Trio of Storms Line Up to Hit Bay Area. But Will They Bring Heavy Rain?

Updated 12:40 p.m. Friday

The Bay Area and Sierra Nevada could be in for several days of rain and mountain snow starting this weekend, but meteorologists said forecast models disagree on the intensity of the largest storm.

After two storms pass over the region from Saturday into Monday, there are at least three possibilities for a third system expected to settle over Northern California: no rain at all, light rain throughout the workweek, or intense rainfall from a building atmospheric river, which can dump precipitation like a firehose.

“We are seeing a signal that we could have some significant rain next week,” said Dial Hoang, a meteorologist with the weather service’s Bay Area office. “However, it is still very uncertain at this point.”

Hoang said part of what’s unknown is where the system building out of the Gulf of Alaska could park over California. While atmospheric rivers have inundated the region in recent history, the effects aren’t unilateral.

At this point, it’s too early to tell where the storm will make landfall. There is a chance for “the perfect conditions for very significant rainfall” in the Bay Area, but the heaviest rain could also veer more to the north or south, Hoang said.

There’s also the potential for minor urban flooding. With all scenarios still on the table, Hoang said people living in low-lying areas should prepare for the worst if the storm comes in on the stronger side.

Forecasters expect steady light rain on Sunday, totalling about a tenth of an inch. As much as a foot of snow could fall across the height of the Sierra — a promising sign for the state’s snowpack, which sits at 90% of normal for this time of year.

The state’s monthly snowpack survey took place Friday, four days earlier than normal, because of the potential atmospheric river next week.

Andy Reising, manager of snow surveys and water supply forecasting for the state Department of Water Resources, said this is the third year in a row that snowpack conditions at the start of April are near or above average for this time of year. Farmers and cities across the state rely on this frozen reservoir for water supplies as the snowpack melts in spring and summer.

“Our hope is that we’ll get a little bit more before this season ends,” Reising said. “While it’s positive news today, we know that our luck could run out, and we could fall into a drought anytime.”

With little to no break in rain, forecasters said Monday’s cold front is expected to bring heavier rainfall over a shorter period, according to the Bay Area office’s daily forecast discussion. Across the Sierra Nevada, there’s a “40 to 70% chance of at least seeing a foot of snow or more above 4,500 feet,” said Idamis Del Valle-Shoemaker, a meteorologist with the weather service’s Sacramento office.

Amanda Young, a meteorologist with the weather service’s Reno office, suggests winter sports enthusiasts head up the mountain on Saturday before the trio of storms begin.

“Sunday should be fine in the morning hours, at least in terms of travel if you’re coming off the mountain trying to get back down to your residence,” Young said.

The first two storms could drop as much as 16 inches of snow. Young said it’s too early to forecast potential snow accumulation for the third storm starting Tuesday.

“One model suggests the system is trending a little bit colder with a lot more snow potential,” Young said. “There’s really a lot of uncertainty with the system coming up midweek. This is one of those wait-and-see situations.”