California is battening down the hatches with another fierce winter storm poised to bring heavy rainfall and strong winds to the western US state, the latest in a series of “atmospheric rivers” that have pummelled residents over the last several months.
Governor Gavin Newsom has declared a state of emergency for 21 counties in anticipation of potential flooding and disruptions on Thursday. Mountain communities, already struggling to cope with extreme snowfall, could be further inundated.
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“The state is working around the clock with local partners to deploy life-saving equipment and first responders to communities across California,” Newsom said in a statement on Wednesday evening.
“With more dangerous storms on the horizon, we’ll continue to mobilize every available resource to protect Californians.”
At least 20 people have died as a result of earlier storms, and residents of some mountain communities have been stranded as snow blocked roads.
The upcoming storm is known as a “pineapple express”, resulting from a buildup of moisture in the Pacific around Hawaii that can bring heavy rainfall to the west coast of the United States and Canada.
On Thursday, the National Weather Service (NWS) said that more than 15 million people in the San Francisco Bay Area and Sacramento region were under excessive rainfall and flood advisories.
The Bay Area and California’s Central Coast could receive up to eight centimetres (three inches) of rain through the weekend.
More than 20cm (eight inches) are expected in the Santa Cruz Mountains while more than 25cm (10 inches) could fall in the Santa Lucia Mountains stretching along the famous coastline of Big Sur.
“Most of the flooding concerns are for the lower-lying areas susceptible to rapid river and stream rises,” said William Churchill, a NWS Weather Prediction Center meteorologist. “It’s really a combination of all this heavy rainfall coming and also rapidly melting snow.”
California declared emergencies in 13 counties after the storm that began on March 1, a number that has now expanded with Newsom’s latest declaration to cover more than half of California’s 58 counties.
In parts of the state at elevation higher than 2,400m (8,000 feet), Thursday’s storm could drop as much as 2.4 metres (eight feet) of snow.
Some of the watches and warnings in California were to remain in effect until Sunday.
Some waterfront communities along major rivers and their tributaries also braced for the possibility of overflowing streams swollen by heavy showers and runoff of melting snow.
In Tulare County, Sheriff Mike Boudreaux issued an evacuation warning on Wednesday for homes and businesses along a stretch of the Kings River, which drains the Sierra Nevada mountain range, in advance of “this rain-on-snow event”.
Elsewhere, the NWS issued “prepare now” alerts for residents along the Big Sur, Carmel, Salinas and Pajaro rivers.