If the roads are bad and your trying to get off the mountain with your TH & it starts sliding your at the mercy of it!
But it sounds like fun to me! I'm not familiar with the road(s) to the ski resort your wanting to go but in MT & WY there are several people who go up steep mountain passes without chains towing a 24-30' bumper pull snowmobile trailers. Probably in the 5-10k lb range.
Use common sense and if the roads are bad, wait it out or leave early if the roads are going to get bad. You could always leave your toyhauler up there and bring it down on a good day. The weather doesn't appear to be that bad at least for the 10 day forecast. We camp in those temps at the end of the camping season in the fall.
I can't imagine a ski resort not having the roads to it plowed and sanded. Go have fun and take some pics and post about your experience.
