Area Forecast Discussion
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000 FXUS61 KPBZ 220418 AAD AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 1218 AM EDT Tue Aug 22 2017 .SYNOPSIS...
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Showers and thunderstorms are expected Tuesday and Tuesday evening with the approach and passage of a cold front. Mainly dry and cooler than average weather is expected the rest of the week under high pressure.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Mainly dry weather is expected overnight with weak shortwave ridging, though increasing mid and high clouds are expected ahead of the next approaching shortwave. Lows around 10 degrees above seasonal levels are expected.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
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A strong upper low will dig into the Great Lakes on Tue and acquire a neutral to negative tilt through the day in concert with the movement of a mid level jet maximum. The system`s associated cold front will approach the Ohio Valley during the early evening, but a prefrontal trough is expected to be the focus for daytime convection in the area. Abundant low-level moisture, steepening lapse rates and strong effective bulk shear will support the development of strong to severe thunderstorms by early afternoon along the sharpening sfc trough. CAPE on the order of 2000 J/kg and effective shear of 40-50kt will promote organized, severe convection. Given the deep-layer shear orientation roughly parallel to the sfc feature, storms should congeal quickly into an intense convective line that will move sewd into the instability axis. Damaging wind gusts will be the primary threat, but hail also is possible in more intense, cellular updrafts ahead of the line. Storms will exit sewd by early evening with rain lingering into the evening behind the storms as the cold front traverses the region. High pressure will build in on Wed/Wed eve, with little chance of rain as dry air invades.
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&& .LONG TERM /THURSDAY THROUGH MONDAY/...
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Although ensembles still show spread in their upper pattern solutions, it appears that broad surface high pressure under an ern CONUS trough/midwestern ridge pattern is progged to support a generally dry air mass through the period. Daily temperatures below climatological average can be expected through early next week.
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&& .AVIATION /04Z TUESDAY THROUGH SATURDAY/...
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Mainly high clouds overnight. Fog does not appear to be much of a threat given the warm overnight temperatures which will not allow crossover values to be reached. As a cold front approaches today, showers and thunderstorms will become more numerous this afternoon and evening. Flight condition deterioration with VCTS and a drop to MVFR visibilities at several terminals during the late afternoon. Expect prevailing winds outside of convection to increase to gust to between 15 and 25 knots out of the southwest during the afternoon. .Outlook... With passage of an early Wed cold front, general VFR can be expected for the remainder of the week.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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