Severe storms trigger flash flood warning, knock out power around Western Pa.

A relentless line of strong thunderstorms triggered flood warnings, knocked out power to tens of thousands of residents and may have contributed to a partial building collapse on Pittsburgh’s South Side on Thursday evening, the chaotic ending to one of the hottest days of the summer in Western Pennsylvania.

A flash flood warning remained in effect for parts of Westmoreland County, including West Newton, Mt. Pleasant and Youngwood.

The creek is running high and fast in front of Valley High School after the storms came through. pic.twitter.com/17JeD6p9Hh

— Brian Rittmeyer (@BCRittmeyer) August 13, 2021

In Pittsburgh, the flood gates on Washington Boulevard were lowered around 8 p.m. A tweet from Allegheny County described the conditions as “impassable.”

Earlier in the evening, Allegheny County reported a flood of calls to 911, though call volume had returned to normal soon after.

Please avoid flooded roadways as the Pittsburgh metro area receives another round of heavy rains. The Flash Flood Warning remains in effect until 10:30pm. https://t.co/MOqSafM4X6

— NWS Pittsburgh (@NWSPittsburgh) August 13, 2021

The National Weather Service also issued a severe thunderstorm warning for western Allegheny County, parts of Washington County and parts of the West Virginia panhandle.

By 11 p.m., Duquesne Light was reporting 115 outages in Allegheny and Beaver counties affecting more than 24,000 customers. West Penn Power was reporting more than 7,500 customers without power in Allegheny County, more than 900 in Armstrong County and about 2,790 in Westmoreland County, as of 11 p.m.

Severe Thunderstorm Warning including Weirton WV, Steubenville OH, Toronto OH until 9:30 PM EDT pic.twitter.com/55G12E017D

— NWS Pittsburgh (@NWSPittsburgh) August 13, 2021