After a brief respite from rain, Southern California is bracing for another powerful atmospheric river storm, predicted to be the largest of the season. The National Weather Service anticipates dangerous and potentially life-threatening impacts from this impending weather system.

Timeline of Rainfall in Southern California

The storm is set to make its presence felt starting Saturday evening and is expected to persist until Tuesday and Wednesday, potentially delivering a continuous 48-hour deluge. Key timelines include:

• Saturday 6 p.m.: Showers beginning in Ventura County, with possible snowfall in mountainous areas.
• Sunday 5 a.m.: Light to moderate showers advancing into Los Angeles and Orange counties.
• Sunday 12 p.m.: Anticipated heavier rain with the possibility of lightning in Los Angeles and Orange counties, and showers reaching San Bernardino County.
• Sunday 11 p.m.: Continuing heavy rain across Southern California.
• Monday to Tuesday: The storm’s progression through the region with increased concerns about flooding.

Snowfall in Southern California Mountains

Snowfall is expected to commence Sunday night in the mountains, intensifying on Monday and Tuesday. Heavy precipitation in mountain communities raises the risk of flooding.

Understanding Atmospheric Rivers and Their Role in the Storm

This storm is a convergence of a cold front from Alaska and an atmospheric river traversing the Pacific. Atmospheric rivers, common before cold fronts over the Pacific, interact with West Coast topography, resulting in heavy rain along coastal ranges and inland through the Sierras.

Forecasted Rainfall in Southern California

The National Weather Service predicts 24 to 36 hours of continuous rain. Los Angeles and Orange counties may experience up to 5 inches of rain, while valleys and the Inland Empire could witness 3 to 7 inches. Mountain and foothill communities might see 6 to 12 inches, with the possibility of 15 inches, while the high desert may receive 2 to 3 inches.

Anticipated Snowfall in Mountain Communities

Mountain communities may face substantial snowfall, with projections ranging from 2 to 4 feet at 6,000 feet elevation.

Storm’s Dangerous Aspects and Potential Impacts

The storm’s prolonged duration and heavy precipitation heighten the risk of mudslides, dangerous flooding, and snow-related hazards. The most significant flood threat is expected on Sunday and Monday, particularly affecting Ventura and Santa Barbara counties.

Preparedness Measures and Advisory

The California Governor’s Office of Emergency Services has activated its operations center, positioning personnel and equipment strategically. Residents are advised to secure outdoor objects due to expected strong winds, and a high surf advisory is in effect. The National Weather Service recommends charging batteries and phones in case of power outages.

California’s State of Preparedness

The California Governor’s Office of Emergency Services has activated its operations center and positioned personnel and equipment to address the significant threat to safety. The state is on high alert from the Oregon border to San Diego, covering both coastal and mountainous regions.

Subsequent Weather Patterns

Another storm is anticipated on Wednesday, though significantly lighter. Rain is forecasted for the rest of the week.

In summary, Southern California is facing a formidable atmospheric river storm with potential hazards ranging from flooding to significant snowfall. Residents are urged to stay informed and take necessary precautions to ensure safety during this challenging weather period.