Atmospheric river heads for California following ‘bomb cyclone’

A powerful storm system is set to approach the West Coast of the USA this weekend, soon after the 'bomb cyclone' pushes east of the Rockies. The storm will bring more rounds of heavy rain and snow to California, beginning on November 30 and December 1, 2019.

According to AccuWeather, about 76 to 152 mm (3 to 6 inches) of rain can fall over the lower elevations of Northern California, and a maximum of 254 mm (10 inches) can fall on the southwest-facing slopes of the Coast Ranges and hills of the Sierra Nevada.

Over in the high country, AccuWeather added that 0.9 to 2 m (3 to 6 feet) of snow can fall across the four-day period, from Sunday to Wednesday, December 4.

"It is possible that Southern California catches an episode or two of heavy rain and mountain snow as well," said AccuWeather senior meteorologist Brett Anderson. "Right now, the best chance of heavy precipitation for the Los Angeles and San Diego areas would be toward the middle of next week."

The atmospheric river is likely to hit the Bay Area. "The weekend is going to be quite interesting," said Brian Garcia, a meteorologist with the National Weather Service. "The storm door is definitely open. We’ll continue to see showers and really cold temperatures especially into later parts of this week."

However, Garcia added that the air mass will start to feel warmer and the "pattern is setting up" for an atmospheric river to head over the Bay Area overnight Saturday and into Sunday.

Atmospheric rivers are "supercharged" storm systems that can bring huge amounts of snow and rainfall in just a span of few days.

Garcia said the atmospheric river is expected to arrive somewhere along the coast over the weekend but the exact landfall would be complex to forecast for now.

Predicting accurately where it lands would be challenging in advance since it's a narrow band of heavy precipitation, he added.

"It being narrow and the state being so big, 16 to 24 km (10 to 15 miles) north or south can make a world of difference," said Garcia.

Forecasting models show the atmospheric mostly impacting the far southern Bay Area into the Central Coast. However, even a small change of path between November 29 and Saturday night could bring the center nearer the densely populated parts of the Bay Area, or bring piles of snow to the Sierra– all this event on one of the busiest travel days of this year.

"This could have some pretty significant impacts throughout the center portion of the state," said Garcia. The forecast calls for storms to continue slamming the Bay Area over the next 5 to 10 days.

"In a sense, fire season has come to an end, and mudslide and flash flood season is beginning in California," warned Dale Mohler, AccuWeather Senior Meteorologist.

The stormy pattern is not likely to end after mid next week. Storms are piling up across the North Pacific, and at least some of these weather systems will approach Northern California during the first half of December.

Julie Celestial

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