A powerful atmospheric river storm that drenched the North Bay for two days in a row and set rainfall records moved south Friday, bringing steady rain starting around mid-day that was expected to soak the entire Bay Area and Santa Cruz County until Saturday morning.
The National Weather Service issued a flash flood warning for the city of San Francisco as the storm stalled, warning that potentially “life threatening” conditions could be in effect until 6:45 p.m. Friday due to quickly rising creeks, and flooded roads due to backed up storm drains. The agency issued a similar flash flood warning in Northern San Mateo County from Daly City to Pacific until 5 p.m. and in Oakland, Berkeley and Richmond until 6 p.m. Friday.
And it issued a flood advisory for southern San Mateo, northern Santa Clara and Santa Cruz counties until 12:30 a.m. Saturday, telling the public to be alert for flooded roads and fast-rising creeks.
As San Francisco International Airport, roughly 500 flights were delayed by late Friday afternoon — about a third of all the flights — and more than 60 were cancelled. Oakland and San Jose’s airports also saw a combined total of nearly 100 delayed flights with only a handful of cancellations.
“The rainfall rates have increased, and the rain band has slowed down,” said Brayden Murdock, a meteorologist with the National Weather Service. “There’s plenty of rain out there and plenty more to come.”
Murdock said that by mid-day Saturday, when the storm is expected to finally move through the area, San Francisco was forecast to receive 2 to 3 inches of rain, the East Bay 2 to 3 inches, the Peninsula 1 to 3 inches, and San Jose 1 to 2 inches. Parts of the Santa Cruz Mountains could see as many as 5 inches of rain, he said.
Because of its duration and the amount of moisture in it, the atmospheric river that began in the North Bay on Wednesday was ranked as a 4 on a scale of 1 to 5, with 5 being the strongest, according to the Center for Western Weather and Water Extremes at UC San Diego.
In Sonoma County, Santa Rosa was hit particularly hard. The city received more than 7 inches of rain Wednesday and totaled 12 inches over the 72-hour period ending at 2 p.m. Friday.
That total not only equals more than one-third of the city’s average yearly precipitation of 32 inches in just three days, but also comes after the city saw the highest two-day rainfall total, 9.74 inches, for any month since records began there in 1902.
Flood warnings remained in effect Friday in most areas of the North Bay.
Starting Saturday and through the weekend, the weather should return to a more normal pattern, experts said, with occasional light rainfall through Thanksgiving.
“There will still be some scatted showers over the weekend, but there will be a lot more time without showers than with showers,” said Jan Null, a meteorologist with Golden Gate Weather Services in San Francisco. “Any place could get a random shower, but there aren’t going to be big amounts of rain associated with it.”
The storm created havoc across the region Friday, however.
After a slow start in the morning, heavy downpours hit many communities. Streets flooded in the Marina District of San Francisco. Two lanes were blocked on I-280 near Daly City due to flooding.
The National Weather Service issued a wind advisory until 10 p.m. Friday throughout the Bay Area with gusts expected up to 50 mph. Along the coast, there was a gale warning, with seas expected to 13 feet.
The weather caused gutters to overflow and roofs to leak.
“When the rains come you get a lot of phone calls about leaks,” said Shimon Elmadawi, owner of Apollo Roofing Company, based in Walnut Creek. “It’s a big wake-up call for anyone who needs to replace their roof.”
Roofers don’t work in the rain, he said, because its too dangerous. He recommended that homeowners who find leaks place a bucket underneath, use a screwdriver to poke a hole in the drywall at the leak so the damage doesn’t spread, and take photos to document the problem.
“Definitely don’t step on the roof when it is raining,” he added. “When there’s wind and storms like this, it’s a big risk.”
The weather service issued a winter storm warning for the Sierra Nevada, through Tuesday with up to 2 feet of snow possible above 6,500 feet, and 4 feet at higher elevations. The CHP required chains for vehicles driving over Interstate 80 between Truckee and Kingvale. Winds were expected to reach 50 miles an hour, and a staggering 125 mph over the highest Sierra peaks, the weather service said.
Most Bay Area creeks and were not in danger of flooding, since the storm was the first significant rainfall of the winter season.
“We are monitoring the creeks in case the storm sits on us or ends up bringing more rain than forecast,” said Matt Keller, a spokesman for the Santa Clara Valley Water District. “We expect it to be a regular storm.”
Keller said crews from the water district had been out for the past several days removing logs and other debris from creeks to reduce backups that could cause floods.
The one significant flood risk in the 9-county Bay Area came along the Russian River in Guerneville, where a stunning 22 inches of rain had fallen over the past 72 hours in the hills. Since Wednesday, the Russian River had risen from 5 feet to 30 feet, and was expected to crest at 34 feet at 4 a.m. Saturday. That’s the highest level in 5 years, but still far short of the all-time record of 49.5 feet set in 1986. Moderate flooding was expected in some of Guerneville’s most low-lying areas.
In the Santa Cruz Mountains, an area that also historically receives large amounts of rain, by Friday afternoon there were no reports of flooding, mudslides or other mayhem.
“We might get 4 or more inches by Saturday,” said Jason Hoppin, a spokesman for Santa Cruz County. “Our stream beds can absorb that much water without a problem this time in the season. So far, so good. There will be more this winter. I’m sure we’ll get our fair share.”
