Randonneur,
I did get a chance to try out the tarp method of protecting against snow accumulation, however to be upfront, it was not in a heavy snow storm. I believe it will work, just the same, and using a tarp, secured to the truck, is an effective way to remove the snow easily, and prevents ice build up on the camper roof. Here's a couple photos of a snow storm I was in, while elk hunting in Colorado. You never know how bad they're going to be, so I just proactively prepared. Again the idea is getting the tarp over the roof, snug it down with ropes, and when you feel you need to remove the snow, you can either slide the whole tarp to one side and the snow and ice will fall off as you go, or you can throw the ropes back over the top and sort of peal the snow off to one side as the tarp curls over itself. What I like best about it is you don't have to climb a ladder in wet, icy conditions, so it's safer than climbing a ladder. With two people getting the tarp up over the camper it can be done relatively easy, by tying a rope to two corners on each side, and throwing the ropes up over the roof to the other side, and then pulling the tarp up into place, and tying it off on the truck or the camper at the jack mounts. Of course you can't open vents, and your solar panel is covered up, but it isn't much use during the snow storm anyhow.
Poky