I agree with those who say to stay south (I-10) until California and then go up I-5 to Oregon. That puts you over just one serious mountain pass at the CA/OR border and avoids most of the bad stuff that can happen along a cold weather route. Believe me - been there and done that. Have witnessed fatalities caused by loss of control over icy overpasses and bridges; once while sliding along myself without much control on an I-40 overpass. Believe it when the sign says something like "bridge freezes before roadway".