The pattern across the Great Lakes and Ohio Valley region will be a large high pressure area over the Great Lakes, with a low pressure system over the Southeast states. Through the weekend, the low over the Southeast will drift toward the northwest, but the strength of the high will keep it far enough away from Indiana that rain will not be a concern at the Speedway. However, it will bring some increasing cloud cover, starting Saturday afternoon. This will be mainly midlevel and high level clouds, which will produce a milky sunshine - maybe just enough to take the edge off of full sunshine.
Carb Day will be a little breezy, with a northeast wind between 10 and 15 mph, but Legends Day and Race Day will have lighter winds, between 5 and 10 mph.
I'm glad that I picked a year with great weather to be attending the Indy 500 in person. This will be my second Indy 500; my first was in 2014 when Hunter-Reay and Helio had an amazing duel in the closing laps. I expect that this year's edition will be just as thrilling!