Area Forecast Discussion
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000 FXUS61 KPBZ 251851 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 251 PM EDT Mon Sep 25 2017 .SYNOPSIS... High pressure will bring dry and warm weather through mid-week before the passage of a cold front heralds a return to seasonably-cool conditions. && .NEAR TERM /THROUGH TUESDAY/...
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Upper ridging on the nrn side of Hurricane Maria will maintain broad subsidence over the region, leading to dry mid levels and only passing cirrus. Temp maxima in the upper 80s and dewpoints in the 60s should slow the falloff of temps this evening until late tonight, when localized fog may form again in the river valleys as the boundary layer nears saturation. Tuesday will see little change in the overall pattern, and therefore little change in the forecast apart from a slight cooling of H8 temperature. Hence, Tue maxima may end up slightly below those observed today. Despite deep mixing, a mid-level inversion will limit vertical development of clouds, suppressing any precipitation during the day.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
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A shortwave trough will deliver a glancing blow to the western Great Lakes region, driving a cold front sewd on Wed as Maria comes as near as it will get to the Delmarva coastline. After another warm day on Wed, this front will make a swd push Wed evening and help escort the hurricane out to sea, but will also serve to scour out the low-level warmth and moisture from the area. Models are somewhat aggressive on moisture ahead of the approaching boundary, which appears to be contributing to broader coverage of precipitation as the models develop instability. Given a more-realistic dewpoint in the low-mid 60s, instability is more meager, so PoPs with the frontal passage were reduced from the default model blend values. High pressure returns on Thu with a marked cooldown expected. After the summer-like temperature experienced recently, maxima in the upper 60s will feel rather cool, although hardly unseasonable.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/...
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As an upper ridge builds into the Great Plains, a shortwave trough will move sewd across the Great Lakes. Lacking boundary- layer moisture, the extent of any precipitation is unclear. But models signal at least a possibility of measurable light precipitation during the wave`s passage on Fri. In the wake of the wave, high pressure returns for Saturday, with seasonable temperature through the weekend. Models diverge thereafter on the upper pattern, with both models indicating a wrn trough, but the GFS suggesting an amplifying upper ridge for the ern CONUS and a slower approach of the trough to the Great Lakes region. Given these discrepancies, did not deviate significantly from the default model blend values in the extended periods.
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&& .AVIATION /19Z MONDAY THROUGH SATURDAY/... High pressure will maintain light southeast wind and VFR through the TAF period. In the early morning hours of Tuesday morning some non-VFR visibility restrictions possible from patchy morning fog. .Outlook... Restrictions are possible with cold fronts Wed night and Fri. && .CLIMATE...
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While we will not be quite as warm as over the weekend, temperature this afternoon still will be 15 or more degrees above seasonal averages this afternoon. Here are the local record high temperatures for Monday: PIT: 92 (1881, 1900) ZZV: 94 (1908) MGW: 93 (1930) DUJ: 87 (2007) HLG: 91 (1934) PHD: 91 (2007)
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Kramar

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