An Atmospheric River Hitting San Francisco This Weekend

If you’ve been watching the local weather news you know there’s a big storm coming this weekend—part of a 10-day cycle that’s dropping bucket-inches of rain and as much as 20 feet of snow in mountain regions. For powder skiers and snowboarders—according to a story in sfcurbed.com—the potential drop of dry powder is the “most insane forecast ever.” There could be twice the monthly average of Sierra’s snow for January.

What’s coming in is an atmospheric river, a narrow, richly dense trough of moisture transporting vast quantities of water vapor right into us Californians and us San Franciscans. A good analogy is a fire hose with one end in the tropical Pacific and the other end spraying all over California. Two atmospheric events—a blocking high pressure system near the Bering Sea and the jet stream plunging southward off the Pacific Northwest Coast—will cause this rain river to stall over us for 2-3 days starting tomorrow, Saturday.

What’s for us? Two to five inches of rain for the city is going to turn San Francisco super soggy, and there could be high winds that could topple trees and power lines. In surrounding areas there will be flash floods, and the overall flooding could top that of the December 2005 storm. The surf could be pounding in pretty high at Fort Point and other shore or beach areas of the city.