The Bay Area weather forecast for Thanksgiving weekend sums up why many people live in California — sunny skies and temperatures in the 70s — even as other parts of the country, from the Great Lakes to New York, brace for snow or excavation from recent snow storms.
But shortly after Turkey Day and Black Friday fade into the rearview mirror, the first new rain and snow in three weeks is expected to hit Northern California on Monday.
“For Thanksgiving Day, it should be a really nice and pleasant day,” said meteorologist Sarah McCorkle of the National Weather Service in Monterey. “We are seeing a bit of a warm-up. Thanksgiving should be the hottest day of the week.”
Enjoy it, because by Monday a low-pressure system from Alaska is expected to bring moderate amounts of rain, between 0.05 inches and 0.25 inches, at lower elevations around San Francisco Bay, with up to half an inch in the Santa Cruz and Big Sur Mountains, according to the National Weather Service.
The forecast may still sizzle. Any new moisture should continue to reduce the fire hazard in the area. But don’t look for change in depleted reservoirs.
“It won’t be much, just enough to wet things out again,” said Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay. “It will disrupt traffic on Monday, but will not affect the drought.”
The storm is also expected to bring 3 to 6 inches of new snow to the Sierra Nevada. That’s a welcome, albeit modest, boost as ski resorts have begun to open for the winter season in recent days.
“It should be just enough to freshen things up,” said Craig Shoemaker, a forecaster with the National Weather Service in Sacramento.
Thanksgiving week is typically the start of the Sierra ski season, a time when visitors to the Bay Area pack up their SUVs and head for Lake Tahoe. It’s also when California water managers begin to pay more attention to snow levels, which supply about a third of the state’s water supply.
Boreal Mountain Resort, at Donner Summit off I-80, opened Nov. 11. Northstar opened the next day. Palisades Tahoe, Heavenly and Kirkwood opened last week. Other resorts, including Sierra-at-Tahoe, which was rebuilt after being damaged in the 2021 Caldor Fire, are expected to open Dec. 3.
So far, the winter snow season has got off to a good start.
After a dry October, a storm on November 1 was followed by a larger one on November 8, bringing more than an inch of rain to some parts of the Bay Area and three feet of snow to many parts of the Sierra.
As of Wednesday, 13 inches of natural snow remained on the ground at the UC Central Sierra Snow Lab near Donner Summit, due in part to cooler-than-normal temperatures in recent weeks. And the 56 inches that have fallen there since Oct. 1 is 230% of the historical average for that period. Ski resorts have contributed to the natural accumulation of artificial snow from snow machines.
“Our snowpack is in relatively good shape compared to this time last year,” said Andrew Schwartz, chief scientist at the UC snow lab.
It’s early in the season. To end California’s severe drought by the time the winter season ends in early April, the Sierra will need to get about twice as much snow as the historical average, Schwartz said.
“It’s hard to say what winter will be like in general until at least February 1, but we’re hoping the big storm track will start shooting some precipitation at us,” he said.
On Wednesday, 85% of California remained in a severe drought, with 40% in extreme drought, and 13% — primarily the San Joaquin Valley — in an exceptional drought, the worst of five categories, according to the U.S. Drought Monitor, a weekly federal report. .
Last year began a very hopeful trend, as atmospheric river storms drenched Northern California in October. Similar storms brought more rain and snow in December.
But then January, February and March dried out — the driest first months of any year in California’s recorded history. The season ended on April 1 with 37% snow in the Sierra and the state was still mired in drought.
All in all, last year was the least dry of the last three. San Francisco received 84% of its historical average rainfall from October 1, 2021 to September 30, 2022. Oakland fared better at 93%. Los Angeles had 88% of normal. San Jose trailed with 58%.
But the two years before that were so dry that reservoirs and groundwater tables could not be refilled. Many of the state’s largest reservoirs are currently only about half as full as their late November historical average.
The largest, Shasta Lake, near Redding, is 31% full. The second largest, Oroville, in Butte County, is 28% full. Similarly, the Folsom Reservoir is 26% full and San Luis, east of Gilroy, is 25% full.
California’s last drought, which began in 2012, ended in spring 2017 with waves of massive atmospheric river storms. The storms, which showed that persistent droughts can end in one big, wet year if there is enough rain to fill the reservoirs, caused the Oroville Dam to nearly collapse and flooded downtown San Jose, causing $100 in damage. million as a result.
Forecasters say they don’t know what the rest of this winter will bring. They can’t accurately predict the weather until a week from now, even using powerful supercomputer models, satellites, buoys, weather balloons, and other equipment.
“At this time of year, any precipitation is good,” Schwartz said. “We are happy to get something that is not hot temperatures and sunshine. Fingers crossed.”