What do you call snow that has collected between a car body and the tire?

Solution 1:

According to a renowned authority, in the Northeastern part of the United States accumulations as shown are called snow goblins. Other authorities call them snow cuds or snow boogers.

Solution 2:

I just posted my own question about the term we use. I can't believe I missed your question! In New England (in Maine anyway), we call these snow goblins.

Solution 3:

This isn't a very fun answer, but if you're in this situation—already talking about all this snow—you could call it "buildup" or "wheel well buildup".

This strikes me as the type of lingo mechanics use when they say something like, "You've got residue buildup in your cylinder head" or "there's a lot of corrosion buildup on your battery terminal. Better brush 'em off."