Sorry for geeking out on this, but this is the hourly forecast.
I LOVE STL weather - took some meterorolgy classes back in the day. North and South wind streams converge here, forming the Jet Stream - with STL as the border. Those war,m and cool wind streams can jam up as they move East, due to the confluence of the Missouri and Mississippi Rivers - meaning tons of moisture - that hits the eastern bluffs, a natural barrier that causes weather fronts to slow and mix with each other. As such, we e get some wicked storms here with house rattling thunder.
The video at the bottom of this link shows delination of the two streams and it is right where I sit presently.