Thunderstorm Wind in Mifflin County, Pennsylvania

Thunderstorm winds estimated near 60 mph knocked down several large tree branches at the Derry Township Community Park in south Burnham along Derry Park Road and Logan Boulevard. A 16-year-old female was killed when a falling tree branch struck her in the head.

Low pressure tracked east-northeast from the Lower Great Lakes region into the Northeast states, while a cold front trailed southwestward from the surface low through the Ohio Valley and Southern Plains states. Hot and humid conditions ahead of the cold front allowed for strong instability, which allowed for vigorous thunderstorm development by the mid-afternoon. A belt of strong winds aloft on the southern edge of a potent mid-upper level trough over the Upper Great Lakes extended from the Ohio Valley into Pennsylvania. These winds helped to organize storms into lines and bowing segments. In addition, a tornado threat existed over northern Pennsylvania in an area of strong low-level shear in the vicinity of a retreating, diffuse warm front.

Widespread damaging winds accompanied an intense line of severe thunderstorms that moved from the northwest mountains into the lower Susquehanna Valley from the mid-afternoon into the late evening hours. An EF0 tornado was confirmed near Coudersport at 1515 EDT. Two areas of concentrated straight-line wind damage were also surveyed in McKean and Potter Counties, with estimated maximum winds between 70 and 90 mph. A 66-year-old woman was killed by a falling tree near Genesee in northern Potter County.