An intense atmospheric river moves into California, threatening to flood roads and trigger mudslides

KABC, CNN

By Tina Burnside and Nouran Salahieh, CNN

(CNN) — An intense, long-lasting atmospheric river is moving into California Sunday, bringing the potential for “life-threatening” flooding, mudslides and widespread power outages as it dumps heavy rain and snow. Here’s the latest:

• Rare high risk for flooding: A rare Level 4 of 4 risk of excessive rainfall was expanded Sunday to include Los Angeles, in addition to Santa Barbara and Oxnard in Southern California, with the weather prediction center warning of “life threatening flash and urban flash flooding.” Rainfall rates up to an inch per hour will bring 3 to 6 inches of rain across the area. A more widespread Level 3 risk exists for much of coastal California, including San Francisco.

• A month’s worth of rain possible in Los Angeles: In Central and Southern California, widespread rainfall totals of 3 to 6 inches are expected – more than a month’s worth of rain for most. There are indications the storm may be as strong as Tropical Storm Hilary from last August, Los Angeles Mayor Karen Bass said during a news conference Friday, and encouraged residents to take “common sense precautions.”

• Some residents told to evacuate: Mandatory evacuation orders have been issued for communities in Santa Barbara, San José and Ventura County. Officials warned residents of potential “life-threatening” floods and landslides from the atmospheric event. Several school districts in Santa Barbara County have also canceled classes on Monday due to the severe weather.

• First ever hurricane force wind warning: The National Weather Service in San Francisco on Sunday issued its first ever hurricane force wind warning since records have been kept. Wind advisories and high wind warnings are also in effect for nearly 30 million people in inland areas across nearly the entire state from Redding to San Diego.

• “Near impossible” travel in the mountains: The storm is also expected to bring significant snowfall totals in eastern California and along the Nevada border. Heavy wet snow will spread across the Sierra Nevada through Monday with accumulation rates of 2 to 3 inches per hour, according to the weather service. Dangerous wind gusts are expected to produce whiteout conditions making travel above 5000-6000 feet “near impossible,” the weather service said.

• Widespread power outages are possible: Powerful winds will also be a concern across much of California with widespread winds of 40 to 60 mph and some gusts as high as 95 mph in the foothills and mountains. This is likely to lead to downed trees and power outages Sunday and Monday, forecasters warned.

State braces for flooded roadways and swollen rivers

This atmospheric river – a long, narrow moisture band that carries saturated air thousands of miles then discharges it like a fire hose – comes right on the heels of another storm that brought record rainfall to most of California, including Los Angeles.

But this storm is much slower and is expected to stall as it moves onshore, bringing a much longer duration of rain compared to the first.

The worst of the storm will fall between Sunday and Tuesday, according to the weather service.

Parts of the central and southern coastline of the state are expected to see the most significant amounts of rain and flooding. This includes the Los Angeles and San Diego metro areas.

“This damaging flooding will be a threat to lives and property,” Eric Schoening with the National Weather Service said at a news briefing Saturday. “Please, if you come across a flooded roadway, we urge you to turn around, don’t drown.”

Many roads could flood and there could be major rises on creeks, streams and rivers, as well as mud and rock slides and debris flows, Schoening added.

At least 8 inches of rain can fall in less than 24 hours in parts of the Transverse Ranges in Southern California, with over 10 inches possible in some areas, the prediction center cautioned.

More than 8,500 personnel, including swift water and helicopter rescue teams, have been deployed statewide to respond to any potential calls for help, said Nancy Ward, director of the California Governor’s Office of Emergency Services.

“These next storms are going to be impactful and dangerous,” Ward said at a news briefing Saturday. “They’re the most dangerous natural disasters that we have, killing more people from storm damages and flooding than wildfires every year.”

More than 7 million sandbags have been prepared and plenty of rescue equipment is on standby, Ward added.

Californians told to prepare for potential power outages

The impact from powerful onshore winds will be felt across northern and central California through Sunday, eventually shifting to southern California into Sunday night, the National Weather Service said.

Wind advisories and high wind warnings stretch across pretty much the entire state of California from Redding down through San Diego affecting nearly 30 million people.

Officials are urging Californians to plan for other alternative power sources in case power goes out and to avoid non-essential travel during the peak of the storm.

“This is a very, very dangerous storm. So take care of yourselves, your loved ones, … please check on an elderly neighbor, those folks that you know that may be homebound,” Ward said.

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CNN meteorologists Allison Chinchar, Sara Tonks and Elisa Raffa contributed to this report