Here is a notable supercell near Hitchcock, SD. Atmospheric conditions came together on the instability axis. This was the southernmost point where the 700mb temp allowed for surface parcels to ascend. Multiple supercells developed over the same area into the night. 10 inches of rain was recorded in the vicinity. Here are some images of the tornado warned supercell that produced a funnel.

These last two images are interesting in the fact that a lowering is seen and then rain wraps around with something dark in the rain. You can come to your own conclusion.