Area Forecast Discussion
Issued by NWS Burlington, VT

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728 FXUS61 KBTV 102049 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 349 PM EST Sun Dec 10 2017 .SYNOPSIS... Lake effect snow from Lake Ontario will move across parts of the region tonight with minor snow accumulations possible...mainly over portions of northern New York. Relatively dry weather is expected on Monday before a low pressure system moves across the area Tuesday into Wednesday and brings widespread light to moderate snowfall to the North Country. && .NEAR TERM /THROUGH MONDAY NIGHT/... As of 255 PM EST Sunday...Isolated to scattered snow showers will continue for much of the North Country through the afternoon as an upper trough slides eastward across the area. These will wind down later this afternoon once the trough shifts to our east. However, snow chances will quickly ramp up again this evening as the flow backs more to the southwest behind the departing trough. This will allow the lake effect snow band to lift back north into the northern Adirondacks into northern Vermont. In the meantime, weak low pressure crossing southern Quebec will drag its attendant cold front through NY and New England in its wake. This boundary will help serve to focus additional snow shower activity over northern NY and VT later tonight. Winds will turn west and eventually northwest behind the front, once again shifting the lake effect snow back south of our area. Colder and drier air will work in behind the front as well, bringing the snow showers to an end by mid morning Monday. All told, expect southern St Lawrence and Franklin Counties in NY to see the most accumulation, generally 1 to 3 inches with locally higher amounts approaching 4 inches. Elsewhere, snowfall will be 2 inches or less. Overnight lows will range from the teens in the north to the lower to mid 20s in the Champlain Valley and southern VT. For Monday and Monday night...once the aforementioned front moves through...again by mid morning or so...expect drier weather to briefly move in as high pressure quickly skirts across the area. Highs will be in the 20s, with the coldest readings coming in the northern mountains. As we head into Monday night, the focus turns to a clipper system approaching from the west. Precipitation associated with warm air advection out ahead of this system will spread from west to east overnight, but with dry air in place at lower levels, it will take a bit before the snow is able to accumulate. Lows will be in the teens pretty much areawide. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
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As of 345 PM EST Sunday...A winter storm watch has been issued for snow accumulations of 4-7 inches as a well defined northern stream clipper low tracks just south of the North Country. By Monday night a clipper low will be tracking through the Great Lakes and lifting a warm front into the North Country. Warm advection snow will overspread the North Country producing widespread plowable snowfall. The best moisture convergence and lift will be during the morning hours on Tuesday as we see 1-2 inches across southern Vermont before sunrise and then another with another 2-4 inches during the mid morning hours Tuesday. Storm Total accumulations are anticipated to be in the 4-7 inch range so just on the border between advisory vs warning. Being early in the season I opted for a watch to highlight the potential for adverse travel on Tuesday morning. The trends in the 12z guidance were to increase the amount of liquid qpf with the system so even accounting for the normal high bias in warm advection we are in the range of seeing between 0.25-0.4 inches of liquid with snow ratios in the 14-18:1. Will need to watch to see if trends continue to increase the QPF because thats generally not favourable to see high qpf events for the North Country with clipper type systems. Expect with the warm air pushing in on Tuesday temps will be in the upper 20s to low 30s before the cold front from the parent upper level trough swings through. Expect overnight temps to generally be in the 20s until just before daybreak when lows drop into the teens. Then as the upper level trough swings through Tuesday night into Wednesday the pattern will shift to more orographic showers in the western slopes of both the Greens and the Adirondacks. The moisture will be limited but even so another 1-3 inches will be possible in the higher terrain. Cold air moves into the region Wednesday night with both the GFS and EC showing -18C to -20C at 850mb. With a fresh snow pack I`ve got lows in the single digits on Wednesday night. I did trend up a couple of degrees from guidance as even with the snow pack, expect mostly cloudy skies which will dampen how fast we cool.
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&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
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As of 345 PM EST Sunday...The large scale pattern continues with a mean upper level trough over over eastern Canada. We should see one brief quiet day on Thursday but by Friday another weaker clipper system will bring a chance for measurable snow. With the colder airmass still in place anticipate temperatures to remain below normal with teens for highs on Thursday and a gradual warming trend towards upper 20s to low 30s by Saturday.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... Through 18Z Monday...VFR/MVFR conditions will prevail at most sites through 00z Mon, with brief IFR possible in scattered snow showers. More widespread snow showers will move into the region after 00z Mon, both from lake effect as well as a weak frontal boundary sinks south out of Canada. Still expect mainly MVFR conditions, but IFR will be possible in any snow showers. Snow showers will come to an end around 12z Mon, and ceilings will gradually lift to VFR by Mon afternoon. Outlook... Monday Night: Mainly VFR, with local MVFR possible. Chance SN. Tuesday: Mainly MVFR, with local IFR possible. Definite SN. Tuesday Night: Mainly MVFR, with areas IFR possible. Chance SHSN, Likely SN. Wednesday: Mainly MVFR, with areas VFR possible. Chance SHSN. Wednesday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Thursday: Mainly VFR, with local MVFR possible. NO SIG WX. Thursday Night: Mainly VFR, with local MVFR possible. Slight chance SHSN. Friday: Mainly VFR, with local MVFR possible. Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Winter Storm Watch from late Monday night through late Tuesday night for VTZ001>012-016>019. NY...Winter Storm Watch from late Monday night through late Tuesday night for NYZ026>031-034-035-087. && $$ SYNOPSIS...Hastings NEAR TERM...Hastings SHORT TERM...Deal LONG TERM...Deal AVIATION...Hastings

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