By Alex Dobuzinskis
LOS ANGELES (Reuters) - The rainfall that has pummeled the U.S. West this week lightened on Wednesday but that did not keep swollen rivers from overflowing their banks in California, where water lapped up against houses in a wine-growing region, officials said.
In Portland, Oregon, the city's more than 600,000 residents awoke to roughly a foot (30 cm) of snow, which led to city-wide school closures and an emergency declaration by Governor Kate Brown.
This was the latest round of extreme precipitation unleashed by a weather pattern meteorologists call an "atmospheric river" - a dense plume of moisture flowing from the tropical Pacific into California and the West.
"All available state resources will be made available to ensure the safety of communities throughout Oregon," said Brown, urging people not to travel until roads had been cleared and services restored.
The last weeks of 2016 were particularly wet for California, which has struggled through years of drought, and the rainfall has intensified in the past week, officials said.
In wine-growing Sonoma County, north of San Francisco, the Russian River has been flooding since early on Monday and water was lapping at houses in low-lying areas of the town of Guerneville, said Hannah Euser, a spokeswoman for the county.
Local media showed photos of people navigating flooded streets by canoe in the community of less than 5,000 people.
Authorities asked residents of 650 homes in Guerneville to seek higher ground even as officials assess damage to determine how many houses were flooded, Euser said.
The rain had stopped by midday on Wednesday but the floodwaters were not expected to recede until late on Thursday, she said.
Concerns about flooding have also led to the evacuation of about 600 homes in Madera County in central California, Jonathan Gudel, a spokesman for the state Governor's Office of Emergency Services, said.
The nearby Yosemite National Park was open again on Wednesday, after precipitation and rockfalls caused road closures there earlier this week, park officials said in a statement.
Ray Standley, 76, owner of the General Store in nearby Fish Camp which depends on visitors to Yosemite to support local businesses, said the rain had washed away most of the snow in town.
"Thank goodness they've reopened now, so we should be good for the holiday coming on Monday," he said by phone.
Near California's state capital, the Sacramento County Sheriff's Department on Tuesday advised residents of Wilton, a community of more than 5,000 people, to evacuate their homes because of anticipated flooding along the Cosumnes River.
The extent of damage in Wilton was not immediately clear.
During all the rainfall, a small tornado touched down in the Sacramento area on Tuesday, twisting two metal awnings and stripping limbs off trees, Weather Prediction Center meteorologist Bob Oravec said.
The National Weather Service had several flood advisories in effect on Wednesday for areas of Northern California, along with winter storm and avalanche warnings for the Sierra Nevada region around Lake Tahoe, where up to 7 inches of snow was forecast to fall by Thursday afternoon.
The rainfall along the U.S. West Coast was weakening on Wednesday, Oravec said. The weather service expected it to end by Thursday night.
Coastal parts of California could receive up to 2 inches (5 cm) of rain on Wednesday, which is significantly lighter than the 5 inches seen during periods of heavy rain in the past week, said Bruce Sullivan of the Weather Prediction Center.
In Nevada, authorities on social media advised residents to remain vigilant to the threat of flooding, after the Truckee River, which runs through Reno, overflowed its banks earlier this week.
(Reporting by Alex Dobuzinskis; Additional reporting by Brendan O'Brien in Milwaukee and Sharon Bernstein in Sacramento, California; Editing by Lisa Shumaker and Richard Chang)