Whoops, forgot one:
Also in 1997:
4" of rain fell within 90 minutes on a 4-square mile area near Pitcairn, PA and water from the flash flooding over flowed the Dirty Camp Run inundating the elemetary school there through its lower-level windows, and sweeping 13 buildings of their foundations. $10 million in damage was assessed.
The region around Pittsburgh is deep and long valleys. Many of the valleys are stopped at one end by dams. Usually the reservoir behind the dam is near empty, but a good rain day could fill the valley to the top of the dam overnight. The flooding before the dams were installed must have been heroic. Even with the dams, Pittsburgh gets wet now and then.