Authorities urged thousands of people in Northern California to evacuate homes as rivers swollen by four days of heavy rain threatened to crest above flood level, even as another day of showers was forecast for Wednesday.
About 2,000 people in Wilton, a rural California community near Sacramento, were asked to leave their homes Tuesday evening, as emergency crews and officials worked to try to bolster a Cosumnes River levee in Sacramento County. The river was projected to overflow its banks Wednesday morning.
Sacramento County emergency services official Mary Jo Flynn said water was expected to start spill over the levee, flooding low-lying roads and buildings with up to 1 foot of water.
Some 3,000 Sonoma County residents were under an evacuation advisory as the Russian River rose again under pounding rain. Officials red-tagged seven homes, ordering residents out, when a rain-soaked embankment came crashing down.
North of San Francisco, people were evacuated Tuesday evening from businesses and homes in downtown San Anselmo after a rain-swollen creek broke its banks. The Corte Madera Creek was flowing 1 foot over flood stage, the Marin County Sheriff's Office said.
Tuesday's storm was the latest of back-to-back systems — buffered by a brief respite Monday — that have brought the heaviest rain in a decade to parts of Northern California and Nevada. More showers were forecast for Wednesday morning.
The storms are part of an "atmospheric river" weather phenomenon that draws precipitation from the Pacific Ocean as far west as Hawaii.
A blizzard warning was in effect for parts of the Sierra Nevada, the first issued in the past nine years, said Scott McGuire, a forecaster for the National Weather Service based in Reno, Nevada.
"This is definitely a dangerous, life-threatening situation going on up there," he said. "People should not attempt to travel at all."
Forecasters warned of up to 10 feet of snow in the highest mountains, with up to 7 feet of snow around the resorts of Lake Tahoe, high risk of avalanches, and wind gusts to 60 mph. The Sierra ridge had gusts of more than 100 mph.