LOS ANGELES -- Areas ravaged by fires in the last few years are once again on high alert for mudslides as a fierce winter storm moves into Southern California.

The National Weather Service issued a flash flood warning late Sunday evening forecasting heavy rain across much of Southern California after midnight, with precipitation heaviest from the early morning hours through late Monday afternoon. Rain could fall at a rate of more than a half-inch per hour.

With more than two inches of rain expected in Sierra Madre, which was threatened by a fire in the foothills of the San Gabriel Mountains above the town last April, the city issued a "red flag mud alert" to residents on the city’s emergency blog Sunday telling them to be ready to leave their homes in case of mud and debris flows.

Residents of other fire-damaged areas were also vulnerable, including in Sylmar, which was damaged by the recent Sayre fire, Yorba Linda, which was torched by November’s Freeway Complex Fire, and Silverado and Modjeska Canyons in Orange County, which were damaged by the Santiago fire in the fall of 2007.