Powerful storm causes mudslides in California, threatens outbreak of tornadoes and wildfires across U.S. this week

A sign reading 'Possible Mud Flow' on March 12, 2025, in Sierra Madre, California. (Mario Tama/Getty Images via CNN Newsource)

A powerful storm that dropped drenching rain on flood-prone Southern California is raising concern among forecasters that it could produce a dangerous, widespread outbreak of tornadoes, damaging winds and fires along with a blizzard as it crosses the entire United States in the coming days.

The heavy rain triggered mudslides that engulfed part of a roadway and trapped multiple vehicles in San Jacinto in California’s Riverside County Thursday morning. At least six people were rescued, evaluated by paramedics and released, the county’s fire department said on social media.

The storm also produced a short-lived EF0 tornado that damaged some homes and cars in Pico Rivera – southeast of Los Angeles – in the early morning, according to the National Weather Service.

Parts of Los Angeles, Ventura and Orange counties saw flash flood warnings early Thursday, but Southern California’s heaviest rain let up by the afternoon – though the threat of mudslides will persist.

Forecasters also issued a rare increase Thursday in the level of severe thunderstorm risk this storm will bring to the central and eastern US Friday and Saturday. Millions there are facing a dangerous severe weather outbreak capable of multiple strong tornadoes, with level 4 of 5 risks of severe thunderstorms in place both days, according to the Storm Prediction Center.

Setting the second-highest level of risk this far in advance is rare, and happens only when forecasters have great confidence that the ingredients for severe storms will be present. Over the past 15 years, level 4 risks issued three days in advance have resulted in an average of 90 tornado reports on the day of concern.

Similar instances include the 2011 Super Outbreak centered in Alabama that killed more than 300 and was the costliest tornado outbreak on record; another was the Easter Sunday Outbreak in 2020 that produced around 150 tornadoes and killed 35 people.

Ahead of the storm’s arrival Wednesday, evacuation warnings urging people to prepare to leave at a moment’s notice were issued for parts of Los Angeles County, while authorities ordered hundreds of residents in more vulnerable areas to evacuate.

The California Governor’s Office of Emergency Services said it positioned rescue personnel and equipment in 11 counties where heavy impact from the storm was expected, including Los Angeles County.

Emergency management officials in Santa Barbara, just north of Los Angeles, ordered residents in and around the Lake Fire burn scar to shelter in place from Wednesday night through early Thursday, saying “flash flooding and debris flows may be imminent or occurring.”

In the Sierra Nevada, heavy snow brought travel to a standstill along part of Interstate 80 Wednesday night. Multiple crashes occurred in the snow along the eastbound portion of the roadway according to the California Highway Patrol.

Storm’s slew of threats, from floods to fire, spread east

The storm pushed into the Rockies Thursday with additional rain, snow and winds. Winter weather alerts are in place across the highest parts of Nevada, Arizona and Utah, where snow could pile up to 2 feet. Gusts up to 50 mph across the West could make travel difficult and cause power outages.

Gusty winds will also impact the Plains and ramp up a widespread fire threat, especially from the late afternoon onward. More than 800 miles of the central US, from western Texas into South Dakota, are under a level 2 of 3 fire weather risk, according to the Storm Prediction Center. Any spark could turn into a wind-driven blaze in these conditions.

The fire risk will climb higher Friday in tandem with extremely strong winds. “Significant, dangerous wildfire-spread conditions” are expected, and a wildfire outbreak is possible across parts of the Southern Plains, according to the center.

Those winds could gust up to 90 mph at times in parts of New Mexico, Texas and Oklahoma Friday, and also cause power outages and hazardous travel conditions, according to the Weather Prediction Center.

Severe storm outbreak, with tornado threat for millions, expected Friday and Saturday

The storm will strengthen Friday in the central US and become unusually strong for March just before it tracks into an area where atmospheric conditions are primed to set off dangerous severe weather.

Severe thunderstorms will roar to life by the late afternoon in the Mississippi Valley, become more ferocious and pound potentially more than 900 miles of the region – from Louisiana to Minnesota – through the overnight hours.

A level 4 of 5 risk of severe thunderstorms is in place for parts of the region – including St. Louis – Friday, according to the Storm Prediction Center. Damaging winds will be widespread, with some storms producing gusts past 75 mph – on par with a Category 1 hurricane – within the level 3 and 4 risk areas.

Tornadoes and hail are also possible within any storm. Some of the strongest storms will be active after dark, adding another layer of danger: Nighttime tornadoes are nearly twice as likely to be deadly as those occurring during the day, a 2022 study found.

“All are encouraged to review their severe weather safety plans before Friday evening,” the National Weather Service in Central Illinois urged Thursday. “Consider discussing the forecast with family/friends so they are aware in advance.”

Saturday poses another serious threat for dangerous thunderstorms and will see an increased threat of tornadoes, with the Storm Prediction Center pinpointing the South as the area of greatest concern for “significant tornadoes, swaths of damaging (wind) gusts and hail.”

A level 4 of 5 risk of severe thunderstorms is in place Saturday for parts of Louisiana – including New Orleans – Mississippi, Alabama and the extreme western Florida Panhandle.

Severe thunderstorms could be ongoing early Saturday morning after Friday’s activity, but the riskiest thunderstorms will intensify or develop by the afternoon in the South. Storms packing damaging wind gusts, tornadoes and hail will once again persist through the evening and overnight.

Article by Mary Gilbert and Karina Tsui.