I agree on Saturday, in fact I think Sunday has a greater risk of being a bust, at least around DSM/Metro, SW or Western Iowa.
Saturday dew points should be higher-->more low-level moisture to work with. Cap will be an issue, but what does go should be impressive.
I do have reservations about winds being more westerly on Sunday, cranking in more dry air and pushing the dryline through that will hinder the ability to break the cap...even as it weakens. I think a lot of the big-time action Sunday will be much more NE Iowa and into the Twin Cities/SW Wisc area. Still will be a risk along the dryline in central Iowa Sunday, especially if the moisture holds on into early evening as cap breaks.