We are driving from Vancouver to Los Angelas on December the 18th, we are a whole family and has no long driving experience, i heard from friend that the sisiyou pass area is usally icy in this period of time, our car is Mercedes Benz R350, SUV, i did a car check before driving, the dealer tells me that our wheels are at the edge of changing, i want to go change in California, is that safe? Do i need a chain in the sisiyou pass area? what is the weather report about the storm warning mean? i don't get. Anybody can help me?