There will be a good chance of showers and thunderstorms in the area on Friday, and a cold front is expected move through on Friday night. The upper level trough is delayed a little behind the front, which is why I've included a slight chance of showers on Saturday. A dry day is most likely, but I can't entirely rule out an isolated shower until the trough exits the area on Saturday night.
As the trough exits, dry air aloft will build into the region from the northwest, along with surface high pressure. This should provide a nice day for the race on Sunday. There should be a good amount of sunshine, and temperatures will be pretty comfortable too, with highs in the mid 70s.
Unless there's a major shift in the forecast, I should have another update posted on Wednesday afternoon.