Remember 105-degree temperatures? Choking wildfire smoke?
The weather misery that enveloped the Bay Area and much of Northern California over the past two months will be replaced this weekend by cool temperatures, blustery winds, and wait for it … actual rain — the first significant rain in nearly six months, since May 18. Some snow also is expected to fall in the higher elevations across the Sierra Nevada.
It’s not a lot of precipitation, forecasters say, but a storm from Alaska will bring a major shift in the weather Friday and through the weekend across the Bay Area. In short, it’s finally going to feel like fall.
“This is the most significant rain of the season so far,” said Roger Gass, meteorologist with the National Weather Service in Monterey. “It isn’t going to do anything for reservoirs. But we’ll take what we can get.”
The rain is expected to come in scattered amounts, starting with light showers forecast Friday morning, mainly near the coast and hills. The best chances for showers appear to be from about San Francisco to Big Sur on Friday night, but some rain is possible in San Jose and the East Bay as well.
The National Weather Service expects amounts from .10 to .25 inches in San Jose, the East Bay and San Francisco, with more, possibly .25 to half an inch, in Santa Cruz, Half Moon Bay, and the Monterey region, particularly in the hills. There will be less in the North Bay.
“It’s going to feel like fall this weekend — cooler, breezier, with some rain — but not downpours,” said meteorologist Jan Null of Golden Gate Weather Services in Half Moon Bay. “It’s nice to have weather to talk about, instead of all the fires.”
A second wave of rain also is possible with some isolated thunderstorms into Saturday morning and another chance of rain late Saturday night into Sunday morning. Following that, more light rain is possible later next week, on Tuesday and Wednesday, some forecasts show.
Meanwhile, the National Weather Service has issued a winter storm watch from Friday through Sunday in the Sierra Nevada. Snowfall of 6 to 12 inches is expected at elevations over 5,000 feet, with 15 inches possible in the highest elevations. Hazardous mountain travel is anticipated, especially Saturday night into Sunday, National Weather Service forecasters in Sacramento said Thursday. Much of that snow will likely melt over the coming weeks, but like the dampening rain, it will reduce fire danger.
Because of the snow forecast officials at Yosemite National Park announced that the Tioga Road and Glacier Point roads in the park’s high country would be closed from Thursday at 6 p.m. through at least Monday.
The air is going to feel brisk also across the Bay Area. Temperatures, which have peaked in the 70s and 80s this week, will fall as much as 15 degrees in many places starting Friday, forecasters say. Weekend highs should be in the low 60s to the 50s across the Bay Area, with overnight lows dipping into the 40s.
Not cold enough for you? Expect overnight lows in the 30s into next week in some parts of the Bay Area.
“There’s a possibility of frost early next week in places like Morgan Hill and Gilroy,” Gass said.
California will need at least an average winter rain and snow season this year to stave off a new drought. Much of Northern California only received about half its normal rainfall this past winter, and the Sierra Nevada snowpack was only 54% of the historic average on April 1 at the end of the snow season.
The dry trees, brush and grasses — combined with freak lightning storms in August and millions of dead trees left over from the five-year drought that ended in 2017 — have combined to spark the worst fire season in modern California history. More than 4.1 million acres have burned so far this year, an area more than 11 times larger than the city of Los Angeles.
On Thursday, the U.S. Drought Monitor, a weekly federal report, showed that 67% of California was classified in some level of drought, most of it in the north. That’s the highest percentage of the state with drought conditions in early November since 2016, the final year of the five-year drought, when 75% was in drought the first week in November.
Federal scientists say that La Niña conditions are underway in the Pacific Ocean. During La Niña events, strong winds blow warm water at the ocean’s surface off the coast of South America. That causes colder water from deeper depths to rise to the surface, affecting weather patterns over wide areas. A commonly held view among many Californians is that La Niña winters are guaranteed to be drier than normal.
But during the 22 La Niña events since 1954, the Bay Area has received 91% of its average rainfall and areas farther north in the state have received 95% to 102%, according to research by Null. The main impact has been in Southern California, where during those La Niña years, the average rainfall has been 76% of normal.
This fall is already off to a slow start. The average for total rainfall in October in San Francisco is 1.12 inches. This October, only .01 inch fell. That tiny amount of drizzle on Oct. 6 accumulated to a depth of less than the width of a fingernail. It will take a few decent storms in November, Null said, to get the Bay Area back on track.
