California Braces for More Heavy Rain, Possibly Tornadoes

California is bracing for heavy rainstorms Monday that forecasters said might produce tornadoes, a relatively rare phenomenon for a state that has experienced other forms of extreme weather recently.

Much of California faces flood risks, but experts said the state was unlikely to experience damage like that produced by an atmospheric river two weeks ago. That phenomenon dumped up to a year’s worth of precipitation in some areas, knocked out power to nearly 1 million customers and killed nine people.

The Sacramento Valley and the agricultural corridor that includes the cities of Stockton and Modesto may experience tornadoes on Monday, forecasters said. That is south of the state’s “tornado alley,” a 50-mile stretch from Chico to Maysville, north of Sacramento, that is more commonly vulnerable.

California averages 11 tornadoes a year, but they tend to be brief and weak compared with the fearsome twisters that devastate towns in the Midwest or Southeast, said Kate Forrest, a meteorologist with the National Weather Service in Sacramento.

The chance of a tornado in any single 25-mile radius of the danger zone ranged from 2% to 5%, though the cumulative likelihood was higher, said Daniel Swain, meteorologist with the University of California, Los Angeles.

“We’re not expecting a Great Plains-level magnitude outbreak by any means. But this will be potentially a significant event by California standards,” Swain told viewers on his YouTube channel on Sunday.

The U.S. National Weather Service’s Storm Prediction Center has not yet issued a tornado watch but said conditions presented the possibility a twister at the low end of the Enhanced Fujita Scale, such as an EF-0 with winds from 65 to 85 mph (105 to 137 kph) or an EF-1 from 86 to 110 mph.

Under similar conditions in twister-prone areas, forecasters might not even mention it, said Steve Goss, a meteorologist with the Storm Prediction Center.

“When we say tornado, people think of what they see on TV – houses demolished, foundations swept clean. But probably the most you would be looking at in California is a couple of downed trees, maybe you’ll see a few shingles off your roof,” Goss said.

California had experienced extreme drought much of this century until a parade of atmospheric rivers last year dumped historic amounts of rain and snow. Experts expect another wet year in 2024 but with warmer temperatures that leave behind less snowpack.