We've been talking about heavy rain that will arrive this weekend with a deep low pressure that will move from the plains into eastern Iowa. This low will also bring the threat for strong to severe storms through the weekend, though that threat mostly lies south of the Stateline area.
The severe threat will be contained just south of the warm front through Saturday, which will stay in central Illinois. For Friday, there is an enhanced risk of strong to severe storms across southern Illinois, Missouri, and into eastern Oklahoma. On Saturday, there won't be much movement of the front into Saturday and so the severe threat will stay contained through central Illinois.