National Weather Service Graphical Forecast Information
National Weather Service Graphical Forecasts link for the San Francisco/Monterey area.
This link should take you to a view of the Bay Area on the "Loops" tab. If not, zoom to the Bay area and click on the "Loops" tab.
In the pull-down menu, find with the "Amount of Precip" 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 "Element Period" Box. The element period (time period) was 6-hours when this link was established.
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.
Click on the arrow pointing right with the bar next to it. This advances the time one step. Again, note the amount of forecast precipitation shown on the map in Contra Costa County.
Advance the time again until you have gathered 24 hours of forecast precipitation. If this amount is equal to or greater than 2 inches, and the other antecedent conditions are met, flooding may occur sometime in the next 24 hours. The rainfall and agency warnings broadcast via television and radio should be monitored. Your Personal Evacuation Plan should be implemented if you sense flooding may occur.