Are the tires BFG Rugged Trail T/As? Are they new, with lots of tread left?
If so, I don't see any problem heading to the prairies on those. Sure, they're not going to be as good as real winter tires, but if you use a little extra caution, they'll certainly get the job done.
Before I became a winter-tire convert, I had a set of the older BFG Trail T/As on my Pathfinder. Somehow I managed to get through four accident-free winters on those, and that was driving back and forth to the ski hills in the Rockies.