Sierra bracing for extreme blizzard with 10 feet of snow, 100 mph winds

Sierra bracing for extreme blizzard with 10 feet of snow, 100 mph winds

There are few places in the United States that receive more snow than the Sierra Nevada, and that’s exactly where a “potentially life-threatening” blizzard is about to strike. A doozy even by Sierra standards, the massive winter storm is set to drop 5 to 10 feet of snow, which will combine with winds over 60 mph to bring about whiteout conditions.

Blizzard warnings have been hoisted for much of the Sierra Nevada, including the Northeast Foothills, Motherlode and western Plumas and Lassen counties above 2,000 feet in elevation. They cover ski resorts such as Mammoth Mountain and Palisades Tahoe, and stretch as far north as an area near Redding, Calif. Farther north, winter storm warnings blanket the high terrain.

While not exactly the result of an atmospheric river, the days-long winter storm will be caused by persistent Pacific moisture steered ashore by a slow-moving upper-air disturbance. Moderate to heavy snow will fall between Thursday and Sunday, with the worst conditions slated for Friday night, when winds will be the strongest.

The National Weather Service office in Sacramento warned that the storm will bring a dangerous combination of very strong winds and heavy snow that could damage trees and cause extended power outages.

“Mountain travel will be extremely dangerous to impossible, especially Friday,” it wrote.

(National Weather Service)

The Weather Service office in Reno, Nev., was even more stark. “Do not take this storm lightly,” it wrote.

“Whiteout conditions are very disorienting, so this is not the time to gamble with you or your family’s lives,” it said. It also warned of closed roads, air travel delays and cancellations, and an avalanche risk.

Coincidentally, the Sierra Nevada was under a blizzard warning exactly a year ago — but conditions are expected to be worse with this storm.

“This is a little different — it’s a lot heavier and a lot more snow,” Robert Baruffaldi, a senior meteorologist with the Weather Service in Sacramento, said in an interview. “If you’re living in the mountains, you could be snowed in for a week potentially. And if the power goes out, hopefully you have a lot of firewood.”

The setup

The bowling ball of high-altitude cold responsible for steering the jet stream and moisture into California. (WeatherBell)

Unlike atmospheric rivers, which are dense plumes of robust tropical moisture that can stretch thousands of miles, this setup is comparatively tamer from a moisture standpoint for California (just a minor atmospheric river will hit the Pacific Northwest and very far Northern California). In fact, the amount of humidity contained in the air isn’t exceptional — that’s why flooding isn’t anticipated at lower elevations such as the Sacramento Valley.

Instead, it’s a persistent flow of moisture curling east around a zone of low pressure at high altitudes. The upper-level low will meander east from offshore of Vancouver Island and come ashore over southern British Columbia.

Around it, the jet stream will dive and slice east, acting as a conveyor belt to pump the moisture into the mountains. This conveyor belt is moving so quickly that the moisture is constantly replenished. (Picture the factory scene from “I Love Lucy” — even though there aren’t many chocolates on the conveyor belt at any given point, it becomes overwhelming when the conveyor belt speeds up.)

The American GFS model simulates the jet stream racing overhead into California. (WeatherBell)

The mountains too will poke into the strong jet stream, meaning the high terrain will be subjected to very strong winds. That will whip the snow around and knock visibilities below an eighth of a mile, if that.

“There are only so many ways that we can say it will be treacherous to be traveling on the roads or even exiting your home during this time frame,” the Weather Service in Reno wrote. “Whiteout conditions are very disorienting, so this is not the time to gamble with you or your family’s lives, especially over a planned weekend ski vacation.”

The forecast

(National Weather Service)

Conditions will deteriorate during the day Thursday, becoming especially bad later Friday into Saturday, then easing Sunday.

Snow levels will initially hover around 5,000 to 6,000 feet, cold air drops in like a bowling ball, and snow levels will dip to between 3,000 and 5,000 feet Friday and perhaps 1,500 to 2,000 feet Saturday. The lowest snow levels will be found in northern regions, such as Shasta County.

Apropos to snow totals, the Weather Service in Sacramento is forecasting “5 to 10+ feet for elevations above 5,000 feet, with significant disruptions to daily life likely,” it wrote.

The Central Sierra Snow Lab, located at Donner Pass and operated by the University of California at Berkeley, wrote on X that it could see 7 to 9 feet of snow through Sunday and that it has a chance to post its snowiest day on record.

Most of the high terrain will see winds of 50 to 65 mph, with gusts of 125 mph or higher near ridge tops.

How this snow will help water resources

California precipitation since the start of the water year on Oct. 1, shown as a percentage of average, shows drier conditions for the Sierra Nevada compared to the coasts. (Western Regional Climate Center)

The Sierra snowpack is a reservoir for water, a precious resource in California. This year, the snowpack is running a bit below average.

That means the forthcoming blockbuster storm is welcome, considering the bleak start to this year’s snow season. Statewide snowpack was just 28 percent of normal Jan. 1. It’s now at 82 percent and climbing because of an active storm track directed into California during February. Multiple feet of new snow in the coming days could fully lift the region out of those deficits.

El Niño-fueled storms have largely targeted the coasts this winter. Some parts of coastal Southern California have seen nearly double their normal rainfall so far this year, along with damaging floods and mudslides.

This week’s bounty for the Sierra is the result of a much colder air mass combined with a storm track farther to the north. The latest outlooks suggest that the snowy pattern could continue at least into mid-March. Snowpack usually peaks around April 1, which marks the beginning of the melt season.

“The season has panned out really, really well compared to what it could have been,” Andrew Schwartz, lead scientist and manager of the Central Sierra Snow Lab, said in a briefing last week. “We have seen the snowpack really bulk itself up compared to those early-season numbers.”