It lasts a week “ice drought” In Northern California’s Sierra Nevada helped set the stage for Tuesday Fatal collapseAfter several feet of new snow falls on a previous layer, it becomes solid, making it unstable and easy to form, experts said.
New snow didn’t have enough time to bond with the previous layer before an avalanche near Lake Tahoe killed at least eight backcountry skiers, said Craig Clements, a meteorology professor at San Jose State University who has researched avalanches. Six skiers survived and rescuers were still searching for another skier who was still missing on Wednesday.
The group was on a three-day backcountry hike in the Sierra Nevada on Tuesday morning when they were trapped by an avalanche. Winter storm It hit the West Coast.
Clements said risks are generally highest in the first 24 to 48 hours after large amounts of snow fall, and authorities have issued avalanche warnings.
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When the weather is dry and clear, as has been the case in the Sierra Nevada since January, snow crystals change and can become angular or rounded over time, Clements said.
If new heavy snow falls on the crystals, the layers often cannot bond and the new snow forms what is called a storm sheet on top of a weaker layer.
“Because it’s on a mountain, it will slide” when caused by any change in tension above or below, sometimes naturally but also because of people crossing the area, Clements said.
Authorities did not say what caused the avalanche that occurred on Tuesday.
If snowfall had been more consistent throughout the winter, the different layers could have bonded more easily, Clements said. Even when a snowpack forms, the danger often only lasts a few days until the new snow settles, he said.
Although climate change could lead to extreme weather events including drought and heavy rainfall, it is difficult to determine how and whether it will affect avalanches or where they occur, scientists say.
Clements said this week’s avalanche is fairly typical of California’s Sierra Nevada, and he doesn’t think it can be linked to climate change.
He added that avalanches are a mechanism for measuring the amount of snow falling on weak or stable layers, and these avalanches were “an atmospheric phenomenon, not a climate phenomenon.”
Between 3 feet and 6 feet of snow has fallen since Sunday when the group began their journey. The area was also exposed to sub-zero temperatures and gusty winds. The threat is more than that, the Sierra Avalanche Center said Avalanches Wednesday remained and left the snowpack unstable and unpredictable.
Crews found eight bodies Backcountry skiers near Lake Tahoe, California, and were searching for another one after Tuesday’s avalanche, which authorities say is the nation’s deadliest in nearly half a century.
Six of the guided tour were rescued six hours after the avalanche.
Nevada County Sheriff Shannan Moon said on Wednesday that investigators would look into the decision to continue the flight despite the storm forecast.
On Sunday, the skiers traveled to remote huts at 7,600 feet (3,415 meters) in the Tahoe National Forest, carrying their food and supplies. At 6:49 a.m. that morning, the Sierra Avalanche Center issued an avalanche warning for the area, indicating the potential for major avalanches within the next 24 to 48 hours.
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