"Rainfall chances increase beginning Wednesday and last into the weekend as a rather impressive system sets up," the weather service said.
There will be high impacts for the North Bay, with low impacts for the rest of the Bay Area is the theme for the week ahead.
North Bay cities in the yellow portion of the graphic below will almost certainly see flooding beginning as early as Wednesday afternoon and could continue into the start of the weekend.
Cities on the North Coast could be pelted with over 10 inches of rain, while San Francisco and Oakland might get one to four inches, according to the National Oceanic and Atmospheric Administration weather prediction webpage.
The rainiest day for the rest of the Bay Area will be Friday, and by then up to a foot of rain could fall in parts of Mendocino and Lake Counties.
Many Bay Area residents will recall as just one example the atmospheric river of early 2019. It sent heavy rain and gusty wind through the Bay Area, causing flooding, downed trees and other problems. Thousands of utility customers lost power as trees and other debris fell on power lines and airports cancelled or delayed flights.
An atmospheric river, as the name suggests, is like a river of water vapor in the sky flowing from the tropics to higher latitudes, often bringing a huge amount of rain, according to the National Oceanic and Atmospheric Administration.
Like any Atmospheric River, small changes in the track can mean big changes in rainfall totals and impacts.
ABC7 News contributed to this story.
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