Is lightning flash density effected by forest density? Do CGs tend to happen less in areas of dense forest?
I wouldn't make too much of the forest density. The southern part of the state is a patchwork of farmland, forest, lake, and field, with the central region being quite agricultural and therefore open in a lot of places. Lots of corn, wheat, and soybeans. I don't get to the thumb area much, but what I've seen of it has been flat with plenty of muck farms. As you head farther north, the forests become extensive and chasing is impractical, though it can be done. There's an east-west line running roughly from Saginaw to Muskegon which separates the northwoods from southern hardwood forest. That's a simplified description, but you'll find it to be accurate enough. Here's a map that you may find interesting:
As for the effect of forest density on CGs, I highly doubt it makes any difference. I've seen plenty of storms spit out mass quantities of cloud-to-ground with a grin, while others have been all intra-cloud stuff. Lightning type and frequency doesn't differentiate between forest and cropland; it's about the nature of the storm, not the vegetation. A lot of times, the best opportunity for lightning photography comes after the storm, as the storm heads eastward. Kurt Hulst would be the guy to talk to about that, as he loves lightning photography.
The only impact forest density has on lightning that I'd place any stock in is the obvious, which is that trees mess with the viewing. For that matter, even July and August corn can get in the way. But it's not that big a deal. There are places in southern Michigan that you want to avoid, such as the Barry State Game Area, but the roads are good, and you're usually not far from open farmland. I definitely prefer Illinois and Indiana for their vast, flat, open expanses, but this isn't Arkansas or even Wisconsin.
It's really pretty simple. This is not supercell metropolis, but you'll usually get a crack at a few supercells each year. But if you like lightning, you'll be a happy camper. I don't know that it's any better here than anywhere else, but it's certainly not any worse, and July and August keep it coming while the western states bake.
