Area Forecast Discussion
Issued by NWS Burlington, VT

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612 FXUS61 KBTV 042012 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 312 PM EST Sun Dec 4 2016 .SYNOPSIS... Weak high pressure across the area gives way to a weakening warm front that moves into the region on Monday morning with widespread light snow and flurries through the midday. Weather will remain active as we move through the work week with several additional systems bringing renewed chances of light rain and snow. && .NEAR TERM /THROUGH MONDAY/... As of 239 PM EST Sunday...Low level cloud cover in around the region is finally beginning to show breaks with some rarely seen sun peering through many locations right now. Weak northwesterly flow associated with weak high pressure is beginning to shift southwesterly in the St Lawrence Valley as the high shifts out ahead of the approaching warm front. Cloud cover will return shortly after midnight from the south and with that small window of clearing low temps should level out at the mid 20s in the valleys with the higher elevations and NEK dropping to the high teens. Models remain generally consistent with timing of this system with light precipitation overspreading the southwestern half of the forecast area before sunrise on Monday before making its way into the Champlain Valley in time for the morning commute. Thermal profiles continue to be plenty cold enough such that p-type will be all of the light snow/flurry variety with a light accumulation of a dusting to less than 2" across the valleys while higher elevations can expect 2-3" by mid day on Monday. While these amounts are light overall the timing could lead to a slick and slower morning commute to start the work week and as such drivers should take extra caution and time in reaching their destinations. Stuck with blended guidance for high temps on Monday with highs in the lower to mid 30s in the valleys and upper 20`s in higher elevations. Winds look to remain light throughout the period. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 226 PM EST Sunday...The forecast challenge this period will be amount of leftover low level moisture and potential for areas of flurries/freezing drizzle monday night into tuesday...followed by slow clearing by Tuesday afternoon. Best deep layer moisture and lift associated with short wave energy and weak surface reflection will be well northeast of our region by 00z Tuesday...but soundings show plenty of low level moisture between surface and 850mb. Given the lack of any moisture in the favorable snow growth region and thermal profiles supporting temps at or below 0C...thinking areas of flurries and freezing drizzle are likely...especially mountains. Froude suggests flow is highly blocked with values <0.50...supporting low clouds and light precip back into the Champlain Valley on Monday Night. Will mention chance pops with flurries/freezing drizzle as the predominant precip type at this time. 2m temps support lows mainly in the 20s mountains to near 30f champlain and saint lawrence valleys. The question on Tuesday becomes how long the low level moisture prevails and the areal coverage of low clouds. A weak short wave ridge aloft and at the surface builds directly overhead...resulting in very light winds...with some moisture trapped below thermal inversion. Given recent trends will delay clearing until late afternoon...champlain valley and northeast kingdom...but given depth of moisture...some of the higher summits could break out by midday. Temps will be highly depend upon clouds...but will trend cooler...with highs mainly in the 30s. By Tuesday evening...clouds and precip associated with our next weak short wave energy and ribbon of mid level moisture is quickly overspreading our region. Thinking light snow arrives southwest Saint Lawrence County by 00z Weds and quickly lifts from southwest to northeast across our region by 06z Weds. Latest trends show best dynamics and moisture splitting our region to the northwest or southeast...so only expecting light precip amounts. Generally a dusting to several inches in the mountains...with maybe a spot 3 or 4 inches down by Killington. Expecting little change in temps with clouds/precip with low mainly in the 20s mountains and near freezing valleys. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 226 PM EST Sunday...Any leftover precip on Weds morning will end as a period of light valley rain and mountain snow by 15z Weds. Any additional light snow accumulation will be confined above 1500 feet as bl temps warm into the mid/upper 30s by midday. A few slippery spots are possible during the weds morning commute...but overall impacts should be minimal. Still anticipating large scale mid/upper level trof to develop across the eastern conus by late week into next weekend...with temps trending toward below normal values...especially by next weekend. This transition will come with a period of unsettled weather on Thursday...with additional terrain focused snow showers for Friday into Saturday. Our coldest airmass of the season is still anticipated Saturday Night into Sunday...as progged 850mb temps drop between -15c and -17c. Both CMC/GFS 12z runs show a much weaker and unphased system for Thursday...with a period of snow showers expected associated with potent short wave energy and some mid level moisture. Will continue to mention likely pops with some accumulation expected over the mountains...but the lack of organized surface low pres and fast confluent flow aloft will limit significant deep layer moisture from being advected into our region. Progged 850mb and 925mb temps range between -8c and -10c on Thursday supporting highs mainly 20s mountains and 30s in the valleys...very close to normal. By Friday...favorable upslope winds of 30 to 40 knots develop with plenty of lingering 925mb to 700mb moisture leftover in mid/upper level trof axis. This moisture combined with cold air advection helping to squeeze out remaining moisture in the column will produce occasional snow showers mainly in the mountains. While not expecting heavy accumulations...several rounds of 1 to 3 inches of accumulating snow can be anticipated in the mountains given the large scale synoptic pattern. A dusting to an inch or so possible in the valleys. Progged 850mb temps drop between -13c and -15c by 18z Friday...supporting highs mainly teens mountains to upper 20s/near 30F warmer valleys. Saturday/Sunday...Similar to yesterday`s data models come back into better agreement over the weekend...with 1035mb surface ridge building directly overhead by 00z Sunday. This idea supports a general drying trend on Saturday into Sunday...with temps running about 5 degrees below normal based on 850mb temps around -16C. If skies can clear with surface high pres directly overhead with light winds...expect temps could approach near 0F at slk/colder valleys of the Northeast Kingdom by Sunday Morning. At this time will keep lows mainly in the single digits and teens...but could be colder. Lots of uncertainty develops with split flow for Sunday into early next week and associated timing of our next system. Highs only in the teens mountains and 20s valleys for both Saturday and Sunday. && .AVIATION /20Z Sunday THROUGH Friday/... Through 18Z Monday...Overall MVFR/VFR will linger through 20-22Z, then trending to VFR overall by 00Z. VFR will be short lived as thickening/lowering OVC returning after 08Z-11Z Monday and light snows/IFR arrive across the region. Light winds less than 10 knots for the entire period. 18Z Monday through 00Z Tuesday...Widespread MVFR/IFR in periods of light snow/flurries with a possible mix with light rain at KBTV/KPBG/KRUT. 00Z Tuesday through 12Z Tuesday...BKN/OVC VFR/MVFR with scattered flurries. 12Z Tuesday through 06Z Wednesday...VFR/high pressure. 06Z Wednesday through 00Z Thursday...trending MVFR/IFR in rain/snow showers. 00Z Thursday onward...Mix of VFR/MVFR/IFR in periods of light rain/snow. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...MV NEAR TERM...MV SHORT TERM...Taber LONG TERM...Taber AVIATION...MV

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