High winds and blizzard conditions prompted travel warnings and road closures in the eastern Sierra Nevada on Tuesday as another powerful storm moved through Northern California.
The National Weather Service warned that the atmospheric river storm will generate high winds and heavy snow through at least Wednesday.
“Bottom line: Do not travel in the eastern Sierra,” the Weather Service’s Reno office wrote in a forecast Tuesday morning. “Life threatening blizzard conditions are occurring in places and will continue through Wednesday morning. The next 24 hours will be very active to say the least.”
The Weather Service warned that wind gusts of up to 60 mph “will create whiteout conditions along with heavy snow,” accumulating up to 10 feet of snow in higher elevations and several feet at lower altitudes.
Mono County law enforcement officials reported visibility at only 10 feet in some areas, according to the Weather Service.
The storm triggered a number of wind- and snow-related road closures.
That included a 115-mile stretch of U.S. Route 395 from Pearsonville north to Bishop closed because of high winds that were kicking up dust and limiting visibility.
That closure was lifted for passenger vehicles Tuesday morning, but high-profile vehicles still were prohibited from Pearsonville to Lone Pine, according to Florene Trainor, a Caltrans spokeswoman.
Authorities also closed U.S. 395 from a mile north of State Route 203, near Mammoth Lakes, to Bridgeport, because of whiteout conditions, Trainor said.
There also were fears of more flooding, with new warnings issued for the Napa, Russian, Eel and Sacramento rivers.
The risk and timing of flooding along state rivers is a matter of topography.
A relatively narrow waterway like the Russian River, which snakes between steep mountains and hillsides that shed rainfall quickly, poses a greater risk of immediate flooding, according to state climatologist Mike Anderson. Forecasters anticipate that the Russian River likely will flood again Wednesday, affecting hundreds of residents in Guerneville.
The Sacramento River, however — which is bigger and draws water from forests up to 100 miles away — rises more slowly in times of heavy rain.
“It takes three days for water from Shasta to get down to Sacramento,” Anderson said. “So even after we get past the storm, we want to manage the flood space because it’s going to take a few days for it to get through the system.”
Workers have been monitoring the state’s rivers around the clock since the weekend and will continue to do so until possibly Friday, said Doug Carlson, a spokesman for the state Department of Water Resources.
“We’re not going to take our foot off the pedal here,” he said.
By the end of the week, the total snow accumulation in the Sierra Nevada could reach 20 feet, the National Weather Service said. That would add greatly to the existing Sierra Nevada snowpack, which functions as a natural, albeit seasonal, storage reservoir for California water.
On Tuesday, the snowpack measured 135% of average for this time of year, according to the California Department of Water Resources.
“We haven’t seen an event of this magnitude in at least a decade,” Anderson said.
But the next rounds of storms will be colder, meaning more of the snow will stick. That’s good news for the state’s water-collection systems, which rely on snow remaining in the Sierra Nevada into the spring.
Residents, businesses and government agencies are now preparing for a whole different type of storm, even while they scramble to access and address the damage from the last onslaught.
Union Pacific Railroad tracks at Norden near Lake Tahoe were washed out by rain Sunday night, cutting off Amtrak passenger and freight trains into and out of California. A Union Pacific spokesman said the railroad expected to have the line reopened by Monday evening.
11:25 a.m.: This article was updated with travel warnings and road closures.
10:30 a.m.: This article was updated with a forecast of potential flooding.
This article was originally published at 8:20 a.m.