Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 101730 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1230 PM EST Sun Dec 10 2017 .SYNOPSIS... A weak trough of low pressure will move across the area today and bring snow showers to much of the region. Tonight lake effect snow from Lake Ontario will move across parts of the region 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/...
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As of 1223 PM EST Sunday...Scattered showers continue across the Adirondacks and much of northern Vermont at this hour. Have made some adjustments to PoPs accordingly. Any additional accumulation across northern VT should be minimal, while portions of the Adirondacks will see some accumulation toward evening as the lake effect band shifts back north. Overall the forecast is in good shape and mainly minor changes were made. Previous Discussion... Light snow has all but ended across southern and eastern Vermont early this morning. Much of this area received accumulating snow...anywhere from 1 to 5 inches. The winter weather advisory that was in effect for southeast Vermont has expired. Meanwhile...upstream upper trough is moving eastward this morning and has been producing some light snow across southeast Ontario and southwest Quebec Provinces. As this system moves east we should see the potential for snow showers increase across northern New York as the morning wears on and eventually across the northern half of Vermont during the afternoon. Any snow accumulations should generally be less than an inch. With the trough moving across the region today...the flow aloft will be more westerly and this will keep lake effect snow from Lake Ontario to our south. However...tonight the flow backs to the southwest and the lake band will move back up into our area. Once again the southern portions of Saint Lawrence and Franklin counties of New York will have the best potential for some light snow accumulations. Some of the lake effect should make it further downstream across the Champlain Valley and northern portions of Vermont later tonight. Feature weakens late tonight and flow becomes more westerly which will help bring an end to any snow showers by mid-morning on Monday with dry weather expected over the entire area Monday afternoon. High temperatures today will be in the upper 20s to mid 30s and then in the 20s to lower 30s on Monday.
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&& .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/... As of 315 AM EST Sunday...By Monday night into Tuesday a well- advertised northern stream clipper low will take a favorable track toward and atop the area with a widespread light snow event expected. Some surface low re- development of Miller Type-B character does occur to our east in the Gulf of Maine through the day on Tuesday. However the majority of the synoptic forcing for snow in our area will come in two phases, the first occurring during this period from broad warm advective processes and upward lift in the mid-levels as the parent low nears. At this point it appears the primary window for steadier snowfall will occur from the pre-dawn hours through late- afternoon on Tuesday before best synoptic lift pushes to our north and east. Blended 24- 30 hour QPF output, with some downward adjustment owing to typical warm-advective model bias suggests totals in the 0.15 to 0.35 range with slight enhancement possible along eastern slopes of the Greens/Dacks. Time-averaged snow ratios in the 15-20:1 range support totals generally ranging from 3-6 inches with local variation which suggests a potential advisory- level event for favored areas. Time will tell. Temperatures should be on the seasonably cool side with lows mainly in the teens and highs on Tuesday from the mid 20s to lower 30s. Winds light. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 315 AM EST Sunday...Phase two of our prolonged light snow event then evolves over time by Tuesday night and especially into Wednesday as secondary low pressure deepens significantly while tracking into the Maritimes. The parent 700-500mb closed low tracks atop our area during this period with deeper moisture returning on evolving gusty northwest flow as pressure gradient tightens significantly. Areal coverage of light snows/flurries will have initially tapered off during the first half of Tuesday night, but as aforementioned features pivot into the area a general re-blossoming of light snows/snow showers should occur as we progress into the daylight hours on Wednesday. The best coverage should occur across favored northern higher terrain and accompanying western slopes where orographic enhancement will become increasingly favored. Additional light accumulations in these areas look likely at this point which will be welcome for resort areas gearing up for the Christmas Holiday. Temperatures will trend colder during this period with lows Tuesday night in the upper single digits to mid teens and corresponding highs on Wednesday holding nearly steady in the teens with the brisk flow creating somewhat uncomfortable wind chills in the single digits. Thereafter global models suggest the overall large-scale pattern remains generally unchanged with a western CONUS synoptic ridge and a corresponding downstream eastern U.S. trough. Weak ripples of energy moving through the background cyclonic flow aloft will create near daily chances of snow showers or flurries, with higher chances during Friday and possibly again by later next weekend. At least that`s the broad consensus at this point. Temperatures will remain on the chilly side during Thursday (teens for highs), though begin a slow moderation process from Friday onward as core of continental polar airmass lifts gradually northward. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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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.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson/Hastings NEAR TERM...Evenson SHORT TERM...JMG LONG TERM...JMG AVIATION...Hastings

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