On Sunday, the rain chances appear a little lower than before, as the models are trending slower with the approach of another low pressure system from the northwest. There may be enough instability in the afternoon for some scattered showers and thunderstorms to develop, but the chance of one hitting the Speedway is only about 30%. Temperatures on Sunday will be warmer, reaching into the mid 80s. Winds should not be a significant factor, blowing from the south to southwest at 5-10 mph.
I should add that there is still quite a bit of model disagreement for the weekend, particularly on Sunday. One model (GFS) shows a much higher chance of rain than the other (NAM). I think the drier forecast is more likely to be correct, which is why I only have a small chance of rain. Over the past few days, the GFS has been producing more rain over the Southeast than has actually occurred, so I think the NAM has a better handle on this pattern.