Updated

Big surf, rain and snow are heading toward California, including the first significant rains predicted for the southern half of the state since early this month, forecasters said Thursday.

Breaking waves up to 25 feet were predicted through week's end and beyond for parts of the Mendocino coast, with not quite as big — but still double-digit heights — south through the San Francisco and Central Coast regions and surf up to 9 feet along parts of the Los Angeles-area shoreline.

Heavy surf could spell more trouble for Pacifica, 10 miles south of San Francisco, where crashing waves and heavy rains have eaten away coastal cliffs and put residences in danger.

U.S. Rep. Jackie Speier and other officials visited the city Wednesday and pledged to seek state and federal assistance. On Monday, officials tagged an apartment complex of about 20 units as unsafe, ordering people to pack their things and be out by sunset. Residents scrambled to find someplace to go.

Flash flood watches were to go into effect starting late Thursday for the state's northwestern coast and interior, and on Friday in vast forest fire burn scars in the Sierra Nevada Gold Country.

The National Weather Service also issued winter storm warnings for the Southern Sierra from late Friday to Monday morning. Snow accumulations could range from 5 inches to 15 inches, and up to 20 inches above 7,000 feet. The snow level will drop to 4,000 feet or lower by early Sunday.

Continuing to build a significant Sierra snowpack is vital to California's water supply after years of drought. Runoff from the vast mountain range fills major reservoirs as snow melts in the spring.

Recent storms fed by the El Nino warming phenomenon in the eastern Pacific have boosted the Sierra Nevada snowpack to 115 percent of normal — more than the drought-stricken state has seen in five years. State water mangers hope the snowpack to reach 150 percent of normal by April 1.

Southern California, meanwhile, has been missed by most storms this winter except for an El Nino-powered system that brought heavy rains during the first full week of January.

The next chance comes with a bluster low-pressure system expected to bring rain Sunday. The National Weather Service indicated, however, that the amount of precipitation from the fast-moving system would be uncertain, possibly ending as early as midday.

Snow levels may rapidly fall to about the 6,000-foot-level during the storm, but amounts remained uncertain Thursday.