Area Forecast Discussion
Issued by NWS Burlington, VT

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431 FXUS61 KBTV 240805 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 405 AM EDT Mon Oct 24 2016 .SYNOPSIS... A departing low pressure across eastern Quebec will allow for continued clearing this evening, along with diminishing wind speeds. A secondary trough moving into the region from the northwest late Monday into Monday night will bring a chance of light rain showers, with snow showers possible across the northern Adirondacks and northern Green Mountains. A more significant wave of low pressure approaching from the Great Lakes and Ohio Valley will bring the next chance for rain, generally late Thursday, Thursday night, into early Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 149 AM EDT Monday...Shortwave trough embedded in mid level flow passing to our south with an increase in clouds through the next few hours. These clouds along with W to WSW wind flow of 5-10kts keeping temperatures from dropping. Therefore, have increased the morning lows to low 30s mainly in the northeast kingdom and Adirondacks where fresh snowpack will help with cooling. In the broad valleys, expect temperatures to remain in the 40s. Generally quiet weather expected Monday. Broad cyclonic flow remains in place aloft, and it appears we`ll have another surge of low-level CAA and possible passage of weak mid-level shortwave trough. Shallow instability layer will produce clouds by afternoon and possible light upslope precipitation into the Adirondacks and nrn Green mtns. Freezing levels generally 2000-2500ft, so can`t rule out some flurries down to about 1000ft in elevation Monday aftn, especially wrn slopes. May see passing sprinkles in the valley locations, and kept PoPs generally less than 20%. High temps generally low-mid 40s, except upr 40s near Lake Champlain and with downslope warning effects across ern Windsor county/VSF area. Winds will be W-NW winds 8-15kts with gusts developing in the afternoon with presence of steeper lapse rates. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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As of 400 AM EDT Monday...A 1 to 2 STD below normal mid/upper height field associated with a trof across the northeast CONUS will continue to provide our region with below normal temps through midweek. The combination of favorable 925mb to 850mb upslope flow and ribbons of deeper layer moisture associated with cyclonic circulation will continue to produce terrain focused precipitation through Tuesday. The associated low level wind fields are between 20 and 30 knots on Tuesday result in limited low level forcing from upslope component...but weak embedded vort at 500mb and some low level cold air advection will be enough to produce light qpf across the mountains. Will mention likely pops for Tuesday...with qpf generally 0.20 or less across the northern dacks and western slopes...with only a trace to couple hundredths in the valleys. Thermal profiles show both 925mb and 850mb temps below 0c...with 850mb temps near -10c by 00z Weds...supporting mostly snow...except the valleys and near the warmer Lake. Speaking of Lake Champlain...some enhanced precipitation is possible on the east side of the lake with moderate instability created between the air/water temp difference...especially on Tuesday. Also...noted with boundary layer heating and cold air aloft...lapse rates steepen on Tuesday afternoon...supporting some convective elements with potential graupel in the valley. Thinking any snow accumulation below 1000 feet will be difficult during the daytime...but some minor accumulation above 1000 feet between a dusting to several inches is likely across the northern dacks and mountains of central/northern VT. Its never too early to start building the snow pack. Thermal profiles support about a 20 degree difference between lower/mid 20s mountains summits to lower/mid 40s valleys on both Tuesday and Weds...with lows mainly upper teens to lower 30s.
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As of 400 AM EDT Monday...Active pattern continues for days 4 thru 7 with additional chances for rain and snow on Thursday into Friday and another system next weekend. Overall...given the progressive west to northwest flow aloft...temps will stay below normal thru the period with additional chances to increase snow pack across the mountains...especially Thursday Afternoon. GFS/GEM and ECMWF in good agreement with potent 5h energy in the northern jet stream crossing the Great Lakes and NE CONUS on Thursday into Friday. Meanwhile...initial surface low pres tracks across the central Great Lakes with weak secondary development over southern New England by 12z Friday. The combination of 1036mb high pres over eastern Canada and developing secondary low pres...suggests warmer air will have difficulties advecting into our region...supporting potential for additional snow accumulations in the mountains. Sea level pres fields show a cold air damming signature. Latest ECMWF only briefly increases the 850mb temps to 0c around 06z Friday...before winds shift to the northwest and colder air follows. Current thinking a band of rain/mixed with wet snow flakes develops from southwest to northeast on Thursday...associated with moderate to strong warm air advection. The combination of evaporational cooling and progged 925mb to 850mb profiles below 0c initially supports even some wet flakes in the valley with no accumulation...before quickly turning over to rain. Meanwhile...cold air remains locked east of the greens and across the northeast kingdom with a longer duration of snow...with several inches of wet snow accumulation possible Thursday afternoon/evening...before changing over to rain. Mountain thermal profiles are tricky as progged 850mb temps stay near 0c...but warm nose around 5000 feet associated with southerly jet...supports some freezing rain possible near the summits of the dacks and greens on Thursday Night. It shall be interesting to see what the picnic table on Mansfield receives. Otherwise...the potential for gusty downslope southeast winds will have to be latest GFS shows 850mb winds of 40 to 50 knots. The strongest winds are collocated when precip will be falling and difficult to determine how much mixing will occur...but something to watch along the western slopes on Thursday afternoon/evening. Next system arrives late Saturday into Sunday with additional chances for precipitation and once again thermal profiles support mainly rain valleys and a mix in the 850mb 0c line bisects the area. Temps during the period mainly in the 30s mountains and 40s valleys with lows in the 20s to mid/upper 30s.
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&& .AVIATION /08Z Monday THROUGH Friday/... Through 06z Tuesday...VFR conditions persist with potential for intervals of MVFR ceilings at SLK for the next few hours. Westerly winds continue at 5-10kts til mid morning, when winds shift a little more NW at 8-12kts with gusts up to 25 knots during the day. Generally VFR conditions prevail, but some low level clouds develop in the cold air advection between 3500-5000 ft after 15Z. Chances for showers to develop increase late in the period as embedded pieces of energy in the midlevel cyclonic flow move over the North Country. Outlook 06z Tuesday through Friday... 06z Tuesday through 00z Wednesday: VFR ceiling with possible MVFR showers and higher elevation snow snow showers as a broad upper trough remains over the region. Increasing chances for MVFR ceilings at MPV/SLK later Monday night through Tuesday, with periods of light precipitation and MVFR cigs/vsby conditions. 00Z Wednesday through 00Z Saturday: Next low pressure system approaching from the Great Lakes/Ohio Valley brings chances for widespread showers and periods of MVFR conditions late Thursday through the first half of Friday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...KGM SHORT TERM...Taber LONG TERM...Taber AVIATION...KGM is the U.S. government's official web portal to all federal, state and local government web resources and services.