Atmospheric river could soon hit West Coast. How hard will it hammer California?

An atmospheric river is expected to bring heavy rain, powerful winds and snow to the West Coast starting next week.

Residents across California should prepare for above-normal amounts of precipitation from Jan. 30 to Feb. 5, according to the National Weather Service’s Climate Prediction Center.

Forecasts show there is a high risk of localized flooding and landslides across California with heavy rain across the state and snow in the Sierra and Klamath ranges.

“As most systems we’ve had this winter, the further north you go, you can expect to get a little bit more rain,” said Jeffery Wood, a meteorologist with the National Weather Service’s office in Sacramento.

High winds are also expected.

Cory Baggett, a meteorologist with the Climate Prediction Center, said gusts could reach 30 to 35 mph or higher.

“We’re anticipating there’ll be wind advisories issued along the coast for this event,” Baggett said.

What is an atmospheric river?

An atmospheric river is an area in the atmosphere that carries water vapors outside of the tropics, according to the National Oceanic and Atmospheric Administration.

When these so-called “rivers in the sky” make landfall, they drop rain and snow.

“This atmospheric river would be more impactful for the Pacific Northwest states” including Washington state and Oregon, Wood said.

Andrea Clayton of Sacramento walks to her state job in the rain on N Street on Thursday, January 5, 2023.
Andrea Clayton of Sacramento walks to her state job in the rain on N Street on Thursday, January 5, 2023.

How much rain is expected?

While it’s too early to predict exact rainfall totals, Baggett said, the Climate Prediction Center is forecasting a 60% or higher chance of heavy precipitation.

“The heavy rain will work southward as the week progresses,” Baggett said. “It will start along the California border with Oregon and move southward as the (atmospheric river) event progresses, bringing the heavy rain with it.”

In the Central Valley of California, including Sacramento, residents can expect storms similar to what they’ve seen over the past few weeks, Wood said.

The Sacramento area could see about an inch to an inch and a half of rain between Jan. 31 and Feb. 3, he said.

“This could be above average in terms of rainfall in the Valley,” he explained.

Areas further north could see more precipitation during the same time period.

This area, ranging all the way to Shasta, could get an inch and a half to three and a half inches of rain, he said.

The Central Coast, which includes San Luis Obispo and the Monterey Bay area, could see half an inch to about four inches of rain.

In Southern California, where widespread floods have devastated San Diego, Wood said early forecasts indicate lower rainfall totals than what Sacramento will see.

Sun breaks through over palm trees in Pismo Beach during a lull in the rain on Tuesday morning, Jan. 10, 2023, as a series of atmospheric river storms hit the coast.
Sun breaks through over palm trees in Pismo Beach during a lull in the rain on Tuesday morning, Jan. 10, 2023, as a series of atmospheric river storms hit the coast.

Up to 4 inches of snow is expected in the Sierra this week, but early forecasts from the weather service in Reno, which covers the Tahoe region, show warmer conditions through the end of January. The “next shot” at precipitation begins Tuesday, according to the latest Sacramento weather forecast discussion.

What will temperatures be like?

According to weather outlooks from the Climate Prediction Center, temperatures for most of California are expected to be above normal from Jan. 29 to Feb. 2.

Forecasts for Jan. 31 to Feb. 6 indicate that temperatures for California will be near normal.

Temperatures are expected to cool down as the days progress, Baggett said.

“Once you get high enough in the Sierra and Klamath mountains, it should be cold enough for snow in those regions,” he said.

“High pressure will bring dry and warmer conditions through the end of January,” the National Weather Service’s Reno office said on Tuesday. “Wetter conditions may return for early February.”

During the first week of February, “more active weather” is expected to return to the eastern Sierra and western Nevada, the agency said, with a 70% to 80% probability of wetter-than-average conditions in the forecast.

A small portion of Southern California will see below-normal temperatures, Baggett said. which is typical with atmospheric rivers.

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