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, are bracing for snow or digging out from recent snow storms.
But soon after Turkey Day and Black Friday fade in 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 with the National Weather Service in Monterey. “We’re seeing a little bit of a warm-up. Thanksgiving should be the warmest day of the week.”
Enjoy it, because by Monday a low pressure system from Alaska is forecast to bring a modest amount of rain, between .05 inches to .25 inches, at lower elevations around San Francisco Bay, with up to a half inch in the Santa Cruz and Big Sur mountains, according to the National Weather Service.
The forecast could still fizzle. Any new moisture should continue to reduce fire danger in the area. But don’t look for any change in depleted reservoirs.
“It won’t be much, just enough to wet things down again,” said Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay. “It will disrupt traffic Monday but won’t have impacts on the drought.”
The storm also is forecast to bring 3 to 6 inches of new snow in the Sierra Nevada. That’s a welcome, if modest, boost as ski resorts have begun to open in recent days for the winter season.
“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 beginning of ski season in the Sierra, a time when Bay Area visitors pack up the SUVs and head toward Lake Tahoe. It’s also when water managers around California start to pay closer attention to snow levels, which provide roughly one-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 is off to a decent start.
After a dry October, a Nov. 1 storm was followed by a bigger one on Nov. 8, which brought more than 1 inch of rain to some parts of the Bay Area and 3 feet of snow to many parts of the Sierra.
On Wednesday, there were still 13 inches of natural snow 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 has fallen there since Oct. 1 is 230% of the historical average for that time period. Ski resorts have been adding to the natural accumulation with artificial snow from snow machines.
“Our snowpack is in relatively good shape compared to this time last year,” said Andrew Schwartz, lead scientist at the UC snow lab.
It is early in the season. To end California’s severe drought by the time the winter season finishes at the beginning of April, the Sierra will need to receive about twice as much snow as the historical average, Schwartz said.
“It’s hard to say how the winter is shaping up overall until at least February 1st, but we’re hoping to get the big storm track to start shooting some precip at us,” he said.
On Wednesday, 85% of California remained in a severe drought, with 40% in extreme drought, and 13% — mostly 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 with a very hopeful trend, when atmospheric river storms drenched Northern California in October. Similar storms brought more rain and snow in December.
But then January, February and March were parched — the driest first months to any year in recorded California history. The season ended with the Sierra snowpack at 37% of normal on April 1 and the state still mired in drought.
Overall, the past year was the least dry of the last three. San Francisco received 84% of its historical average rainfall from Oct. 1, 2021, to Sept. 30, 2022. Oakland fared better with 93%. Los Angeles had 88% of normal. San Jose lagged with 58%.
But the two years before that were so dry that reservoirs and groundwater tables have not been able to refill. Many of the state’s largest reservoirs are only about half as full currently as their historical average for late November.
The largest, Shasta Lake, near Redding, is 31% full. The second largest, Oroville, in Butte County, is 28% full. Similarly, Folsom Reservoir is 26% full and San Luis, east of Gilroy, is 25% full.
California’s last drought, which began in 2012, ended in the spring of 2017 with waves of huge atmospheric river storms. The storms, which showed that sustained droughts can end in one big, wet year if enough rain falls to fill reservoirs, caused the near collapse of Oroville Dam and flooded downtown San Jose, leaving $100 million damage in their wake.
Forecasters say they don’t know what the rest of this winter will bring. They can only accurately forecast the weather about one week away, even using powerful supercomputer models, satellites, buoys, weather balloons and other equipment.
“This time of year, any precipitation is good,” Schwartz said. “We’re happy to get anything that isn’t warm temperatures and sunshine. Fingers crossed.”
Source: www.mercurynews.com