More heavy rain spread across parts of California (search) on Sunday and snow piled deeper in the mountains as the state sat under a storm system that already had snowbound motorists, caused flooding and even slowed trains.

The latest in a series of storms was blamed for at least four weekend deaths in Southern California, including a homeless man killed Sunday by a landslide. Along the storms' eastward track, two people were killed Saturday by separate avalanches in Utah, authorities said.

Up to 6 inches of rain was expected Sunday in Southern California with at least 2 feet of snow possible in the region's higher mountains. In Northern California's Sierra Nevada (search) and northern Nevada, winter storm warnings were in effect through Tuesday morning with as much as 5 feet of new snow possible on top of Saturday's accumulations of up to 4.5 feet.

Dozens of Sunday church services and all weekend high school sports events were canceled around Reno, Nev., because the area got 18 inches of snow. The region was still digging out from a Dec. 30 storm that dumped as much as 9 feet of snow in the Sierra and 4 feet in the Reno area.

"A combination of two storms of this magnitude hasn't occurred in the city of Reno since 1916," National Weather Service forecaster Shane Snyder said.

Major highways across the Sierra between Reno and Sacramento, Calif., were closed for part of Saturday and the heavy snowfall also delayed Amtrak trains through the mountains.

"There was just too much snow on the tracks," said Amtrak spokesman Mark Magliari.

Flash flood warnings were posted throughout Southern California and authorities kept close eye on foothill neighborhoods below the San Bernardino Mountains where slopes burned bare by wildfires were especially prone to mudslides.

Two traffic deaths were blamed on wet pavement on Saturday and one man died when he tried to cross a swollen stream in Ventura County, police reported.

The storms have been caused by cold low pressure off Oregon's coast colliding with a stream of moist air from the southern Pacific known as a "Pineapple Express," said forecaster Ted Mackechnie of the National Weather Service.

"These are pretty rare events and when they hit, they hit hard," Mackechnie said. "It's very dangerous."

On Saturday, up to 4 feet of snow stalled motorists in their cars along a 5-mile stretch of highway between the Snow Valley ski resort and the Big Bear dam in the San Bernardino Mountains about 90 miles east of Los Angeles. Rescue crews had to use tracked vehicles to rescue people.

At lower elevations, landslides closed roads in San Bernardino and Santa Barbara counties, and firefighters rescued at least three people whose cars got stuck in rushing water.

Elsewhere, flooding along the Ohio River had chased hundreds of Ohio, West Virginia and Kentucky residents from their homes. Meteorologists predicted the river would reach its highest level in eight years at Louisville, Ky., this week at about 5 feet above flood stage.