A very, very dangerous situation has gotten underway.
We have two Particularly Dangerous Situation (PDS) Tornado Watches. The newest PDS is for the Ohio Valley and includes Columbus, Dayton, Cincinnati, Louisville and Lexington until 9pm.
The first PDS continues in effect until 6pm and includes Indianapolis, Evansville, and Paducah.
If you've read Warnings: The True Story of How Science Tamed the Weather you know how the most violent tornadoes come from supercell thunderstorms. Those are supercells (arrows) moving into the area of high significant tornado index values (2 is the threshold).
I expect violent, possibly long-tracked, tornadoes to move across this area in the next few hours.