Just wondering why you want to pull a 5th wheel into the northern climes during the dead of winter. Unless you "have" to be up here then, is it possible to make the trip a couple of months later? Moving into spring is a beautiful time in the Far West and hopefully weather conditions will be more stable.
I am an experienced winter mountain pass driver and have had to chain up a number of times over the years heading to college or visiting relatives east of the Cascades. Chaining up in the snow or in the slush/sleet of lower elevetations while heading into a mt pass is a real chore which would be multiplied several times if needing to chain up a 5th wheel well. If you're young and haven't experienced this it might be a new adventure for you. If you're my age I can pretty much guarantee you will not enjoy it.