The bit of clearing we'll see this afternoon after this morning's storms pass off to the east should help to destabilize the atmosphere in preparation for development of severe storms this afternoon. If this clearing doesn't materialize and we stay more cloudy than sunny across the area, the severe threat will be much lower. These storms should fire up in the mid afternoon across southwest Indiana and Western Kentucky and impact the Louisville area this evening. While most of these will be your run-of-the-mill severe storms with 60mph winds and hail, a few could have supercell structures or bowing segments. The embedded or isolated supercell structures will be powered by the small amount of wind shear (changing wind direction and speed with height - see 5pm NAM model output left) and helicity (turning in the atmosphere) we'll have in the area as storms form. This means a couple isolated tornadoes are possible.
The bowing segments could produce wind damage as a cold pool of air collects behind some of the more linear storms. These storms will likely last well into the evening and overnight hours and be out of the Louisville area by mid morning tomorrow or earlier. Since there is the risk for wind damage and an isolated tornado or two, the Storm Prediction Center has issued a Slight Risk area for most of Kentucky, Southern Indiana, and portions of Middle Tennessee. A 5% tornado risk exists from Chicago and St. Louis to along the Ohio River, while a 2% risk extends further southward.