Hidden cavities of fresh, loose snow known as tree wells that separately killed two people on Mt. Bachelor in Bend last week are hazards most prevalent after snowstorms and can quickly turn fatal, an expert says.

Powder snow is often a welcome sight for skiers and snowboarders, but thrill can quickly turn to tragedy if people travel too close to trees while the snow is still loose, according to Mark Morford of Portland Mountain Rescue.

Tree wells form around the base of trees when low-hanging branches block snow from filling in. The voids are often hidden from view because of the tree branches, and can be several feet deep.

Skiers and snowboarders typically fall into the tree wells headfirst and land upside down or at a 45-degree angle, Morford said. Once inside, they can either suffocate from inhaling the powdery snow, or the snow can turn to ice around their mouths, blocking their breathing.

"It's not far off from drowning in water, and it can happen in minutes," Morford said. "Once a person gets caught in, it can be tremendously difficult to get out."

Authorities are drawing attention to the dangers of tree wells after the deaths of 24-year-old Alfonso Braun and 19-year-old Nicole Panet-Raymond on Mt. Bachelor on Friday.

Braun was discovered in a tree well in an expert-level area of the mountain around noon. He was pulled out and died about an hour later. Panet-Raymond was reported missing around 3:30 p.m. and was discovered about five hours later in a tree well in an intermediate-level area of the mountain. She was pronounced dead at the scene.

The Deschutes County Sheriff's Office said Panet-Raymond was found beneath 6 feet of snow.

Drew Jackson, a Mt. Bachelor spokesman, said the ski resort has had warnings on the dangers of tree wells on the snow conditions portion of its website for about three weeks. He said there are also signs at some tree-filled areas of the mountain telling riders to be on the lookout for tree wells and to not travel alone.

A patroller with the ski resort was at the top of the mountain Monday, checking on riders heading downhill to see if they were traveling with at least one other person, Jackson said.

"Skiing in the trees can be a safe and fun activity, but it's important for people to have a strong understanding of what could happen, and that's why being with another person is essential," he said.

Morford said if a person is riding alone, they should carry an avalanche beacon, a shovel and a snow probe in case they need to be rescued.

Once in a tree well, try to stay as still as possible, Morford said, because struggling could cause the snow around the stuck person to settle and further trap them.

Morford said people should try to dig out a pocket of snow around their mouths to allow themselves to breathe, or, if they can't move their hands, they should shake their heads to create a breathing space

.

If possible, a stuck person should try to grab a tree limb and hold on, Morford said. If the tree well is shallow enough and the tree limb is sturdy enough, a person may be able to pull themselves out.

If you're unable to move after creating a breathing space, wait for rescue, Morford said. Creating a breathing space buys time, he said, noting that it can take hours for hypothermia to be fatal.

-- Everton Bailey Jr.

ebailey@oregonian.com

503-221-8343; @EvertonBailey