The approaching weather system has the potential to be the wettest storm since before December of 2012; but is a very long way from being a "drought buster". To put it in context, I have looked at both San Francisco rainfall and the rainfall for the 8-Station Index (8SI, which averages rainfall in the Northern Sierra Nevada from about Interstate 80 to Mount Shasta).
So far in the 2013-2014 rainfall season San Francisco has had just over 3 inches of rain since July 1st, or about 22% of the 13.59 inches normal to date amount. Forecasts are that over the weekend San Francisco may see about 2 more inches of rain; but it would take four more of these 2-inch storms to erase the over 10 inch rainfall deficit.
Likewise the 8-Station Index has had about 20 percent (4.9") of their normal 27" to date. The forecast of the weekend is for as much as 5 inches falling in the 8SI area, But again it would take the equivalent of at least four more 5" storms to get the Index to near in this watershed.
The bottom line is that even though the "storm door is open" it will need to remain open for there to be a significant easing of the drought.