BERKELEY, Calif. — Already waterlogged from a historic storm on Saturday, Northern California began bracing for a second blast from an atmospheric river that is expected to be unleashed on Wednesday.
On Dec. 31, San Francisco received 5.46 inches of rain, just 0.08 inches shy of the all-time daily precipitation record set in 1994. The torrential downpour flooded streets and highways around the Bay Area, caused rivers and streams to overflow their banks and knocked out power to more than 140,000 homes.
With residents still cleaning up, officials warned that Wednesday's storm would likely be even worse. Propelled by a bomb cyclone — a rapid drop of atmospheric pressure that can supercharge storms — round two of the atmospheric river will dump several more inches of rain on the saturated ground and be accompanied by strong winds capable of toppling trees.
The National Weather Service has posted flood watches on Monday for the San Francisco Bay Area and surrounding counties.
From the Bay Area down to the Central Coast, winds between 20 and 40 mph winds are expected, with gusts reaching as high as 70 mph, the National Weather Service said in a separate advisory Monday.
“People should avoid being outside in forested areas and around trees and branches,” a warning issued for the North Bay stated. “If possible, remain in the lower levels of your home during the windstorm, and avoid windows.”
Another warning issued Monday from the Bay Area office of the National Weather Service put a fine point on the risks posed by the incoming storm.
"To put it simply, this will likely be one of the most impactful systems on a widespread scale that this meteorologist has seen in a long while. The impacts will include flooding, roads washing out, hillside collapsing, trees down (potentially full groves), widespread power outages, immediate disruption to commerce, and the worst of all, likely loss of human life. This is truly a brutal system that we are looking at and needs to be taken seriously."
State officials have made 3.7 million sandbags available to residents of areas most at risk of storm impacts, the San Francisco Chronicle reported. The rain is expected to resume falling at roughly 4 a.m. Wednesday and continue into Thursday.
After having endured years of extreme drought, rain, though not the rate at which it is falling this week, is welcome in much of California.
"This is really going to help a lot with the short-term drought in Northern California, perhaps even erase short-term drought conditions,"UCLA climate scientist Daniel Swain said in a YouTube forum with reporters on Tuesday. "But it's going to take a lot more to completely obviate the longer-term, multi-year impacts, and in the broader Colorado River Basin context, this isn't really going to do much at all."
Swain co-authored a recent study that found that rising global temperatures due to the burning of fossil fuels have doubled the chances for a mega-flood in California born of a series of atmospheric river rainfall events.
"We're nowhere near that yet, and we're probably not headed there, but this is definitely one of the higher-impact wet periods that we've seen in recent years," Swain said Tuesday.