by Los Angeles, California — Southern California is bracing for a powerful atmospheric river expected to intensify over the Christmas holiday, with forecasters and climate experts warning that rainfall totals could reach dangerous and potentially catastrophic levels in some areas.
As rain began moving into the region Tuesday afternoon, officials urged residents to prepare for flooding, mudslides, strong winds, and possible evacuations, especially in vulnerable mountain and burn scar zones.
Climate Blogger Warns of Extreme Rainfall Potential
Concern escalated after Colin McCarthy, who runs the weather-focused platform U.S. Stormwatch, shared model projections showing more than 20 inches of rain could fall in Southern California’s mountain regions within a 48-hour period.
“This would lead to potential catastrophic flooding and is exactly why a rare high risk for flash flooding has been issued,” McCarthy warned.
Such rainfall totals, if realized, could overwhelm drainage systems, trigger debris flows, and cause life-threatening conditions in steep terrain.
Rare High Risk Flash Flood Alert Issued
The National Weather Service Weather Prediction Center has issued a high-risk alert for flash flooding in parts of Southern California, primarily at higher elevations.
This designation signals a 70% or greater chance of flash flooding, a threshold rarely reached. Officials say the last time a high-risk alert was issued for the region was during the January 2023 atmospheric river, which caused widespread flooding, mudslides, road closures, and evacuations across Southern California.
Forecasters emphasize that this level of risk reflects not just heavy rain, but rain falling too quickly for the ground to absorb, especially in areas already vulnerable.
Rainfall Totals and Timing Across the Region
According to the National Weather Service, the storm is expected to bring:
- 2 to 4 inches of rain across coastal areas, valleys, and basins
- Significantly higher totals in foothills and mountains, with some areas potentially exceeding forecasts
- Periods of heavy rain through Christmas Day, with showers lingering into the weekend
Rainfall began increasing Tuesday afternoon and is expected to intensify overnight, continuing in multiple waves rather than a single downpour.
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Flood Watch Covers All of Southern California
A Flood Watch has been issued for all of Southern California, underscoring the widespread nature of the threat. Officials warn that flooding may occur outside traditional flood zones, including urban neighborhoods, underpasses, and normally dry washes.
“Significant flooding issues are likely along with the potential for strong thunderstorms,” the National Weather Service said.
Residents living near recent wildfire burn scars have been specifically advised to prepare for possible evacuations, as loose soil in those areas can quickly give way to debris flows and mudslides when saturated.
Strong Winds Add to Storm Hazards
In addition to heavy rain, the storm is expected to bring damaging winds.
A High Wind Warning is in effect for interior areas, while a Wind Advisory covers portions of Los Angeles County, Ventura County, Orange County, and the Inland Empire.
Gusty winds could topple trees, down power lines, and cause power outages, especially as the ground becomes saturated and tree roots lose stability.
Emergency officials warn that falling trees and debris could block roads and delay emergency response during the height of the storm.
Holiday Travel Could Be Severely Impacted
With the storm coinciding with Christmas travel, authorities are urging residents to avoid unnecessary driving, particularly during periods of heavy rain.
Flooded roadways, low visibility, and strong winds could create hazardous driving conditions, while mountain travel may become dangerous or impossible at times.
Officials stress that drivers should never attempt to cross flooded roads, noting that even shallow moving water can sweep vehicles away.
Preparedness Urged as Storm Intensifies
Emergency agencies are urging residents to take precautions now, including:
- Monitoring official weather alerts closely
- Preparing evacuation plans if living in high-risk areas
- Securing outdoor items ahead of strong winds
- Avoiding flood-prone roads and low-lying areas
Authorities say the situation remains fluid, and forecasts could change as the storm unfolds.
As Southern California heads into Christmas under the threat of severe weather, officials emphasize that preparation and caution will be critical to keeping communities safe.
Are you experiencing heavy rain or storm impacts in your area? Share what you’re seeing and how conditions look near you in the comments below.
