Michigan to California this December

Since you're going to So Cal, I'd take 69 to Indianapolis. Pick up 70 to St Louis (you can spend the night in the Costco parking lot if you're a member). From there take 44 to Oklahoma City and then 40 to Barstow. From Barstow take 15 into the LA Basin. We've done this route from Battle Creek to Barstow about 5 times but never in winter.

Notice that all of these roads are interstates. If you do get a storm they'll be the roads to be cleared and maintained first.