Cyclonic Winds, Heavy Rain Lash State : Weather: Gusts uproot trees and damage homes. Mudslides clog mountain roads. Storms expected to persist through Tuesday.

Striking with unexpected fury before dawn Thursday, a departing storm system raked Southern California with cyclonic winds and intense rain that uprooted trees, damaged homes, downed power lines and set off mudslides that blocked dozens of roads.

Farther north, heavy rain undermined tracks and derailed a freight train near King City. A helicopter plucked two teen-age boys from a rain-swollen creek near Gilroy after they were stranded for seven hours in chest-deep water after a failed rafting excursion.

Snow forced motorists to use chains on Interstate 80 and California 50, the two principal routes across the Sierra, and on a number of smaller roads there and in the mountains of Southern California.

Forecasters said more rain is expected across the Southland today, Saturday and Sunday, with showers on Monday and no real clearing until Tuesday.

Brief but intense downpours hit communities in the San Gabriel Valley shortly after 1:30 a.m. Thursday, spinning off fierce cyclonic winds that ripped through a small section of Pomona, uprooting about 50 trees.

No one was hurt, but at least three houses and two cars were damaged by falling trees, said Ron Gomez, a Pomona Fire Department spokesman.

Victor Lara and his wife, Debbie, said they and their four children were asleep in their house on Titus Avenue when they were awakened by the storm. Lara said his wife “looked out the window and there was so much stuff flying through the air that she couldn’t see the house next door.”

Then a 70-foot-tall pine tree crashed onto their roof. One limb broke through the ceiling of their bedroom and another crashed into a bedroom where three of their children were sleeping, dumping rain and mud inside. The couple grabbed their children and ran to another part of the house.

Five blocks away, on Marquette Avenue just north of the Pomona Freeway, James Hite was watching television “when the wind and rain picked up very heavy.”

“All of a sudden, there was a big rumbling sound like a freight train coming through the living room,” Hite said.

A large deodar tree had just crashed down onto the roof of the house.

Hite and his wife, Viola, escaped unhurt, but the tree punched holes in the roof and shattered a window.

Daryl Russell, a tree maintenance supervisor for the city of Pomona, said at least 40 to 50 trees were uprooted or destroyed in a three-block-wide swath near the Pomona Freeway.

In Orange County, violently spinning winds that may have formed an actual tornado hopscotched across about 110 homes at 1:40 a.m., causing damage estimated at $200,000.

The roaring and shaking in the pre-dawn darkness resembled an earthquake, one resident said.

“I thought it was the Big One,” said Eleanor Mirasim. “The whole house was shaking.”

Property damage included a hole blown in one roof and the uprooting of a tree, which crashed into a parked, empty mobile home. The storm caused power outages in some parts of Buena Park, but, ironically, houses in the immediate path of the tornado did not lose electricity.

“I thought we traded tornadoes for earthquakes when we left Kansas and came to California,” said Wilma Downey, 71, who lives with her husband, Travis, in the 6100 block of Pershing Way. “I’ve never heard anything like it before, but I’ll never forget it. It was an awful sound.”

Mudslides were reported on lower-elevation highways in the Santa Monica, San Gabriel and San Bernardino mountains, but in most cases Caltrans crews were able to reopen the roads by midmorning. At higher levels, chains were required on many of the highways leading to winter resorts, and skiers were advised to check road conditions before heading for the slopes.

In the San Fernando Valley, a teen-ager tried the same stunt as the youths near Gilroy when he attempted a rafting trip on a wash in Sunland. He was plucked from the water by a helicopter rescue crew after his raft overturned. In this case, the boy was in the water for only a few minutes, and the rescue was effected swiftly.

In the Agua Dulce area, sheriff’s deputies allowed residents to return to the Vasquez Paradise recreational vehicle park to move their trailers out or collect belongings.

The park was evacuated Wednesday when an upstream pond overflowed, flooding the park with up to four feet of water. County engineers determined Thursday that an earthen dam at the pond was structurally unsound, and the evacuation order will remain in effect until the pond can be drained.

