Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 181229 AFDBTV AREA FORECAST DISCUSSION National Weather Service Burlington VT 729 AM EST Fri Jan 18 2019 .SYNOPSIS... Scattered snow showers spread across the region today with a coating to two inches expected. A significant snowstorm will affect the area Saturday night and Sunday. Six to eighteen inches of snow are expected by late Sunday, isolated higher amounts in the Southern Greens. Bitterly cold temperatures are then expected for Sunday night through Monday night with dangerous wind chills. && .NEAR TERM /THROUGH SATURDAY/... As of 636 AM EST Friday...Light snow has begun to move into the area and has generally been light so far. No big changes for 700 am update. Previous discussion follows. Weak low pressure system passes well to our North today, bringing scattered light snow showers to Northern New York and Vermont. Not a lot of forcing or moisture, but could see a coating to two inches by the end of the day. Warm southerly flow will push temps into the upper 20s to around 30. Behind this system, cold high pressure will briefly ridge into the area. Temperatures drop into the single digits above and below zero tonight. Temperatures will be cold on Saturday as well with highs only in the single digits. Will see increase in clouds through the day with next significant storm approaching from the Ohio river valley. Snow will begin during the evening hours, spreading from southwest to northeast across the area. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 323 AM EST Friday......WINTER STORM WARNINGS AND ADVISORIES IN EFFECT... Very little change made to the forecast from previous thinking for the weekend storm as 00Z NWP remained very consistent with the previous runs with the only notable change being a slight change in timing. With that in mind, confidence is now high enough to warrant winter storm headlines for Saturday night through Sunday. Borrowing from my discussion yesterday to describe the synoptic setup, energy dropping into the four corners early this morning remains progged to lead to lee side surface cyclogenesis later this afternoon over the southern Plains. Meanwhile, strong arctic high pressure located near Hudson Bay will be providing the Northeast with a bitter cold and dry airmass Friday night into Saturday with 925mb temps in the -15C to -25C range. This will set the stage for a strong thermal gradient to develop across the Tennessee Valley where the developing surface low will track east-northeast to near D.C by Sunday morning, and further on over Cape Cod and into the Bay of Fundy by Sunday night. Snow spreads into the forecast area from southwest to northeast Saturday evening, with the worst travel conditions expected early Sunday morning from roughly 06-15Z with 1- 2"/hr snowfall rates possible, especially across central/southern Vermont where an enhanced band of 850mb fgen is progged to pivot. A change from previous model runs is that by 18Z the best deep layer moisture and lift begin to quickly lift east-northeast away from the region so expect snow to rapidly taper off towards sunset instead of later into the evening. Now that we`re entering time range of mesoscale models we`re able to begin to provide better detail to the expected QPF and subsequent snowfall accumulations which based on mean SLR`s of 15-20:1 will yield a wide area of 12+ inches. Thinking the St. Lawrence Valley sees the least amount of snowfall due to drier northeasterly flow and being further removed from the surface low on the coast with accumulations mainly in the 6-8" range. The Adirondacks to the Champlain Valley should see 10-14", 12-16" central/northeast VT, and the big winners will be southern VT where Rutland/Windsor/Orange counties see 16-20" with locally up to 2 feet possible across the higher terrain. An additional hazard during the storm will also be increasing northerly winds during the daylight hours Sunday, with areas of blowing snow likely. North winds of 15-25 mph, with gusts to 35 mph are likely in the Champlain Valley, resulting in low visibility in blowing snow at times. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 323 AM EST Friday...Bitterly cold wind chills continue to be main highlight for the long term as a strong pressure gradient develops over the region Sunday night through Monday as departing low pressure deepens across the Canadian Maritimes, and arctic high pressure builds into the Northeast. Strong low level cold air advection noted by 925mb temps dropping into the -25 to -30C range combined with northerly winds of 15-25 mph will yield wind chills of 20 to 30 below, and locally as low as 35 below across the Northern Adirondacks Sunday night. Temperatures don`t budge out of the single digits above and below zero either Monday despite winds beginning to abate as high pressure will center overhead Monday night. Wind chill warnings and advisories look probable, but we will address this later on down the road. High pressure builds over region for Monday night through Tuesday with continued arctic temps of -5F to -20F for lows Monday night, but light southerly return flow Tuesday will offer highs warming into the teens above zero. Our next system approaches Tuesday night with a drastic change in temps possible as surface low pressure looks to track northeast through the St. Lawrence Valley ushering in a much warmer airmass. So much warmer than ptype will be an issue as highs surge into the 30s Wednesday with a mix of rain and snow possible through Wednesday night before a cold front passage early Thursday morning. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... Through 12Z Saturday...1500 to 2500 foot overcast deck has overspread the North Country. Snow showers are expected to move across the region today which will create some localized IFR visibilities at MSS and SLK. Other locations may see brief periods of IFR/MVFR visibilities with snow showers but MSS and SLK are the most likely locations to see snow showers through Friday afternoon. Winds have shifted to the south 5 to 12 knots. It looks like ceilings will improve and snow showers will exit the region after 18Z Friday but lingering MVFR ceilings will be seen across northern New York and southern Vermont. Ceilings will continue to improve to VFR overnight. Outlook... Saturday: VFR. Chance SN. Saturday Night: Mainly MVFR and IFR, with areas VFR possible. Definite SN. Sunday: Mainly MVFR and IFR, with areas VFR possible. Definite SN, Chance SHSN, Areas BS. Sunday Night: VFR. Chance SHSN. Martin Luther King Jr Day: VFR. Slight chance SHSN. Monday Night: VFR. NO SIG WX. Tuesday: VFR. Slight chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Storm Warning from 4 PM Saturday to 4 PM EST Sunday for VTZ001>012-016>019. NY...Winter Storm Warning from 4 PM Saturday to 4 PM EST Sunday for NYZ028>031-034-035. Winter Weather Advisory from 4 PM Saturday to 4 PM EST Sunday for NYZ026-027-087. && $$ SYNOPSIS...Neiles NEAR TERM...Neiles SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Neiles is the U.S. government's official web portal to all federal, state and local government web resources and services.