At least 11 million people in California were under flood watch Monday as a series of storms bring rain, snow and potential flash flooding across the state this week.
Up to 4 inches of rain are forecast for California's coast and valley areas, with as much as 7 inches in the foothills and mountains.
In addition to flash flood risks, residents in burn scar areas in Los Angeles County face a threat of mudslides as the rainfall accumulates.
An evacuation order when into effect on Sunday night for the Palisades, Sunset and Hurst burn scar areas. It remains in effect into Tuesday evening. Los Angeles Mayor Karen Bass urged residents to follow the guidance.
"Ahead of heavy rain forecasted this week, first responders, Public Works crews, and City personnel are taking action to keep Angelenos safe and will be ready to respond to any potential impacts," Bass wrote in a post on X. "This is likely to be another significant rain event."
Burn scars areas are those where wildfires have killed off vegetation and changed the soil, making the land less able to absorb rainwater. These areas can "be as water-repellant as pavement," according to the National Weather Service, causing runoff that can create conditions for flash flooding, mudslides and debris flow.
San Francisco's Department of Emergency Management, meanwhile, warned residents of potential flooding in low-lying areas. Parts of the Bay Area are under a coastal flooding advisory through Tuesday.
"Help your community prepare for the upcoming storm by clearing out storm drains and checking in with friends and family who may need assistance during extreme weather," the department said in a post on X.
As the storm system moves east across California, torrential downpours are expected, with wind gusts as high as 70 mph on Tuesday.
Meteorologists said the system is likely to bring heavy snow to the Sierra Nevada: 5 to 8 feet is forecast to fall from Tuesday through Wednesday.
Though the snow can create dangerous conditions on roadways, its arrival is somewhat of a relief given the extremely low snowpack that has plagued the West this winter. If the season ends with insufficient snow, that creates problems for water supplies and increases the risk of wildfires when the weather warms.
Climate scientists have been calling attention to the snowpack shortages in nearly every region of the West this year. Although it's not unusual for some areas to lack snow, it's rare for the problem to be this widespread. Philip Mote, a professor at Oregon State University’s College of Earth, Ocean, and Atmospheric Sciences, told NBC News last month that he had observed dramatic deficits.
“Washington, Oregon, California and many Western states had their warmest December ever on record, and so the torrential rains that we had with the atmospheric river and the flooding and damage from too much water — none of that stayed in the mountains,” he said.
On Wednesday, the storm is expected to head east, moving out of California and bringing beneficial snow to the Rockies, as well.
