California Faces More Flooding as ‘Atmospheric Rivers’ and ‘Bomb Cyclone’ Approach

Ryan Morgan
By Ryan Morgan
January 4, 2023Weather
California Faces More Flooding as ‘Atmospheric Rivers’ and ‘Bomb Cyclone’ Approach
People look on as a tow truck pulls a car out of a flooded intersection in Mill Valley, Calif., on Jan. 4, 2023. (Justin Sullivan/Getty Images)

A series of strong weather systems are set to hit Northern California starting on Wednesday, and they’re expected to bring about heavy rains and flooding throughout the area for the rest of the week.

“Widespread flooding and damaging winds expected from Wednesday afternoon through Thursday as a strong weather system and atmospheric river moves through the region,” the National Weather Service (NWS) said in its Wednesday forecast for the San Francisco Bay Area. “Subsequent weather systems will bring additional precipitation and periods of stronger winds this weekend and into at least early next week.”

An atmospheric river is a column of concentrated moisture that can bring about heavy rains.

The fresh set of intense weather systems comes just days after another atmospheric river hit Northern California, which caused two levees to break down near Sacramento and caused flooding throughout the area.

The NWS said the new waves of heavy rainfall over already saturated soils “will result in rapid rises on creeks, streams and rivers as well as flooding in urban areas.” The NWS forecasted rain and thunderstorms across nearly the entire coast of California on Wednesday, along with flood warnings over most of Northern California and along most of the coast.

Parts of Northern California have seen rains and high winds Wednesday morning. The NWS also forecasted that wind gusts of 60 to 80 mph will be possible as the atmospheric river started to move south in the early afternoon on Wednesday.

“If these winds do materialize, the threat for scattered to widespread power outages and property damage will greatly increase,” the NWS said.

Bomb Cyclone Likely to Impact Californians

Californians will likely also feel the effects of what’s known as a bomb cyclone. A bomb cyclone typically occurs in winter when cold and warm air masses collide, causing the weather system to rapidly intensify. A bomb cyclone spread across much of the United States last month.

Daniel Swain, a climate scientist with the University of California–Los Angeles (UCLA) and the National Center for Atmospheric Research, said in a Tuesday YouTube briefing that the state will feel the effects of the bomb cyclone throughout Wednesday and Thursday.

“This storm will be a pretty high-impact storm. Rainfall rates are going to be high for a few hours around the time of cold frontal passage,” Swain said. “Winds will be quite strong even at lower elevations and so given how saturated the soils are this is likely to produce pretty widespread minor to moderate flooding.”

Swain told NBC News the eye of the bomb cyclone isn’t likely to make landfall over California, but that the storm system will still add to the heavy flooding and rain.

“We’re locked in this prolonged wet pattern. It looks like it’s going to continue for a while, in fact, really for the foreseeable future now,” Swain said.

Communities Brace for Floods

Following the flood warnings throughout large sections of the state, California officials have been taking measures to stay ahead of the heavy rainfalls.

San Francisco officials announced they have about 2,500 volunteers who are ready to help clear about 3,800 storm drains to help reduce flooding risks.

Swain said the flooding will help alleviate some of the drought conditions throughout Northern California in the short term.

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