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Ice Jam Break on Allegheny Triggers Flash Flooding as Region Remains on Alert

Forecasters urge residents to be ready to evacuate due to the potential for sudden river changes.

Overview

  • An ice jam broke near Emlenton on the Allegheny River on Feb. 20, prompting a Flash Flood Warning for parts of Venango, Armstrong, Butler and Clarion counties and causing downstream flooding.
  • Emergency officials in Emlenton reported water rapidly approaching River Avenue and asked residents in flood‑prone spots to prepare to evacuate, while some sections of River Avenue were closed.
  • Flood Watch conditions have shifted: Venango County’s watch was lifted early Feb. 21, with Armstrong, Butler and Clarion counties still under a watch, and Pittsburgh under a Flood Advisory through 1 p.m. Sunday with the Ohio River expected to crest over 19 feet.
  • Earlier impacts included a Route 956 closure near Neshannock Falls due to ice on Neshannock Creek, and residents downriver toward Foxburg reported water at the bases of homes and campers underwater.
  • River watchers in Harrisburg are tracking Susquehanna River ice with a projected crest near 6.2 feet on Monday and note 4–8 inches of remaining ice and chokepoints that could foster new jams.