Just drove down to BC from Fairbanks Alaska and camped along the way. I believe we took highway 2. We stopped at Whitehorse and a hot springs campground. Realistically finding a place along the coast of Alaska would probably greatly your improve chances of surviving the winter. Much much milder winters next to the Ocean. And better availability of food. Though Alaska cities might be targeted. Nuke Map might be of help

https://nuclearsecrecy.com/nukemap/