Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
324 FXUS61 KPBZ 151640 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1240 PM EDT Tue Sep 15 2026 .WHAT HAS CHANGED... Shower and thunderstorm chances have increased for Wednesday, with locally heavy rain and gusty wind possible. && .KEY MESSAGES... 1) Shower and thunderstorm chances return Wednesday and Thursday, with locally heavy rainfall and gusty wind possible 2) Unsettled pattern returns this weekend into early next week && .DISCUSSION... KEY MESSAGE 1... A surface cold front is expected to drift sewd tonight, reaching Lake Erie/northern Ohio Wednesday morning. A few showers are possible, mainly across NW PA late tonight into Wednesday morning with convergence ahead of the front. Recent model data has trended toward a more rapid weakening/southward shift of a ridge across the Upper Ohio Valley region, which results in a faster arrival of a cold front on Wednesday. This front should drift southward to central Ohio/west central PA by late Wednesday afternoon. Increasing moisture and a weak mid level shortwave trough is also expected to approach the region at the same time, sparking scattered showers and thunderstorms. 0-6km shear is progged to remain at or below 20kt, though ML CAPE of 1000-1500 j/kg and some DCAPE (500-700 j/kg) could result in a gusty wind potential in some of the storms. In addition, PWATS increase 1.8 to near 2.0 mainly north of I-70 by late in the day, resulting in a locally heavy rain/flash flood potential. The extent of the storm coverage is still uncertain, though recent trends do show some increased potential for the heavy rain/strong storm threat late Wednesday. The intensity of any showers/storms should decrease Wednesday night with waning instability, though with the front in the area and another approaching shortwave scattered showers/isolated storms are still expected. The flow should back aloft Wednesday night/Thursday morning, resulting in the front stalling across the region. This wave should track across the Upper Ohio Valley region Thursday, with additional showers and thunderstorms expected. WNW flow aloft behind the wave should push the front through the area Thursday afternoon and evening. Diurnal instability and continued high PWATS will result in mainly a locally heavy rainfall potential through the day. The showers and storms should gradually end by Thursday night as the front exits, with dry weather returning for Friday. KEY MESSAGE 2... Model ensembles indicate a WNW flow aloft across the region this weekend into early next week, as a surface front approaches and stalls across the Upper Ohio Valley region. Multiple waves embedded in the flow will result in periodic showers and thunderstorms across the region, especially late Saturday into Monday. Uncertainty remains in how long this pattern will persist, with some guidance indicating some improvement toward mid week. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR with lighter southeasterly to southerly wind under the influence of high pressure is favored through the TAF period. Areas of mid-to-upper level clouds will occasionally cross, most notably over northwest PA. Low probability shower chances (that could result in a period of restrictions) exist near/north of FKL/DUJ after 06z tonight but are too low for mention at this time. Outlook... Gradual shortwave progression over the top of the current upper level ridge will increase shower and thunderstorm chances along with resultant restrictions Wednesday evening into Thursday. Brief passing high pressure Friday offers quieter weather before a potentially active pattern develops Saturday into next early next week. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ DISCUSSION...WM AVIATION...Frazier