(Bloomberg) — A severe winter storm is lashing Southern California, prompting California Gov. Gavin Newsom to declare a state of emergency in Los Angeles and neighboring counties. Coastal communities are bracing for months of rain within days, while areas burned by wildfires face the risk of mudslides.
A third person died as a result of the storm, according to the Los Angeles Times. Meanwhile, a flood watch has been extended to cover most of Southern California.
“There is a slight risk of excessive rainfall in parts of Southern California,” the U.S. Weather Forecast Center said early Thursday morning. “Numerous flash flooding is possible. In addition, many streams may flood, potentially affecting larger rivers.”
The historic storm, which will hit the region over the Christmas holidays and into Saturday, has prompted some evacuations in Los Angeles County and Orange County Canyon, bringing road closures, flooded highways and flight delays.
A portion of Angeles Crest Highway north of La Cañada Flintridge was closed Wednesday morning due to hazardous conditions, according to a post from the Los Angeles County Sheriff’s Department’s Crescenta Valley Station at Station X.
About 10,700 customers in the Los Angeles Department of Water and Power service area were without power Wednesday morning due to debris from the rain, according to a company statement. Southern California Edison also reported some outages due to the stormy conditions.
The state has pre-deployed emergency response assets across the state, including 55 fire trucks and 10 swift water rescue teams, to protect communities from dangerous winter storms, Newsom said in a statement.
Heavy rains threaten more extreme flooding in Pacific Palisades and Altadena, communities in Los Angeles County that were devastated by massive wildfires nearly a year ago. Charred vegetation makes the ground impermeable to water, increasing the risk of landslides, mudslides and power outages.
It’s a risk that will persist as atmospheric rivers attack Southern California until the soil recovers and vegetation regrows.
“These soils are still hydrophobic, meaning that rain runs off as if it were on hard clay or concrete,” said Scott Kleebauer, a meteorologist at the Weather Prediction Center. “There are burn scars that took four or five years to see any improvement.
A combination of factors makes it a once-in-five-to-10-year event, he said.
A trough of low pressure stretching across the Pacific Ocean is pushing moist air directly against the coastal mountains of Southern California, Kleebauer said. “It’s called the Pineapple Express because the moisture supply goes all the way to Hawaii,” he said.
The moist air hits California at a perfect right angle for maximum precipitation. “You get this source of tropical moisture up into the mountains and then it rains on its own,” he said. “This affects one of the biggest travel days of the year. It’s definitely going to mess up a lot of people’s plans.”
Further north, the San Francisco Bay Area was threatened with severe thunderstorms, the local branch of the National Weather Service said in a post on X. The storm is expected to include wind gusts of up to 70 mph or higher.
Up in the mountains, Mammoth Mountain said it expects to open its main lodge at 10 a.m. local time due to continued heavy snow and thunderstorms. The center expected up to 24 inches (61 centimeters) of total daily snow accumulation on Thursday, according to its website.
–With help from Robin Paxton, Derek Wallbank and Lisa Pham.
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