Storm brings widespread flooding across Northern California; more rain on the way

The roaring “Pineapple Express” weather system that drenched the northern Sierra Nevada over the weekend has begun to ease, but forecasters warned Monday that it would soon be replaced by yet another storm and plummeting temperatures.

“It’s not over yet,” said Alex Hoon, a meteorologist in the National Weather Service’s Reno station. “The flooding concerns are going to start going down, but everything is going to get a little colder.”

The latest storm, the third in a series of weather events that have pounded the Sierra Nevada and swollen Central California rivers, could bring seven feet of snow in higher elevations and three feet at lower altitudes, according to the National Weather Service.

“Now our threat has changed again to heavy amounts of snow, blizzard conditions, white-out conditions and avalanche dangers,” Hoon said.

On Monday, the weather service issued a storm warning for Northern California, western Nevada and southern Oregon for Tuesday through Thursday. During that time, several feet of snow are expected to pile up in high mountain passes and valleys, forecasters said.

Already, the storms have boosted seasonal rainfall totals to levels not seen in years across California, and wreaked havoc on transportation arteries over the rugged Sierra.

With additional snow this week, some Sierra Nevada peaks could have received up to 20 feet of snow in the first two weeks of the year, Hoon said.

Lake Tahoe and Mammoth Mountain could receive up to 4 feet of snow by Thursday, and higher elevations could see twice that, Hoon said. The people who should be the most concerned are residents there and any unlucky motorist who has to drive across the mountains. Interstate 80 could be closed, as it was this weekend following a huge mudslide Sunday, Hoon said.

The overnight closure on the 80 was lifted Monday. 

Elsewhere in the state, the atmospheric river event caused widespread flooding, downed trees and unleashed mudslides.

“I mean, we’re in the heart of our wet season where these storms can happen,” said state climatologist Mike Anderson.

The storms have dropped enough water that Folsom Reservoir, among others, was forced to release water Monday for flood control, Anderson said. The back-to-back storms from last week and the weekend have also most certainly helped replenish depleted groundwater basins depleted from years of drought, though the full benefits of the rain won’t be known for some time, he said.

“We haven’t seen an event of this magnitude in at least a decade,” Anderson said.

The upcoming storm is colder than the weekend one, meaning it should add more to California’s snowpack, a precious water supply a third of the state relies on in the spring and summer months when it melts.

The Sierra Nevada snowpack statewide was at 126% of its average for this time of year on Monday, the California Department of Water Resources stated.

One of those areas hard-hit by the weekend storm was Yosemite National Park, which closed popular Yosemite Valley over the weekend in anticipation of the Merced River flooding. Though the waters did overwhelm the river, it wasn’t to the degree that park officials anticipated. Yosemite Valley will reopen to the public Tuesday morning, officials said.

On Sunday, hundreds of people were evacuated from their homes as rivers overflowed their banks. Several key highways including Interstate 80, Interstate 280, U.S. 395 and U.S. 101 were closed for periods because of hazardous conditions.

Authorities were trying to determine whether the deaths of three people in the Bay Area — one killed by a falling tree, two others by car accidents — were related to the storm.

In Sonoma County, emergency officials issued voluntary evacuation orders to hundreds of households along the Russian River and the Truckee River in Reno as the rivers reached the flood stage. 

The Truckee River topped its banks, submerging picnic tables on riverside campgrounds along Highway 89 north of Lake Tahoe. Forecasts from the U.S. Geological Survey called for the river to rise another 3 feet, imperiling private bridges to cabins alongside both banks.

Along the Russian River, about 650 homes and a handful of businesses in the low-lying areas of Monte Rio and Guerneville were advised to evacuate. County officials expected the river to reach flood stage late Sunday and stay at flood levels through Tuesday.

Ten homes in the Carmel Valley were partly flooded late Sunday after a river swelled from the heavy rain, authorities said.

Rising flood waters have also triggered actions to protect the town of Sacramento itself.

For the first time in a decade, the floodgates of the Sacramento River opened Monday morning, releasing a wall of water downstream into the Yolo Bypass. The National Weather Service warned farmers in that region of the Sacramento River valley to have livestock and farm equipment moved out of the way. The California Department of Water Resources last opened the gates of the manually operated weir, built in 1916, in 2005.

The low-level Yolo Bypass is one of several drainage areas designed to catch floodwaters in such situations, but is used for farming in dry years.

Perhaps most worrisome, the storm is one of a string that is expected to continue dumping more rain and snow through Thursday, part of a so-called atmospheric river of moisture known as the Pineapple Express.

“This is a serious situation," said Mark Faucette, a National Weather Service forecaster based in Reno.  “There's a significant threat to life and property as we go through the next couple of days with widespread flooding, continued road closures and high water in low-lying areas.”

Live updates on the storms »

The powerful storms are the latest in a series of weather systems that are beginning to make a dent in California's six-year drought.  

Officials said the drought still persists but that 2017 could mark a turning point if the deluge of rain and snow continues into the spring.

In Southern California, rain rolled in late Sunday and was expected to bring up to 2 inches of rain to Los Angeles County, disrupting the Monday morning commute. 

After a brief lull Monday afternoon, another storm is expected to roll through the Southland on Tuesday night and Wednesday, delivering up to half an inch of rain. That system will bring potential snowfall above 6,000 feet. A third storm late Thursday could bring snow as low as 4,000 feet and affect the commute in mountain passes, including Interstate 5 at the Grapevine.

The rainfall totals in Southern California over the weekend were less than in the northern parts of the state, but officials said that the speed of the downpour — up to a half-inch per hour — elevated the risk of flash floods and mudslides.

In Nevada, where Gov. Brian Sandoval issued a state of emergency, Washoe County officials asked residents to stay home Monday, when courts and several government offices were closed. Local high schools were quickly transformed into evacuation centers.

The storm toll included one of Calaveras County's oldest residents, a giant sequoia called the Pioneer Cabin for the tunnel that had been carved into its broad base 137 years ago. It was located in Calaveras Big Trees State Park and toppled Sunday during the storm.

"We lost an old friend today," wrote county resident Jim Allday, who posted a picture of the fallen titan on Facebook . His photos show the tree trunk splintered heavily at its base. The giant sequoias in the state park are estimated to be more than 1,000 years old.

As heavy rain fell Sunday, melting mounds of piled-up snow and sending water and slush into the streets of the eastern Sierra Nevada ski town of Mammoth Lakes, residents girded for flooding.

"My garage is flooding with 2 inches of water," said Nick Criss, 40, as he shoveled sand into bags at the town’s public works yard.

Criss, a 12-year Mammoth Lakes resident, worries that his home and many others will be damaged by the gush of rainwater and melted snow.

"There's nowhere for the water to go," he said.

Lifts at Mammoth Mountain resort were shut down Sunday because of high winds, thunder and lightning. They were reopened Monday, according to the resort’s website.