This link should take you to a view of the Bay Area on the If not, zoom to the Bay area.
In the pull-down menu, find with the "Precip Amount (in)" option. The map will show the QPF (Quantitative Precipitation Forecast), which is the forecast amount of rainfall at the end of the time shown in the "slider" above the map.
Note the amount of forecast precipitation shown on the map in Contra Costa County and the time the map is valid for at the bottom of the map.
Move the slider bar or click the buttons on either end of it to change the 6-hour time window QPF.