Area Forecast Discussion
Issued by NWS Burlington, VT

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791 FXUS61 KBTV 271901 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 301 PM EDT Thu Oct 27 2016 .SYNOPSIS... Precipitation will continue to overspread the region this afternoon with light rain or light snow at the lower elevations and light snow in the mountains. Eventually the lower elevations will change to rain tonight with snow continuing in the mountains. Watch for gusty southeast winds along the western slopes of the Green Mountains and the higher terrain this evening through the overnight hours. Rain will taper off by Friday afternoon before our next system arrives on Saturday for more precipitation. && .NEAR TERM /THROUGH FRIDAY/... As of 142 PM EDT Thursday...Forecast playing out with temperatures in the mid 30s to lower 40s right now...but still some larger temperature dew point spreads over the area. As light precipitation continues to move in from southwest to northeast this afternoon...cooling will take place and allow for a mix of rain and snow at the lower elevations due to wet-bulbing...but snow continuing at the higher elevations with no warm layer aloft moving in. Could get a little slippery east of the Green Mountains later this afternoon and evening with light snow followed by rain and colder pavement temperatures on secondary roads. Special weather statement issued earlier has this scenario handled well. Otherwise...going forecast in good shape. Previous Discussion... For tonight...initial band of warm air advect lift is located near the international border by 06z...with additional forcing arriving with potent short wave energy and strong upper level divergence signature. This combined with a deepening and closing off 5h/7h circulation moving from the Eastern Great Lakes into southern New England will produce additional precip across our region overnight into Friday. Models show good 1000 to 500mb relative humidity with favorable 850 to 500mb q-vector forcing parameters from 06z to 18z Friday. Will continue to mention pops near 100% overnight...before tapering off from west to east on Friday. Given the track of surface low pressure into the Gulf of Maine and closed 5h/7h circulation...thinking additional moisture with area of rain and summit snow continues for most of VT on Friday...including the Champlain strongly blocked flow develops. Total precipitation will range between 0.50 Saint Lawrence to 1.50 southern Greens and eastern Dacks. Given developing 925mb to 850mb low level jet of 40 to 50 knots from the southeast...expecting some impacts of terrain on precipitation fields. Highest amounts will be along the southeast upslope regions from Ludlow/Killington to Stowe to Jay Peak...with some shadowing in the Champlain Valley/Northeast Kingdom initially. wind shift to the northwest on Friday...the northeast kingdom and western slopes/champlain valley will see some additional precipitation. Snow levels become very tricky overnight into Friday as soundings show warm layer developing between 5000 and 7000 feet associated with southwest winds with cold pocket from 2500 to 3500 feet associated with upslope cooling on southeast winds. By 15Z Friday...cooling aloft occurs as winds change to the east then north by early afternoon and progged 850mb temps drop below 0c. Current thinking snow continues near the summits through early this evening...then changes to a wintry mix with pockets of freezing rain in the midslopes...before changing back to all snow by midday friday at the summits and cold rain below 2000 feet. Once again snow accumulations will be very elevation dependent with summits above 4000 feet seeing around 6 inches with several inches possible around 2000 feet and some minor ice accumulation in between. This should have very limited impacts...given elevation. Still anticipating breezy to gusty southeast winds along the western slopes from near Rutland to East Middlebury to Nashville tonight. The strongest winds will occur between 7 PM and 2 AM associated with 925mb to 850mb jet of 40 to 50 knots. Thinking localized surface wind gusts to 35 knots is possible with a few isolated power outages possible. Temperatures mainly in the mid 30s to mid 40s today...fall back only into the lower 30s to lower 40s overnight...with similar profiles expected on Friday. Hourly temps will drop several degrees when precip starts today and during higher precip rates...have tried to show this detail in grids. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... As of 316 AM EDT Thursday...Brief ridging at the surface and aloft builds in over the North Country for the first half of Friday night before heights begin to fall again ahead of weak low pressure which will pass north of the Canadian border on Saturday. Overnight temp forecast will be tricky as winds slacken in the wake of an exiting system to our east, but pick up again markedly after midnight from the southwest. Not expecting a whole lot of clearing, so think mins will be mild and slightly above freezing. Timing of lows I think will fall early across the St. Lawrence and Champlain Valleys before warming slowly through the night with increasing winds, but elsewhere likely follow the normal diurnal curve. Weak low passes north of the border on Saturday and while low/mid level moisture is abundant with this system, overall forcing is rather weak so even though we continue to highlight likely PoPs for showers, QPF will be light with temps pushing well above seasonal normals into the upper 40s east to mid 50s west. By nightfall, the deepest low level moisture begins to shift east as the low tracks off into the Canadian maritimes and thus precipitation will gradually taper to nil by Sunday morning as high pressure building eastward into the Great Lakes approaches. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 316 AM EDT Thursday...The extended period looks to be fairly dry with a fast zonal flow aloft Sunday trending towards ridging for Monday and Monday night. A strong low developing out of the northern plains Monday afternoon tracks north of Lake Superior Monday night to the tip of James Bay by Tuesday night pushing a dry warm front through the area. We remain mainly dry all the way through Wednesday with temps warming well into the 50s for Tuesday and Wednesday in increasing south/southwesterly flow. && .AVIATION /19Z Thursday THROUGH Tuesday/... Through 18z Friday...Current VFR conditions will quickly lower to MVFR by 20z as light precipitation moves into the region. Precipitation should be a mix of rain and snow at the lower elevations before becoming all rain after 00z...with snow in the mountains. Winds will be from the east and southeast with gusts in the 15 to 25 knot range through about 12z...then shift around to the northwest after 12z. At this point...ceilings and visibilities will lower into the IFR and MVFR categories for the remainder of the period. Outlook 18z Friday through Tuesday...Conditions will gradually improve back to MVFR and VFR after 18z Friday as precipitation comes to an end. A warm front feature lifting across our taf sites on Saturday morning will shift the winds to the southwest with some scattered showers possible...especially mss/slk. Expecting mainly vfr conditions with intervals of mvfr cigs possible across northern NY taf sites on Saturday. Gusty southwest up to 35 knots are possible at MSS with 30 knots expected at SLK/BTV on Saturday. Another wind shift to the west/northwest will occur Sat Night into Sunday with additional scattered showers. Drier conditions with vfr flight conditions for Sunday afternoon into Monday. && .MARINE...
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As of 255 PM Thursday...Several bouts of strong winds and rough conditions are expected on the lake the next few days. South/southeast winds of 15 to 25 knots are expected through late evening, before diminishing after midnight. During the day Friday, winds will switch to the northwest and strengthen, with winds approaching 25 knots for the afternoon and early evening. Winds will diminish Friday night, but then switch to southerly on Saturday morning. Winds will quickly increase again to around 25 knots during the mid-day hours. These strong and gusty winds will result in choppy conditions out on the lake.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Taber NEAR TERM...Evenson/Taber SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Evenson/Taber MARINE...Nash is the U.S. government's official web portal to all federal, state and local government web resources and services.