Long story short: It’s slated to be a wet 10 days, especially next Monday, according to John P. Monteverdi, professor emeritus of meteorology at San Francisco State University.
At least that, is the outlook from today’s weather maps, he said. And, for now, San Francisco is unlikely to have any storms comparable to the record-setting rain of New Year’s Eve.
The first wave of downpours will begin in the middle of tonight and extend through Sunday morning.
The major disturbance, however, will be the one that comes on Monday and continues through Wednesday. “It does look like Monday will be an extremely stormy day, into Tuesday morning, perhaps into Wednesday, but definitely on Monday,” Monteverdi said, who gave a broad-brush estimation of two to three inches of precipitation for San Francisco during that time.
Thanks to San Francisco’s unique advantage of not having any above-ground creeks or rivers, most residents of the city don’t have to worry about flooding, unless you live around areas built over subterranean water, such as the corner of Folsom and 17th streets or along Cayuga Street.
There are still a few things residents can do to avoid any flooding. The first is to remove all leaves from their gutters, and the second is to stay home on Monday, especially during commuting hours, when the rain is expected to be heaviest.
Monteverdi noted the association of a very strong, but relatively narrow, atmospheric river, a type of water vapor that can be converted by nature into rain and clouds. “It looks like the way that nature takes that and creates clouds is going to be maximized over our area,” he said.
He also warned of the possibility of flooding, debris flows, and mudslides caused by the already saturated soils.
As for a more detailed description, it is impossible to know at this moment. “This far in advance, even though we’re only three days in advance, it’s not possible to say if and when that will happen over any given area,” he said. “It depends on where that actually ends up on Monday, where the heaviest rainfall is going to occur.”
Fortunately, the upcoming storm, or storms, is unlikely to reach the intensity as the one that upset everyone’s New Year’s Eve. Both storms are about the same size, but the atmospheric river of the Dec. 31 storm, by happenstance, became stationary over San Francisco and brought the city its second wettest 24 hours in 174 years.
“That’s extremely rare,” Monteverdi said. “So, it’s unlikely that will happen in San Francisco again. It could, but I don’t think so.”
Monteverdi declined to comment on the city’s lack of preparation for the Dec. 31 storm, saying that he didn’t know what the National Weather Service (NWS) told the city in advance of the storm.
Controversies took place earlier this week as city officials blamed the insufficient planning on incorrect weather forecasts from the National Weather Service, which was not impossible, Monteverdi said. He noted that the day before the historic storm, models showed that one of its atmospheric rivers would be over Marin County, unless it paused over San Francisco. “And that’s what happened; it paused for nine hours,” he said.
Even so, Mayor Breed “shouldn’t have taken a shot at the weather service. That’s kind of unfair, because no matter what, they’re just doing a job, even if they were wrong. I don’t know if they were wrong.”