What is a derecho? Meteorologists weigh label after powerful storms slam Western Pa.

After powerful storms swept through Western Pennsylvania this week, meteorologists hesitated to apply labels — though terms like derecho began to circulate.

A derecho is a fast-moving, long-lived windstorm that the National Weather Service says can produce tornado-like damage — but in a single, straight path. To qualify, it must leave a trail of wind damage stretching at least 240 miles, with gusts reaching 58 mph or more.

Tuesday’s storm appeared to meet those standards, said Colton Milcarek, a meteorologist with the National Weather Service in Moon.

But a third criterion — reports of several, separate wind gusts with speeds topping 75 mph — did not appear to be met, he said.

A different conclusion could come in subsequent study of the storm.

Yesterday's storm is not considered a "derecho", primarily because it lacked periodic measured gusts in excess of 75 mph along the damage swath (keyword: measured). That is not to diminish the impact of the experience, however, as it was still a very strong bow echo/squall line. pic.twitter.com/WYh3GzgtZY

— NWS Pittsburgh (@NWSPittsburgh) April 30, 2025

A National Weather Service team Wednesday trekked to the Wilkinsburg area to survey the damage, according to meteorologist Liana Lupo.

Surveyors did not confirm a tornado touchdown, Lupo said. But, she added, the Wilkinsburg damage could have been caused by winds gusting up to 90 mph.

A National Weather Service team also plans to survey damage in Brooke County, W.Va., in the northern part of the state’s panhandle, she said.

The squall line formed in western Indiana around 11 a.m. and quickly gathered strength and size as it sped eastward, the National Weather Service said. By 1 p.m., meteorologists had deemed it potentially dangerous as it headed toward Pennsylvania.