Storm brings rain and snow to Southern California – NBC Los Angeles


What there is to know

  • A holiday week storm that inundated northern California has moved to southern California.
  • The heaviest rains for SoCal will fall from Thursday evening through Friday.
  • Conditions dry up later on Friday before another storm hits this bank holiday weekend.

A storm that will bring rain and snow from Thursday to Friday has arrived in southern California.

Mountain snowfall and widespread rains are expected, with most precipitation falling from late Thursday through Friday. The same system hit the northern West Coast with rain and snow earlier this week, offering a glimpse of what’s to come.

Here is the storm outlook. This article will be updated.

The rain chronology for a December storm in Southern California.

Holiday week storm timeline

Showers inundated Ventura County overnight, adding up to nearly half an inch in some areas. The storm moved to Los Angeles later Thursday morning before spreading to communities in Orange County and the Inland Empire later Thursday morning.

“At this time, it’s rife,” said Belen De Leon, forecaster at NBC4. “Better not to be on the roads. Expect travel delays.”

  • Thursday morning: rain increases in LA County
  • Thursday afternoon to Friday: general rain
  • Friday afternoon: the rain decreases
  • Saturday: a cold storm brings more rain

Showers will be light in the morning and the heaviest rain will arrive from Thursday evening to Friday morning.

Water vapor imagery over the Pacific showed an atmospheric river developing as a flow of moisture from an area east of Hawaii. Atmospheric Rivers are long plumes of moisture in the skies over the Pacific that have fueled some of the West Coast’s most powerful and damaging storms.

Moderate to heavy rain over forest fire burn scars. A flood watch was issued Thursday evening and Friday morning in the mountains of Riverside County and San Bernardino, the valleys of Riverside County and the San Gorgonio Pass near Banning. The watch includes Bond, Apple and El Dorado burn scars.


Here are the impacts of a December storm.

Coastal areas and valleys will see 1 to 3 inches of rain, mountain communities will experience 2 to over 5 inches.

Snow levels will remain high with accumulations of 4 to 8 inches above 7,000 feet.

The gusts will pick up on Thursday, reaching 50 to 60 mph in the mountains.

Another system comes on Christmas Day with downpours that last until Sunday.

“This one will be colder with less rain,” De Leon said. “We are still several days away, and this stormy system could take another path.”

This graph shows the weather conditions throughout the weekend in Southern California.

Vacation Travel Forecast

The window of opportunity quickly closed for drivers as the West Coast storm hit northern California with heavy rain and snow in the mountains, making travel difficult statewide .

Travel, especially through high passes, turns into a mess due to the constant and multiple cycles of rain, mountain snow and gusty winds. Winter storm warnings were in effect in parts of the Sierra Nevada and will last until Sunday, the National Weather Service said.

Chain requirements were already in effect for vehicles on certain stretches of road through the Sierra, according to the California Department of Transportation.

Precipitation was light to moderate in the San Francisco Bay Area and slowly spread along the coast, arriving in Ventura County Wednesday evening.

The weather overview for December in California

In October, the National Oceanic and Atmospheric Administration announced that the Pacific Ocean was showing signs of a new La Nina, the flip side of the El Nino warming ocean pattern, which tends to cause weather changes around the world.

Forecasters said much of California would have a 33% to 50% chance of below normal precipitation, while only the northern part of the state had an equal chance of above or below normal precipitation.

The California Drought Monitor Map.

United States Drought Monitor

The California Drought Monitor card for December 21, 2021.

But the storm’s track turned farther south than usual during La Ninas. After a series of storms in mid-December, California’s overall snow water equivalent – a measure of the amount of water in the snowpack – fell 19% from normal so far on December 10 at 76% of normal on December 17, according to the latest seasonal drought outlook in the United States.

While the current wet trend is positive, it is too early to know if it will last through January and February. The snowpack normally does not reach its maximum until April and last spring the runoff was minimal as much of the water was absorbed by the drought-dried landscape.


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