Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 261144 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 744 AM EDT Wed Oct 26 2016 .SYNOPSIS... The cyclonic flow that has produced cool temperatures and mainly mountain snow showers will slowly weaken today...with some peeks of sunshine possible by this afternoon. Temperatures will continue to be below normal with lighter winds. The next system arrives late Thursday into Friday with mainly a cold rain in the valleys and mixed rain and snow in the mountains. A wet snow accumulation of several inches is likely overnight Thursday. && .NEAR TERM /THROUGH TONIGHT/... As of 742 AM EDT Wednesday...Just received report of freezing drizzle along the western slopes near Underhill so have done another update to place this into the weather grids. Not expecting much impact as temperatures are very close to freezing. This threat should end by 9 or 10 am. This threat will linger into the mountains as moisture is lacking in the favorable snow growth per latest RAP13 sounding data. Latest ir satl pics show clouds increasing across portions of northern NY and eastern side of Lake Champlain. Have updated grids to capture these trends through 15z...before clearing slowly develops first across northern NY then VT by sunset. Western Champlain Valley will see some clearing by mid morning due to downslope flow off the dacks. Also...adjusted hourly temps up several degrees to match current conditions. Still have chance pops thru the morning hours to capture light upslope snow showers. Deep cyclonic moist northwest flow which produced 4 inches of snow atop Lincoln Peak per latest web cam will slowly breakdown today as weak high pres builds into the region. The combination of lingering mid level moisture...upslope flow...and some lake enhancement may produce some additional scattered snow showers along the western slopes this morning. Have continued to mention chance pops...but any qpf/snowfall will be light. Hourly temps continue to run several degrees above guidance because of clouds/winds early this morning...making for a tricky afternoon forecast. Have noted progged 925mb to 850mb temps are 1 to 2 degrees cooler today...with 850mb temps near -10c. Thinking highs will generally be in the 30s mountains and lower 40s Champlain Valley...some sun in the Saint Lawrence and western Champlain Valley should help with surface heating. Tonight...weak ridge of high pressure builds into the region....between departing closed cyclonic circulation and approaching energy and moisture from central Plains. Forecast challenge will be amount of clouds and impacts on temps. Guidance is very chilly with values near 10f SLK and mid teens northeast kingdom...with lower 20s Saint Lawrence Valley and mid 20s Champlain Valley. These values could be reached if skies are clear and winds are light...but thinking lingering clouds and some wind will keep temps several degrees warmer...mainly mid teens SLK/Northeast to mid/upper 20s Saint Lawrence and Champlain Valley...except near freezing by the lake. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... As of 418 AM EDT Wednesday...Overall idea from the previous forecast and mine before that remains in place for the end of the work week as low pressure pulling out of the Eastern Great Lakes and Ohio Valley will bring mixed precipitation mainly in the form of rain and snow to the North Country. Main change with this morning`s forecast is to offer a slower arrival time of the onset of precipitation, and adjust temps warmer for the bulk of the event. Consensus amongst the latest NWP guidance is that deeper layer moisture doesn`t really arrive until at least mid-day as the parent surface low tracks northeast through northern New York. Precipitation at the onset will mainly be in the form of rain for most locations with boundary layer temps in the 40s, but across the Adirondacks temps will likely wet-bulb down to support snow. As we move into Thursday evening and night, a developing 925/850mb southeasterly jet of 40-50kts will usher in above freezing temperatures aloft transitioning ptype to a rain/snow mix for the Adirondacks and portions of eastern Vermont, and eventually all rain area-wide after midnight. Thereafter, potent shortwave energy rounding the base of an upper trough swinging to the area develops a weak surface low along the frontal wave and eventually the aforementioned parent low transitions its energy to this new low over southern New England by Friday morning. Wrap- around moisture combined with developing northwesterly flow on Friday will keep precipitation going, especially across the upslope regions of the Adirondacks and northern Greens but remains mainly rain as surface/boundary layer temps remain mild. All in all impacts from this event are very limited at the surface, with any snow on the front side of the system only a dusting to perhaps 2", and any downslope winds along the western slopes Thursday night limited to 20-30 mph as the timing of max winds aloft coincide with the heaviest precipitation occurring. That said, it will be a different story across the higher peaks above 2000 feet where thermal profiles still support storm total accumulations in excess of 6" to up to as much as a foot of heavy wet snow through Friday. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 418 AM EDT Wednesday...In general, the long term period from the weekend into early next week has begun to trend more quiet than what we`ve seen the past few days. Trends are for another northern stream clipper to track north of the BTV CWA Saturday offering a return to above normal temperatures and just some light rain showers. Behind that, high pressure builds in and dominates for Sunday and Monday before a strong low develops out of the northern Plains and tracks well to our northwest on Tuesday. A weak front traverses the forecast area Tuesday afternoon, but with limited moisture to work with, we`re not expecting a whole lot of precipitation. Temperatures though sky- rocket well above freezing aloft supporting highs pushing back into the mid-40s to low 50s on Monday, and further into the mid/upper 50s for Tuesday. && .AVIATION /12Z Wednesday THROUGH Sunday/... Through 12z Thursday...Clouds have increased and lowered to mvfr conditions at several taf sites this morning. The combination of upslope flow and lingering moisture around deep cyclonic flow will continue to produce plenty of clouds with periods of mvfr cigs through 15z at mss/btv and 17z at slk/mpv. Surface high pres will result in developing vfr through tonight with northwest winds at 5 to 15 knots becoming light overnight. A few isolated to scattered snow showers are possible this morning with summits obscured in clouds. Outlook 12z Thursday through Sunday... An active pattern will changeable flight conditions expected during this time period. Clouds will quickly increase on Thursday with widespread precipitation expected by Thursday Afternoon. Thermal profiles suggest precip could start as a 1 to 3 hour period of snow with ifr conditions at mpv/slk...before switching to rain. Mainly mvfr cigs develop on Thursday into Friday...with some ifr cigs possible at slk/mpv. In addition...strong low level jet of 50 knots around 5000 feet will produce areas of turbulence and wind shear during this time period with localized gusts to 30 knots at RUT. Winds shift to the northwest on Friday with some lingering upslope precip and mvfr cigs likely at mpv/slk/btv/rut. Next system with breezy southwest winds arrives late Saturday into Sunday with additional precip and potential impacts to aviation. && .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.