Strongest storm in years to drench Southern California It's the strongest storm to hit the region in several years.

 -- Southern California is bracing for torrential rain and powerful winds today in what could be the strongest storm to hit the region in years, if not decades.

The massive storm took aim at the West Coast this morning and will dump heavy rain across southwest California today, with numerous rain showers lingering into Saturday, according to forecasts. Flash flood watches are in effect for Los Angeles, Ventura and Santa Barbara counties from Friday morning through Saturday morning.

"The storm looks to be the strongest storm to hit southwest California this season," the National Weather Service office for the Los Angeles region wrote. "It is likely the strongest within the last six years and possibly even as far back as December 2004 or January 1995."

The storm is expected to generate a total of 3 to 6 inches of rain in Los Angeles County beaches and valleys and 5 to 10 inches of rain in south-facing foothills and coastal mountain slopes, according to the National Weather Service.

Heavy rainfall and gusting wind moved into Southern California this morning around 7 a.m. local time. Los Angeles will start to see the heaviest downpour this afternoon. By 6 p.m. local time, heavy rainfall will move further south into San Diego, according to ABC News meteorologists tracking the storm.

With soil already soaked from significant rainfall this winter, forecasters warned of the potential for flash floods and debris flows, especially near areas stripped bare by wildfires.

“A combination of the Pacific jet stream and a storm system will bring copious amounts of rain to Santa Barbara, Los Angeles and San Diego today into tonight,” said ABC News senior meteorologist Max Golembo. “This will lead to major flash flooding in urban areas. Mudslides and rockslides are possible in the recent burn areas.”

Numerous showers in Southern California will continue through Saturday, Golembo added.

Strong winds capable of taking down trees and power lines are also expected, along with heavy snow in Southern California's mountains.

Mandatory evacuation orders were issued for 180 homes below a burn scar in Duarte, a city nestled in the foothills of the San Gabriel Mountains east of Los Angeles.

The Associated Press contributed to this report.