Area Forecast Discussion
Issued by NWS Burlington, VT

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337 FXUS61 KBTV 220342 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1042 PM EST Tue Nov 21 2017 .SYNOPSIS... A cold front will move through the region later tonight and the first half of Wednesday, bringing rain and snow showers. The snow showers will be most prevalent over northern New York and the mountains. Thanksgiving Day is expected to be dry with temperatures in the 30s. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... As of 1042 PM EST Tuesday...Overall forecast in good shape with some minor tweaks to temperatures east of the Greens in Vermont where decoupling has taken place and some cold pockets are developing. Otherwise remainder of forecast on track. Previous Discussion... Satellite and radar trends indicate a later onset to the deeper moisture and precipitation across the area tonight. Not expecting precipitation to reach the Saint Lawrence Valley of New York until about midnight and then eventually spreading east reaching the western half of Vermont by the morning commute time on Wednesday. Of note are the warmer surface temperatures and colder air aloft does not move in until after the cold front moves through the area Wednesday morning. Cooling does occur generally above 3000 feet and mountain locations will have the best chance for some minor snow accumulations with mainly rain below that. Later Wednesday morning any lingering orographically driven rain/snow showers in the valleys and snow showers in the higher terrain will gradually wind down during the afternoon. Expecting temperatures to hold fairly steady from around 30 in the Adirondacks to 40 in the valleys before falling again toward dark. Should be quiet Wednesday night as a weak ridge of high pressure builds in from the west and height rise aloft. Still could be some pesky clouds hanging on in the mountains with low temps ranging from the mid teens to mid 20s depending upon cloud cover. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... As of 318 PM EST Tuesday...12z guidance still all indicate that Turkey Day daytime will be uneventful weatherwise. Ridge of surface high pressure over the area will keep us dry. However, clouds will be on the increase as a weak upper trough and surface cold front quickly approaches from the west. With 925mb temperatures around -5C, daytime highs will be seasonably cool and generally in the low-mid 30s. The surface high moves off to the east as the trough and cold front approaches, and causes the low/mid level flow to become more southwesterly. The trough and relatively cold air aloft will help to activate some lake effect snow showers off Lake Ontario late in the day and during the evening. With the southwest flow, expect snow showers to push into the St Lawrence Valley and western part of the `Dacks. This moisture will also get entrained into the overall trough and advected toward northern Vermont during the overnight hours. Have used a blend of guidance for the precipitation probability forecasts, with a little extra detail in timing/placement via the BTV 4km WRF output, resulting in roughly 30- 45% PoPs across parts of northern NY diminishing to 15-25% for the higher terrain of northern Vermont. Net result is that we`ll probably see about 1" of snow across parts of northern NY, with just a coating in northern VT at best. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 318 PM EST Tuesday...While the long term period continues to look active, there are no really no big systems on the horizon to speak of. The tail end of a decaying cold front will bring some scattered snow showers to the region Thursday night into Friday morning, followed by brief high pressure for the remainder of Friday into early Friday night. The weekend continues to look unsettled, but the latest trends are for one area of low pressure to track well north of the region, and another well offshore on Saturday, both delivering limited impacts to the northeast. The best chance for precipitation actually now appears to be post-frontal passage Saturday afternoon/night and through the weekend where upslope flow will enhance snow shower activity across the higher elevations. It will be noticeably warmer for Friday and Saturday though with deep southwesterly flow developing aloft. Highs should bump into the 30s/40s before falling back into the 20s/30s for Sunday/Monday as the upper trough settles overhead. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... Through 00z Thursday...Overall looking at increasing mid and high level clouds through about 10z...but ceilings will remain in the VFR category. After deeper moisture moves in ahead of a cold front and ceilings will lower into the MVFR and IFR categories for the remainder of the period. Visibilities will also lower into the MVFR category between 10z and 18z with rain and snow showers moving across the region. Once the precipitation ends...VFR visibilities are expected for the remainder of the period. South to southwest winds will prevail through about 12z...then a cold front moves in and winds shift to the west and northwest for the remainder of the period. Outlook... Wednesday Night: VFR. NO SIG WX. Thanksgiving Day: VFR. NO SIG WX. Thursday Night: MVFR. Slight chance SHSN. Friday: Mainly VFR, with local MVFR possible. NO SIG WX. Friday Night: VFR. Slight chance SHSN. Saturday: Mainly VFR, with local MVFR possible. Chance SHRA. Saturday Night: Mainly VFR, with local IFR possible. Chance SHSN, Chance SHRA. Sunday: Mainly MVFR, with local IFR possible. Chance SHSN. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Evenson/Sisson SHORT TERM...Nash LONG TERM...Nash AVIATION...Evenson is the U.S. government's official web portal to all federal, state and local government web resources and services.