An imminent atmospheric flood and rapidly melting snow have put communities on edge California on high alert for flash flooding, mudslides and landslides as the subtropical storm surge moves across the state. Rivers and streams could also quickly rise above capacity and shortages, the National Weather Service warned. Overall, about 16 million people are under flood warnings.

The state’s governor, Gavin Newsom, has declared a state of emergency for 21 counties, including some mountain communities still digging out of the snow. “The state is working around the clock with local partners to distribute life-saving equipment and first responders to communities across California,” Newsom said Wednesday night. “With more dangerous storms on the horizon, we will continue to mobilize all available resources to protect Californians.”

This week’s storm is the latest in a series of extreme weather events that have hit the western United States in recent weeks. At least 12 people have died in Southern California since late February, after massive snowstorms cut off communities in the San Bernardino Mountains and the adjacent San Gabriel Mountains east of Los Angeles. Only one of the deaths was clearly weather-related, according to the San Bernardino County Sheriff’s Department, but blocked roads, lack of access to medical care, food and other supplies may have contributed to the toll, the Los Angeles Times reports.

Quick guide

Quick glossary of extreme weather terms


A brief glossary of the storms and their elements buzzing in the previously parched state.

Atmospheric rivers: Long streams of moisture — or, as the National Oceanic and Atmospheric Administration simply puts it, “rivers in the sky” – which transports water vapor from the tropics, after warm water has evaporated from the Pacific Ocean. They can sometimes be incredibly destructive, often accompanied by strong, gusty winds.

Pineapple express: A particularly strong system, the pineapple express delivers moisture from around Hawaii to the West Coast which then hammers other regions of the US and Canada with rain and snow.

Bomb Cyclone: These low-pressure storm systems help create atmospheric rivers that propel them from the Pacific Ocean to the coast. Unlike hurricanes or other storms where the center is strongest, bomb cyclones can generate the worst weather at their edges.

La Niña: This is a climate pattern characterized by a cooler than average sea surface in the Pacific near the equator. The region is in the grip of a third year of La Niña conditions, which tend to steer storms north into Washington and Oregon.

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In some societies, roof collapsedpower went out and authorities reported possible gas leaks and fires due to storm damage. Across the state, including in tourist destinations like Lake Tahoe and Yosemite National Park, people were trapped in their homes and vacation rentals. Yosemite is closed until at least the end of the week due to the hazardous weather.

The deep snow has hampered rescue efforts, with crews literally digging people out of their homes where some had been trapped for more than a week. Firefighters have also helped shovel off roofs, which could collapse with the combined weight of snow and rain. In rural areas still cut off from supplies, officials have also aired hay stranded cattle.

There have also been remarkable stories of survival, including an 81-year-old man trapped alone in his car for nearly a week near the California-Nevada border after his vehicle got stuck in a snowbank. Jerry Jouret, who was rescued last week, subsisted on croissants, candy and biscotti he kept in his car and kept warm with a blanket and towel, according to to CNN.

Residents shovel snow in front of a church after winter storms dumped more than 100 inches of snow in the San Bernardino Mountains.
Residents shovel snow in front of a church after winter storms dumped more than 100 inches of snow in the San Bernardino Mountains. Photo: Mario Tama/Getty Images

The fresh round of atmospheric torrential rains, expected to pick up Thursday afternoon and continue through the weekend, could bring as much as 3 inches (8 cm) of rain to the San Francisco Bay Area and the Central Coast. Inland and coastal areas could get up to 6 inches of rain, and the Santa Cruz Mountains could get 8 inches. Officials are also telling residents near Big Sur to stock up on supplies and sandbags, after earlier storms shut down a major highway and shut down communities.

Climate chaos, including frequent storms and extreme droughts, is expected to increase in California due to global warming, experts have warned. The weather swings could also make it harder for California to manage its water resources, straining infrastructure amid a cycle of floods, droughts and fires.

While the previous blizzards were caused by an Arctic air mass diving down the West Coast, the upcoming rains are caused by a wave of subtropical moisture, known as a “pineapple express,” that built up in the Pacific Ocean around Hawaii.

“This is going to be a fairly warm storm right on the heels of what were historically cold storms,” ​​UCLA climate scientist Daniel Swain said in a video update.

“Flooding of roads, rivers, streams, creeks and other flood-prone areas will be possible, especially in areas that have poor drainage due to snow-blocking drains and culverts,” the National Weather Service warns.

The state is placing flood control teams in anticipation of upcoming rains. Crews are also working to clear roads of snow and have so far removed 12.6 m3 of snow from state highways, the governor’s office said, the equivalent of more than 3,800 Olympic-sized swimming pools.