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Coming storm brings mudslide risk to Southern California

October 13, 2009 |  9:21 am


As the first storm of the season moves into Southern California, the National Weather Service is issuing flash-flood watches for mountain burn areas from Santa Barbara to San Bernardino counties.

Slick roads and the threat of mudslides have prompted traffic officials to close several mountain roads as forecasters predict .75 to 1.5 inches of rain along the coast and valley areas. Up to 4 inches of rain is expected in the mountains starting this afternoon.

Officials said residents in burn areas should prepare for possible mudslides, rock slides and debris flows "even during periods with little or no rain falling."

The powerful winter storm started moving into Southern California on Monday, combining the force of a storm from Alaska with the moisture-laden remnants of a typhoon from the western Pacific.

The National Weather Service issued the flood watches for areas burned by recent fires in Santa Barbara, as well as the massive Station fire in Los Angeles County and the Sheep fire near Wrightwood. The watch also covers areas burned in last year's Sayre and Marek fires in the San Fernando Valley area.

"This storm is expected to tap into subtropical moisture, giving it the potential to bring moderate to heavy rain," according to a weather agency statement this morning. "This heavy rainfall may create significant hazards in and around recent burn areas, with a threat of flash flooding and debris flows over the burn areas of Santa Barbara, Ventura and Los Angeles counties."

A high wind warning is in effect for all L.A. County mountain areas from noon today to Wednesday morning, accompanied by winds of 35 to 40 mph and gusts up to 60 mph.

The storm system is wetter than normal for October, when the average rainfall for the entire month is about half an inch, weather officials said. The rains are being driven by strong winds blowing from the south, intensifying rainfall on south-facing mountain slopes that burned from Altadena to Acton during the 250-square-mile Station fire that broke out in August.

The U.S. Geological Survey released a grim forecast last week for communities hit by the Station fire, saying major mudslides are likely during the winter rainy season. The locations most at risk for mudslides are La Cañada Flintridge, La Crescenta and a few areas of Pasadena against the San Gabriel Mountains, geologists said.

The California Highway Patrol has closed some mountain roads because of the coming rains, said Officer Francisco Villalobos, a spokesman for the agency. Big Tujunga Canyon Road is closed 1 1/2 miles north of Mount Gleason Avenue to Angeles Forest Highway. Aliso Canyon Road was closed in the Angeles National Forest.

Authorities said they were seeing an increase in the number of accidents this morning and advising drivers to watch out for slick conditions.

"It's the first significant rainfall of the season," said Rich Thompson, a weather service meteorologist. "So the roads can be slicker than you might expect because of all the oil coming up."

-- Tony Barboza

Photo: Luis Fernandez helps to build a barrier in front of the home of a friend who lives on Canyonside Road in the Briggs Terrace neighborhood of La Crescenta. (Al Seib / Los Angeles Times) More storm photos

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