Adaquate. Only kidding, more like spectacular!!! Love that you shot a long exposure to smooth out the cloud layer. One of the best landscape images I've seen recently...or even in a long time.
Voted! This is a beautiful shot, any advice on predicting the best conditions for undercast? I feel like I either luck out or just get stuck in the clouds.
Honestly, I would say look at the cameras for Mt. Tam an hour to hour an half prior. They should be able to tell you roughly what will happen. Sure you might get robbed sometimes where the fog is low and then it rises when its sunset time but that's the way of the game. Cameras are really helpful
and a 6 stop ND from Polar Pro (Landscape kit)