FXUS61 KPBZ 190616 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 216 AM EDT Tue May 19 2026 .WHAT HAS CHANGED... The forecast remains largely unchanged, with continued confidence in storm arrival in eastern Ohio and northwest Pennsylvania after 8 PM tonight. && .KEY MESSAGES... 1) Highest risk for severe storms/damaging wind gusts will be in areas of northwest PA/eastern OH, with diminishing risk near Pittsburgh. Conditional severe threats remain on Wednesday southeast of Pittsburgh with a departing front. 2) Heat impacts for sensitive populations continue early this week, with temperatures up to the upper-80s to low-90s. && .DISCUSSION... KEY MESSAGE 1... An outflow boundary from earlier convection to our west is moving west-to-east south of Pittsburgh this morning. It would not be a surprise to see an isolated shower pop along it, but with buoyancy largely tapped out and HRRR/RAP/HRW soundings showing capping at around 500mb, anything more than that is not expected. That capping is maintained through the morning and into the afternoon, even as the heat-providing upper ridge begins to break down in response to an Upper Midwest/Great Lakes shortwave, and as 1500-2000 J/kg of MUCAPE develops. Thus, only isolated/widely scattered activity is forecast at most through sunset, with areas north of I-80 perhaps a bit more likely to see a shower/storm through then given that area's proximity to the shortwave and perhaps the development of a lake breeze boundary. As far as the more organized convective threat tonight, the most likely scenario presented by CAMS remains the development of strong to severe thunderstorms in western Ohio in the 22Z-00Z window ahead of a cold front, perhaps associated with a prefrontal trough. These storms should be weakening as they approach northwest PA/eastern OH after 01Z or so due to diurnal buoyancy loss as well as 20-25 knots of 0-6km shear fostering only loose organization/limited cold pool consolidation. Still, with up to 900 J/kg of DCAPE available north and west of Pittsburgh, strong to severe downdraft winds remain a decent possibility in the taller storms; this is the area highlighted in SPC's day 1 Slight (level 2 of 5) Risk. Hail is a lesser concern due to the lower shear and poor mid-level lapse rates less than 6C/km. Also, with around 100 m2/s2 of 0-1km storm- relative helicity available north of I-80, a tornado cannot be totally ruled out in this area as LCLs lower, although 0-3km CAPE may be a bit low. Convective intensity is expected to wane overnight as the parent cold front moves in, but some showers and storms will continue. Wednesday still presents a more limited and conditional severe threat in the Laurels and in the WV ridges. This will depend on frontal timing and the amount of rain/cloud cover in the region during the morning into the afternoon. A slower front, with less precipitation and some cloud breaks out ahead, could allow sufficient destabilization for an isolated damaging wind threat. Scenarios with a faster front and more solid cloud cover could largely choke off the threat for strong convection. This will need to be monitored, and the SPC Marginal (level 1 of 5) risk southeast of Pittsburgh shows the potential threat area well. After Wednesday, severe chances taper off. KEY MESSAGE 2... With temperatures hovering mostly in the upper 60s and lower 70s this morning, a few maximum low temperature records may be challenged today. As the ridge breakdown alluded to above takes place today, 500mb heights should experience a slight decrease as compared to yesterday. Coupled with the likelihood of a bit more daytime cloud cover with lingering moisture, high temperatures are likely to reach levels a degree or two cooler than yesterday. This will keep most locations in the upper 80s, with lower-mid 80s north of I-80 and in the terrain. The NBM continues to show a warm bias with its mean values, and kept the forecast numbers lower as a result. The NWS Heat Risk remains in the "moderate" range given the cumulative effect of the warmth since yesterday. Another warm and muggy night is possible ahead of the cold front and thunderstorms tonight, but the passage of the cold front on Wednesday will definitively end the risk of excessive heat for the foreseeable future. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... VFR is expected through much of the day as mid and high clouds continue to increase ahead of an approaching cold front. Model soundings and the CU rule indicate scattered cumulus clouds should develop by mid morning with surface heating. There is a potential for a shower or thunderstorm to affect a few airports from late morning into early afternoon with leftover boundaries from earlier convection to our west, though this potential is limited, and too low for TAF inclusion at this time. In addition, SW wind is expected to gust to around 20kt during the day with mixing. More showers and thunderstorms are expected to track across Ohio late this afternoon and evening in advance of an approaching cold front. It appears that the instability should be diminishing as these storms advance eastward, with an overall weakening trend by late evening. Included prob30 mentions for most sites across Ohio and western PA, from mid to late evening as these storms approach. Outlook... Restrictions and showers are likely by late Tuesday night into Wednesday as the cold front slowly crosses the Upper Ohio Valley region. A few thunderstorms are also possible. Restrictions are possible mainly south of PIT Wednesday night and Thursday as a wave of low pressure tracks along the front. Restrictions and showers return from S-N Friday into Saturday as a warm front lifts north across the area. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$ DISCUSSION...CL AVIATION...WM