Area Forecast Discussion
Issued by NWS Burlington, VT

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198 FXUS61 KBTV 060056 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 756 PM EST Mon Dec 5 2016 .SYNOPSIS... Occasional snow showers will taper off to flurries and areas of patchy freezing drizzle tonight...with minimal additional accumulation expected. Temperatures will cool back into the 20s to near 30s. Tuesday will feature plenty of clouds in the morning with some late day clearing possible...before our next system arrives on early Wednesday Morning. This system looks to bring another round of light accumulating snow during the early morning commute. && .NEAR TERM /THROUGH TUESDAY/...
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As of 726 PM EST Monday...Not much change to the forecast as cloud cover will persist through the evening limiting how cold we get especially with marginal warm air advection in the lowest levels of the atmosphere. Expect lows overnight to occur just before sunrise in the upper 20s to lower 30s in the Champlain Valley. Previous discussion...An overachieving warm front this morning produced a widespread 2 to 6 inch snowfall across our region...causing a difficult morning commute...but outstanding early season ski conditions at local resorts per pictures received this afternoon. For tonight...weak surface boundary near the international border will drop south this evening and winds will shift to the northwest. Soundings show 10 to 20 knots through 850mb this evening...which combined with some leftover 1000 to 700mb moisture through 03z...will support occasional snow showers. An additional an inch or so is possible...before limited moisture in the favorable snow growth decreases toward midnight...resulting in mainly flurries and areas of light freezing drizzle. Always difficult to determine areal coverage of freezing drizzle associated with light flow and abundant low level moisture. Not expecting any ice accumulation...but could impact snow surfaces for the slopes on Tuesday. Expecting limited diurnal change in temps overnight with plenty of clouds and areas of light precip...mainly 20s mountains to near 30f champlain/saint lawrence valleys. Tuesday...the big question becomes do we see any sunshine...especially eastern side of the champlain valley...mountains of ny/vt...and northeast kingdom. Latest nam12km and 4km soundings show plenty of low level moisture between surface and 925mb...with much drier air aloft through 18z. Thinking low level inversion combined with very weak wind profiles will result in plenty of clouds through 18z...before some clearing occurs toward sunset. Better chances of seeing sun will occur across the lower ct river valley....western cpv...and parts of the saint lawrence valley on Tuesday. Temps hold mainly in the 20s mountains to mid 30s warmer valleys with more clouds and less sun.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 220 PM EST Monday...By Tuesday night into Wednesday another weak warm thermal advection episode is progged to advance northeast into the region while weakening over time as primary energy bundle exits the mid-Atlantic seaboard. The idea of a thickening and lowering overcast with light snows arriving southwest to northeast after midnight Tuesday still appears reasonable at this point, though some minor timing details do exist among this morning`s deterministic guidance. Light snows will then slowly taper to scattered rain and snow shower activity through the day on Wednesday as lower boundary layer warms above freezing in most valley locales. Similar to this morning`s event, minor snow accumulations of 1 to 3 inches will be possible with the highest totals generally in elevated terrain. Temperatures will remain fairly uniform during this period with overnight lows steady in the upper 20s/lower 30s, and corresponding highs on Wednesday from 35 to 42. By Wednesday night the mean background flow remains deep southwesterly with plenty of mid-level moisture keeping skies mostly cloudy as a whole. Some minor lake effect response and associated snow showers may tend to form to the northeast of Lake Ontario over time, but boundary layer thermal progs quite marginal for anything heavy. Elsewhere just some scattered flurries here and there, mainly across the north. Low temperatures in the 20s to around 30 look reasonable. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 220 PM EST Monday...looking at this morning`s medium range guidance the models remain on board showing a gradual cooldown from Thursday into Saturday of next weekend as our first true modified continental polar airmass pushes into the area. Some important caveats lie beneath the bed so to speak, not the least of which is the fact that the mean flow aloft will be predominantly west to southwest through much of the period and quite moist. Thus no true push of arctic air will occur and given the abundant clouds overnight lows won`t be all that chilly by December standards despite the fact the readings as a whole will trend colder. This flow also proves a tad problematic with precipitation chances with transition to the colder airmass coming in several discrete frontal/trough passages. Overall theme will be for lake effect snow to generally blossom across the Lake Ontario snowbelts on Thursday/Thursday night with activity becoming more pronounced across the northern portions of VT as well over time as moisture feed deepens and aforementioned troughing swings into the area. Some light accumulating snows still appear reasonable in this period with slightly fluffier/higher totals possible in the snowbelts. Clouds continue to hang tough on Friday as we gradually enter the colder airmass and shsn/flurries wane over time, though at least some partial clearing is expected by Friday night into Saturday with high pressure at the surface building across the eastern seaboard. Temperatures will be on the cool side, but not excessively so with highs by next Saturday in the upper teens to mid 20s and overnight lows generally from 5 to 15 above. By next Sunday into Monday our next system is progged to swing into the region as low pressure across the northern Great Lakes drives additional warm advective precipitation into our area. These latter periods are of lower confidence with distinct differences in timing and thermal profiles. For now have leaned toward a blended output suggesting additional chances for light snows, though if some of the deterministic guidance like the ECMWF are correct, boundary layer temperatures may warm enough by next Monday for mixed rain/snow shower activity or all rain. && .AVIATION /01Z Tuesday THROUGH Saturday/...
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Through 00Z Tuesday...Aviation conditions will be tricky overnight as mvfr conditions will deteriorate to ifr for all sites with the possible exception of RUT and PBG. A weak front will shift our winds to the northwest and the flow becomes blocked with developing low level moisture trapped under a temperature inversion. This will lower cigs after 03z to ifr levels at btv/slk/mpv with periods of ifr possible at rut/mss. In addition...this moisture may produce areas of freezing drizzle or light snow flurries...especially slk/mpv with a light glaze possible after 06z. Anticipating mvfr to ifr vis in the mountain taf sites (mpv/slk) with mainly mvfr vis at btv/rut/mss. Conditions will slowly improve from ifr to mvfr to vfr across our taf sites by 15-18z Tues as high pressure crests overhead. Outlook 00z Tuesday through Saturday... Vfr with some lingering mvfr cigs at slk/mpv on Tuesday...before another warm front produces another round of widespread light snow across our region on Weds. Similar to Monday`s event thinking a period of ifr/lifr likely between 12z-18z Weds across our taf sites with vis below 2sm and cigs between 500 feet and 2000 feet. An arctic boundary will produce more scattered snow showers and potential snow squalls on Thursday into Friday with brief periods of ifr conditions possible. Improving conditions with mvfr valleys and ifr/mvfr in scattered snow showers persist on Saturday.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Deal/Taber SHORT TERM...JMG LONG TERM...JMG AVIATION...Deal/Taber

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