I've lived in the SF Bay Area about 20 years, and love visiting Yosemite (about a 4 hour drive) in all seasons. You can never go wrong visiting Yosemite, it's just one of the best places on earth.
For anyone doubting the beauty of the Sierra's in a deep winter freeze, let me say, I was once a doubter too. I have been stuck in a few blizzards, and yes, I knew bad weather was coming. But after this particular storm cleared in February 2011, about 100 photographers from all over California came out, and took photos all over the valley. It was hard for me to pick just one for this Afar Highlight, but the falls are so iconic (like many features in Yos) that I choose this photo. Thick snow had coated everything, but the sun came out and produced a spectacular blue sky and prisms off of the ice all day.
I say brave the roads - the tourists are few, the snowshoeing is a great work out, there will be stew, and beer and cheer near any public fireplace.
Yosemite in winter. I love it.