I 80 across Nevada that time of year could give you all kinds of bad weather, even the passes Reno to Sacramento can be trouble. All depends on storms.
I 90 Missoula to Spokane can be a real pain for the same reasons, high passes and storms. But the Interstates do see major maintenance when storms happen, but can be closed for days at a time if the storms are bad enough.
Because of chain up regulations; I don't have chains for my coach and would be reluctant to use them if I did; I carry food and water for at least 3 days, every trip through the areas. In case I have to stop in a rest area, and wait out the storm and chain up requirements.
No real low county, anywhere on the routes, but you may want to consider , I 80 to Salt Lake City, I-15 North, then I -84 to Portland , then south on I-5
Baker City to Pendleton on this route can be a challenge, there is one
of a drop going down to Pendleton but after that your along the river, to Portland and the one pass, Sexton Summit , on I-5, is usually clear by the afternoon any day they have snow in the area.
Easier route than the Siskiyou , Weed CA, & Mt. Shasta areas.
I have the web site for all OR traffic cams. I'll dig it out and post it.
I'll check to make sure these links work.