Storms With a Twin Punch Head for L.A.

A twin storm system is expected to pound Southern California with heavy rain today, Wednesday and Thursday, hammering beachfront property with powerful waves, setting off canyon mudslides and flooding low-lying areas of the Los Angeles Basin.

The National Weather Service issued a special weather statement Monday afternoon, warning of the potential for damage and “strongly urging” residents to monitor radio and television broadcasts for emergency advisories.

“It looks like some pretty phenomenal amounts of rain--2 to 4 inches in Los Angeles, 4 to 8 in the foothills and 8 to 10 inches in the mountains, by Thursday night,” said Rick Dittmann, a meteorologist with WeatherData Inc. “At this point, I’m very concerned about flooding and mudslides.”

The Weather Service predicted that beaches will be mauled by windswept, 10-foot waves cresting atop 6 1/2-foot tides. The positions of the sun and moon are boosting the tides above normal levels.

Residents in the Malibu area began shoring up their homes with sandbags Monday as the dual storm system headed toward Southern California.

In the Siskiyou and High Sierra mountains to the north, where up to eight feet of snow fell last week, more heavy snow is expected during the next few days. Caltrans said some of the state’s major highways--including Interstate 5 near the Oregon border and U.S. 50 and Interstate 80 over the High Sierra--could be closed today by drifting snow, just as they were last week.

The rain should start falling here this morning with the arrival of a vast pool of warm, moist air from the south-central Pacific, meteorologists said. They said the rain should build gradually during the day, intensifying dramatically with the arrival of a much colder Arctic storm from the Gulf of Alaska late tonight or early Wednesday.

Dittmann said that because the first system is relatively warm, it will melt the snow at lower elevations in Southern California’s mountains, accelerating the runoff and increasing the likelihood of flooding when the Arctic storm arrives.

Los Angeles County fire officials advised residents in flood-prone areas to stop by local fire stations for sandbags and sand before the main force of the storm system arrives.

“We’re trying to get people to prepare ahead of time, rather than wait until the flooding starts,” said Capt. Tony Duran, commander of Fire Station 70 in Malibu. “Once you’ve got four or five feet of water, there’s not much you can do.”

The county’s Department of Beaches and Harbors bulldozed sand barriers in front of county-owned restrooms, concession stands, parking lots and lifeguard stations at beaches in Malibu, Topanga and other danger points as far south as Torrance Beach.

While the tropical storm system is the first one due into Southern California, the Arctic storm struck Northern California about a day earlier, spreading snow across the upper end of the Sacramento Valley and throughout the Siskiyou Mountains north of Redding by Monday afternoon. The snow, generally light during the day, was expected to increase at night as the cold frontal system moves south and east, into the Sierra and the San Joaquin Valley. Forecasters said as much as a foot of new snow could be added to the snowpack above Lake Tahoe by this afternoon, with more expected tonight and Wednesday.

The heavy snow in the High Sierra is a mixed blessing.

The Sierra snowpack, the principal source of water for urban Californians, is above normal for the date for the first time in years, and state officials say the forecast of continuing snow raised hopes that California’s seven-year drought may be coming to an end.

But the snow also brought tragedy. Last week, a 20-year-old man died in Mammoth Lakes when he was buried in an avalanche, and two snowboarders froze to death after they fell in deep powder near Lake Tahoe.

Temperatures plummeted in the Sierra during the lull between last week’s blizzards and the snow that began falling late Monday. Weekend readings included 27 below zero at Truckee and 21 below at Lake Tahoe. The low at Susanville on Sunday morning was the same as at Fairbanks, Alaska--15 below.

The Arctic storm will still be well to the north when the rain begins falling here from the tropical storm sometime this morning, Dittmann said. When the Arctic storm finally gets here, sometime tonight or early Wednesday, the two systems should collide and merge in spectacular fashion, he said.

“That’s when it will really begin to rain, especially over the mountains, all the way through Thursday,” Dittmann said.

The high temperature at the Los Angeles Civic Center on Monday was 61 degrees, following an overnight low of 42. Total rainfall for the season stood at 5.84 inches; the season’s normal for the date is 5.24 inches.

The Weather Service said 4.68 inches of rain fell in Los Angeles during December, making it the second wettest December on record. The wettest was in 1889, when 15.80 inches fell.