This loop of GOES-8 visible imagery covers the period from 15:45 to 23:45 UTC on 30 May 1998, leading up to the development of the convection that eventually spawned the Spencer SD multiple vortex tornado 2 hours later (at 01:44 UTC on 31 May). The counties in southeastern South Dakota with preliminary tornado reports (from west to east: Davison, Hanson, McCook, and Turner) are outlined in blue, and Spencer is located at the filled blue box in extreme western McCook county. Hourly surface reports of wind and dewpoint are shown in red.