State and federal officials are deploying flood teams and staffing emergency centers as back-to-back storms move into California.
Governor Arnold Schwarzenegger says the state Office of Emergency Services will activate its emergency center on Friday.
City officials in Truckee say the American Red Cross is setting up at shelter there at Sierra Mountain Middle School.
The school on Donner Pass Road is scheduled to open at eight a-m Friday and remain open as conditions warrant.
Sand bags also will be available at the Truckee Fire Station in the event of flooding.
Officials are asking residents to avoid driving across flooded roads or into the Sierra, where about 10 feet of snow is predicted for higher elevations.
Forecasters say three major storms will dump rain on the mudslide-prone canyons of Southern California, produce high winds in the Sacramento Valley and create blizzard conditions in the Sierra.