Rivers Pose Flood Risk in N. Calif. : Weather: Rising waters in Napa, Sonoma counties force evacuations. A new storm is due in the Southland later today.

Torrents of rain pelted Northern California’s wine country on Sunday, boosting rivers to dangerously high levels, activating sandbag brigades and forcing hundreds of residents from their homes.

Officials in Napa and Sonoma counties declared local states of emergency Sunday as river levels crept upward and forecasters warned that rainfall could continue through midweek.

The rain-swollen Russian and Napa rivers reached flood stage at several points Sunday, and the National Weather Service issued a flood warning for both rivers through today.

Officials were paying close attention to the Sonoma County town of Guerneville, where the Russian River, already at flood stage, was expected to continue swelling overnight, triggering what the weather service called potentially disastrous flooding.

Sonoma County assistant administrator Mike Chrystal said Sunday evening that mandatory evacuations could be called for today.

Amid the downpour, Guerneville store co-owner Andi Dalton switched from unpacking Valentine’s Day merchandise to candles, batteries, lamp wicks and other wet weather supplies.

“Nobody wants Valentines. They want lamp oil,” reported Dalton, who sold nearly 100 bottles of the oil Sunday and sold out her supply of batteries.

Up to three inches of rain fell in six hours in the area, and officials worried that flooding in the two counties could approach the devastating levels of February, 1986, when storms caused millions of dollars in damage.

“There’s no real letup in sight,” said Bob Benjamin with the National Weather Service in Monterey. “The ground has reached saturation, and everything right now is just piling up.”

In Petaluma, about 250 people were evacuated from a mobile home park and a housing subdivision in low-lying areas near the Petaluma River. And in Calistoga, elderly residents of two nursing homes were evacuated to the nearby fairgrounds.

In Southern California, three of four northbound lanes of Interstate 5 were closed near Castaic for some three hours Sunday evening after a 1,500-pound boulder tumbled onto the freeway, wedging itself under a truck.

The lingering Pacific storm put a damper on most outdoor activities here Sunday, but in the waters off Venice and Malibu, where people don’t mind getting wet, the rain and wind brought big, ridable surf.

Despite warnings of bacterial contamination from storm drains, surfers poured into the water off Topanga State Beach to enjoy the unusually large eight-foot waves that were breaking with good shape. “It was packed,” said lifeguard Mark Bitler. “You needed a ticket to get on a wave.”

Off Venice Beach, waves of up to 15 feet were crashing throughout the morning Sunday, providing local surfers with the unusual opportunity to ride “double-overhead waves”--those twice the height of the surfer.

Another in a series of winter storms brewing in the mid-Pacific is expected to lash the Southland later today and could once again bring in waves like those that accompanied last week’s storms, meteorologists forecast.

The new storm is expected to begin in earnest this evening and continue through Tuesday night, leaving more than one inch of precipitation, according to meteorologist Curtis Brack of WeatherData, which provides forecasts for The Times.

The new storm could also bring snow as low as the 5,000-foot level in Southland mountains, Brack said.

But the precipitation will still measure far less than last week’s punishing storms, which brought more than two inches of rain on Wednesday and 1.21 inches Thursday at the Los Angeles Civic Center.

“It’s your basic storm system setup,” said Brack, referring to the traditional California winter weather pattern in which storms begin circulating in the Pacific and head east toward the California coast. Most of these pass north of Los Angeles.

In the past week, Northern California has suffered the brunt of the series of storms, with several inches of rainfall in the lower elevations and several feet of snow in the Sierra Nevada.

On Sunday, heavy seas were reported from Point Conception north to the Oregon border.

Hazardous conditions prompted the U.S. Coast Guard to bar ships from entering or leaving San Francisco Bay from late Friday night until early Saturday morning--the first such closing since 1982, Coast Guard officials said. Farther north, strong winds forced a tugboat and a barge ashore at Crescent City early Saturday.

Southland mountains, which enjoyed up to a foot of coveted powder snow and the attendant throng of skiers in last Wednesday’s storm, were largely socked in with fog and drizzle Sunday.

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