Area Forecast Discussion
Issued by NWS Pittsburgh, PA
Issued by NWS Pittsburgh, PA
937 FXUS61 KPBZ 160418 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1218 AM EDT Wed Sep 16 2026 .WHAT HAS CHANGED... Update to Aviation Discussion. && .KEY MESSAGES... 1) Shower and thunderstorm chances linger today and tomorrow with a low risk of localized flooding and a non- zero chance of severe weather. 2) Unsettled weather returns late Saturday into next week. && .DISCUSSION... KEY MESSAGE 1... In line with the prior forecast update, this one maintains the earlier arrival time of a cold front, sweeping down across the area this afternoon and evening, before stalling tonight. Provided that southwesterly surface flow through much of the day will keep dew points >70F with 60% to 90% confidence and temperatures climbing into the mid to upper 80s, the thermodynamic setup will feel more like summer than fall. Ascent aloft seems to be subtle during the day, which might hint to convective chances being mostly tied to the front itself (north of I-70), though warm and moist conditions with 500-1500 J/kg SBCAPE (25th-75th percentile), and broad ascent mean pop up storms could theoretically develop anywhere. Sfc-6km shear is fairly weak, though most of this is packed into the sfc-2km layer, meaning a spin up couldn`t be ruled out. That being said, most of this is straight-line and westerly, so any rotation would be dependent on a right moving (southeast moving) cell. DCAPE will be more marginal, with 500-700 J/kg forecast, most reliant on deep vertical development to realize gusty wind potential. ML Outlooks are not very bullish at on on severe potential, with both right movers and deep storms generally unlikely, but the severe risk is non-zero nonetheless. What may be more likely is localized flood in the event of any training that might occur (particularly for urbanized corridors), with PWATS pushing 1.8-2.0 inches (above the daily record) and warm rainfall processes leading to efficient, heavy rainfall in and storms that do develop. 00Z models have been more consistent with a second round of storms developing upstream early Thursday morning, as a mid- level shortwave accelerates low level flow above the nocturnal inversion. Sfc-3km shear may increase to 20-30kts, with >90% chance of non-zero MUCAPE with the 90th percentile as high as 1000 J/kg. Convective chances have increased, but timing still remains uncertain. Most ensembles have these storms progressing into the area around 6am Thursday, but outliers (NAM), show development potential as early as midnight. Should this occur, severe risk will be low with decoupling, but PWATS will remain above record levels (1.9-2.1 inches), so localized flash flood potential lingers for training storms or areas already hit from the day prior. In the slowest scenarios for this passage, a very low severe risk (weak spin up / winds) lingers for west PA / north WV early Thursday should the atmosphere decouple late morning. Coverage during the afternoon Thursday has trended down behind this morning wave, but still non-zero storm chances linger for the day (though severe and flood risks may be lower than the prior update). Storm coverage Friday has also trended lower with the only chance of rain/storms south of I-70 in the event the front hasn`t fully cleared yet. KEY MESSAGE 2... A parade of shortwaves in WNW flow aloft allude to more chances of rain and thunder by the weekend. Confidence remains highest late Saturday into Monday (75% chance of rain). This will carry more low-end severe/flood risks. The pattern by the middle of next week remains uncertain, with one camp of ensembles remaining unsettled and seasonable, in a pattern similar to that of this weekend. Another camp bring a cold front through, with cooler and drier conditions. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Confidence remains high that VFR conditions will prevail from now through a majority of tomorrow afternoon. Showers and thunderstorms are expected to develop across the Ohio River Valley between 20Z to 24Z Wednesday with surface heating and increasing low-level moisture from the southwest, coinciding with a nearby frontal boundary over the Great Lakes. Given the disorganized nature of convection depicted by high- resolution models, PROB30s remain in place for -TSRA potential Wednesday evening. Outlook... Gradual shortwave progression over the top of the current upper level ridge will increase shower and thunderstorm chances along with resultant restrictions into early 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...Milcarek AVIATION...Hefferan/Frazier