LOS ANGELES COUNTY : Flash-Flood Watch Issued in Burn Areas

A flash-flood watch was issued for the Altadena and Malibu burn areas until 9 a.m. today as the chilly arm of a Pacific storm began to swing through Southern California on Monday.

Although rainfall was generally light Monday, forecasters said occasionally heavy rain, and possibly a few thunderstorms, could tie up traffic during this morning’s rush hour.

Up to an inch of rain is expected in the Los Angeles Basin, with perhaps twice that much in some foothill communities, before the storm system moves out to the east tonight. Snow will fall above 6,000 feet, with as much as 10 inches expected at some resorts in the San Gabriel and San Bernardino mountains.

Curtis Brack, a meteorologist with WeatherData Inc., which provides forecasts for The Times, said the arctic storm was moving inland across the Pacific Northwest, spinning off a chilly arc of unstable weather that was swinging rapidly through the Southland.

Temperatures will be cool today, with highs in the mid-50s forecast for the Los Angeles area.

Brack said the rain will continue off and on until tonight, with skies clearing by Wednesday morning. He said a ridge of high pressure should build up along the coast later in the week, blocking the approach of any more stormy weather. Mostly clear skies are forecast for Thursday, Friday and Saturday, with temperatures warming to near 70 by the weekend.