I don't live in MI anymore, but thought I'd give my opinion on some options for "local" places to go.
I see that some of you have mentioned 6-10 hour drives. Mt Bohemia shows as taking about 10 hours from Detroit, but I bet you could make it in 8 or 9 depending on the weather. My family has a cabin up in the Keweenaw and I used to go up every single summer, so I'm familiar with the drive. Once you get over the bridge... its pretty much all just 2 lane "highway" with long stretches of nothing (stretch from Engadine to Munising, Marquette to Houghton, etc.).
You could do Bohemia (which is actually a pretty bad ass place to ride, especially for the midwest - 790' vertical) as well as a couple of stops in the UP, such as the Porcupines (641' vertical), Mont Ripley (right at Michigan Tech, 440' vertical), Marquette Mountain (604' vertical), Ski Brule (500' vertical), etc.
Obviously a trip to the east could provide more vertical (NH, VT, NY, etc), but there are some options in MI and it would probably be a pretty cool road trip to hit up all of the UP resorts. Also, I would assume that it could be a low budget type trip (besides the fuel).