Storms Pack Powerful Double Whammy : Weather: Two colliding blasts, combined with some of the highest tides of the year, could bring damaging surf and flooding.

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 region.

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.

In Orange County, officials expect flooding in some coastal areas and are warning motorists to avoid Pacific Coast Highway between Golden West Street and Warner Avenue in Huntington Beach. They also warned people to stay away from traditional trouble spots, such as Laguna Canyon Road, Carbon Canyon Road, Ortega Highway and other one-lane roads without cross streets.

The National Weather Service expects that beaches will be mauled by wind-swept, 10-foot waves cresting atop 6 1/2-foot tides. The positions of the sun and moon are boosting the tides above normal levels. Newport Bay, for example, will have a high tide of 5.8 feet today at 6:13 a.m. Wednesday’s high tide will be 6.2 feet at 6:54 a.m., and 6.5 feet at 7:36 a.m. on Thursday.

Residents in the Malibu area began shoring up their homes with sandbags Monday as the dual storm system headed toward Southern California. But there were no reports of sandbagging in Orange County.

“People don’t like to fill sandbags until they have to,” Steve Chafe, a Seal Beach lifeguard, said. “It’s kind of a panic thing.”

Rick Dittmann, a meteorologist with WeatherData Inc., predicted total rainfall of two to four inches in Santa Ana and four to eight inches in the foothills. A strong Pacific storm combined with high tides, strong winds and saturation from recent rainfall could produce flooding inland.

“When you have high tides coming in, it’s difficult to drain the flood control channels,” said Bill Reiter, Orange County operations manager for the Environmental Management Agency. He said said county workers on Monday inspected drainage systems and cleared any blockages in anticipation of the storms.

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.

In Orange County, sandbags will be available in Huntington Beach through the Department of Public Works at the Corporation Yard, 17371 Gothard St. Bags are 35 cents each, but residents must fill their own and provide shovels. Sand is free and available from 7:30 a.m. to 3:30 p.m. Hours may be extended if the need arises.

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 snow-boarders froze to death after they fell in deep powder near Lake Tahoe and were unable to free themselves.

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. “There could be a little clearing on Friday, then more rain on Saturday and Sunday.”

High Tides May Mean Flooding

A new set of winter storms is expected to hit this week at the same time Orange County experiences extremely high tides. The combination could result in coastal flooding. Tides listed are for Newport Bay.

Day Time Highest Tide Forecast Tuesday 6:13 a.m. 5.8 ft. Rainy Wednesday 6:54 a.m. 6.2 ft. Stormy Thursday 7:36 a.m. 6.5 ft. Showers Friday 8:18 a.m. 6.7 ft. Clearing

Source: Los Angeles Times, WeatherData Inc.