Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 231906 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 306 PM EDT Thu Mar 23 2017 .SYNOPSIS...
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Clear skies will give way to increasing clouds and the threat of light snows by tomorrow morning as a warm front pushes into the area. Mixed precipitation or rain will be likely on and off into the coming weekend as this front waffles south and north across the region. Temperatures will moderate back toward more seasonal late March values through the period.
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&& .NEAR TERM /THROUGH FRIDAY NIGHT/...
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As of 306 PM EDT Thursday...A nice rebound in temperatures under full sun has occurred this afternoon as northwesterly flow slowly diminishes with modifying arctic high pressure sprawled across the eastern seaboard. KBTV has hit 32F as of 230 pm. For tonight clear skies will slowly give way to thickening and lowering mid and upper level clouds as we progress after midnight as winds trend light. An approaching warm frontal system will be approaching from the south and west during this time frame and the leading edge of its precipitation shield will begin to encroach into our far western counties toward sunrise Friday in the form of light snows. Temperatures will bottom out early given the clear skies (5 to 15 above in the mountains/teens to lower 20s valleys) but will trend steady or slowly rise overnight as clouds arrive and light southerly return flow develops. A messy day then on tap for Friday as the warm front marches into the region under strengthening southerly flow and widespread mixed precipitation. Some channeling effects likely in the Champlain Valley where gusts to near 30 mph look plausible at this point. Boundary layer to mid level thermal profiles will be critical in determining eventual p-type as widespread light snows slowly transition to a mix of snow/sleet and eventual rain from the Champlain Valley west. P-type should hold more in the form of snow and/or a mix of snow/sleet across much of east central and northeastern VT where mid level warming will be less and colder near surface layers will be harder to scour out. Mixed precipitation top down methodology using a variety of model output continues to support the idea of little in the way of freezing rain with this feature, which appears reasonable seeing the primary mid-level warm layer generally runs in the 0-3C range through 21Z. Experience would suggest however at least some patchy -fzra may occur here and there through the morning hours. Front end snow totals should generally run in the 0.5 to 2 inch range, with slightly higher totals from 1.5 to 4 inches likely across east central and northeastern VT. Given the front end light snows will inhibit any pavement icing and only low probabilities of a few hundredths of ice accumulation are suggested (if any) will hold off on issuing any advisories at this point. Late day high temperatures should range from the lower to mid 30s east and north, and the upper 30s to lower 40s elsewhere. By Friday night widspread light rains (or mixed precipition north and east) will gradually wane over time as best warm thermal advection lessens. Later at night models continue to suggest building high pressure to our north will push the front back southward into the area with flow transitioning to a light northerly regime by daybreak Saturday. This will tend to shunt the precipitation shield southward as well as coverage/intensity lessens. Some lingering light rains/mixed precipitation/light snows will remain possible though settle generally into our southern counties by morning. Lows a bit tricky though with expected abundance of clouds upper 20s to lower 30s looks reasonable for most spots.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 200 AM EDT Thursday....High pressure shifts east of our longitude overnight and into the Gulf of Maine by 09-12z Friday. This will allow for a light S-SW return flow to develop. Aloft, will see a warm front approaching from wrn NY and sern Ontario, and increasing 850-700mb WAA will result in thickening mid-level overcast. These factors will keep overnight temperatures generally in the mid teens to lower 20s, with a tendency for a slow rise in temps toward daybreak Friday, especially west of the Green Mtns. Moderately strong 850-700mb WAA with approaching warm front brings developing stratiform precipitation beginning during Friday morning from SW-NE. It appears thermal profiles will initially support snow, with a transition to sleet/rain as the day progresses. Subfreezing thermal profiles will persist longest across central/ern VT and in the nrn Adirondacks, where 1-3" of wet snow/sleet are forecast. Should see generally 1" or less wet snow in the Champlain Valley as PBL temperatures warm more quickly thru the 30s. Could see some minor impacts to travel especially around the time of onset of the mixed wintry precipitation (and especially away from the Champlain Valley), and will continue to highlight in the Hazardous Weather Outlook. Afternoon highs on Friday generally 36-39F, except 33-34F across portions of ern/nern VT. First wave of low-level WAA passes to our east Friday evening/night, but E-W oriented low-level frontal zone will become quasi-stationary across nrn NY/nrn VT. May be a tendency for a shallow nly wind shift after midnight with strong high pressure building into wrn Quebec, so we`ll need to monitor trends with the frontal position overnight with possible shallow CAA near the intl border. Anticipate continued overcast skies, but with just very light rain/drizzle or isolated pockets of snow/sleet/freezing drizzle across far nrn areas. Temperatures will generally hold in the low-mid 30s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... As of 309 AM EDT Thursday...Interesting forecast with rather active period expected and above normal chances for mixed precipitation. Large high builds down from Canada on Saturday and pushes surface boundary southward out of the area...which will help bring precipitation to an end during the morning hours. Highs will range from the mid 30s along the Canadian border to the upper 30s and mid 40s elsewhere. Northwest flow aloft Saturday night continue to bring colder and drier air into the region. An upper trough will move east from the Ohio Valley and this will allow the boundary that moved out of our area on Saturday to return northward into our region and enhance the potential for precipitation...especially Sunday afternoon and night. Thermal profile suggests mixed precipitation with surface cold air holding in the longest across eastern Vermont Sunday night into Monday. Precipitation should become rather widespread Sunday night into the first part of Monday as the trough moves across the area. Will have to monitor this situation closely in case there will be a need for a winter weather advisory. There will be a brief respite in precipitation Monday night into the first part of Tuesday...but another trough of low pressure will move toward the region later Tuesday into Wednesday and bring more precipitation to the area. Still cannot rule out some mixed precipitation...but at this time looking at either rain or snow with this system. The precipitation should be fairly widespread as well given the strength of the upper trough moving into the region. && .AVIATION /19Z THURSDAY THROUGH TUESDAY/... Through 18Z Friday...VFR through 12Z as high pressure gives way to approaching warm front and associated pcpn. SKC expected through 00Z, then slowly thickening/lowering VFR OVC in the 00Z to 12Z time frame. Winds light/modest northwesterly through 00Z, trending light overnight. After 12Z Friday widespread snow overspreads all terminals, likely transitioning to a snow/sleet/rain mix from Champlain Valley terminals west toward the end of this forecast cycle. Winds trending southerly 5 to 15 knots, most pronounced at KBTV/KPBG where valley channeling effects may push gusts near 25 kts. Outlook 18Z Friday through Tuesday... 18Z Friday through 18Z Saturday...widespread light mixed pcpn likely, slowly settling southward and lessening in coverage by Saturday afternoon affecting mainly southern terminals at that point. Highest threat of mix to occur at northern terminals. 18Z Saturday through 12Z Sunday...trending mainly VFR/pcpn-free as Canadian high pressure noses briefly southward into the area. 12Z Sunday through 12Z Tuesday...widespread mixed pcpn and/or rain return to the region. 12Z Tuesday onward...light and spotty mixed pcpn transitions toward a period of steadier rains by Wednesday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...Banacos LONG TERM...Evenson AVIATION...JMG

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