‘Brutal System’ Will Unleash Flooding And Possible Mudslides In California, Forecasters Warn

Topline

Weather forecasters warn a bomb cyclone will hit California on Wednesday with “life threatening” flooding and high winds, less than a week after another storm brought near-record rainfall to San Francisco, risking mudslides in areas that had been experiencing an extreme drought.

Key Facts

Forecasters with the Weather Channel predict as much as eight inches of rain will fall in some areas of northern California, along with 60 mph wind gusts in Mammoth Lakes, California, in the Sierra Nevada mountains.

The storm is expected to stretch from Humboldt and Mendocino counties, north of San Francisco, to Santa Barbara County in southern California, where the National Weather Service has issued flood watches, high wind warnings and coastal flood watches Wednesday into Thursday.

The NWS Bay Area branch warns the long, narrow stretch of heavy rain, called an “atmospheric river,” will connect with a low-pressure system that’s expected to develop into a bomb cyclone—an intense storm triggered by a sudden drop in air pressure.

The storm will “increase the threat for widespread flooding and wind damage” in the San Francisco Bay area, the NWS said, advising residents to “Make a plan now!”

According to the Center for Western Weather and Water Extremes, which rates atmospheric rivers, the upcoming river is a category-three event (out of five)—although that rating does not consider previous rainfall or the saturation of the ground.

Surprising Fact

The massive cyclone is expected just days after an unusually rainy New Year’s Eve, which was the second wettest day on record in San Francisco, with 5.46 inches of rain, just short of the 5.54 inches recorded in a 1994 storm. It was also the third wettest day on record in Redwood City, California, which received 4.47 inches—under the all-time record set in 1962 (4.88 inches), according to the NWS.

What To Watch For

Mudslides. Two consecutive atmospheric rivers, including the New Year’s Eve storm, unleashed over California will not only cause roadway flooding, but increase the risk of mudslides—which can last days after the rain ends, according to AccuWeather chief meteorologist Jon Porter. A New Year’s Eve mudslide blocked portions of a highway outside Oakland.

Crucial Quote

The storm will “likely be one of the most impactful systems on a widespread scale” that has impacted the area in a “long while,” likely causing “widespread flooding, roads washing out, hillside collapsing, trees down (potentially full groves), widespread power outages, immediate disruption to commerce, and the worst of all, likely loss of human life,” the National Weather service said in a statement posted on Twitter by NBC Bay Area meteorologist Rob Mayeda.

Further Reading

Bomb cyclone to unleash life-threatening flooding in California (AccuWeather)Massive ‘atmospheric river’ to bring heavy rains, winds, flooding across California (Los Angeles Times)A truly ‘brutal system’: Atmospheric river to slam California (Washington Post)