Sierra Madre Guards Against Mudslides | NBC Southern California

Sierra Madre Guards Against Mudslides

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    NEWSLETTERS

    LOS ANGELES -- A second storm system is battering the Southland, promising another round of drenching and heavy snowfall at higher elevations in the mountains of Los Angeles and Ventura counties.

    In Sierra Madre, work crews have been busy. The rain sent mud down from burned slopes of the San Gabriel Mountains.

    Mud up to 2 feet deep flowed onto some streets and properties since the storm moved into Southern California.

    A "yellow flag alert" was posted Friday in the foothill community. Officials have warned residents to watch for debris and mudflows in areas left vulnerable by an April 2008 fire above the city. Public works director Bruce Inman says two streets have been closed for debris removal and one home has been evacuated.

    The storm is the second of a one-two punch that began Thursday with a bout of rain that left motorists on the ropes. The National Weather Service reported that the departing storm generated, on average, between a half-inch and an inch-and-a-half of rain over most of the Southland, although some areas in the mountains, foothills and valleys of Los Angeles and Ventura counties received more than 2 inches.

    Thursday's rainfall set a record of 1.46 inches at Bob Hope Airport in Burbank, beating the 1.02 record set on Feb. 5 1948, and a record of 0.48 inches at Fox Field in Lancaster, breaking the record of 0.12 inches set on Feb. 5, 1978.

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    The second storm, a product of the same large upper-level low out of the Eastern Pacific, "will cause precipitation to increase in coverage and intensity Friday, with rain and mountain snow continuing into tonight," according to an NWS statement.

    "Rain will turn to showers late tonight, but plenty of shower activity will linger through Saturday," it said.

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    Rainfall Friday and Saturday is expected to average a half-inch to an inch-and-a-half of rain in coastal and valley areas, and between an inch-and-a-half and 3 inches in the foothills and mountains, below the snow level, with the highest volume expected on or below south-facing slopes.

    The heaviest rain generated by Friday's storm was to appear late this morning or early this afternoon, said NWS meteorologist Curt Kaplan, adding that an influx of cold air will cause atmospheric instability, making the chance of thunderstorms Friday and Saturday greater than Thursday.

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    NWS forecasters said that any thunderstorm could produce heavy downpours, approaching or exceeding U.S. Geological Survey estimates of the volume of rain needed to trigger flash flooding and debris flows in areas previously denuded by wildfire.

    The snow level is expected to fall to around 5,500 feet by Friday afternoon and drop down to about 4,500 feet tonight and Saturday, although some snow could fall as low as 4,000 feet, an NWS statement said.

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    "There is a chance that some accumulating snow could affect travel across the Interstate 5 corridor near The Grapevine," it said.

    Through Saturday, 12 to 24 inches of snow are expected in the mountains of Ventura and Los Angeles Counties, mainly above the 5,000-foot level, according to the NWS.

    "The expected snowfall combined with gusting winds will make for treacherous driving conditions in the mountains through Saturday," the NWS statement said.

    The NWS Friday morning issued a winter storm warning scheduled to be in effect until 6 p.m. Saturday in the mountains of Ventura and Los Angeles counties, excluding the Santa Monica Mountains Recreational Area.

    The warning reflects the expectation that the snow combined with 15-25-mile-per-hour winds gusting up to 45 mph could reduce visibility on mountain roads to near zero.