The admission average uwGPA at UMich was 3.87 last year. So your GPA of 3.5-3.6 appears low to them. Since you are only half way through in the cumulative GPA for college application, you may still be able to bring it up to the admission range. There are a couple things you can do now to figure out your target uwGPA. First, check the Naviance data at your HS to see what is the average GPA needed for UMich. Second, try to re-calculate your uwGPA without subgrades to see if that helps. If you have mostly A-, the recalculation will bring up your GPA.