snow usually closes the Grapevine on I-5

Because most people in southern California don't have snow tires or chains so they usually close it because most people in Southern California (except for off roaders) don't know how to drive in snow at all. So, it becomes very very dangerous if not fatal if it snows on the Grapevine on I-5 if they keep it open after it snows.

So, just expect to see I-5 closed if this kind of weather continues at the very least at the Grapevine on I-5.

So, the best alternative Route is usually 101 by going over at Highway 46 if you are heading south on 5 from Seattle or Sacramento or wherever from the north. IF you are heading north from San Diego or Los Angeles just head towards Santa Barbara on 101 and head up north until at least Highway 46 at Paso Robles and then over to Interstate 5.

101 along the coast almost never ever sees snow simply because it is so close to the Pacific ocean and 101 is almost always near to sea level as a highway within usually about 500 to 1000 feet vertical of the ocean.