Tree wells claimed two lives at Whitefish Mountain Resort within 10 days of each other, causing skiers, snowboarders, and resort officials to assess ski habits. The deaths are two of five tree well fatalities in North America this winter and a sobering start to a winter of big snows.

A 29-year-old male snowboarder died after falling into a tree well Jan. 8 at Whitefish Mountain Resort. A 16-year-old male skier was found buried in a tree well Dec. 29 and died four days later when taken off life support. Both had been cruising the off-piste trees alone. 

Tree well deaths stand in a class by themselves known as Non-Avalanche Related Snow Immersion Deaths (NARSID). In short, a skier or snowboarder falls upside down in the soft, loose snow at the base of a tree and suffocates.  

Over the holidays, tree wells claimed the lives of a 29-year-old male snowboarder at China Peak Resort, Calif. and a 32-year-old female snowboarder on a snowcat trip at Retallack Lodge, B.C. A 20-year-old male snowboarder found dead in a creek on Dec. 25 at Whistler Blackcomb was trapped in an inverted position after falling in deep snow. His death is classified also as NARSID. Several other deaths were originally reported as tree well fatalities, such as a female snowboarder at Alpine Meadows, but findings later revealed other causes.

"The number one danger with this type of accident is that the risk is completely under-appreciated," Paul Baugher, director of Crystal Mountain Ski Patrol, told OnTheSnow. Baugher, who has been researching NARSID incidents, has formed a North American database of trends going back to the 1970s.

"About every four or five years, we have a spike of five or six tree well deaths in the U.S.," said Baugher. "It correlates well with deep snow winters." U.S. tree well fatalities currently stand at three for the 2010-11 season. In many years, NARSID accounts for 10 percent or more of the annual average U.S. ski resort fatalities. Most are skiers, but Baugher has watched the snowboarder numbers climbing.

"If this is one of these big years, it's conceivable we'll have a couple more this year," he added.

La Nina winters with their prolific snow across much of the West aid in turning tree wells into death traps. "The key ingredients are deep snow and unconsolidated snow. Those make the tree wells deadly," explained Baugher. "The coniferous forests of the West promote this trouble. Whoever's got lots of good gladed tree skiing and lots of big deep snow will have the risk factors go up."

Survival for tree well victims is slim. NARSID deaths involve falling head first into the tree well or inverting like a lawn dart into loose snow. Suffocation happens within 20-50 minutes, according to the anecdotal information Baugher has collected. "But I would suspect in most cases it's even shorter than that, perhaps even 10-to-15 minutes," he said.

Baugher experimented with burying people upside down in loose-packed snow to explore techniques to see if skiers could extract themselves. He learned a startling fact: Once the victim struggled to get out, the snow packed in more tightly around the face. "That's why partners have to be in position to come to their aid," he said. "You may even have to struggle back up the hill in deep snow and get them out."

Skiers and snowboarders can avoid tree wells by staying on groomed runs. But for many, the thrill comes from plunging through powder pillows off piste. Baugher recommends skiing with a partner as the number one way to mitigate risk. Most NARSIDs in his database got separated from their ski buddies or skied alone. "But the thing about partners is that they have to keep each other in sight," he said. "Lose sight of your partner, and you may lose your friend."

Baugher equates the danger of being caught in an avalanche when using lifts to ski outside ski area boundaries as the same as NARSID deaths. But he points out the irony that most skiers going out of bounds take precautions, but not when skiing inbounds. "When you leave the piste inside the ski area, nobody thinks the same as if going out of bounds," he said.

So what advice does Baugher give besides skiing with a partner? "Ski in widely spaced trees, look in between the trees rather than at the tree, and remove pole straps to avoid getting immobilized in the snow," he said.

Other safety tips are available online. They are provided in collaboration with the NW Avalanche Institute, Mt. Baker Ski Area, Crystal Mountain, and Dr. Robert Cadman.

Get educated about tree wells, deep snow, NARSID, safety, and prevention of accidents if you ski or ride off groomed runs.

More information.