Aug 19, 2018
Thunderstorms formed along the fringes of an area of upper-level low pressure drifting across southern Nebraska during the afternoon. Nearly saturated lapse rates through a deep layer promoted heavy rainfall from storms, which drifted northwest across the Sioux Falls metro area late in the afternoon. Two cells merged across southwest Sioux Falls and produced excessive rainfall along with widespread flash flooding.
Source: NOAA National Weather Service Storm Events Database (event 780596). Narrative written by NWS staff at the time of the event.
This event is one of many recorded floods in Minnehaha County. See the full FEMA flood zone map, NFIP claim totals, and disaster history for the area.