I will be going to Alaska sometime this winter or next and I'm trying to figure out my clothing system. I realize that the Windcheater is basically a wind shirt with no insulation, and that it is not waterproof. But I am curious what the coldest you all have had it is with proper layering underneath and a Coyote Ruff? Has anyone used it sub -10 degrees? If not, what would a good jacket to serve the same purpose for colder weather be, seeing as the Mountain Parka is still on the back burner?