Flooded street in Aptos
A resident walks along a flooded street, after “atmospheric river” rainstorms slammed northern California, in the coastal town of Aptos. REUTERS

Yet another “atmospheric river” of dense, moist tropical air will clobber California on Monday with rain and mountain snow – the fifth of the weather phenomenon since Christmas – even as the state was being pummeled by storms this weekend, forecasters said.

The current bout of heavy showers and gale-force winds swept into the northwestern corner of California late on Friday and spread southward into the San Francisco Bay Area and central coast on Saturday afternoon and will linger on Sunday, said David Roth a meteorologist from the National Weather Service‘s Weather Prediction Center.

In San Diego, by contrast, the weather service expects “mostly dry and cool conditions continue through Monday evening” with highs in the 60s in most area. Rain is forecast for Tuesday, though not as intense as elsewhere in the state.

The next in a back-to-back parade of storm systems – described by forecasters as a “relentless parade of cyclones” – will hit on Monday and last through the middle of next week at least, affecting Los Angeles, Sacramento, up through the San Francisco Bay Area and toward Oregon.

“We expect to see the worst of it still ahead of us,” Gov. Gavin Newsom said.

Roth offered more details, saying, “We’re talking 3-to-6 inches of rain, several feet of snow in the mountains … because the area is so saturated we could see flash floods, mudslides, rockslides and avalanches.”

Hillsides and canyons already stripped bare of vegetation by past wildfires are especially vulnerable to rock and mudslides according to forecasters.

In addition to heavy rains, up to 2 feet of snow was expected to fall by the end of Sunday in higher elevations of the Sierras, where accumulations of a foot to 18 inches or more were measured earlier this week.

More than 500,000 homes and businesses were without electricity on Sunday morning, largely in the Sacramento area and northern California, according to tracking site Poweroutages.us.

Some 424,000 California homes and business remained without power as of the afternoon, state officials said at a news conference.

It marked the third and strongest atmospheric river to strike California since early last week.

Howling winds uprooted trees already weakened by prolonged drought and poorly anchored in rain-soaked soil, taking down power lines with them and blocking roadways across the region.

A weather alert on Saturday warned that the cumulative effect of successive heavy rain storms since late December could bring rivers to record high levels and cause flooding across much of Central California.

What’s to come is the result of two overlapping phenomena – an immense airborne stream of dense moisture from the ocean called an atmospheric river and a sprawling, hurricane-force low-pressure system known as a bomb cyclone..

At least 12 people have died from weather-related incidents in California in the past 10 days, Governor Gavin Newsom told a news conference. Among the victims was a toddler who was killed by a redwood tree that fell and crushed a mobile home in northern California.

A woman living in a homeless encampment along the Sacramento River died Saturday night during a raging storm when a tree branch fell on her tent.

The rapid succession of storms left downtown San Francisco drenched in 10.3 inches of rain from Dec. 26 through Jan. 4, the wettest 10-day stretch recorded there in more than150 years, since 1871, according to the weather service.

Roth said the atmospheric river “isn’t close to being over,” and that the storm patterns will persist until the middle of January.

Reuters contributed to this article.

Updated 7:15 p.m. Jan. 8, 2023

Chris Jennewein is Editor & Publisher of Times of San Diego.