It's raining, and it's going to keep raining. A lot. As forecast, a powerful cold front moved over the California bight early this morning (Tuesday) where it interacted with a potent Left-Front-Quadrant (LFQ) of a jet streak, evident here:
This, combined with an elongated train of moisture stretching back to Hawaii (seen below), colluded to rapidly intensify the cold front.
Here is a GIF of the rapid intensification:
A look at the radar in the basin shows very heavy rain (rain rates approaching 0.8"/hr) covering almost everything:
The rain will continue for another 2-3 hours in the basin before tapering off late this afternoon.