Here is the precipitation over the past 7 days over the southwest U.S. Some locations in the northern Sierra range have gotten over 6 inches of liquid water, as have the coastal mountains over the northwest corner of the state. Not too much to cause flooding, but enough to provide large volumes of water.
California has a LOT of reservoirs with a huge, multi-year, storage capacity. A nice summary of some of the major reservoirs are shown below.
The three biggest reservoirs are Lake Shasta, Lake Oroville, and Millerton Lake; Folsom Lake is near the precipitation maximum. Looking at the big Kahuna first, Lake Shasta, one sees a precipitous and huge increase in water storage (the blue color shows average levels for various times of the year). Impressive.
The second largest reservoir shows a similar, but more modest, large increase.
But if you really want to be impressed, take a look at Folsom Lake--now above normal!
And even with the substantial atmospheric river activity, the California snowpack has been maintained at above-average levels.
California is going to have be content with their watery bounty for a while, since the circulation is shifting with more ridging along the West Coast and rainfall moving back towards the Northwest. To illustrate, here is the 10-day total precipitation from the NWS GFS model. Plenty in our mountains and enough to keep northern CA moist, but nothing over the southern half of the state.
It will be cold enough for lots of snow in our mountains. The Northwest drought is over and I suspect the same will be said for California in a few months.