California braces for more heavy rain after days of flooding

A plume of moisture from the Pacific Ocean is expected to bring additional rainfall to the US state in the coming days.

Weather forecasters predict another round of torrential rain in California, which has struggled to cope with flooding and power outages from an “atmospheric river” that drenched the West Coast of the United States over the weekend.

Atmospheric rivers are long columns of moving water vapour that usually release heavy rain and snow when they reach land. The US National Weather Service expects that a second atmospheric river will move in from the Pacific Ocean and bring more rain to California by late Tuesday.

“Rainfall today looks modest, but the system after continues to look impressive,” the service’s bureau in the San Francisco Bay Area posted on Twitter on Monday. “Winds during the Jan 4-5 rain event will increase risk of downed trees & power outages. Gusts of 35-55 mph, locally higher over ridges are possible.”

As of Monday, several areas of Northern California remained under flood watches, which mean conditions are favourable for rising water levels, or flood warnings, which means flooding is imminent. The weather service predicted that some coastal regions could receive as much as six inches (152mm) of rain from the incoming storm.

The rockstars that make up the night shift have switched our radar back into precip mode in preparation for our rain today. #CAwx

Rainfall today looks modest, but the system after continues to look impressive.

Here are the fresh out of the oven rainfall forecasts: pic.twitter.com/cqfVSduAKM

— NWS Bay Area 🌉 (@NWSBayArea) January 2, 2023

In Sacramento County, an agricultural region east of the San Francisco Bay Area where the state capital is located, flooding breached levees and swamped roads and highways. Evacuation orders were issued over the weekend.

Emergency rescue teams helped stranded drivers and found at least one person who had died in a submerged vehicle on Sunday.

“Too many road closures to count at this point,” the weather agency in Sacramento said in a tweet over the weekend.

Power outages also impacted more than 150,000 people in the area, a number that had been brought down to about 6,300 as of Monday.

Dozens of drivers were also rescued on New Year’s Eve on Interstate 80 near Lake Tahoe, east of Sacramento in the Sierra Nevada Mountains. Officials warned residents that strong winds could topple trees and result in power outages. Across the California border on the Nevada side of Lake Tahoe, American movie star Jeremy Renner was among those injured in weather-related accidents.

In the Bay Area, fallen trees closed roads, and the city of San Francisco received 140mm (5.5 inches) of rain on Saturday evening, making it the second wettest day on record.

As the state struggles to cope with a withering drought that has made the past three years the driest on record, the heavy rain is a welcome respite. However, much more precipitation would be needed to make a significant difference.