Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 250219 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1019 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 /UNTIL 6 PM TUESDAY EVENING/... As of 1018 PM EDT Monday...Precipitation arriving on-cue in broad NW flow coming from Quebec down across northern higher terrain in VT. Previous forecast well covered and these trends expected to continue overnight. Previous discussion issued at 253 pm...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 /6 PM TUESDAY EVENING THROUGH WEDNESDAY/... As of 332 PM EDT Monday...The upper level trough will slowly drift towards the east as persistent cold air advection continues to provide below normal temps in the short term through the mid week. The continued northwest flow aloft will cause some light upslope snowfall. The flow will be unblock so areas with the highest accumulations will be in the western upslope locations such as Underhill, Jericho, Bolton etc. However with total qpf will be less than 0.10 which ultimately means we`ll only see an inch or two of snow fall. Wednesday we will be in sort of a lull between two systems. Expect cloudy conditions in the higher terrain with some breaks in the cloud cover in the Saint Lawrence and Champlain Valleys. The low and mid level moisture will be decreasing and so while the orographic forcing is still favourable for snow I dont anticipate much in the way of accumulation along the ridgeline Wednesday. The cold air advection even as a weak ridge starts to build in. Expect max temps to remain below normal as the entire column of air above 925mb is below 0C. Highs will be in the upper 30s to around 40 in the valleys. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... As of 425 PM EDT Monday...By Thursday the pattern picks up again with several chances for rain and snow. The upper level trough builds back in thus the upper level flow will remain west to northwest through the end of the week and into the weekend. The first surface low pressure system will track through the Great Lakes into New England on Thursday night and should bring quite a bit of warm advection to the area. The rain vs snow forecast will be quite tricky as the overnight temps will be supportive of snow however the warm air advection will be advancing rapidly with a southerly 850mb jet of 40-50kts bringing warmth from the Atlantic west of the spine of the Green mountains. However on the eastern side of the Greens the cold air will be trapped longer due to the high pressure system located over Nova Scotia. So I anticipate precip beginning first as snow across the entire area however by mid morning on Friday that will transition to a mix of rain and snow except for areas east of the Green mountains. Temp profiles in the higher terrain suggest they will stay all snow. The bigger issue will be the potential for gusty downslope winds. The track of the low pressure system will be critical as if the GFS is correct the low tracks across the CT/MA/NY border and the winds will be due east over the southern Green mountains. However the EC is slightly further north and thus the strongest winds dont turn east until the system is already east of the forecast area. If the GFS is correct there will be a 35-45kt 850m easterly jet over the southern Greens which would be supportive of downslope gusty winds. We will need to continue to monitor that as the forecast becomes clearer. Next system arrives late Saturday into Sunday with additional chances for precipitation however most of the guidance is warm enough that the system will produce mainly just rainfall. Based on GFS and EC soundings the entire column below 850mb is positive so based on the 12z suite of guidance I anticipate rain and max temps in the mid to upper 40s and lows in the 20s to mid/upper 30s. && .AVIATION /02Z Tuesday THROUGH Saturday/... Through 00z Wednesday...OVC VFR ceilings to predominate most of this TAF period under cold cyclonic flow aloft. Potential for scattered rain/higher elevation snow showers after 07z. In the snow showers, visibilities may briefly drop to IFR with ceilings in the MVFR range. The best shot at seeing snow showers will be at MPV and SLK. Northwest winds stay steady 8-14 kts. Gusts to 25 kts abate early this evening, and pick up to around 20 kts on Tuesday as mixing depth increases. Outlook 00z Wednesday through Saturday... 00Z Wednesday 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/SLW SHORT TERM...Deal LONG TERM...Deal AVIATION...Banacos/Loconto MARINE...Team BTV is the U.S. government's official web portal to all federal, state and local government web resources and services.