Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 180630 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 130 AM EST Thu Jan 18 2018 .SYNOPSIS... Light snow, mainly over southern and eastern VT, will be ending this evening. A westerly flow of air with near normal temperatures will follow with a few light snow showers through the end of the week along with a general warming trend going into the weekend. Our next storm system will arrive early next week with a mix of precipitation. && .NEAR TERM /UNTIL 2 PM THIS AFTERNOON/... As of 656 PM EST Wednesday...The upper level trough is crossing through the region and the snow is slowly coming to an end across portions on the North Country. Expect that to continue with snow ending across Vermont in the next couple of hours. There will be some light lake effect across portions of the northern Adirondacks but accumulations should be minimal. Previous Discussion...The flow will become increasingly westerly with Low-level cold advection as 925mb temps fall to -10 or slightly cooler overnight. Steepening lapse rates with some light lake effect snow east and northeast of Lake Ontario tonight through tomorrow. Southern Saint Lawrence and Franklin counties in New York could pick up a dusting out of the band by Thursday night. An upper level trof may enhance the lake effect snow showers or flurries elsewhere as it moves quickly through the region Thursday night. Temperatures will remain fairly seasonal through Thursday night with highs generally in the 20s and lows in the high single digits to teens tonight under partly clear skies. && .SHORT TERM /2 PM THIS AFTERNOON THROUGH FRIDAY NIGHT/... As of 400 PM EST Wednesday...Looks rather uneventful weather wise as we end the work week. Low/mid level flow starts to veer to the southwest. This will start to bring in some warmer air aloft, which in turn will probably keep skies mostly cloudy from isentropic lift at mid levels. Models do suggest a few light snow showers coming off Lake Ontario during the first half of the day, before warming air aloft stops that process. Could see a residual flurry or snow shower in the St Lawrence Valley through mid-day. Otherwise expecting dry conditions, with temperatures topping out in the upper 20s to lower 30s. Should be quiet Friday night as well, though perhaps a light flurry close to the Canadian border where moisture will be a bit deeper. Lows won`t go down too far, generally 20s, with ongoing warm air advection and clouds. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 400 PM EST Wednesday...12z runs of the GFS and ECMWF weren`t too different with the overall large scale scenario, but differ with the smaller, but still significant details. Still looking at a fairly significant low pressure system to move through the region in the Monday-Tuesday timeframe. Still looking warm enough that we will be dealing with a mixed precipitation event, rather than all snow. But it`s not going to be warm enough to have an all rain event either. Stuck close with the overall model blend, but did raise low temperatures a little bit for Monday night. A few notes with regard to each day follow. Saturday: Westerly and relatively mild flow. Looks like 850mb temperatures surge above 0C, though the warm air doesn`t fully come in below that level. Still looking like lower 40s for highs are in the cards. Could be a bit breezy (gusts 20-25mph) at times as well. Not looking for any precipitation. Late in the day or evening, it appears a weak cold front will move into the region. Sunday: Some conflicting temperature signals in the guidance. ECMWF shows some chilly air pooling up just north of the border, while the GFS keeps it much further north. With light northwest flow, it`s possible we`ll see some of that colder air ooze southward, especially down the Champlain Valley, and keep highs only in the lower 30s. Both 12z models have trended a little cooler than their counterparts on previous runs. Thus the blended approach I used which gives highs in the upper 30s north to lower 40s south may be a bit too warm. Still looks to be mostly dry in either case. Monday/Tuesday: Still timing differences between models, with GFS running 6-12 hours faster, but the idea is still similar to our previous forecast. Namely a fairly deep low will move across the Great Lakes and into Ontario sometime early Tuesday. Ahead of this low, clouds and chances for precipitation will increase during the day Monday. Both models are now indicating there will be a secondary surface low develop along a cold front and ride up over our region on Tuesday. With this secondary low, that means the warmer air at lower levels will have a harder time of really coming in force and scouring out the low level cold air. Both the GFS and ECMWF suggest a widespread mixed precipitation event, with a general light snow to start, a good amount of sleet and perhaps areas of freezing rain in the middle, and ending as snow later Tuesday or Tuesday night. Given the increasing likelihood of such a messy scenario, I used a blend of a warmer GFS and colder ECMWF to drive the precipitation-type determination rather than keep to a simple rain/snow type forecast. Don`t put too much stock in exactly when snow or sleet or rain may occur in any specific location as forecasts will change a lot between now and then. If there is any good side, a colder solution means less of a hydro worry due to rain and snowmelt given the ice jams in place. High temperatures will most likely only top out in the 30s. Wednesday: No real cold air behind the system, so expecting seasonable conditions with highs in the 20s to lower 30s. Can`t rule out a few snow showers here or there. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... Through 12Z Friday...Latest IR satellite imagery shows region of stratus clouds extending from Lake Ontario ewd across much of nrn NY and far nrn VT. Should see persistent MVFR ceilings at MSS/SLK in association with expected low cloud trends, and may see occasionally lower (IFR) conditions at SLK with wswly upslope flow conditions. Other TAF locations from the Champlain Valley ewd should generally remain VFR through the period, with occasional ceilings 3.5-5kft. Winds generally expected S-SW throughout the TAF period at 5-10kts. Some valley channeled flow vcnty of KMSS will yield slightly higher wind speeds, generally 10-15kts. A modest northern stream shortwave trough may bring a few passing snow showers Thursday night. Coverage generally expected to be limited, and have only carried VCSH group at KSLK after 02Z for now. Outlook... Friday: Mainly VFR, with areas MVFR possible. NO SIG WX. Friday Night: Mainly VFR, with local MVFR possible. Slight chance SHSN. Saturday: Mainly VFR, with local MVFR possible. NO SIG WX. Saturday Night: Mainly MVFR, with local IFR possible. Slight chance SHSN. Sunday: Mainly MVFR, with local IFR possible. Slight chance SHRA, Slight chance SHSN. Sunday Night: Mainly MVFR, with local IFR possible. Slight chance SHSN. Monday: Mainly MVFR, with local IFR possible. Chance SHSN, Chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Sisson NEAR TERM...Deal/Sisson SHORT TERM...Nash LONG TERM...Banacos/Nash AVIATION...Banacos is the U.S. government's official web portal to all federal, state and local government web resources and services.