Just quickly, I was looking out of the window one afternoon last thursday and noticed how snow was just settling where cars used to be parked, which seemed quite strange because one would have thought that a car having been parked over the tarmac should be warm and make the snow less likely to settle.
The only possibilities I can think of are that either the sun had been out in the afternoon so the car was acting to keep the ground in the shade. I don't think it was sunny that afternoon, although it is quite hard to tell from our office. The other thing the car could have been shading the ground from is warm rain. which would definitely have warmed up the ground and made it wet improving the thermal connection between the ground and the snow, so the snow in the dry shadow was better insulated from the ground.