Thunderstorm Wind in Kingsbury County, South Dakota

Thunderstorm outflow winds churned up large waves on Lake Henry after 2000 CST. Indirect fatalities occurred when two persons on flotation devices were overcome by the high wave action and drowned.

A very moist and unstable atmosphere was present in the wake of earlier day convection, as another stronger mid-level wave and associated frontal boundary pushed through southeast South Dakota and southwest Minnesota during the evening and early overnight hours. Initial development of an isolated supercell in south central South Dakota resulted in hail up to 2 inches in diameter, but more widespread convection along the boundary later in the evening led to areas of damaging wind and excessive rainfall in east central South Dakota and southwest Minnesota. Rainfall was heaviest near the Brookings area with several gauge amounts of 4 to 8 inches around the city.

Indirect fatalities occurred when increasing wave action on an area lake associated with thunderstorm winds resulted in the drowning of two individuals.