A powerful atmospheric river will arrive Sunday, bringing very heavy rain and potentially life-threatening flash flooding as well as mountain snow to much of the Southland through Tuesday, National Weather Service said.

The rain will continue through Tuesday with a high threat of excessive rainfall and flooding. As of 11 a.m. PT, the National Weather Service said the heaviest rain has shifted to Los Angeles County and will last longest over the region as the system arrives. High rainfall totals are anticipated, including 4″-8″ for LA County, 8″-14″ for the mountains and foothills, with a 20-percent chance of thunderstorms. But widespread flooding will be the biggest threat.

According to the NWS, the strongest rain and wind will arrive by afternoon and into the evening through Monday morning. Forecasters say the coastal side of the mountains will also be affected. Heavy rain will linger, which is why the NWS has asked the public to work remotely, if possible, Monday.

NWS issues “Flash Flood Outlook”

A flood watch remains in effect for all areas. According to forecasters, flooding is possible along freeways, as well as in neighborhoods, impacting even parked cars due to the sheer amount of anticipated rain. Commuters are urged to avoid freeways Monday morning. 

Strong, damaging winds are likely, prompting the NWS to issue a rare, storm warning for Ventura County and northward, which means excessive rainfall that could produce flash flooding. Los Angeles County is not under the storm warning, but is under a gale warning. 

Winds will be lighter Monday and into Tuesday. Stronger winds could return by Wednesday.

Evacuation orders and warnings issued

Parts of Ventura County were already under evacuation orders because of the storm, including for unincorporated Ojai, which includes residents living near Matilija Canyon, North Fork, Camino Cielo until Sunday at 5 p.m. Evacuation warnings have been issued for the community of Foster Park/Camp Chaffee, Creek Road/Old Creek Road and 2 homes on Grada Avenue and 2 homes on Trueno Avenue.

“We’ve already seen the storm hit us last week and soil is already saturated. Flash floods as a result can occur without warning,” said Sgt. Cyrus Zadeh of the Ventura County Sheriff’s Department. “Please stay alert not only to the road conditions, but we’re asking people to be alert to our evacuation warnings, evacuation orders, and advisories.”

An evacuation center has been established at Ventura College Gymnasium, located at 4667 Telegraph Rd, Ventura, CA 93003. 

In addition, residents along La Tuna Canyon Road area–with borders of Horse Haven Street to the north, Martindale Avenue to the east, Penrose Street to the south, Ledge Avenue to the west–were under evacuation orders due to the high risk of debris flow. 

An evacuation center for those with household pets has opened at Sunland Senior Citizen Center, located at 8640 Fenwick Street Sunland, 91040, as well as at the Lake View Terrace Recreation Center, located at 11075 Foothill Blvd, Lake View Terrace, 91342).

Large animals can be evacuated to Hansen Dam Horse Park, located at 11127 Orcas Avenue, in Lake View Terrace, and the LA Equestrian Center, located at 480 Riverside Drive, Burbank, 91506. 

Elsewhere, in Malibu, an evacuation order has been issued due to possible mud and debris flows in the area along Santa Maria Road, north of Topanga Canyon Boulevard through 6 p.m. Tuesday. 

Snow levels to fall 

In addition, snow levels were still fairly low but are expected to increase to 6500-7500 ft. By Monday, the NWS says that snow levels will drop to 5000-6000 ft, and will fall further to 4000-5000 ft on Tuesday.