountains to lower 40s valleys today and Wednesday. A widespread precipitation event is expected on Thursday into Friday with some snow accumulation likely in the mountains and breezy southeast winds along the western slopes. && .NEAR TERM /THROUGH TONIGHT/... As of 347 AM EDT Tuesday...Water vapor shows deep cyclonic flow associated with mid/upper level trof across the northeast CONUS...with sharp moisture gradient from very dry air central NY to some mid level moisture northern New England. The combination of this moisture...with favorable upslope flow will produce mainly mountain focus snow showers today. So far activity has been very limited due to the very dry low levels and lack of upper level support. Thinking as weak embedded vort in the flow aloft drops across our northern cwa between 15z-20z today and interacts with some instability from surface heating...scattered valley rain and mountain snow showers will develop. Hi resolution composite reflectivity progs show popcorn nature to returns...with greatest concentration over the northern mountains. Will continue to mention likely pops northern green mountains from Mansfield to Jay Peak with a dusting to several inches possible. Elsewhere...will mention slight to chance pops...with some enhancement possible on the east side of Lake Champlain associated with lake effect. Would not be surprised to see a few wet snow flakes in the valley....given the chilly 925mb to 850mb thermal profiles. Models in good agreement of values between -7c and -9c today at 850mb and -1c to -3c at 925mb...these temps support highs low/mid 30s mountain towns and upper 30s/lower 40s warmer valleys. Still expecting breeze northwest winds at 10 to 20 knots with some locally higher gusts especially midday. Tonight...areal coverage of any leftover precip will dissipate by drier air at all levels develops across our region. Will mention chance pops mainly in the mountains...and will still need to watch the potential for some lake effect clouds and flurries on east side of champlain overnight. Temps will cool into the lower/mid 20s mountains to lower/mid 30s valleys. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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As of 411 AM EDT Tuesday...Wednesday and Wednesday night will likely be the quietest 24 hours of the next 7 days as a brief area of high pressure both at the surface and aloft swing through the North Country. The day will begin fairly cloudy across the higher terrain with perhaps a few mountain snow showers lingering, while in the deeper Saint Lawrence and Champlain Valleys some breaks in the clouds will be developing. By the afternoon low/mid level moisture will be decreasing with cyclonic flow aloft trending to anti-cyclonic as an upper trough exits to our east and high pressure builds in. Strong cold air advection remains in place on brisk northerly flow so expect highs to continue to run well below normal in the low 40s across the deeper valleys to upper 30s elsewhere. Wednesday nights temps follow suit, running about 5-10 degrees below normal, mainly in the 20s to locally around 30 in the Champlain Valley along Lake Champlain, to upper teens in the coldest hollow of the Northeast Kingdom and northern Adirondacks.
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As of 411 AM EDT Tuesday...Thursday onward through the weekend the pattern becomes quite active again with mean troughiness redeveloping aloft across the eastern CONUS and 2 clipper-like systems bringing mixed precipitation to the North Country. The first and more robust system comes Thursday mid-day through Friday as low pressure develops out of the Great Lakes/Ohio River Valley region and tracks northeast to the Maine coast by Friday night. Precipitation along a warm frontal boundary works its way into the area fairly quickly by mid-day on the nose of a strong 40- 50kt 925-850mb south-southeasterly jet with thermal profiles initially supporting a mix of rain and snow in the valleys and snow at the higher summits, but by the afternoon and overnight the ptype forecast become a bit more tricky. Latest trends in NWP guidance indicate a warm nose slightly above 0C at 925-850mb works in after 00z and this coupled with marginally warm boundary layer temps supports rain in the deeper valleys and a mixed bag of rain/snow with possible brief periods of sleet and/or freezing rain across the Adirondacks and eastern Vermont. As the low pushes east on Friday, temps aloft support a transition back to snow for the summits, but the boundary layer remains too warm at the surface supporting showers/rain as precip becomes more orographic in nature on developing northwest flow. Early thoughts on storm totals through Friday show the highest elevations the big snow winners with 6-8" along the Green Mountain spine, to 8-12" across the high peaks of the Adirondacks. Below 1500 feet, a dusting to perhaps 2" is possible outside of the Champlain and St. Lawrence Valleys. The strong jet mentioned above also presents the potential for gusty downslope winds along the Green Mountain spine Thursday night, but currently coincides with the bulk of precipitation falling which limits mixing potential. While I think winds will be gusty across the southeast downslope communities along the western slopes, overall impacts should be minimal with gusts peaking only in the 20- 30mph range. Next system looks to swing through Saturday through Saturday night, taking a more northern track than its predecessor, offering even warmer thermal profiles, enough to produce mainly rain showers with highs pushing into the mid/upper 40s. Behind it, high pressure looks to return for Sunday night into Monday.
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&& .AVIATION /08Z Tuesday THROUGH Saturday/... Through 06z Wednesday...Mainly vfr conditions with occasional mvfr possible at mpv/slk this morning associated with lowering cigs and chances for mountain snow showers. The limited moisture both at the surface and aloft will limit impacts on tafs with regards to vis/cigs. Otherwise...still expecting breeze west to northwest winds 10 to 20 knots with a few higher gusts through today...before decreasing around sunset this evening at 4 to 8 knots. Outlook 06z Wednesday through Saturday... Active weather pattern continues with vfr trending toward mvfr/ifr Thursday into Friday. Expecting a period of snow at most sites on Thursday afternoon...with vis between 1-3sm...before changing to rain in the valleys by evening. Also...gusty southeast winds are possible...especially at rutland...creating areas of low level wind shear and turbulence. As winds shift to the northwest on Friday...ifr cigs are possible at BTV/RUT/SLK/MPV with areas of scattered rain or snow showers. Next system arrives late Saturday with additional precipitation and breezy southwest winds. Occasional mvfr/ifr conditions are likely by late Saturday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Taber SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Taber is the U.S. government's official web portal to all federal, state and local government web resources and services.