Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 141255 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 855 AM EDT Wed Mar 14 2018 .SYNOPSIS... Widespread snowfall will continue across the North Country through tonight as strong low pressure over Nova Scotia combines with an upper level trough moving into the region. Snow showers continue across the higher terrain Thursday into Friday before high pressure brings an end to precipitation area-wide on Saturday. Colder than normal temperatures will move in for early next week. && .NEAR TERM /THROUGH THURSDAY/...
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As of 838 AM EDT Wednesday...Quick update to issue winter storm warnings for vt side of the CPV and western slopes. No really change to expected snowfall amounts, just updated to warning. We continue to experience 1/2sm to 3/4sm here at BTV with a snow increase of 1 inch in the past hour and 13 inch snow depth. Impacts will continue to be very poor traveling conditions this morning with snow covered and slippery roads. In addition, some snow loading on trees has resulted in some isolated power outages already being reported. Treated road surfaces should improve by midday as temperatures hold steady near freezing, especially champlain valley. Water vapor continues to show deep easterly flow aloft while closed 5h/7h circulation slowly drifts toward southern New England. The combination of deep moisture and favorable surface to 850mb flow from the north/northwest will continue to produce widespread light to occasional moderate snow across the northern NY into parts of VT. Thinking best snow accumulations today will be across northern Dacks and eastern side of the CPV, including the Western Slopes and parts of the NEK. Downslope flow will limit additional snow accumulations over the lower CT River Valley. RAP/NAM show 925mb to 850mb relatively weak flow btwn 10-20 knots from 15z-00z today...which may limit lift, but as closed system and associated sfc cyclone retrogrades back into northern Maine, expect upslope snow to redevelop this evening and continue overnight. Additional 3 to 6 inches with isolated 8 inches amounts are possible overnight across the western slopes and parts of northern VT/NY Mountains. Previous Discussion...Well, we continue to roll with the punches with this long duration snow storm, and we`ve made further modifications to our hazards with additional warnings posted and extensions to current advisories. Big picture hasn`t changed much with coastal low pressure now centered over Nova Scotia and a deepening upper trough shifting east out of the Ohio Valley. Aloft we`re still seeing a good easterly fetch from the coastal system at 700-500mb but the flow from 700mb down to the surface has shifted to the north which has locally enhanced snowfall in the Champlain Valley and portions of northern New York. Over the past few hours an impressive mesoscale band developed across the northern Champlain Valley with 20-35 dBz radar returns, nearly 2 tenths of liquid reported at KBTV and 1-2" snowfall rates. Currently the band seems to letting up a little bit, but won`t be surprised to hear reports of overnight snow locally in the 3-6" range north of BTV by 12Z. For the rest of today, widespread snow will continue to fall but as surface temps climb a few degrees accumulation rates will lessen. Additionally, the mean 925-850mb flow weakens as the upper low centers just south of the area and the coastal low continues to pull northeast into New Brunswick and we begin a slow transition to more orographic snow. Highest accumulations during the day will be across the west slopes of the Adirondacks where upslope northwest flow develops first and continues through tonight. Accumulations are expected to be in the 8-12" range through tonight there and thus, we`ve hoisted a winter storm warning. Elsewhere today, accumulations will generally be in the 3-6" range where we continue warnings and advisories. Tonight, northwest upslope flow slowly begins to develop across the northern Greens and really gets going towards the midnight hour. Additional accumulations through the night are expected to be in the 4-6" range so we`ve extended the winter weather advisory here through 12Z. Elsewhere, snow begins to taper off after midnight will overnight accumulations generally in the 1-3" range. Finally on Thursday, snow continues across the higher elevations in the favored upslope regions of the northern Greens through mid-day while snow tapers off elsewhere. Additional accumulations of a few inches above 1500 feet can be expected, while the valley floor begins to dry out.
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&& .SHORT TERM /THURSDAY NIGHT/... As of 330 AM EDT Wednesday...Not much change in thinking from 24 hours ago for the Thursday night through Friday time frame. The large upper trough remains across the region while the deep maritime storm pulls slowly away to the northeast. As deeper moisture wanes, we expect a gradual decrease in areal coverage of light snows/snow showers across northern counties accordingly. Light additional accumulations in these areas will be likely, but impacts should be minor at best. Northwesterly flow will be persistent however, and with a modest pressure gradient remaining in place breezy conditions look to be a given. With plenty of lingering clouds diurnal temperature ranges will remain more narrow than normal, with lows from the upper teens to mid 20s and afternoon highs in the 20s to locally near 30 in warmer valley locales. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 330 AM EDT Wednesday...Any remaining light snows/snow showers then end Friday night, setting the stage for mainly quiet weather under a modified CP airmass for the upcoming weekend into early next week. There could be a few additional snow showers Saturday night with passage of a late season arctic frontal boundary, though by and large dry weather is expected. Temperatures will trend steadily below normal through the period, with daily highs in the 20s to around 30 and overnight lows in the single digits and teens - more representative of mid- January like readings. Looking further out - there still remains quite a bit of model spread on another potential system toward the middle of next week. For now have kept the chances for precipitation in the slight to low chance category until better consensus can be reached. Definitely something to monitor however as there is potential for yet another coastal system and possible snowfall in the Tuesday/Wednesday time frame. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... Through 12Z Thursday...Persistence will be the forecast for the next 24 hours with widespread IFR/LIFR conditions continuing in light/moderate snow. Vsby will generally range from 1-2SM and ceilings 700-2000 feet AGL with the lowest flight conditions occurring in the Champlain Valley. Winds will generally continue at 8-12kts from the north-northwest through the period. Outlook... Thursday: Mainly VFR, with areas MVFR and IFR possible. Likely SN, Chance SHSN. Thursday Night: VFR. Chance SHSN. Friday: Mainly VFR, with areas MVFR possible. Chance SHSN. Friday Night: Mainly VFR, with local MVFR possible. Slight chance SHSN. Saturday: Mainly VFR, with areas MVFR possible. NO SIG WX. Saturday Night: VFR. NO SIG WX. Sunday: MVFR. NO SIG WX. && .BTV WATCHES/WARNINGS/ADVISORIES...
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VT...Winter Storm Warning until 8 AM EDT Thursday for VTZ002>006- 008-009-011-016>019. Winter Weather Advisory until 8 PM EDT this evening for VTZ001- 007-010-012. NY...Winter Storm Warning until 8 AM EDT Thursday for NYZ029>031. Winter Weather Advisory until 8 PM EDT this evening for NYZ026>028-034-035-087.
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