Jun 9, 2021
While a shortwave trough moved south of the Ohio River Valley, isolated to scattered convection initiated in an area of low confluence north of Pittsburgh. As a result, slow moving heavy downpours ignited. Relief from rain didn't come for the city of Butler until outflow boundary collision.
Source: NOAA National Weather Service Storm Events Database (event 960847). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Butler County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.