EF1 tornado in Butler County, Pennsylvania

This is a continuation of the tornado track that began in Franklin Township, Beaver County. The summary of the full tornado path is included below.

The National Weather Service in Pittsburgh conducted a storm survey

in far northeastern Beaver County in Franklin Township eastward to

Harmony Township, Butler County. The damage, much like previous ones

for this event, was regulated to hardwood and softwood trees. There

was no structure damage observed along the track.

Damage initially started on American School Road then east along

North Camp Run Road. The most intense damage was recorded farther

down American School Road where at least 30 hardwood trees were

uprooted or had large branches blown down. As the tornado continued down

American School Road, downed softwood trees and hardwood trees snapped

at the trunk were observed. The tornado lifted as it crossed into

Butler County just beyond the intersection of American School Road

and Scott Ridge Road.

A broken line of supercells, which formed along a front, moved quickly through the Ohio River Valley the evening of October 21st and spun off several tornadoes. The number of tornadoes, time of year, and intensity (one long track EF2 tornado) will mark this event as very rare and significant for this region.

Prior to tornado development, surface temperatures warmed into the low-mid 60s; dew points topped out near 60F. Forecast soundings indicated modest levels of mean layer CAPE, and a relatively straight hodograph yielding marginal but sufficient storm relative helicity. The overall quick track of the broken line and eastward propagation helped cells sustain rotating updrafts.