Heavy rains are poised to hit Los Angeles this week, raising concerns about flooding, mudslides, and debris flows in a region already struggling with the aftermath of previous wildfires. The National Weather Service has placed millions across California on alert for potential flooding during the Christmas holiday, particularly focusing on Southern California where a major atmospheric river is expected to deliver prolonged rainfall starting Tuesday night and extending into Thursday.
Significant rainfall is forecasted with amounts ranging from 3 to 7 inches, and some localized areas could receive up to 9 inches. The initial wave of rain is set to begin around 9 p.m. Tuesday, initially affecting the Santa Barbara region before shifting to the Los Angeles area around midnight. Rainfall rates could exceed 1 inch per hour, especially in elevated areas—a concerning potential when coupled with the already vulnerable burn scars from recent wildfires.
A unique and rare “High Risk” alert (level 4 of 4) has been issued for parts of Southern California, including counties across Santa Barbara, Ventura, Los Angeles, and San Bernardino. Historically, such high-risk alerts correlate with severe flooding events—responsible for about one-third of all flood-related fatalities. In addition to this, evacuation warnings are now in place in areas impacted by the recent Palisades and Eaton fire scars, signaling a heightened risk of flash flooding and debris flows.
Experts caution that soil burned in wildfires becomes less absorbent, significantly increasing the likelihood of runoff during heavy rainfall—a mere half inch of rainfall within an hour can trigger flash floods in burn areas. The threat is particularly heightened in the first two years following a fire, as the landscape struggles to regain its absorptive capacity.
Urban areas may face severe roadway flooding and other hazards as water levels rise quickly in creeks and streams, with swiftwater rescues anticipated. Residents are advised to prepare for major travel disruptions including road closures and cancellations. In addition to flooding, strong winds are projected to exacerbate conditions, with gusts of 60-70 mph expected in some areas, potentially causing power outages and damage.
As California faces the dual challenges of heavy rain and strong winds, the need for caution and preparedness is paramount. Communities are urged to remain vigilant and heed local evacuation orders to ensure safety as the storm approaches. This period of climate variability, which experts term hydroclimate whiplash, illustrates the shifting dynamics of California’s weather patterns, transitioning rapidly from drought to extreme precipitation.