Maybe a tarp with a steep angle so that the weight of the snow causes it to run down the tarp sooner than sit on top of it. Try and position the tarp so that the longest open side is against a hill. This will then give you protection on two sides. It depends also on wind direction as this method will create a wind tunnel if one of the open ends are facing into the wind. You could try pegging down one of the open ends( if the tarps big enough) and then once your under it, shove your pack in the other end. You just have condensation to think about then. The whole thing needs only to be about 3 foot high off the ground, just big enough to get in, the less surface area you have exposed to the snow, the less chance you have of it falling in under the weight.
i suppose you could build a debris shelter but put your tarp over the frame and the debris on top. I personally wouldnt build a debris shelter in the snow, it takes too long and the debris is already covered in snow. for me the idea is to construct a shelter quickly with minimum effort in order to keep warm and dry. Just a thought.
