A front has stalled out in the Midwest and will be the focus for showers and thunderstorms throughout the day on Wednesday. There has been some uncertainty on exactly how far north the warm front gets and that will make a difference in the strength of the storms. Along and south of this front is where the greatest instability will exist.
Here's the surface pattern Wednesday afternoon on the Euro:
The European has the front furthest north from Kansas northeast through Dubuque, Iowa. With that position of the front, here's the CAPE on the Euro:
The GFS solution is further south.. here's the surface pattern and resulting CAPE:
The GFS has the front south of I-80 in Iowa and that's where the strongest storms would be. We won't know until it happens but I'm thinking the front will set up pretty close to I-80. Here's the area the SPC is monitoring for severe weather:
These storms will be capable of producing strong winds and large hail wherever they do set up. Near and south of the front, decent wind shear is expected to be in place. An isolated tornado cannot be ruled out if any individual supercells form and not just a line of storms.
Bottom line is.. there is still uncertainty on where the front sets up and where the severe risk will be highest. There's also the potential for some morning convection and clouds in my local area.. if that occurs then the front will likely set up further south and the severe risk would be lower. Here's a hi-res version of the NAM showing a simulated radar for Wednesday: