Two weeks ago, an "atmospheric river" brought absurd amounts of rain to the San Francisco Bay Area. October the 24th was the 4th wettest day ever in the region, and the wettest ever recorded during the month of October. Whether you chalk that up to an unusual weather event or the early impacts of climate change, it was quite an unusual day.
This week, the deluges are coming back, as another "atmospheric river" like the one from two weeks ago is expected to strike the Bay Area. According to the National Weather Service, rains are expected to begin in San Francisco after around 4pm on Monday, with the really heavy rains likely starting later Monday evening.
The rain will intensify after 10pm, and there might even be a thunderstorm overnight. The good news there? Although a thunderstorm two years ago ignited a whole set of wildfires, the Bay Area's ground is sufficiently soaked from the last atmospheric river that fire danger in many regions is moderate or better.
Rainfall overnight is all but certain--in a relatively rare move, the Weather Service pegs the probability at 100%. No margin for error or equivocation there--it's definitely going to be a rainy night.
Winds are expected to pick up in the evening, too, eventually reaching speeds that could exceed 40 miles per hour. For that reason, the National Weather Service has issued a wind advisory, saying that high winds could blow down tree limbs or cause other damage.
Rains and high winds are expected to continue at least through mid-morning on Tuesday, making a mess of the morning commute. After the rains stop, the day is expected to clear up and temperatures should rise, peaking in the mid 60s. The rain should be pretty much gone by Tuesday afternoon or evening.
This atmospheric river, then, is unlikely to rival the torrential one we experienced last month. Still, any rain is good for the region's ongoing drought, and many in the Bay Area welcome stormy skies, as long as the damage isn't too great. Still, with gusty winds combining with this week's river, it's likely that some localized power outages could hit the region, and flooding is possible, too.
Clear out your drains, use caution on the road, get ready for the potential of a day or two without power, and expect to wake up to rain tomorrow, especially if you're just a bit north of the city, where the atmospheric river is expected to deliver its biggest punch.