Roads Wash Away As Millions of Californians Face Risk of Flooding

Flood watches and advisories are in place for a large swathe of California as another atmospheric river storm brings heavy rain and strong winds to the state.

Coastal parts of Southern California, including the greater Los Angeles area and Santa Barbara, are under flood warnings, while much of the rest of the coastline and inland areas of central and Northern California face flood watches due to the intense precipitation.

According to CNN, some 27 million people are under the threat of flooding, which could bring mudslides, with pictures already emerging of roads being washed away near San Jose.

The latest atmospheric river storm to drench the West Coast made landfall on Monday, bringing more than 4 inches of rainfall in areas including Malibu and Beverly Hills in the past day. Flooding of the airfield at Santa Barbara Airport prompted it to close.

The National Weather Service (NWS) expects precipitation and thunderstorms to ease off on Tuesday as the storm moves inland. However, in its latest forecast it said that another 1-3 inches of rain were possible for parts Los Angeles and Orange Counties, with additional snow accumulations in the Sierra Nevada mountain range of up to a foot.

Many of the flood warnings and advisories will remain in place into Tuesday afternoon or Wednesday morning.

Powerful atmospheric river storms have already caused areas of flooding and mudslides and several deaths, prompting Gov. Gavin Newsom to declare a state of emergency for several counties earlier in February.

Around the same time last year, California was battered by a succession of deadly storms that brought severe flooding. Thousands of homes were left without power and many people were evacuated.

At the time, climate scientists attributed the severity of the storms to climate change pushing more moisture into the atmosphere and energizing weather systems. The extended storm period this winter has led to historic levels of precipitation.

Flood warnings are in place for Sonoma County, where flooding of rivers and streams “is imminent or occurring,” the NWS said. Parts of the Sacramento River are already at flood stage or are expected to reach it by Tuesday afternoon.

Minor flooding is also forecast for southwest California, including Riverside and San Bernardino Counties, as well as in the Santa Monica mountains. Elsewhere, flash flooding caused by excessive rain is possible, which could create debris flows.

Atmospheric rivers are narrow channels in the atmosphere that can carry a large amount of moisture with them. They form when cold air from the Arctic meets warm, moist air from the tropics, cooling it to form heavy precipitation.

A strong river can transport as much as 15 times the amount of water flowing through the mouth of the Mississippi River, according to the NOAA.