The proposed weather for the coming week for Oregon and Washington from the coast to the east is not pretty, Harvey and Marilyn. I empathize with you; my cousin, Doris, in Calgary, often writes of her weariness from the long winter there, and longs for her old life and mild weather near Victoria. My mother often told of the severe winters growing up in a sod home on the Alberta prairie.
If you leave as planned, you will likely end up holed up somewhere for awhile. I guess if you have snow tires or carry traction devices you meet most states' requirements. But since snow tires in our size aren't readily available, and most of us would rather not actually risk damage to our coaches from chains, we opt to just not travel when the chances are good we'll need to put them on. I think you will find "traction devices required" signs in snow-hazard areas of all western states, and given the anticipated midweek weather, the Bulls will be looking to see that you actually have them
on in any passes that remain open at all.
Starting for Snowbird Country this late can be a crapshoot, but as pointed out in an adjoining thread, there are weather maps that can give you fair warning. Personally, I like the online weather predictor, HAMWeather. It has proven itself exceedingly accurate from my point of view, and has been spot-on for mountain weather for the several years I've consulted it. You can see a prediction for places on your projected route for as many as 15 days ahead.
http://www.hamweather.com/ . Just enter in their search field the zipcode or local area you want the weather for, and choose option tabs as needed.
In your shoes, I'd wait for the Canadian Cold layer to recede back out of the states a bit before venturing out, but that's just my 2 cents, and you are used to driving on snow all winter. Although I've driven coach and toad in snow and blizzard conditions, and have experience and confidence with other vehicles, I'd not deliberately put Monty Rae, toad, and family in jeopardy because I was in a hurry to get to warmer weather.
That said, if you still opt to venture forth, there are state transportation department camera systems in place, accessible online, where you can see what you might be getting into. For example, Oregon's Tripcheck feature is at
http://www.tripcheck.com/Pages/RCmap.asp?curRegion=0&mainNav=RoadConditions. If you are thinking I-15, then this Idaho feature will prove most helpful:
http://hb.511.idaho.gov/main.jsf, as will this Alberta information site:
http://www.ama.ab.ca/road-reports?old=/road_report.jsp?menu=ea_road_report , and this Montana site:
http://www.mdt.mt.gov/travinfo/.
-Joel