The Cat's Meow is not a winter bag, although I used mine on an alpine climbing course in NZ. We were in huts most of the time, which makes a big difference. I did a short winter trip to Mt. San Jacinto a while back. I took the tram from Palm Springs and then skied into the park a ways. I took my down bag with a light bivy sack. The weather was calm and clear so I didn't bother to put up my tent.
The Cat's Meow will be a good SoCal three season bag. I loaned it to a friend when we went up to Chantry Flat over the 4th of July one year. Not exactly cold weather of course, so it worked fine even though being an old bag, the insulation is pretty well broken down.