Hail in McCook County, South Dakota

Most hail was pea to quarter sized, but a few were as big as golf balls. Farm fields farther north are more damaged than those at the site.

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.