Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 101416 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 916 AM 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 911 AM EST Sunday...No changes were needed with this update. Two areas of light snow continue to slowly move eastward this morning...one over northwestern VT and the other across the Adirondacks. Expect this precipitation will wane a bit through the morning hours as it pushes east, but snow showers should increase this afternoon, particularly over the higher terrain, as the upper trough swings across the region. The forecast has this all well in hand, so have only updated to incorporate the latest conditions. 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 /14Z SUNDAY THROUGH THURSDAY/... Through 12Z Monday...Generally looking at VFR and MVFR conditions through the period. Some brief MVFR/IFR conditions will exist at KBTV and KRUT through 13z as a band of light snow moves across these areas. Otherwise looking at scattered snow showers throughout the period which could briefly produce MVFR/IFR conditions. Light winds this morning but a front is moving across the area and winds will become more southwest and west with gusts in the 15 to 20 knot range before gradually tapering off after 00z. Outlook... Monday: Mainly VFR, with local MVFR possible. NO SIG WX. Monday Night: Mainly VFR, with local MVFR possible. Likely SN. Tuesday: Mainly MVFR, with areas IFR possible. Likely SN. Tuesday Night: Mainly MVFR, with areas IFR possible. Chance SHSN, Likely SN. Wednesday: Mainly MVFR, with local IFR possible. Chance SHSN. Wednesday Night: Mainly MVFR, with local VFR possible. Chance SHSN. Thursday: Mainly VFR, with local MVFR possible. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson/Hastings NEAR TERM...Evenson SHORT TERM...JMG LONG TERM...JMG AVIATION...Evenson

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