If you're traveling on Friday, expect to encounter weather. But if you're going to the mountains, at least you'll enjoy a white Christmas.
From the National Weather Service:
Our forecast confidence continues to increase in a potentially strong weather system moving through Northern California Friday into Saturday. This system has the potential to cause substantial headaches to travel leading up to Christmas. The greatest impact may be to the mountains, where heavy snow with gusty winds and low snow levels could cause near-whiteout conditions and significant travel delays. Gusty winds are also expected for the Valley, but precipitation is expected to be less than recent rainstorms.
Significant travel delays possible, especially over the Sierra
Snow and blowing snow could cause near-whiteout conditions over mountain passes
Slick roadways could result in increased traffic accidents
Gusty winds could bring down trees and cause power outages
Timing and Strength
Friday into Saturday (greatest impact Friday & Friday Night)
Light to moderate precipitation across the Valley, heavy over mountains
Heavy snow appearing more likely over mountains. Snow levels initially 4500-6000 feet, potentially rapidly lowering to 2500-3500 feet Friday night