Weather Pittsburgh turned sharply active Thursday night as a tornado watch for most of the area expired at 11 p. m. ET while severe weather began to move out, and a flash flood warning remained in effect for central Allegheny County into early Friday.
What happens when the tornado watch expires but flooding concerns remain?
A tornado watch that covered much of the Pittsburgh area was set to run through 11 p. m. ET Thursday night across Allegheny, Armstrong, Beaver, Butler, Lawrence, Mercer, Washington, and Westmoreland counties. As that watch window closed, a flash flood warning stayed in place for central Allegheny County until 12: 45 a. m. ET Friday.
Earlier in the evening, a tornado warning had been issued for parts of Mercer and Lawrence counties, along with parts of Ohio, but it expired before late Thursday night. Even as the tornado-related alerts eased, rainfall remained a key concern. Heavy rain was still possible overnight, and localized flash flooding was not out of the question given the amount of rain described for the region.
There was also attention on how runoff could translate into water level impacts. As water drains from the ground into creeks and streams and then into larger waterways, rises at the rivers near the Point were a possibility. One projection cited the Ohio River at the Point cresting around 18 feet, a level that would put water on the Mon Wharf.
What if the worst storms track just west of the city, but the region still takes hits?
Thursday’s setup featured warm temperatures and enough daytime heating to support stronger storms later. Temperatures climbed well into the 70s in several areas, and the main threats highlighted for storms approaching the Pittsburgh area were damaging wind, large hail, and flooding. There was also mention that some ingredients could attempt to lead to rotation, underscoring why tornado-related watches and warnings were in play for parts of the region.
The overall severe thunderstorm risk was described as scattered severe thunderstorms, a level 2 out of 5, with the level 3 out of 5 area “knocking on the door. ” The best ingredients were described as lined up just west of Pittsburgh, putting added emphasis on monitoring activity nearing the state line.
Timing mattered for impacts. Storms were expected in northern counties around 8 p. m. to 9 p. m. ET, then progressing south toward Pittsburgh by 10 p. m. to 10: 30 p. m. ET before continuing southward. In a separate forecast framing, storms were expected to roll into the region around 8 p. m. to 9 p. m. ET, with forecasters focusing primarily on damaging winds while noting the possibility of an isolated tornado or two and some hail.
One meteorologist noted severe storms could produce winds up to 70 mph, enough to knock down tree limbs and cause damage. Isolated flash flooding late Thursday and early Friday was also a concern, especially in flood-prone areas.
What happens when storms give way to cooler, drier conditions into the weekend?
After the Thursday night storm threat, the region was expected to stay dry from Friday through Sunday. The forecast outlook included a notable cool-down: temperatures rising to the high 40s on Friday before dropping below 30 overnight, followed by a Saturday forecast with a high of 43 and a low of 30 in the evening. Sunday was expected to rebound into the high 50s, cooling down to 45 overnight.
The run of gusty conditions had also been a theme this month. The region experienced a high-wind event on March 13 that left about 260, 000 West Penn Power and Duquesne Light customers without power. The recent spate of high winds was characterized as not unusual for spring in Pittsburgh, even if it has felt especially active over the last month.
As the late-night alerts changed from tornado-focused to flood-focused in spots, the immediate takeaway for Weather Pittsburgh was that the most intense severe weather signal was moving out, while lingering heavy rain and localized flooding remained the concern into early Friday.