The Sierra Highway was closed 10 miles north of Santa Clarita after runoff undermined a 100-foot section of the road, causing it to collapse.

Along the beaches of Santa Monica Bay, waves of 10 to 15 feet were reported, and lifeguards warned surfers to avoid the water unless they are very experienced.

“It’s the first big surf we’ve had in six, seven, maybe 10 years,” said lifeguard Lt. Dan Cromp, who was working at Santa Monica State Beach.

“Stay out of it, unless you’re a big-wave surfer from Hawaii,” Cromp said. “This stuff is hairy. Real hairy.”

Hurricane-force winds gusting at more than 90 m.p.h. were reported at offshore oil platforms in the Santa Barbara Channel, and military officials said that winds up to 70 m.p.h. knocked over a guard shack at Vandenberg Air Force Base, breaking a guard’s leg.

The San Luis Obispo County Office of Emergency Services said Thursday that winds and lightning downed electrical lines throughout the county, knocking radio and television stations off the air and forcing the county Fire Department to switch to emergency power.

The winds and lightning felled trees that toppled onto buildings and vehicles, causing extensive damage. Several homes in the coastal community of Cambria were flooded, and a walkway collapsed at a motel in Pismo Beach, injuring one person.

In Monterey County, 15 cars from a 56-car freight train derailed two miles south of King City, blocking the Southern Pacific mainline and disrupting Amtrak’s passenger traffic between Los Angeles and the Bay Area.

Mike Furtney, a Southern Pacific spokesman, said the derailment occurred after storm runoff undermined the tracks, causing them to give way beneath the weight of the freight train.

Amtrak spokesman Bruce Heard said buses would be used to bridge the gap in passenger service. There was no immediate estimate when track repairs would be completed.

In Santa Clara County, an Air National Guard helicopter was used to rescue two 17-year-old boys from Uvas Creek after their nighttime rafting trip went awry.

Officials said Joey Limon, Nick Eredia and three other teen-agers had set out in a rubber raft for an impromptu ride on the roaring creek. When the raft capsized, the three other youths--one of them a girl--were able to swim to shore, but Limon and Eredia were stranded on a small island in water that rose slowly to their chests.

Gilroy police dispatcher Steve Ynzunza said the boys clung to roots and branches while Santa Clara County sheriff’s deputies tried in vain to throw them lifelines.

Finally, after an initial rescue attempt by a Coast Guard helicopter had to be abandoned because of poor visibility, a second, successful attempt was made by an Air National Guard crew.

“They are typical boys,” Joey’s mother, Virginia Clark, said after the youths were rescued. “They just wanted to have some fun, and it turned into a nightmare.”

Near Coalinga, the California Highway Patrol escorted cars along Interstate 5 through water a foot deep, and officers said roads were flooded throughout Fresno, Madera and Tulare counties. In Fresno, intersections were blocked with traffic after the pavement flooded and signal lights were knocked out by power failures.

In the High Sierra, it has been the same story for the past several weeks: Chains were required on most highways above 4,000 feet as the snow continued to fall.

For Caltrans, the snow has been a headache, requiring snow-removal crews to work around the clock.

For state water officials, it’s been a blessing. The snowpack, the principal source of water for urban Californians, is well above normal and getting deeper, bolstering optimism that the state’s prolonged drought is finally coming to an end.

Steve Burback, a meteorologist with WeatherData Inc., said that in the Los Angeles area overnight showers should continue throughout today, with steady rain and a chance of occasionally heavy rain tonight, Saturday and Sunday.

“There’s a chance of showers on Monday, but by Tuesday it should finally dry out,” Burback said. “After that, it looks like there might actually be some clear weather for a couple of days.”

Between midnight and 3 p.m. Thursday, .94 of an inch of rain fell at the Los Angeles Civic Center, raising the total for the season to 13.59 inches. The normal season’s total for the date is 6.22 inches.

Contributing to this story were Times staff writers Bill Billiter and Timothy Chou in Orange County and Tracey Kaplan and Julie Takami in Los Angeles.