A large high pressure area will be tracking from the Great Lakes to New England over the weekend, and as it extends southward on the eastern side of the Appalachians, there will be a slight increase in moisture on Saturday. This could result in more cloud cover, and a light sprinkle cannot be ruled out entirely. The chance of measurable rain is too low to mention a percent chance of rain (less than 10%), but a few drops of rain may be felt at the track. It shouldn't have any impact on the racing at all.
Temperatures all weekend are expected to be below normal for late August in southern Virginia, and humidity levels will be quite comfortable too.
I hope to see you at the track!