Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 250712 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 312 AM EDT Thu Aug 25 2016 .SYNOPSIS... High pressure will provide another nice evening across the region with mainly clear skies and seasonal temperatures. An approaching surface trough will bring increasing clouds and the threat of showers across northern counties by Thursday morning, and a few thunderstorms across the entire area by Thursday afternoon into Friday morning. Behind the front a return to seasonably mild and dry weather is expected for the upcoming weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 105 AM EDT Thursday...Overall forecast in good shape with only tweak being the onset of any showers across northern New York early this morning. Looks like it will be a bit closer to sunrise and have slowed everything up by about two hours. other changes needed. By Thursday we continue to advertise an increasing threat of scattered showers and a few thunderstorms as weak surface trough will interact with mid-level energy and nominal instability. Height falls remain negligible and given rather meager mid level lapse rates severe weather is not expected. However, latest AMSU/SSM-I PWAT analysis does show the northern periphery of a very moist airmass currently residing across the Upper Ohio Valley and Great Lakes (1.6 to 2.0 inches). It is this airmass that will advect east- northeast and reside across our area during the day, so the idea of brief tropical-like downpours in scattered convective cores still appears reasonable at this point. Mid-level flow looks strong enough to keep activity moving however, so from a hydrological standpoint I`m not overly concerned. With higher coverage of clouds I did trend maximum temperatures downward just a tad and in closer agreement with blended bias-corrected output offering readings in the 78 to 84 range. Dewpoints will be rather high though (65 to 72F) so it will feel rather muggy. && .SHORT TERM /FRIDAY THROUGH SATURDAY/...
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As of 253 AM EDT Thursday...Forecast challenge continues to be areal coverage of potential precip on Friday morning across our eastern forecast area. NAM/GFS are in good agreement with best 850 to 500mb moisture at 12z from the Champlain Valley eastward...while ECMWF shows a moderate band of qpf from eastern Lake Ontario into central VT around 12z. This seems to be related with some convective feedback issues...therefore will trend toward chance pops from Champlain Valley eastward through 15z...then taper to <14% by afternoon. Soundings show deep dry layer and associated subsidence between short wave energy pw values fall from 1.75 to 0.75 inches by 00z saturday. This drying will support mostly sunny skies by afternoon with temperatures warming into the 80s...with only weak cold air advection behind boundary. By 12z saturday a 1025mb surface high pressure is building into the North Country with dry north winds continuing. A seasonably cool day with low relative humidity values are expected on Saturday...with temps mainly in the 70s. Winds will generally be from the north/northwest at 5 to 15 mph.
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As of 253 AM EDT Thursday...Overall large scale pattern supports building ridge across the Mid Atlantic States with moderately fast westerly flow aloft over the NE CONUS. Both ECMWF and GFS show next short wave energy and ribbon of enhanced mid level moisture approaching our western zones by 00z Monday...and quickly spreading eastward overnight into Monday. Will continue with previous forecaster idea and mention chance pops during this time period. Instability looks minimal with surface based CAPE values <500 J/kg and lis around -1c. Thinking best window for showers will be between 21z Sunday into 06z Monday...based on 850 to 500 moisture and progged position of 5h vort associated with trof lifting across southern Canada. Surface high pressure redevelops across the region for Tuesday into Wednesday with dry conditions anticipated. Surface analysis shows breezy southwest winds are likely on Sunday ahead of boundary with gusts to 30 mph possible Saint Lawrence and Champlain Valley. Progged 850mb temps warm to 16c by 18z Sunday...supporting upper 70s mountains to mid 80s valleys. If clouds arrive sooner than anticipated temps will be 4 to 8 degrees cooler on Sunday...based on this have stuck very close to superblend numbers. On Monday very weak low level cold air advection develops behind front with progged 850mb temps dropping back between 12c and 14c...supporting highs l/m 70s mountains to upper 70s to lower 80s valleys. Warmer temperatures build by the midweek with progged 850mb values around 18c by 12z Thursday. This will support highs well into the 80s with lows mainly in the 50s mountains to 60s valleys. Overall...rh values will remain in the comfortable zone through midweek...before increasing toward next weekend. Next chance of showers/storms arrives late next week.
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&& .AVIATION /07Z Thursday THROUGH Monday/... Through 06Z Friday...Overall looking at VFR conditions through the period. Expecting scattered showers and isolated thunderstorms to move across the area mainly between 16z and 00z...but again looking at VFR conditions with some MVFR ceilings and visibilities in and near any of the showers or storms. Winds will be increasing from the south and southwest this morning with gusts in the 15 to 25 knot range...especially this afternoon...before gusts taper off after 00z. NOTE: Rutland AWOS (RUT) is now operational. Outlook 06Z Friday through Monday... 06Z Friday through 18Z Friday...VFR with scattered MVFR/brief IFR in scattered showers/thunderstorms. Brief heavy downpours with reduced visibility and turbulence in stronger convective cores. 18Z Friday through 00Z Monday...VFR/high pressure. 00Z Monday onward...VFR with scattered showers/MVFR possible. && .EQUIPMENT... As of 0730 PM EDT Wednesday...The AWOS (automated weather observing system) at the Rutland-Southern Vermont Regional Airport (KRUT) is now back in service and operational. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...Evenson/JMG SHORT TERM...Taber LONG TERM...Taber AVIATION...Evenson/JMG EQUIPMENT...WFO BTV is the U.S. government's official web portal to all federal, state and local government web resources and services.