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000 FXUS61 KPBZ 261813 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 213 PM EDT Tue Sep 26 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 lasting through the weekend. && .NEAR TERM /THROUGH TONIGHT/... High pressure continues to dominate the weather pattern today amid subsident air on the nwrn side of Hurricane Maria and amid an upper ridge. Tonight, the moist boundary layer remains in place amid light wind and generally clear sky. With radiational cooling conditions optimized, fog (localized to the river valleys and other sheltered valleys) seems a likely outcome. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A shortwave trough will graze the northern Great Lakes region on Wed as a cold front progresses sewd late in the afternoon. Models continue to lack wholesale agreement on the possibility of showers with the frontal passage, so confidence in rain chances tomorrow is low. The models that do generate precipitation do so in an environment characterized by a moist boundary layer and modest instability capped by a warm layer in the mid levels of the atmosphere. Lacking focused upper forcing for ascent and an instability profile generally below the freezing level, any showers that do form amid this environment will be sparse in coverage and likely driven by warm-rain processes. With a boundary and moisture present, PoPs were limited to no higher than climatological values during Wed afternoon. With the loss of diurnal heating and the passage of the cold front, chances for rain will wane rapidly Wed evening as moisture is scoured and cool, dry air invades in its wake. Regardless of the rainfall with the front, temperatures look to drop off quite a bit. While early in the week 18-19C will be common at 850 mb, by Thursday, northwesterly flow will have dropped those numbers back toward 6-7C, and this will yield a more seasonable diurnal trend. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As an upper ridge builds into the Great Plains, a shortwave trough will move sewd across the Great Lakes. Models do seem to show greater consistency in forecasting an increase in boundary-layer moisture ahead of a Fri cold front as it crosses the relatively-warm Great Lakes. All models now depict QPF affecting the area, especially nrn sections, late Fri into Fri evening. In the wake of the wave, high pressure returns on Sat, with seasonable temperature through the weekend. The coldest morning of the period is expected to occur on Sunday, as minima drop into the upper 30s across the nern zones. As the Plains ridge spreads ewd and insolation resumes under high pressure, temperature will begin a slow rebound through the early part of next week. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR will prevail with cumulus diminishing this eve. Expect some valley fog once again tonight, which could impact terminals similarly to this morning. Brief MVFR/IFR restrictions are forecast until fog lifts around dawn. Wind will remain light through the period under high pressure. .Outlook... Restrictions are possible with cold fronts late Wed and again Fri. && .CLIMATE... Temperature this afternoon will be at least 15-20F above seasonal average. Here are the local record high temperatures for Tue: Current Forecast PIT: 94 (1881) 89F ZZV: 94 (1900) 89F MGW: 91 (1900, 1908) 88F DUJ: 84 (2007) 86F HLG: 90 (1930, 1934) 89F PHD: 87 (1986, 1998) 90F && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.