Flash Flood in Hanson County, South Dakota

Several public social media posts and photos indicated numerous roads in and around the community of Emery were underwater as a result of the heavy rainfall. Standing water, at least several inches deep, was also observed in many yards, including some up against structures.

A trough lifted through the western High Plains as a weak convergence boundary drifted eastward into southeast South Dakota during the late afternoon. Near the boundary, a diurnally destabilized air mass focused convective development in a fairly weak shear environment across the lower James River Valley. Thunderstorms largely produced large hail up to ping-pong ball size during periods of stronger updrafts within the storm clusters. Shear concentrated in lower levels and storm interactions combined to produce several brief tornadoes in southeast South Dakota. Slow moving storms also produced spotty heavy rainfall, some of which that fell on areas that received heavy rainfall west of Sioux Falls in the previous night.