Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 310534 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 134 AM EDT Wed Aug 31 2016 .SYNOPSIS... Clouds will be on the increase across the north country overnight, as a cold front approaches from Ontario. There will be a chance of showers after midnight across northern Vermont and northern New York. On Wednesday, a cold front will move south from Canada and will bring rain showers to the region, along with a chance for thunderstorms, especially during the afternoon hours. A high pressure area over Ontario and the western Great Lakes on Thursday will build slowly east and bring fair and dry weather to the north country from late Thursday through Labor Day. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 1017 PM EDT Tuesday...Surface cold front extends from southwestern Quebec swwd across Georgian Bay and Lake Huron at 0215Z. Attendant mid-level closed low appears fairly vigorous on IR imagery, and is located west of James Bay, along with band of 60kt mean flow in the 500-300mb layer across nrn Ontario. Will see gradual height falls overnight in advance of this system as it translates esewd in prevailing wnwly flow regime. Widespread mid and upper level clouds in place across all but s-central VT late this evening. These clouds should preclude fog formation, and keep temps mild overnight (mainly in the 60s). Adjusted temps upward a couple of degrees above the MOS consensus for most areas (including a low of 67F at BTV). With mid-level height falls occurring during the pre-dawn hrs, some remnant shower activity may reach nrn NY into nwrn VT toward/after midnight. PoPs increase to 30-40 percent across nrn CWA during the pre-dawn hours. Question on Wednesday will be how much surface heating/destabilization can take place as surface and mid-level trough sharpens across sern Ontario during the afternoon hours. With S-SW winds in place, should see 2-M dewpoints climb into the low to mid 60s, but prevailing cloudiness should keep temps mainly mid 70s to around 80F for afternoon highs. With 700-500mb lapse rates generally < 6C/km, it appears SBCAPE values will be limited to below 1000 J/kg. Will see moderate 0-6km bulk shear (20-30 kts), and can`t rule out a few stronger storms with locally gusty winds, if sufficient PBL heating can occur. Otherwise, precipitable water values reach 1.5" or so, suggesting some locally heavy downpours are possible with embedded convective elements. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... As of 407 PM EDT Tuesday...chance for showers persists as cold front progresses from NW to SE across the North country Wednesday night into early Thursday. Showers will become less numerous during the day Thursday as the surface front exits SE VT during the morning. 500mb trough will continue to provide some lift with plentiful clouds and slight to low chance for showers. Otherwise NW flow will filter into the area with gradually drying conditions. Expect the base of the mid level trough to move across the region Thursday night with continued clouds. Temperatures Wednesday night will be near normal to slight above with cooler air more evident as max temps on Thursday peak in the 60s to mid 70s. Cooler temperatures expected Thursday night with mins in the mid 40s to mid 50s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 407 PM EDT Tuesday...Mid level trough exits south and east on Fridays with an isolated shower possible. After that, N to NW flow persists into Saturday as high pressure at the surface and aloft affect the region. This will result in mostly clear skies and dry weather with below normal temperatures moderating into the weekend. Overnight min temperatures Friday night and Saturday night will fall into the low 40s to low 50s as the surface ridge crests over the region and 850mb temps fall to 7C-8C. This ridge will also help keep a tropical system offshore Sunday into Tuesday, but run to run consistency is lacking at this time with regard to track. Will have to continue to keep an eye on this system. && .AVIATION /06Z Wednesday THROUGH Sunday/...
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Through 06Z Thursday...Mainly VFR through 14Z with sct/bkn cigs from 050-100 AGL at most terminals. A few showers may encroach toward KMSS/KSLK toward 12Z per output from a few of the hi-res models. However, paucity of current activity upstream across southern Ontario leaves low confidence of occurrence and will not include in the forecast at this point. After 14Z surface trough will swing into the area with scattered showers and a few storms expected. Mainly VFR continues, though brief MVFR/IFR possible and turbulence with any heavier convective cores. Severe weather is not expected at this point. Given scattered nature of convective coverage, only VCSH mentioned in forecast at this point and we`ll be able to fine tune this better later today once activity develops. Surface trough departs south by 00Z with cold front approaching from the northwest late. General coverage of shower/storm activity should wane over time with loss of heating, but enough dynamic support aloft to continue mention of VCSH. Winds light through 12Z, then trending south to southwesterly 6 to 12 knots thereafter. Outlook 06Z Thursday through Sunday... Wed night: LCL MVFR/IFR in showers and thunderstorms tapering off. Thu-Fri: A few light showers/sprinkles possible with local MVFR cigs but confined mainly to the mtns on Fri. Sat-Sun: Mainly VFR with building surface high pressure.
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&& .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...WGH NEAR TERM...Banacos/WGH SHORT TERM...KGM LONG TERM...KGM AVIATION...JMG/Sisson is the U.S. government's official web portal to all federal, state and local government web resources and services.