Heavy rains are expected to hit southern California this week, which carry the risk of mudslides to an area recently scarred by intense and widespread fires.
Wildfires in California are a regular phenomenon, but last month’s fires in the Los Angeles area were a rare breed. The blazes grew rapidly, fueled by gusty Santa Ana winds out of the east, which helped carry the fire across the parched landscape. Now, significant precipitation will bring on a hydroclimate whiplash event—the kind of rapid swings in wet and dry weather that climate researchers warn will worsen as climate change continues.
Though the wildfires flared to life last month, they were years in the making; a team of researchers at the University of California, Los Angeles, reported that wet seasons between 2022 and 2024 led to a buildup of vegetation in the area that subsequently dried up in a sustained drought, turning the area into a tinderbox.
According to Cal Fire, the Palisades and Eaton fires—two of the worst in the recent spate—together burned 37,728 acres (153 square kilometers) of Los Angles County. Swaths of the county, including the neighborhoods of Altadena and Pacific Palisades, were razed, with only the occasional chimney indicating where a home used to be.
According to a National Weather Service bulletin, a flash flood watch is in place for most of southern California from Thursday afternoon through late Thursday night. Simply put, a flash flood is a sudden inundation of an area—often a low-lying area such as a stream or riverbank—that occurs within six hours of significant rain and is typically caused by intense storms, NASA stated on its website.
California is a stranger neither to fires nor to floods—atmospheric rivers often bring torrential rain to the northern half of the state—but the timing of the forecasted flood event is especially poor.
The NWS alert warns that “flash flooding and debris flows caused by excessive rainfall are possible … in and near numerous burn scars in much of Los Angeles and Ventura Counties with the greatest risk within or near the Eaton, Palisades/Franklin, and Bridge burn scars.”
NASA’s Global Precipitation Measurement site notes that densely populated areas are at high risk for flash floods because “buildings, highways, driveways, and parking lots increase runoff by reducing the amount of rain absorbed by the ground.” Los Angeles’ car culture and intricate network of freeways amplify the risk posed by the incoming rain event.
That said, Los Angeles is not the only county that will face dangerously wet conditions. San Luis Obispo and Santa Barbara counties to the northwest will bear the initial brunt of the storm, which will then make its way east into Ventura and Los Angeles counties.
The flood risk is a real one-two punch for southern California, which is still coming to grips with the devastation wrought by the wildfires. The warning also comes on the heels of NASA research indicating that the Palos Verdes peninsula south of the city of Los Angeles is slipping towards the Pacific Ocean at a faster clip than its historic rate.
According to an NWS Los Angeles/Oxnard forecast issued early Tuesday morning, “The large winter storm is still on track to affect the area Wednesday through Friday. On Wednesday a slug of moisture with weak dynamics will race out ahead of the storm and move over [Southern California.]”
The forecast stated that the Central Coast could receive an inch of rain, while the foothills north of Morro Bay could receive up to three inches. Those rainfall rates are “non threatening” at less than half an inch per hour, but the main storm will move in early Thursday morning and “Potentially dangerous rainfall rates near an inch per hour will be possible with the front and a few hours ahead of it.”
For more information on how to prepare for inclement weather and flooding, please refer to the National Weather Service’s flood safety page and the California Department of Conservation’s landslide database.
English (US) ·