Saturday will likely have a good amount of cloud cover all day, and it is possible that a few sprinkles could occur as early as the morning hours. But I think that any chance of measurable rainfall (at least 0.01 inches) will hold off until the afternoon. I expect that some scattered showers and thunderstorms will be around north Georgia in the afternoon, and the chance of one hitting the track is about 30%. With a lot of cloud cover expected, highs will only reach the mid 70s.
After sunset, the chance of rain showers will start to increase as that warm front gets closer and the flow of moisture up and over the front picks up. Sunset is around 7:15 pm, and from that time to the end of the race festivities around 11 pm, I would put the chance of rain at 50%. It does not look like heavy rain, more of a light rain that might pick up to a moderate rainfall at times. If rain occurs during the race, I expect amounts to be just a tenth of an inch or less. Thus, I have the impact on the race as low, meaning that the race should be able to continue through the rain (unlike 2015). However, rain chances will continue to rise overnight (70%), with an additional 0.1 to 0.3 inches possible. This will make for some messy conditions for campers at the track.
Rain is expected pretty much all day Sunday, and may be heavy at times. Rain amounts on Sunday are expected to be between a half inch and one inch.
I'll be providing weather updates through the race on my Twitter feed - @Race4caster.