Christmas will be a soggy one this year as another round of wet weather approached Santa Cruz County and the Bay Area, kicking off an expected week of rain, according to the National Weather Service.
“It’s a rare setup in the Pacific where it’s sending low pressure, one of the bigger drivers of rain, coming down from British Columbia and meeting up with us,” said NWS forecaster Brayden Murdock.
A cold front attached to the low-pressure system over the Pacific Ocean and off the coast of the Oregon-California border will rotate and push moisture toward Northern California, resulting in a steady band of rain with sporadic breaks over the region for several days.
Another low-pressure system will move down Friday night into Saturday and deliver another helping of rain.
“We may have a conveyor belt situation that will get us more and more prolonged chances of rain,” Murdock said. “This is uncommon for it to happen to begin with, but for a La Niña year, which tends to be drier for the Bay Area, this is even more uncommon.”
The first lull in the rain was expected Wednesday morning, with showers likely to resume by the afternoon. Another break should come Thursday morning, with more rain resuming by Friday afternoon and possibly lasting through the weekend. The storms may last through Dec. 28 before tapering off, although some weather models show rain in the forecast for the rest of next week.
The National Weather Service is calling for rain likely in Santa Cruz County for Wednesday after patchy morning dense fog. The NWS is calling for a 70% chance of precipitation.
For Wednesday night in Santa Cruz County, the forecast is much of the same, but with a little wind as well. Winds could gust as high as 18 mph Wednesday night.
“We’re going to have minor waves of rainy activity through the course of the week. We’re going to be constantly adjusting the forecast depending on what we see,” said NWS forecaster David King.
During the next week, coastal mountains in the North Bay could get 3 to 5 inches of rain with a few spots in the higher elevations receiving closer to 6 inches. Meanwhile, the Santa Cruz Mountains are expected to receive 3 to 6 inches while the North Bay valleys could get 2 to 3.5 inches of rain. The East Bay, South Bay and interior San Francisco Bay may receive 1 to 3 inches of rain. San Jose and Livermore could receive up to 2 inches of rain, San Francisco and Concord up to 3 inches, and Santa Cruz up to 4 inches.
Unlike atmospheric river storms that deluge the Bay Area within a few days, the potential for debris flows in areas burned by wildfires appears limited this time since the rain will be spread out over many days instead of continuous heavy rain in a short timeframe, according to the weather service.
“It’s going to be easier to manage this water because because it’s going to be persistent,” Murdock said. “We’re not too worried about drainage systems or water overfilling in places where it’s collected. It gives people who need to react to this plenty of time to react while an atmospheric river, there were places that got their monthly rainfall totals in a day. This is going to be easier for a lot of people.”
The rain will bring other impacts, including the potential for flooding in low-lying or poor drainage areas. Wet roads coupled with increased holiday traffic could make driving more hazardous.
There will be chances for a light dusting of snow on the highest peaks of Mount Diablo and Mount Hamilton toward the later part of the storm, but accumulations won’t be too substantial, Murdock said.
The storms will bring a “few breezy moments” to the Bay Area but will be a lot calmer compared to windier conditions seen during the recent atmospheric river storms. Ahead of the first storm, gusts are expected to reach 20 mph.
Temperatures will also be mild, with the North Bay likely to see weather in the 50 degree range while the South Bay could warm up into the 60s.
The storms were also expected to dump several feet of snow on the Sierra Nevada, likely posing a headache for travelers during the holidays. The weather service has issued a winter storm warning and Northern California mountains were set to receive 6 to 8 feet of snow through Sunday, with up to 10 feet of snow in some localized areas.
The heaviest snow was expected to last from Wednesday evening through the weekend. The weather service said that after midday Tuesday, mountain travel would get more difficult, with the substantial snowfall likely causing lengthy delays.
The snowfall could also spell good news for ski resorts in the Lake Tahoe region, which were inundated with several feet of snow during an atmospheric river storm earlier this month.
“We’re thrilled with the upcoming forecast, and our teams are hard at work to prepare as far ahead in advance as they can,” said Sara Roston, a spokesperson for Vail Resorts. “Because we can’t predict exactly how much snow will hit the ground, or other conditions (e.g. wind), it’s hard to say exactly how our operations may need to react. Our teams remain focused on ensuring the safety of all of our guests and employees, making sure each resort is ready for skiing and riding.”
Despite the possible pitfalls, the rain is needed to help lift the Bay Area and state out of a devastating drought.
Recent “atmospheric river” storms have helped push rainfall totals well above normal. San Jose International Airport, for example, has received 4.85 inches since Oct. 1, the start of the water year. That’s 147% of normal for that time period.
San Francisco and Oakland international airports were at 206% of normal, having received 11.24 inches and 10.98 inches, respectively, during that time period.
This year could prove to be one of the top 10 wettest water years on record for San Francisco, which has already received 12.50 inches of rain since Oct. 1, according to the weather service.
The most recent deluge last week boosted California’s statewide snowpack from 19% of historic averages on Dec. 10 to 95% as of Monday, according to the National Weather Service’s California Nevada River Forecast Center.
“It’s nice to have a good mount of steady rain coming,” Murdock said. “The last few years, we only got to about 40% of average so seeing another good rain system going through, that’s a step forward but over the last few years we’ve been taking a few steps back. It’s a dent but it probably won’t be something that’s going to be a cure-all for us.”
Sentinel Assistant City Editor Donald Fukui and the National Weather Service contributed to this report.
