Area Forecast Discussion
Issued by NWS Burlington, VT

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421 FXUS61 KBTV 261030 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 630 AM EDT Tue Jul 26 2016 .SYNOPSIS... High pressure slowly builds into the region today and Wednesday. Dry weather is expected along with a warming trend as temperatures by Wednesday will be well into the 80s with a few lower 90s expected. The pattern will change later Wednesday night through Friday as a broad trough of low pressure moves into the region and enhances the potential for precipitation. High temperatures will be at or slightly above normal on Thursday and Friday. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM EDT Tuesday...Quiet weather is expected in the near term period. Have made just some minor tweaks based on current temperatures and some clouds already developing over parts of northern New York. Today: Dry weather is expected as high pressure begins to slowly build into the region. Water vapor imagery shows plenty of dry air over the region in the mid and upper levels...but there will be lower level moisture in place. This combined with steepening lapse rates should help generate some shallow cumulus clouds over the higher terrain...but no precipitation is expected. Temperatures at 925 mb support the idea of highs in the upper 70s to mid 80s with a few spots reaching the upper 80s. Tonight: High pressure continues to build into the region for a continuation of dry weather. Any shallow cumulus over the higher terrain will dissipate around sunset and clear skies/light winds will take over. This could lead to some fog in the favored locations. Low temperatures will range from the mid 50s to mid 60s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 331 AM EDT Tuesday...00z guidance suite did not indicate the need to make any substantial modifications to the forecasts we`ve been offering for the last couple of days. So with that, a few thoughts on each day Wednesday: all guidance indicates 925mb temperatures will be about 23C (give or take a degree) as the westerly flow aloft will advect in a little piece of the heat that is solidly in place to our west and south. given plenty of sunshine and expected deep mixing to about 6000ft (800mb), we`ll end up with a deep dry adiabatic lapse rate and even super-adiabatic near the surface. what does this mean? well, a hot day. 23C at 925mb supports temperatures topping out into the lower 90s in the valleys. Well into the 80s elsewhere. Followed the previous forecaster and painted in temperatures that were closer to the warmest guidance. There will be a weak cold front north of the border during the day that will likely spark some t-storms across Quebec. By very late in the afternoon/early evening, that front will have sagged south enough that we may have and isolated shower/t-storm working their way through US Customs and Border Protection. Thinking any isolated convection would probably be getting into far northern NY and Vermont just before sunset. Minimal instability, so not looking for anything strong. Given the warm airmass, we will continue to have minor amounts of instability much of the night. Add in a little bit of low-level forcing with that weak front, and isolated shower or t-storm Wednesday night for northern sections seems reasonable. Temperatures will only drop to the mid-upper 60s for most areas. Thursday: Weak front continues to slowly move south, and will act as a focus for scattered showers and a few t-storms. Models show precipitable water values rising above 1.5" as the moisture pools along the front, so could be an isolated heavy downpour. More in the way of clouds and a bit cooler temperatures aloft will result in temperatures about 5 to 7 degrees cooler than Wednesday. Still above normal however. Ranging from lower 80s across the north to perhaps around 90 down in the Connecticut River valley around Springfield VT. Kept PoPs in the 35-45% range at this point. Later forecasts may show an increase. At this point not expecting any strong storms as guidance doesn`t show over the top instability or dynamics. Probably more just "garden variety" type stuff. Thursday night the bulk of the showers will push south of the region -- perhaps still hanging on around Rutland. Overnight lows will range from the upper 50s to lower 60s. Might be still a bit muggy down south. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 331 AM EDT Tuesday...00z GFS and ECMWF continue to be similar to their own previous runs, and have diverging solutions between one another. So confidence is not all that high, especially for the weekend and early next week. At least there does not appear to be any high impact/significant weather on the horizon. Friday: Weak/diffuse front will be somewhere to the south, but close enough that southern sections will see more clouds and a chance for a shower or isolated t-storm. Could end up being a sunny/dry day closer to the Canadian border. GFS and ECMWF are in decent agreement, though GFS has a low pressure moving south of New England during the day. Not really a player in our weather. Temperatures should be close to normal (upper 70s to lower 80s). Saturday/Sunday: Model differences more significant. GFS takes it`s surface low off the coast, and we have a light northerly flow develop which cools us down and dries us out. At face value, GFS says below normal temperatures with highs only in the 70s on Saturday, and back to near normal Sunday with plenty of sun. ECMWF keeps the diffuse front stationary to our south thru the weekend, and has a couple of weak lows move along that front. It paints a generally mostly cloudy weekend with scattered showers both days. Given this continued uncertainty, the best course of action remains sticking to a blend. Thus 20-35% PoPs for both days (lowest north, highest south). Monday: both models indicate a shower is not out of the question, but how they get to their solution is different. GFS in the process of bringing back warmer air and more moisture, while ECMWF shows a shortwave zipping out of the region during the afternoon with slightly cooler temperatures coming in. We`ll know exactly how things will turn out on Tuesday of next week. For the time being, the forecast will feature a blend of the previous 12z data plus the latest 00z output from the GFS and ECMWF. && .AVIATION /12Z Tuesday THROUGH Saturday/... Through 06z Wednesday...Relatively quiet weather is expected with VFR conditions expected through much of the period. There may be some brief periods of MVFR and IFR conditions between 08z and 12z...mainly at KSLK due to fog and low clouds. Winds between 12z and 16z will become west-northwest at speeds of 10 knots or less before become light and variable after 00z. Outlook 06z Wednesday through Saturday... 06z Wed - 00z Fri: Mainly VFR under high pressure. Isolated showers possible Wed/Thu afternoons. 00z Fri - Sat: Increasing chances for widespread MVFR showers and isolated thunderstorms. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Evenson NEAR TERM...Evenson SHORT TERM...Nash LONG TERM...Nash AVIATION...Evenson/Neiles is the U.S. government's official web portal to all federal, state and local government web resources and services.