Traveling through Idaho, Utah in Late November.

We have been on that route one time at Thanksgiving. We went from Reno to Three Forks, MT and back. Going up was fine, going back was a white knuckler. It had snowed, the I 15 was icy and we were pulling a 38' 5'r. We stopped in Pocatello, the rv park had 6" of snow in the park and ice. I still don't know how the hubby pulled us out the next morning. So, I'd say your odds are 50/50, the 15 could be ok or a nightmare. Just watch the weather forecasts.