Series of Storms Over Atmospheric River Heading Northern California

Several strong storms are rushing through central and northern California, bringing much-needed rains to drought-affected areas from Thursday evening, but also raising fears of flooding in further scars of fire.

A large low-pressure trough hovering off the coast of the Pacific Northwest is driving repeated rounds of precipitation across northern California and ushering in the first major storm of the season, National Weather Service forecasters said.

What is called a “atmospheric river” continuously pumping humidity over the area, said Ryan Kittell, a meteorologist at the Weather Service’s Oxnard station.

Scattered showers were reported in central and northern California on Thursday morning, and more storms are setting in. A storm system arriving in the evening and continuing through Friday is expected to be “significant,” said Emily Heller, of the Sacramento weather station. .

The northern Sierra Nevada had already received about 10 inches of snow at the start of the week, and an additional 1 to 2 feet could be dumped in the area early next week, Heller said.

Weather officials said the Sacramento area and the north could receive half an inch to 2 inches of rain, with the majority falling along and north of Interstate 80. Mountain areas could be as high as 4 inches. About half an inch could fall over San Francisco, and northern coastal areas, including parts of Sonoma and Trinity counties, could receive 1 to 2 inches of rain.

Another storm, which Heller called a “really heavy hitter”, is expected to occur Sunday night and will be even stronger.

About 3 to 4 inches of rain is expected to fall in the Sacramento and San Francisco areas from Saturday evening to Tuesday, with most of the precipitation falling from Sunday to Monday. By the time the skies clear next week, mountainous areas could see up to 10 inches.

While most of the rain will be in the north, the storm system will also drift towards southern California. Weather officials predict metro areas in Los Angeles County could receive about half an inch of rain and 1 to 1 1/2 inches in the mountains.

Graphic illustration showing the moisture plume in an atmospheric river rising above the coastal mountains and Sierra Nevada, dropping rain and snow.

(Paul Duginski / Los Angeles Times)

Heller described the atmospheric river as bringing long periods of rain in a narrow corridor of humidity to the atmosphere.

“It’s almost like a facade, except [where the moisture is] is just more focused. Whoever hits northern California is considered moderate to strong.

“Normally the way it works is we just have this band of moisture moving along the coast. And that’s the kind we’re going to see in Southern California, ”Kittell said. “But up there, they actually have it where it stalls.” The storm system could hover for days over the central part of the state.

Storms this time of year are not uncommon, Heller said, but it’s been several years since they arrived so early.

And not a moment too soon. California fair recorded its driest year of water in a century. The state’s average precipitation for the 2021 hydrologic year was about half of what experts consider typical.

Earlier this week, Governor Gavin Newsom declared a statewide drought emergency, imploring Californians to conserve water in the face of one of the most severe droughts on record in the state.

There are cautious hopes that the coming rains will provide relief and reduce the risk of fires in parched parts of the state, but they are not expected to end the drought.

“Unfortunately, two years of drought – one storm is not going to fix it,” Heller said. Sacramento typically registers 12.63 inches of rain per water year. Last year it was closer to 7 inches.

Rain can be beneficial, but it also comes with risks. The national meteorological service issued a flood watch from Thursday afternoon to Friday morning for Nordic burn scars, including Dixie fire and the North complex from 2020.

There are also fears that the influx of heavy rains “could bring potential flows of ash and debris on recent burn scars in Shasta, Tehama, Butte and Plumas counties,” the meteorological service said in an advisory.

Concerns are less in southern California, where less rain is comparatively expected and some burn scars are older, and therefore less prone to landslides and flooding, weather officials said. .

But officials are “moderately concerned” about the area charred by the recent Alisal’s fire in western Santa Barbara County, which caught fire on October 11.

“It’s really cool,” Kittell said. “There are a few vulnerable areas where any kind of mudslide and debris would cause problems.”

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