California is set to be pelted with heavy rain from Los Angeles to San Francisco as an ‘atmospheric river’ engulfs the Golden State. 

The City of Angels could be lashed by more than six inches of rain, while the Bay Area could see up to four inches.

The predicted deluge is due to a weather phenomenon known as an atmospheric river, a band of water vapor that can stretch 1,000 miles long and 350 miles wide.

As the moisture moves inland, it can bring extreme snow and rainfall, as well as the possibility of flooding.

The squall is set to batter the Golden State from Monday through to Friday, with experts warning the conditions could be the first ‘significant’ storm of the season.

California is set to be battered by up to six inches of rain in parts as an ‘atmospheric river’ sweeps in from Monday

Forecasters said there is a high chance most of the state will see at least one inch of rain with many parts expected to receive the most precipitation since the start of this year’s rainy season

The expected deluge is linked to an atmospheric river, an airborne band of moisture which can cause extreme rainfall as it moves in. This aerial view shows a damaged pier in Capitola, California, on January 9, 2023 following an atmospheric river earlier this year.

‘This is really our first winter storm,’ Todd Hall, a meteorologist with the weather service’s Los Angeles office told SF Gate.

‘We’ve had rain but it hasn’t amounted to much. It has ingredients to be a very significant storm system for this early in the season. It seems very similar to something we usually see in January and February.’ 

Residents in Los Angeles have already been urged to clean out their gutters amid warnings of ‘potential for flooding, heavy snow about 6,000ft, strong southerly winds and large surf’.

Elsewhere, in the north where it is expected to be wettest, up to five inches of rain have been forecast. 

The state is set to be drenched by the most rain it has seen since the start of the wintry season last month. 

‘We’re looking at rainfall starting to increase in aerial coverage in Northern California and pretty much down toward the Bay Area by Tuesday morning,’ Richard Bann, a meteorologist with the weather service’s Weather Prediction Center told SF Gate.

‘And then as we go through the day Tuesday and into Wednesday, the area of rainfall covers much of Northern California and now even into the Central portion.’

Southern California is likely to feel the impact from Wednesday until Friday.

Modelling for the full impact is still uncertain, but there is a high chance most of California will see at least one inch or more of rain, according to The Center for Western Weather and Water Extremes. 

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Atmospheric rivers can stretch 1,000 miles long and 350 miles wide, a strong AR transports an amount of water vapor roughly equivalent to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River

Atmospheric rivers regularly occur across the United States during the winter months, and account for 50 per cent of all rain and snow in the West of the country. Pictured: A mudslide which flooded parts of Studio City, California following an atmospheric river in January 

The weather feature is due to move in from Monday and last until Friday (file photo of the Golden Gate Bridge)

The center added that some parts could see ‘fairly high’ snowfall, with the National Oceanic and Atmospheric Administration forecasting service predicting a 80 per cent chance of 12 inches of new snow across the Sierras. 

The National Weather Service Forecast Office in Sacramento is warning locals of ‘potential heavy mountain snow’ between Monday and Friday.

However, Bann did not think the storm would bring as much snowfall.

‘In the northern end of the Sierras, we’re probably looking at perhaps an inch to an inch and a half of liquid,’ he added.

‘At this point, I don’t have a real good feel what the snow levels will be, but I know with the altitude of the elevations involved, certainly some of that could be in the form of snow.’

While this atmospheric river is not expected to be particularly strong, at their peak they can transport an amount of water vapor roughly equivalent to 7.5–15 times the average flow of liquid water at the mouth of the Mississippi River.

Last winter, California was battered by 12 atmospheric rivers which claimed the lives of 22 people and wrought havoc due to widespread flooding and landslides.

In December, a winter storm shut down mountain highways, toppled trees and triggered flood and avalanche warnings from the coast of Northern California to Lake Tahoe.

Last winter’s atmospheric rivers resulted in extreme snowfall and led to highways being closed down due to the whiteout conditions such as those seen here at this rest stop in the  Sierra Nevadas 

A month later, a state of emergency was declared after more than 10 days of storms across the state resulted in the deaths of 14 people.

Torrential downpours caused rivers to overflow, submerged vehicles and sparked mass power outages. 

The state faced the brunt of two overlapping weather systems – atmospheric rivers and bomb cyclones, causing extreme weather phenomena. 

While in March, 27,000 people were put under evacuation orders after 16 major rivers in the state to overflowed.

A broken levee on the  Pajaro River a broken levee caused by a similar storm on Friday was again overwhelmed, flooding farms, roads and submerging the entire town of Pajaro and forcing thousands of residents to flee.