(CBS/AP) Areas of the Sierra Nevada, famous for paralyzing amounts of snowfall, have been hit with a dumping like they haven't seen in generations, with steep drifts stranding an Amtrak train, knocking out the Reno airport and shutting down major highways across the mountains.

In the East, heavy rain and snow is causing flooding and ice damage along the Ohio River.

In Pennsylvania, a tug boat sank when it was pushed against a dam early this morning killing three crew members. A fourth is missing. The strong current was caused by recent flooding.

Rain-swollen rivers continued to rise in southern Indiana, threatening some communities with the highest floodwaters in nearly a century.

Storms also have caused flooding in Southern California and Arizona and deadly avalanches in Utah.

The relentless storms have killed at least 12 people.

In areas of Sierra Nevada, the string of moisture-laden storms has dropped up to 19 feet of snow at elevations above 7,000 feet since Dec. 28 and 6½ feet at lower elevations in the Reno area.

Meteorologists said it was the most snow the Reno-Lake Tahoe area has seen since 1916.

"I've lived here for almost 40 years and I've never seen anything like it," Peter Wolenta, 69, said Sunday from his home in Stateline, on the southern end of Lake Tahoe. "This baby just seems to be stretching on forever. Right now I'm looking out the window and it's dumping."

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

A lull in the storm allowed the reopening Sunday of Interstate 80 over Donner Summit and U.S. 50 over Echo Summit after the highways were closed off and on for more than a day. The highways connect Sacramento, Calif., to Reno.

"The snowbanks along Interstate 80 are about 8 to 10 feet high. It's like you're going through a maze," said Jane Dulaney, spokeswoman for the Rainbow Lodge west of Donner Summit.

More than 220 Amtrak passengers were back in Sacramento on Sunday after spending the night stuck in their train in deep snow west of Donner Summit, spokesman Marc Magliari said.

One car of the California Zephyr, eastbound from Oakland, Calif., to Chicago, derailed in the snow Saturday evening. No one was hurt. Amtrak officials moved the passengers to other cars and the train reversed course and returned to Sacramento about 6 a.m.

Because of the derailment, a westbound Zephyr had to stop in Reno and its roughly 140 passengers completed their trip to California by bus.

Reno-Tahoe International Airport was closed for 12 hours overnight for the second time in a week, and only the third time in 40 years, because plows could not keep up with the heavy snowfall, spokeswoman Trish Tucker said.

"It's nice to know that there are places with more snow than the Dakotas," Wendy Wollmuth said while waiting for a flight to her home in Moffit, N.D. "We're a bit spooked about being here with all this snow."

Church services and weekend high school sporting events in the Reno area were canceled. Reservations at the Arch of Reno wedding chapel were down 50 percent from a normal weekend, spokeswoman Kathy Allen said.

When the latest storm hit, the Reno region had still been digging out from a Dec. 30 storm that dumped as much as 4 feet of snow on the city.

"You'd have to go back to 1916 to top this sequence of storms," National Weather Service forecaster Tom Cylke said Sunday of the snow accumulation in Reno.

Flash flood warnings were posted throughout Southern California. Residents of a mobile home park in Santa Clarita, northwest of Los Angeles, were evacuated Sunday after 5 feet of water spilled in from a creek.

"An eight-foot masonry wall that was protecting the structures gave way and water is rushing into all the houses," said Inspector John Mancha. Authorities weren't immediately sure how many people were evacuated.

A two-story home collapsed in the Studio City area above the San Fernando Valley. A man and his two children were pulled from the rubble with minor injuries.

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. Cincinnati was already more than 2 feet above its 52-foot flood stage Sunday, with forecasters expecting a crest at 57.5 feet.

The storm that fed the flooding also knocked out power last week in parts of western and northern Ohio. Utilities said Sunday that about 66,000 customers remained without electricity, down from a peak of 250,000. In Pennsylvania, PPL Corp. said more than 37,000 of its customers were still blacked out Sunday.

A tug boat sank after being pushed through a dam on the Ohio River Sunday by currents made stronger by recent heavy rains, killing three crew members. One person was missing and believed to be aboard the submerged boat.

Three people on the Elizabeth M. were rescued by crews of other tugs and taken to a hospital. Fire crews arriving on the scene determined the muddy water was too dangerous to enter, said Chuck Ward, assistant fire chief in Industry.

"The worst thing was, you could see two people in the boat screaming for help" over the rush of the water, he said.

The tug was pushing six barges of coal north on the river when it went through the lock at the Montgomery Island Dam about 2:30 a.m. and was rammed against the dam by strong currents, said fire chief Thomas Llewellyn. The barges also sank.