So, the gvine might be closed, how/when do I get to Southbound 101 from Southbound I-5 before gvine?

So, the gvine might be closed due to snow this weekend, and I need to get to San Diego coming from San Francisco. Now, I plan on taking I-5 as far south as I can before I get to the gvine, but I want to know when is the latest point I can chose to take 101 instead of I-5...Basically, what is the most south I can get on I-5 and still transfer over to 101 without having to backtrack. Bakersfield? Fresno? Where is my point-of-no-return? When is the latest I can make my choice, and quickly get over to 101 from I-5, heading out, before the gvine? Gracias Amigos!