Atmospheric river

‘Threat to life likely’: Atmospheric river headed for SF Bay Area

Major damage expected as big storm with high winds nears

Amy Graff

Tuesday marks the calm before the storm in the San Francisco Bay Area, as Wednesday is expected to bring another whack of insanely wet and windy weather.

An approaching atmospheric river is threatening to kick up powerful winds and dump up to another 3 inches of rain in urban areas, including San Francisco, and up to 5 to 8 inches in the valleys and mountains of the North Bay, the National Weather Service said.

With similar or worse impacts expected with this system compared to the Dec. 31 event, the weather service warned, "Threat to life likely during this storm." Widespread flooding and wind impacts are expected.

Forecasters are also referring to the system as a "bomb cyclone" as it is forming rapidly while pressure decreases. "As long as pressure is dropping, that means the storm is strengthening," said Rick Canepa, a forecaster with the weather service. "It's a strong storm, no doubt."

A potent atmospheric river caused widespread flooding across the Bay Area in the final days of 2022, and the big question is: Will the second storm be worse than the New Year's Eve deluge?

This storm is expected to bring more rain to the North Bay and less rain in the San Francisco area. Coastal mountain ranges are forecast to record 3 to 8 inches Wednesday through Thursday, while most urban areas are forecast to pick up 1 to 3 inches. Valley areas of the North Bay could see up to 5 inches, the weather service said. In the New Year's Eve storm, downtown San Francisco saw its second-wettest day since record keeping began in 1849, recording 5.46 inches across 24 hours, according to the weather service. 

Southerly winds are expected to be much stronger than with the earlier storm. Gusts between 40 and 60 mph are likely at the highest ridges and peaks. "These winds combined with already saturated soils will likely result in downed trees/limbs causing isolated to scattered power outages as well as potential property damage," the weather service warned. A high wind watch was issued for Wednesday and Thursday, and the weather service said it's likely to be upgraded to an advisory or warning. 

"It's a lot different than the previous system that went through," said Canepa. "What this system has got going for it is rapid strengthening as it approaches the West Coast, sweeping a frontal system across the area with rain and wind."

Flood watches have been issued for most of the Bay Area and throughout Northern California. The weather service warned of flooding in urban areas and on rivers and streams. Shallow land- and mudslides are also possible. 

The first rains are forecast to arrive Wednesday morning and strengthen throughout the day. The heaviest rainfall is expected Wednesday night into Thursday morning.