Area Forecast Discussion
Issued by NWS Burlington, VT

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015 FXUS61 KBTV 241900 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 300 PM EDT Wed Aug 24 2016 .SYNOPSIS...
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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 thundestorms 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.
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&& .NEAR TERM /THROUGH THURSDAY/...
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As of 300 PM EDT Wednesday...Another quiet evening is expected across the area as high pressure progresses offshore while a few high clouds filter in from the north and west. Dry weather is expected as temperatures fall into the 70s, bottoming out in the 60s to around 70 by morning as clouds slowly increase north and west with the approach of a weak surface trough. Latest CAM output suggests at least a nominal threat of a few light showers or sprinkles far west toward morning, but most areas should remain dry under continued light southerly flow. 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.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/... As of 301 AM EDT Wednesday...Timing of energy and associated moisture continues to be the challenge in developing fast westerly flow aloft. Models continue to show system coming in several different pieces...making the exact window for predicting the highest pops difficult. Initial 5h vort over the northern plains will shear out in flow aloft and weaken across our region on Thursday morning. This energy...along with increasing 850 to 500mb moisture will result in chance pops across northern NY. This feature will quick exit our region by 18z...before more energy and moisture arrives around 00z Friday. Higher surface dewpoints from earlier showers...along with surface heating will produce surface based CAPE values up to 800 J/kg across the Saint Lawrence Valley around 00z. Have mention chance of thunder with likely rain showers for the combination of instability and dynamics. The actual surface boundary crosses northern NY overnight and is located in the Champlain Valley on Friday morning. Will continue to mention chc to likely pops overnight Thursday into Friday...before tapering from west to east by Friday afternoon. I realize we will have 12 to 18 hours of pops for only a 2 to 4 hour window of precip...but timing of multiple short waves in fast flow aloft is difficult. PWS surge to 1.75 ahead of boundary...supporting some isolated heavier downpours...especially in the stronger convective elements over northern NY/VT on Thursday evening/night. Still thinking qpf will range between 0.25 and 0.75...with some downslope on breezy 850mb southwest winds of 35 to 40 knots. These winds and pressure analysis support some localized surface gusts to 30 mph across the saint lawrence and champlain valleys on Thursday afternoon/evening. These winds shift to the west and much drier air arrives on friday afternoon...with cooler temperatures by the weekend. Progged 925mb temps between 22-24c...support highs well into the 80s on Thursday...with maybe a spot 90 in the warmer valleys...expecting clouds to limit surface heating some. Temps will be slightly cooler on Friday...behind boundary. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 301 AM EDT Wednesday...1026mb surface high pressure will build into the north country on saturday and continue for sunday. This will result in plenty of sunshine with mild days and cool nights. Given the very dry profiles...expect large diurnal swings in the temps from mid 40s to lower 50s to mid 70s to lower 80s. Next system in the fast westerly flow aloft approaches our region late sunday night into monday with a chance of showers. Progged instability parameters are minimal so no mention of thunder thru 16z monday. Better surface heating and weak surface boundary on Monday afternoon may produce a few rumbles of thunder. Will mention chance pops with best chance of thunder based on surface based cape values of 500 j/kg will be over central/eastern vt. Progged 850mb temps range between 12-14c for monday into tuesday...supporting highs mid 70s mountains to lower 80s valleys with lows mainly in the 50s to lower 60s depending upon elevation. && .AVIATION /19Z Wednesday THROUGH Monday/... Through 18Z Thursday...VFR under light to moderate southerly flow and SKC-SCT250 through 06Z Thursday. After 06Z thickening cloud cover to BKN/OVC 060-150 AGL with scattered showers/isolated thunderstorms arriving from the west with approach of cold front. Activity should be scattered with highest coverage generally toward the end of the TAF forecast cycle at northern/western terminals. NOTE: Rutland AWOS (RUT) is not operating. Because of the lack of disseminated observations, we continue our suspension of amendments for the RUT TAF. Once the communication problem has been resolved, and we again get routine observations automatically transmitted, we will lift that restriction. Outlook 18Z Thursday through Monday... 18Z Thursday 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 118 PM EDT Wednesday...The AWOS (automated weather observing system) at the Rutland-Southern Vermont Regional Airport (KRUT) remains out of service at this time. The FAA has advised us that a new computer is on order to fix the problem at the KRUT AWOS. There remains no estimated return to service at this time. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...JMG NEAR TERM...JMG SHORT TERM...Taber LONG TERM...Taber AVIATION...JMG EQUIPMENT...WFO BTV

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