Bay Area storm snarls traffic and floods roads, but causes no major havoc

A pedestrian in downtown Oakland crosses the street during a rainstorm that hit the Bay Area on Friday April 6, 2018. A pedestrian in downtown Oakland crosses the street during a rainstorm that hit the Bay Area on Friday April 6, 2018. Photo: SF Gate / Douglas Zimmerman Photo: SF Gate / Douglas Zimmerman Image 1 of / 45 Caption Close Bay Area storm snarls traffic and floods roads, but causes no major havoc 1 / 45 Back to Gallery

A subtropical storm that forecasters dubbed a “Pineapple Express” doused the Bay Area on Friday, causing minor flooding, a few major accidents, widespread traffic snarls and a baseball rainout.

The tempest didn’t lay waste to any metropolitan areas like its Godzilla billing led some people to believe it would, but it dropped a heck of a lot of water for this time of year.

The storm, also known as an atmospheric river, began Thursday night, kept up a steady patter Friday and is expected to last through Saturday morning.

“I would say it is absolutely as advertised,” said Mike Pechner, a forecaster for Golden West Meteorology. “There has been a lot of rain.”

The waterworks caused 147 flights to be canceled at San Francisco International Airport on Friday. Yosemite Valley was closed to the public as the storm moved in, and the opener of a three-game series between the rival San Francisco Giants and Los Angeles Dodgers was rained out.

“Rainfall amounts are certainly above average for this time of year,” said Jan Null, a meteorologist with Golden Gate Weather Services. “It’s a big, long front stretching from here out to the Southwest.”

The deluge is being generated by what is left of Typhoon Jelawat, which originated in the Philippines. It swirled past Hawaii, coasted over the Central Pacific and settled over Northern California.

The storm concentrated its wrath mostly on the North Bay on Friday, but a secondary pulse is expected to pound the South Bay until about noon Saturday. An inch to 2 inches of rain fell in most areas of the North Bay on Friday afternoon, with parts of Marin, Sonoma and Mendocino counties seeing more than 2 inches by midafternoon, according to the National Weather Service. Northwest Sonoma County was expected to see around 5 inches of rainfall throughout the evening.

Nearly 5 inches of rain had fallen in towns along the Russian River. The coastal hills are expected to get as much as 8 inches of rain.

Forecasters said some daily rainfall records could fall.

Downtown San Francisco saw record-breaking levels of rainfall Friday. About 1.9 inches had fallen by 8 p.m., according to the National Weather Service, easily outpacing the record for April 6 — 1.28 inches — set in 1871. The city usually sees an average of 1.46 inches for the entire month. As much as 4 inches was expected to fall in San Francisco by night’s end.

The storm also forced the city’s Public Works Department to temporarily close the Great Highway’s southbound lane around 8:20 p.m. Friday.

Still, Null said, the rainfall totals are likely to be far below the record levels for a multiday storm. He said the two-day record in the city was set April 16 and 17 in 1853 when 3.59 inches of rain fell. The record for the month is 10.06 inches set in April 1880.

The torrent didn’t do much for the hopes of spring ski aficionados. Rain was reported at most of the ski resorts Friday and in the lower Sierra Nevada, raising fears of flash flooding.

Fortunately, the storm hasn’t wreaked too much havoc on communities around the Bay Area.

A handful of traffic accidents was reported by the California Highway Patrol, including a crash on Highway 4 in the Pittsburg area that injured at least two people and temporarily shut down eastbound lanes. The incident west of Willow Pass Road was cleared shortly after 7 a.m.

Some roads and low-lying areas were flooded, especially in the North Bay. More than two dozen roads were closed in Sonoma County due to localized flooding, landslides, erosion, and downed trees and power lines.

In San Francisco, an on-ramp to Interstate 280 at Sixth Street was under 6 to 8 inches of water, according to the CHP.

“We’ve never seen that before, so we think it might be due to a clogged drain,” said CHP Sgt. Rob Nacke. The on-ramp remained open.

There was also flooding on northbound Highway 101 in Marin County, just south of Lucky Drive. The road was open, said CHP Officer Todd Smith, but a flood advisory had been issued.

At San Francisco International Airport, nearly 400 flights were delayed or canceled, most of them short-haul flights along the West Coast, airport officials said.

“This is kind of a typical number for when we have weather, but this is more than a normal day,” said Dennis Zamaria, the duty manager at SFO.

In the Sierra, reservations for camp spots and other accommodations in Yosemite Valley were canceled Friday and Saturday nights.

Flash-flood watches were issued through Sunday on the western slopes of the Sierra, along the Carquinez Strait and in the Sacramento-San Joaquin River Delta. A flood warning was also issued in Portola (Plumas County) along the Feather River, which is expected to go above flood stage Sunday evening.

The storm is being called an atmospheric river because it formed as a long, narrow water column in the atmosphere over the ocean, like a river in the sky.

These types of storms can sprawl out over 1,000 miles and carry as much water as a Category 5 hurricane. When the vapor cloud hits land, the water falls. Most of the storms that hit California originate over Hawaii, which is why they are often nicknamed “Pineapple Express.”

The atmospheric rivers that hit California in the winter of 2016-17 caused flooding in San Jose that inundated hundreds of homes and caused Oroville Dam to overflow, creating a torrent that damaged the spillway and prompted officials to evacuate nearly 200,000 people downstream.

Officials with the California Department of Water Resources don’t expect any problems during the current storm, but said they might have to open the newly repaired spillway next week to accommodate all the runoff and snowmelt.

Chronicle staff writer Dominic Fracassa contributed to this report.