equinox bivy

According to the manufacturers website it has a hood:

http://www.equinoxltd.com/the-gear/tarps-and-bivis-and-ground-cloths/sprawler-ultralite-bivi.cfm

I have used the old rectangular, non-hooded version as my winter bivy for a few years. It is useful as a groundcloth on snow and to keep spindrift off your bag… I do notice some frost on the silnylon floor, and a very little bit on the inside of the top at times. Still, for use with a tarp, especially in winter, I think it's far and away the best bang-for-the-buck out there.

Edit: Not sure about use in a snow shelter if you might have actual dripping water. The top is not very water-resistant (perfect for snow though). For that use, I'd go with Event.