After a temporary respite from rain, Southern California is gearing up for another atmospheric river storm set to strike on Sunday. This upcoming weather system, heralded by the National Weather Service as the “largest storm of the season,” poses significant risks, including flooding, heavy mountain snow, and strong winds.

Forecast Overview

The National Weather Service predicts that the storm’s impact will be stronger and more prolonged, lasting from Saturday evening until Tuesday and Wednesday. The forecast suggests that the storm will bring light showers to Ventura County by 6 p.m. on Saturday, with spotty showers anticipated in Los Angeles County. Heavy rain is expected in northern areas of Ventura and Santa Barbara counties by Sunday morning, progressing to Los Angeles County by 5:30 p.m. Showers are projected to continue into Monday and linger through Tuesday.

Snowfall in the Mountains

Snowfall in the mountains is anticipated to commence on Sunday night, intensifying on Monday and Tuesday. With heavy rain expected in the area, mountain communities face a significant risk of flooding.

Unraveling the Atmospheric River

The storm is a result of a combination of a cold front from Alaska and an atmospheric river sweeping across the Pacific. Atmospheric rivers typically precede cold fronts across the Pacific, leading to heavy rain along coastal ranges and inland through the Sierras when interacting with West Coast topography. Models suggest the storm could undergo bombogenesis, a process where a low-pressure system rapidly deepens, creating a bomb cyclone effect.

Rainfall Estimates

The weather service estimates 24 to 36 hours or more of continuous rain, with Los Angeles and Orange counties expecting up to 5 inches between Sunday and Tuesday. Valleys and the Inland Empire could witness 3 to 7 inches, while mountain communities may experience 6 to 12 inches, possibly reaching 15 inches. The high desert is forecasted to receive 2 to 3 inches of rain by Tuesday.

Snow Accumulation in Mountain Communities

Mountain communities may witness 2 to 4 feet of snow at 6,000 feet elevation.

Recognizing the Danger

The storm’s prolonged duration and the forecasted significant rainfall raise concerns about mudslides and dangerous flooding from Monday through Wednesday. Ventura and Santa Barbara counties face the highest risk, with a 20% to 25% chance of the Ventura River reaching flood stage by Monday due to consecutive storms. Strong winds and a high surf advisory further contribute to the storm’s dangerous nature.

Preparedness Efforts in California

The California Governor’s Office of Emergency Services has activated its operations center, deploying personnel and equipment in vulnerable areas. Brian Ferguson, the office’s deputy director of crisis communications, characterizes the situation as a “significant threat to the safety of Californians” across a broad swath of the state.

Ongoing Vigilance

As the storm unfolds, California remains on high alert. The state’s preparation and response efforts underscore the gravity of the situation, emphasizing the need for residents to stay informed and take necessary precautions. The storm’s impact, including potential flooding, snowfall, and strong winds, will continue to be closely monitored throughout the week.