Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 262311 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 711 PM EDT Wed Oct 26 2016 .SYNOPSIS... Partial clearing and light winds are expected tonight as high pressure briefly settles over North Country. This will lead to chilly temperatures tonight, with lows generally in the 20s. The next low pressure system will approach from the Great Lakes later Thursday, with the primary low tracking into the St. Lawrence Valley before a secondary low takes over closer to the New England coast during Thursday night. After increasing cloudiness Thursday morning, looking for precipitation to develop Thursday afternoon and continue through Thursday night into Friday morning. After a brief rain/snow mix, precipitation will be predominantly rain at elevations below 2000 feet. Several inches of wet snow accumulation is possible at the higher summits. Total rainfall amounts generally a half inch to one inch, highest along the eastern slopes of the Adirondacks and Green Mountains. && .NEAR TERM /THROUGH THURSDAY NIGHT/...
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As of 711 PM EDT Wednesday...Only small changes to sky cover the early part of the overnight period. IR satellite loop showing low clouds have eroded a small amount, however high clouds in advance of tomorrow`s system are moving across the region from west to east. Otherwise have left temperatures alone as previous forecast still had considerable cloudiness in place to keep temperature from radiating down too far. Previous discussion...Mostly cloudy to cloudy conditions persist in NW flow, with lingering inversion near 5kft (per RAP soundings) helping to trap moisture and stratocu layer. Sfc ridge axis across sern Ontario will gradually shift ewd this evening into tonight. Effect will be for winds to become light and variable, and should see some partial clearing during after sunset. Depending on amount of clearing and radiational cooling, should be a chilly night. Certainly lows in the 20s for most sections. If skies can become mostly clear, may see a few readings in the teens for the nrn Adirondacks. Other than a lingering flurry across n-central into nern VT late this aftn, expecting dry conditions overnight. Dry conditions will be short-lived as next wave of low pressure approaches from the Great Lakes region on Thursday. Surface low will shift across Lake Erie/nwrn PA late Thursday morning, with increasing mid-upr clouds across our area. Leading surge of 850-700mb warm advection and associated precipitation arrives around 18Z across s-central VT and into the Adirondacks of NY. Precipitation will overspread the remainder of the North Country late in the afternoon...early evening for far nern VT. In terms of precipitation type, PBL will have a chance to warm out ahead of the arriving precipitation, generally into the low 40s. Anticipate some wet-bulb cooling with precip onset as column saturates, allowing for wet snowflakes as low as 500ft elevation mid- afternoon Thursday, but thereafter, looking at mainly a rain event below 1500ft with continued WAA and strengthening S-SE flow. Generally no snow accumulation at all below 1500 ft. May see a slushy coating to an inch 1500-2500ft. Above 2500ft, temps will hold on below freezing longer, and could see 4-8" across the highest summits of nrn NY and central/nrn VT through Thursday night. With a 50-kt sly low-level jet, there is a warm (above freezing) layer that comes in above summit level, so may see some periods of sleet as well into Thursday night. So, not expecting any impact for population/roadways, but the highest summits could see a moderate accumulation of wet snow based on current trends. Highs on Thursday generally in the low-mid 40s, and near freezing across the highest summits of VT and nrn NY. One other issue will be moderate winds on the western slopes of the Green Mtns, and across all of the higher terrain. SE winds peak during Thursday evening, and should see 15-25 mph with a few gusts 30-35mph possible along the immediate western slopes, as primary surface low tracks into the St. Lawrence Valley. Later Thursday night, gradient slackens as secondary low development takes place across sern new England...and should see sfc winds weaken. Stable low-level conditions will limit areal coverage of gusty winds to the immediate wrn slopes. Winds at summit level could reach 50mph consistent with model soundings closer to 4-5kft. In terms of total QPF, looking for some precipitation enhancement along the ern slopes of the Greens and into the ern slopes of the Adirondacks given low-level sely (upslope) conditions. Total rainfall amts ranging from 0.6" across the St. Lawrence and Champlain Valleys, but locally around 1" in aforementioned upslope flow areas, from Ludlow up to Bethel, and across portions of Essex/Clinton Counties in NY.
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&& .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 328 PM EDT Wednesday...The potential low pressure system will be losing energy Friday morning as a shortwave vorticity maxima pushed the center of the low south and east from the Saint Lawrence to off the coast of New Hampshire. As this happens the warm air will continue to surge north and generally rain will be falling over the North Country except for a few higher elevation sites over the Adirondacks and northern edge of the spine of the Greens. By mid day northwest flow develops and there will still be some low level moisture at 925mb rh still exceeds 98% however moisture in the snow growth zone will be minimal so any snow/flurries will be confined to the areas with orographic lift. Friday should only see 0.10-0.20" of qpf across the eastern Vermont zones mainly falling as rain with a couple of hundredths of qpf across the rest of the north country. Snow totals will really be continued to elevations 2500-3000 feet and above and should only amount to an inch or two of additional accumulation of heavy wet on Friday adding to the 4-8 already from Thursday. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 357 PM EDT Wednesday...To start the weekend we will be under marginal warm air advection on Saturday. A ridge of high pressure will be slowly moving east in and 850 temps warm to +6C - +8C. Clouds will be increasing and thickening as a weak northern stream low tracks well to the north of the forecast area. With boundary layer temps warm and little cold air to speak of it will be just a typical late October rain event. QPF totals will be on the lower side but most of the area should see some light rain showers. Behind that low, a eastern conus ridge builds in and leads to dry air through the mid week before another low pressure system tracks just north of the Great Lakes and brings an additional chance for showers to start November. && .AVIATION /23Z Wednesday THROUGH Monday/... Through 18z Thursday...Localized MVFR ceilings at SLK this afternoon, but otherwise VFR at the TAF sites with cigs generally 3.5-5kft. HIR TRRN will remain obscd into tonight with prevailing stratus/stratocu. Anticipate partial clearing and light winds overnight, with VFR conditions. Approaching low pressure from the Great Lakes will bring increasing clouds above 10kft Thursday morning, lowering to near 8kft SLK/RUT toward 18Z Thursday. Most of the precipitation should hold off until after 18Z Thursday, but did include VCSH at RUT/SLK in line with 30-50percent chance of toward the end of the TAF period. Outlook 18z Thursday through Monday...An active pattern with changeable flight conditions expected during this time period. Mainly a rain event beginning Thursday aftn. However, initial precipitation will be a rain/snow mix, especially at MPV/SLK, and snowfall could result in some IFR conditions for several hours Thursday aftn. A slushy accumulation possible at SLK (coating to 0.6"), but no snow accumulation expected at the other TAF locations. Rain continues at the TAF sites Thursday night with widespread MVFR, and intervals of IFR. SE wind gusts in excess of 25kts possible at KRUT 22Z Thu thru 04Z Fri. In addition...strong low level jet of 50 knots around 5000 feet will produce areas of turbulence and wind shear during this time period areawide. Low pressure departs across the Gulf of Maine during the day Friday, with winds shifting into the NW. Will see diminishing precipitation chances from west to east through the day. Next system with breezy southwest winds arrives late Saturday into Sunday with additional precip and potential impacts to aviation. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Banacos NEAR TERM...Banacos/Hanson SHORT TERM...Deal LONG TERM...Deal AVIATION...Banacos/Taber is the U.S. government's official web portal to all federal, state and local government web resources and services.