Thursday is expected to have some showers and thunderstorms in the area that develop in the afternoon. Most of the day should be mostly sunny and dry, with comfortable temperatures around 80 degrees.
On Friday there will be a low pressure system tracking east across the upper Great Lakes, so there will probably be increasing moisture over Ohio. An upper level disturbance may also be crossing the area, so I think the chance of rain on Friday is probably the highest of any day of the event. But coverage is expected to be scattered, so there will still be plenty of opportunity for dry racing.
On Saturday there may be some dry air building into the area behind the exiting upper level disturbance, but the models don't completely agree on this. While I think a dry day is most likely, I will have to keep a small chance of rain in the forecast as it can't be ruled out completely at this point.