Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 241930 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 330 PM EDT Mon Oct 24 2016 .SYNOPSIS... The North Country will remain in cyclonic flow with variable cloudiness and cooler than normal temperatures through most of the week. A weak upper disturbance embedded in northwest flow aloft will bring mostly cloudy skies tonight through Tuesday. This feature will bring a chance of light rain showers in the valleys. Snow showers are expected across the Northern Adirondacks and north-central into northeastern Vermont tonight through Tuesday. High pressure brings briefly drier conditions Wednesday into Wednesday night. A more significant wave of low pressure approaching from the Great Lakes and Ohio Valley will bring periods of rain, generally late Thursday into the first half of Friday. Precipitation may begin as a wintry mix across higher terrain areas on Thursday before changing to rain. && .NEAR TERM /THROUGH TUESDAY/... As of 253 PM EDT Monday...Little overall change in the large-scale pattern during the next 24 hours across northern NY and VT. Deep layer W-NW flow continues west of mean mid-level trough axis, but within broad upper level trough across the nern CONUS and sern Canada. This is contributing to below climo average temps this afternoon, with readings generally in the mid-upr 40s, and only in the upr 30s across the Northeast Kingdom. Will see increase in cloud cover overnight as embedded shortwave trough translates sewd out of srn Quebec across the area, with cloud heights generally 3-5kft. Limited moisture (PW values 0.3-0.4"), however orographic ascent will bring light rain/snow shower activity overnight into the day Tuesday, especially across the nrn Adirondacks and nrn Green Mtns into far nern VT. Freezing levels initially around 2500ft this aftn, will generally fall to near 1000ft during the pre-dawn hours Tuesday. Thus, will see falling snow levels overnight, and then rising a bit during the day Tuesday. Not expecting any snow accumulation in the Champlain Valley, but could see a dusting to 1" for towns in central/nrn VT and across the nrn Adirondacks. The highest summits of nrn VT could see 2-4" snowfall, including at Jay Peak and Mt. Mansfield by Tuesday evening. Winds will generally continue from the NW. Generally 10-20 mph gusting to 25 mph thru early evening, diminishing to near 10 mph overnight, and increasing again to 10-20 mph for Tuesday. Low temps tonight generally low-mid 30s, except 28-32F 1-2kft elevational band. Highs on Tuesday generally low to mid 40s under cloudy skies. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/... 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. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... 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. && .AVIATION /19Z Monday THROUGH Saturday/... Through 18z Tuesday...Persistent W-NW flow will bring variably cloudy conditions, but mainly VFR (ceilings 3.5-5kft) at the TAF locations. Sole exception should be at SLK, which will occasionally see ceilings 2-3 KFT. Visibility generally unrestricted with gusty/well-mixed low-level conditions. Will see a few orographic showers/snow showers develop as we head into tonight thru Tuesday morning. This may bring some VSBY restrictions vcnty of the HIR TRRN. Also, may see brief MVFR at SLK in snow showers toward daybreak. W-NW winds will remain moderately strong...12-15kt with gusts to 25kt thru sunset. Winds will diminish somewhat overnight (8-10kt), then increase to similar speeds (12-15ktG25kt) from the NW during the daylight hours Tuesday. Outlook 18z Tuesday through Saturday... 18Z Tuesday through 12Z Wednesday: Isold/sct rain and snow showers will persist vcnty of the nrn Adirondacks/nrn Greens Tuesday aftn into first half of Tuesday night. Could see intervals of MVFR conditions at SLK, and possibly also at MPV. At the remaining TAF sites, BKN-OVC conditions but with VFR ceilings expected. Winds NW 8-15kts. 12Z Wednesday Through 12Z Thursday: Surface high pressure across the region will bring generally VFR conditions and lighter winds. 12Z Thursday Through Saturday: Low pressure system approaching from the Great Lakes/Ohio Valley brings developing rain Thursday afternoon into Thursday night, with MVFR and intervals of IFR conditions possible. After a brief break on Friday, another wave of low pressure brings additional showers and possible MVFR conditions on Saturday. && .MARINE... AS OF 308 PM EDT MONDAY...Lake Wind Advisory continues through this evening with northwest winds 15-25kts and waves 2-4kt. Highest waves along eastern shores exposed to a greater fetch on northwest winds; specifically those locations adjacent to the open waters north of the Charlotte Ferry and south of Valcour Island. Expect these strong winds and waves to gradually diminish overnight as wind speeds decrease slightly to 10-20kts. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos SHORT TERM...Taber LONG TERM...Taber AVIATION...Banacos MARINE...Team BTV is the U.S. government's official web portal to all federal, state and local government web resources and services.