Sioux Falls Tornadoes of September 10

Jan 31, 2017
Joplin, MO & Iowa City, IA
I am very surprised there has been no discussion of this event. Please help me make sense of what happened.

This page from NWS Sioux Falls says all three EF2s came from a line of severe storms. An EF2 is a pretty strong vortex to come from a squall line, let alone three of them within four minutes. Was this a true QLCS, or did the storms retain enough of their supercellular characteristics to make this happen.

Here's the summary, with a radar loop: