Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 261839 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 239 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/... As of 138 PM EDT Wednesday...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. && .SHORT TERM /FRIDAY/... As of 418 AM EDT Wednesday...Overall idea from the previous forecast and mine before that remains in place for the end of the work week as low pressure pulling out of the Eastern Great Lakes and Ohio Valley will bring mixed precipitation mainly in the form of rain and snow to the North Country. Main change with this morning`s forecast is to offer a slower arrival time of the onset of precipitation, and adjust temps warmer for the bulk of the event. Consensus amongst the latest NWP guidance is that deeper layer moisture doesn`t really arrive until at least mid-day as the parent surface low tracks northeast through northern New York. Precipitation at the onset will mainly be in the form of rain for most locations with boundary layer temps in the 40s, but across the Adirondacks temps will likely wet-bulb down to support snow. As we move into Thursday evening and night, a developing 925/850mb southeasterly jet of 40-50kts will usher in above freezing temperatures aloft transitioning ptype to a rain/snow mix for the Adirondacks and portions of eastern Vermont, and eventually all rain area-wide after midnight. Thereafter, potent shortwave energy rounding the base of an upper trough swinging to the area develops a weak surface low along the frontal wave and eventually the aforementioned parent low transitions its energy to this new low over southern New England by Friday morning. Wrap- around moisture combined with developing northwesterly flow on Friday will keep precipitation going, especially across the upslope regions of the Adirondacks and northern Greens but remains mainly rain as surface/boundary layer temps remain mild. All in all impacts from this event are very limited at the surface, with any snow on the front side of the system only a dusting to perhaps 2", and any downslope winds along the western slopes Thursday night limited to 20-30 mph as the timing of max winds aloft coincide with the heaviest precipitation occurring. That said, it will be a different story across the higher peaks above 2000 feet where thermal profiles still support storm total accumulations in excess of 6" to up to as much as a foot of heavy wet snow through Friday. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 418 AM EDT Wednesday...In general, the long term period from the weekend into early next week has begun to trend more quiet than what we`ve seen the past few days. Trends are for another northern stream clipper to track north of the BTV CWA Saturday offering a return to above normal temperatures and just some light rain showers. Behind that, high pressure builds in and dominates for Sunday and Monday before a strong low develops out of the northern Plains and tracks well to our northwest on Tuesday. A weak front traverses the forecast area Tuesday afternoon, but with limited moisture to work with, we`re not expecting a whole lot of precipitation. Temperatures though sky- rocket well above freezing aloft supporting highs pushing back into the mid-40s to low 50s on Monday, and further into the mid/upper 50s for Tuesday. && .AVIATION /18Z 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 SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Banacos/Taber is the U.S. government's official web portal to all federal, state and local government web resources and services.