538 FXUS61 KPBZ 061612 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1212 PM EDT Mon Sep 6 2021 .SYNOPSIS... Mainly dry weather and seasonable temperatures are expected through Tuesday under building high pressure. Shower chances return Tuesday night and Wednesday with a crossing cold front. && .NEAR TERM /THROUGH TONIGHT/... Surface high pressure is dominant this afternoon, as shortwave support moves to the northeast. With lingering vorticity advection over the eastern Great Lakes, lake enhanced and upslope clouds are likely north of Pittsburgh. High temperature will be near or just below the climatological norm. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Sfc high pressure is expected to move east across the region, maintaining dry weather through Tuesday. Patchy river valley fog is possible tonight with warm water temperatures in place, and mostly clear skies. As short range models indicate, the pattern is becoming more reminiscent of autumn with the polar jet dipping back southward toward the Ohio Valley. Another low pressure on the northern periphery of the polar jet will develop on Wednesday, and its associated surface cold front is forecast to provide precipitation chance beginning Tuesday evening, overnight into Wednesday morning. With the timing of the precipitation chance, it appears widespread shower activity is more likely than thunderstorms, but thunderstorms will be possible on Wednesday afternoon, if surface temperature is able to rebound from morning precipitation. && .LONG TERM /THURSDAY THROUGH MONDAY/... Model ensembles indicate the main upper trough is expected to persist across the Ern CONUS through Friday, with the potential for a secondary cold front and vorticity advection to allow for continued shower chance on Thursday before broad ridging ensues. Generally dry weather is then expected through the weekend as sfc high pressure builds under northwest flow aloft. Below average temperatures late in the week should return to or above seasonable levels through the weekend. && .AVIATION /16Z MONDAY THROUGH FRIDAY/... VFR is expected through the remaining TAF period as sfc high pressure gradually builds in. West winds gusting up to 20 knots will continue this afternoon with a sufficient pressure gradient and mixing. Some cloud cover may linger in the north over FKL and DUJ. Mainly clear skies are expected tonight with fog development in the river valleys towards dawn. Most of the terminals should escape this fog potential. .Outlook... Restrictions are possible with a Tue night/Wed cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$