How about hitting the road before that to be ahead of the mess?
Monterey and Big Sur are great, but just getting home seems like a better idea.
Even if you can't leave Tuesday, you did say you had planned for Monterey on Wed. So leave early Wed, cruise down I-5 and you'll be at the grapevine with time to spare.
If "I-15" is shorthand for "395 to I-15", I would recommend against it. Cold snow after wet snow is a manor avalanche condition. It would be unlikely to hit you of course, but the roads may become impassable in ways that are far worse than I-5.
Stay safe. Leave early.