Just checked out the latest RUC2 point soundings for north central IA, and they are looking pretty scary. SBCAPE values are between 2000-2500J/KG, and helicity is near 550m2/s2...Putting EHI values close to 8! Looking at the radar, storms appear to be SFC based so, I believe a tornado threat will develop very shortly, but it will be of short duration...Probably 1-2 more hours at most, before storms become elevated. Modified 00Z GRB sounding for southwest WI conditions show elevated CAPE of 2250J/KG (from 850MB) and decent shear...So expect a large hail threat in this region, but tornado threat will quickly diminish.
Robert