FXUS61 KPBZ 181217 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 817 AM EDT Mon May 18 2026 .WHAT HAS CHANGED... As discussed below, there is now a conditional risk of strong storms/damaging wind gusts in portions of the region today. The risk for Tuesday is now focused to the northwest of Pittsburgh with a bit higher confidence. The rest of the forecast remains relatively unchanged. && .KEY MESSAGES... 1) Heat may impact sensitive populations early this week. 2) Highly conditional and localized severe wind risk today. A bit better chance of severe storms northwest of Pittsburgh Tuesday, and perhaps in the higher terrain Wednesday ahead of a cold front. && .DISCUSSION... KEY MESSAGE 1... The Atlantic coast/southeast CONUS ridge provides our highest 500mb heights of the week today, around 587/588dm across the Upper Ohio Valley. The lack of cloud cover for the most part across the region today will lead to efficient heating and likely the hottest temperatures. Heights begin to back off Tuesday as an Upper Midwest shortwave induces a downstream response of kicking the ridge axis further east. This, along with the potential for some afternoon clouds/isolated convection, makes temperatures a bit more uncertain. Continued to run a bit below the overly bias-corrected NBM mean suggestions for highs both days. Went with numbers closer to the LREF means overall, but did account a bit for strong sun/relatively dry ground. This leads to max values in the upper 80s to around 90 today for the majority of the region, with lower/mid 80s in the higher terrain. Went a degree or two lower Tuesday given the factors mentioned above. Urbanized valleys could crack into the lower 90s in the worst case both days. Record high values for today could be approached in higher-end scenarios. Record maximum low temperatures may also be challenged Monday night. The NWS heat risk shows mostly a moderate risk Monday into Tuesday, whereby heat may generally impact the most sensitive populations. Make sure to stay hydrated or monitor for signs of heat illness if spending excessive time outdoors. KEY MESSAGE 2... While the ridge is expected to largely suppress convective development via mid-level capping today, there are a couple of caveats. Localized convergence along the highest terrain of northern West Virginia could overcome the capping influence and take advantage of surface-based CAPE over 1500 J/kg to create isolated storms rolling northeast off of the ridges. With potential for DCAPE of 800-1000 J/kg, a brief window may exist for strong downburst wind, but the main risk area is off to our east where storms will have longer residence time. Also, a couple of the CAMS develop some isolated convection over eastern Ohio and/or southwest Pennsylvania during the late afternoon/early evening today, likely off of outflow from convection to our west. Confidence in this is quite low given the expected ridging, and no mention of precip was made for this for now, but hi-res trends should still be monitored. IF storms can manage to overcome the ridging here as well, there could be an isolated downburst risk here as well, mainly near/north of I-80 along the northwest side of the ridge. Potential for thunderstorms increases Tuesday, especially during the late day and evening, as the ridge breaks down and as a cold front advances into the Middle Ohio Valley. The most-likely scenario at this time involves convection forming to our west and flowing into the region mostly after 21Z, with a high DCAPE environment providing a downburst wind risk. The risk appears highest generally north and west of Pittsburgh, as storm strength should be on a downward trend through the evening with the typical loss of diurnal buoyancy. Models have the cold front near or just west of Pittsburgh by 12Z on Wednesday. This makes sufficient heating for strong convection highly questionable for the region, with any threat likely focused more towards the higher terrain, conditional on the development of adequate CAPE. A damaging wind threat would be most likely in any severe scenarios. Cooler temperatures behind the cold front will end any severe threat for the remainder of the week. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... High confidence VFR through the TAF period under the influence of high pressure east of the region. A few cu develops this afternoon with peak heating/mixing while southwest winds occasionally gust between 15-25kts (near 0% likelihood of exceeding 25kts). Any convective chances are tied to weak convergence along the WV ridgeline, with storms drift northeast, further cementing minimal terminal concerns. Nocturnal increases in the low-level jet may create brief periods of LLWS, but the lack of duration or meeting criteria (either by speed/direction or by height) led to an omission from TAFs. Area mid to high level cloud cover increases overnight into Tuesday morning in association with an eastward moving but decaying MCS. There is a non-zero chance for isolated showers and thunderstorms develop off its outflow near to after 00z around northwest PA but probability is too low for TAF mention. Outlook... Outside of an isolated afternoon thunderstorm Tuesday, VFR persists until an upper shortwave and surface front push a shower/thunderstorm axis east Tuesday evening through Wednesday afternoon. Initial restrictions will be tied to rainfall intensities with height falls not occurring until after frontal passage. High pressure and VFR returns by Thursday areawide before an active pattern feature multiple rain chances develops Friday into the weekend. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ DISCUSSION...CL AVIATION...Frazier/Lupo