Some meteorologists described the coming storm in Northern California at mid-week as an atmospheric river in contrast to the National Weather Service’s storm forecast that says it is more likely a typical winter system.

Storm approaching the Bay Area

Brooke Bingaman, a weather service forecaster, explained that the agency expects widespread light rainfall in the Bay Area on Tuesday and Wednesday. The storm would come from the Gulf of Alaska and will be moving fast.

The coming storm is similar to the weekend events as it is forecasted to be weak and have a warm frontal boundary followed by a cold frontal as it moves across the region. 

Bingaman said, “While it will tap into subtropical moisture, we’re not seeing a typical atmospheric river where it’s a fire hose of rain, bringing warming temperatures. With an atmospheric river, we usually have higher snow levels, and it will last for a few days at least. I don’t know that I’d classify this as a typical atmospheric river.”

Atmospheric rivers are like rivers in the sky with long and narrow regions -ranging between 250 to 375 miles wide, in the atmosphere. They mostly transport water vapor outside the tropics.

When an atmospheric river crossed the Bay Area in 2018, it caused the wettest rainy season in 20 years. And the term atmospheric river was commonly used by meteorologists, the San Francisco Gate reported.

The storm’s eye may land directly on North Bay or north of it and most likely deliver heavy rainfalls. The expected rain from Tuesday to Thursday in coastal North Bay is 1.0-1.5 inches while 0.25 to 0.75 inches in North Bay Valley, the Central Bay Area, and San Francisco.

The weekend storm recorded 0.75 inches in San Francisco, 0.34 in San Jose, and was at a rate of 0.84 in the Oakland hills, and 0.39 in the San Francisco International Airport.