There is a small chance of some showers around the area this evening. The qualifying session ends at 5 pm, so I don't think any on track activity will be affected if there is an isolated shower.
Saturday continues to have a good chance of showers and thunderstorms, and the timing of the best rain chances is coming into better focus. While there is a chance of showers any time of the day, it appears that the best rain chances are in the late afternoon and evening, during the second half of the race. This should make for an interesting finish.
Here's the latest NWS forecast of rainfall amounts: