© Nick Ut/APHeavy rains in the forecast for Southern California through the weekend.
A powerful winter storm dumped about a half-inch of rain on Los Angeles and forecasters say more wet, messy weather is expected.

The National Weather Service says another mass of cold air moving into Southern California could bring thunderstorms Saturday afternoon and into Sunday.

This latest storm could drop up to four inches of snow at elevations as low as 3,500 feet, causing potential traffic snarls on mountain passes.

Rain began to move into the region from the north Friday afternoon and made a mess of the evening commute. The California Highway Patrol says there were approximately 158 collisions between 3 p.m. and 7 p.m. Friday, compared with 80 for the same time period one week ago.

A flash-flood watch was issued for mountain areas that have been scorched by wildfires in recent years, but there are no immediate reports of any problems.