The risk of a significant atmospheric river storm is increasing for Southern California, potentially leading to heavy rainfall and heightened concerns about mudslides and debris flows in areas affected by recent wildfires. The National Weather Service has indicated a 30% chance of experiencing high amounts of rain between February 12 and 15, up from a previous estimate of just 10%. This forecast includes Los Angeles, Ventura, Santa Barbara, and San Luis Obispo counties.
Meteorologist Ryan Kittell from the National Weather Service office in Oxnard emphasized that while the range of possible outcomes remains uncertain, the potential for a strong and wet storm system is notable. He stated, “This risk is definitely higher than most of our storms.” The likelihood of moderate or low rainfall is also pegged at 30%, with a 10% chance of no rain at all.
Forecasters are particularly concerned due to the nature of the soil in recently burned areas, where vegetation has been stripped away. This lack of plant life compromises the soil’s ability to absorb water, increasing the risk of surface runoff that can lead to mudflows. These mudflows can swiftly transform into debris flows, which are capable of carrying rocks and other debris at dangerously high speeds.
The anticipated storm could deliver rainfall rates of half an inch to an inch per hour, potentially resulting in total accumulations of 2 to 4 inches along the coast and in the valleys, and up to 8 inches in mountainous regions. Kittell warned that such rainfall could pose a “high risk for flooding and debris flows.” He noted that while this scenario is not the most likely outcome, the risk is significantly elevated compared to typical storm events.
The region’s vulnerability to mudslides is underscored by past events, including a devastating debris flow in Montecito in January 2018, which resulted in 23 fatalities and extensive property damage. At that time, the area had been burned just weeks earlier, highlighting the dangers of heavy rain following wildfires.
As Southern California braces for this potential storm, a weaker atmospheric river is currently moving through the region, expected to bring rain before the more severe system arrives. This initial storm is anticipated to be less impactful, with minor flooding expected in some areas but no significant debris flow risk.
Despite the recent rains, drought conditions continue to worsen across Southern California. The latest data indicates that much of the region is now classified as being in “extreme drought,” with rainfall levels significantly below average for this time of year. Downtown Los Angeles has recorded only 1.02 inches of rain since the beginning of the water year on October 1, well below the average of 7.8 inches.
Officials are monitoring reservoir levels, with some, like Shasta Lake, rising significantly due to recent precipitation. However, the overall water deficit remains a concern, and experts warn that prolonged dry spells could quickly elevate fire risks again.
As the community prepares for the upcoming storm, residents are urged to stay informed about weather updates and to take precautions, especially in areas prone to flooding and mudslides.