SAN DIEGO - A low pressure system swept into the region on Sunday, bringing rain, gusty wind and mountain snow to San Diego County, according to the National Weather Service.

By late afternoon, one-and-a-half inches of snow had fallen on the 6,100-foot-high summit of Palomar Mountain. The county's Department of Public Works reported the snow level had dropped to 5,000 feet, and snow chains were required on vehicles.

Chains were also required nearby at South Grade Road and state Route 76, according to the California Highway Patrol.

The cold low pressure system should move through Southern California through Monday morning, and was expected to bring showers and isolated thunderstorms through this evening and decreasing showers near the mountains Sunday night and early Monday.

One-tenth to a quarter of an inch of rain was expected to fall near the coast and a quarter to half an inch could fall on coastal mountain slopes.

Forecasters said there would be a slight chance of thunderstorms through late Sunday.

"Small hail is possible from isolated thunderstorms and heavier showers, mainly later this afternoon into this evening for areas along and west of the mountains," a NWS statement said.

Snow levels were expected to drop to altitudes as low as 3,500 feet Sunday night into Monday morning. Between 2 to 4 inches of snow could fall in areas higher than 4,500 feet, the NWS said.

West winds in the mountains and deserts were also expected, with gusts that could reach about 45 miles per hour this evening near mountain ridge tops, along desert mountain slopes and into adjacent areas.

The wintry weather could cause problems for motorists along Interstate 8 and on other mountain roads.

"Driving through the mountains may be difficult at times due to locally reduced visibility, slick roads, strong winds and snow," according to the NWS.

Fair weather should return Monday, as the weather system moves east, forecasters said.