‘A Conveyor Belt of Storms’: Bay Area Braces for Rain, Snow and Potential Flooding

Back-to-back storms will bring widespread rainfall, potential snow at high elevations and a slight chance of flash floods across the Bay Area this week.

The storms will also drop a fresh blanket of pearlescent snow across the Sierra Nevada, according to the National Weather Service — giving a boost to the state’s snowpack, which has been hovering around average.

“We’re setting up for a conveyor belt of storm systems,” said Brayden Murdock, a meteorologist with the weather service’s Bay Area office.

In the Bay Area, forecasters expect the heaviest rain on Wednesday into early Thursday — up to an inch in populated areas and 2 inches at higher elevations, like Mount Tamalpais. There will be a slight chance of thunderstorms, as well as gusty winds and high surf.

While the coastal range could get up to 4 inches, meteorologists said the East and South Bay could see moderate to heavy rainfall on Wednesday, with gusts of up to 80 mph.

The early-week system could also cause minor flooding in areas with poor drainage systems, and the Weather Prediction Center forecasts a 5% probability of rainfall exceeding its flash flood guidance.

Murdock said snow could also fall at elevations above 2,500 feet in places like Mount Hamilton in the South Bay and the Big Sur coast.

“There could be some snow on those mountain tops, especially the highest of the high elevations for the areas to the south,” he said.

A second round of rainfall arrives Friday morning as a weak surface cold front extends from southern Oregon through the region. The storm will likely drop just as much rain as the first system.

By Sunday morning, forecasters expect a third storm to park over the Bay Area. Meteorologists said it is too early to tell how the storm will play out, but they expect multiple rounds of impactful rainfall, especially across the North Bay.

“We’re looking at a pretty wet environment into next week; maybe our first real break will be next Wednesday,” Murdock said.

During the first round of rain, Murdock expects only nuisance flooding. But as back-to-back storms hit, the flood risk may grow into next week, he said, “especially in urban environments — if there’s not enough of a break in between, it’s harder to drain that water out of those areas.”

Potential for the snowpack to rebound

Forecasters expect the first storm to drop up to 4 feet of snow at the highest peaks of the Sierra starting Wednesday. By Thursday morning, the snow line could drop to 2,000 feet as the system progresses.

A winter storm watch is in effect for much of the mountain region from 10 p.m. Tuesday through 10 p.m. Thursday.

“It’s an above-average snow event, but nothing historic for the Sierra,” said Dakari Anderson, a meteorologist with the weather service’s Sacramento office.

Snowfall in the Sierra on Wednesday will be thick, Anderson said, with up to 70% of rates exceeding 2 inches per hour. He also said the heavy snowfall and gusty winds of up to 60 miles per hour may likely create significant visibility issues and whiteout conditions.

Travel impacts are expected Wednesday into Thursday, and people driving to Lake Tahoe on Interstate 80 or Highway 50 could experience delays and chain controls.

“We expect snow-covered and slippery roads,” Anderson said. “The snow will be heaviest in the afternoon commute hours.”

Altogether, more than a foot of snow could fall in the Tahoe basin and several feet across the Sierra crests, said GiGi Giralte, a meteorologist with the weather service’s Reno office. She adds that the storms in the Tahoe area will drop more fluffy, dry snow than storms earlier in the winter.

At least two additional storms will add to the snowpack this weekend into next week, with snow in the foothills on Friday. As a result, Giralte said the best time to travel across the Sierra is before Wednesday afternoon or next week.

“We’ve got a lot of weather going on in the Sierra this week,” she said. “We could be seeing snowpack levels get back up to normal for the Sierra with this system.”

Courtney Carpenter, warning coordination meteorologist with the weather service’s Sacramento office, said all the snow over the next week is good news for building the snowpack.

“It’s a little bit of a miracle March good news for our Sierra snowpack,” she said.

Carpenter said the region is forecast to dry out by mid to late March with near-normal rain and snow conditions.