Updated

The first in a new series of winter storms is soaking much of California — snarling commutes, downing trees and dumping heavy snow in the mountains.

Up to 3 inches of rain was expected through Thursday in parts of the San Francisco Bay area.

In Southern California's Santa Monica Mountains, rain was falling at rates of up to a half-inch per hour.

Flood advisories and watches are posted on the far north coast. Winter storm warnings are in place across the Sierra Nevada.

Forecasters warn that mud and debris flows could occur as heavy rains fell on wildfire burn scars east of Los Angeles.

The National Weather Service office in San Diego warns that five-day rainfall totals will likely be substantial.

Storms are expected to bring precipitation across California into early next week, with brief breaks between systems.