U.S. Forest Service Avalanche Ranger Eric White patrols the backcountry outside Mount Shasta, Calif. White and other avalanche rangers produce the avalanche danger warnings posted regularly on the Internet and at ranger stations.

Avalanche ranger Eric White digs a snow pit.

Jim McCarthy was about a dozen turns into his backcountry powder run when he heard a low rumbling sound and saw the slope above him begin to move.

He had slowed to check on the skiers in his party behind him, but in no time at all found himself neck-deep in snow, shooting downhill, desperately swimming with his arms to keep his head above the snow.

“Time seemed to slow down and my mind sped up. I thought I was about to die, and blamed myself for ignoring the warning signs,” McCarthy wrote in a report for the U.S. Forest Service. “I could have avoided this avalanche, but instead I had chosen the risky thing. Now I was watching my own death come at me in slow motion.”

McCarthy survived the 2005 avalanche in the Trinity Alps Wilderness of Northern California, but he was lucky.

With unusually deep and unstable snowpacks in many areas of the country this winter, and more skiers and snowmobilers hungry to make fresh tracks, 30 backcountry users weren’t so fortunate this avalanche season. The 30 avalanche deaths have this season nearing the record of 35 from the winter of 2001-02.

Often the victims – even those with training, equipment and experience – ignore the danger signs.

Rangers on alert

Forest Service avalanche rangers regularly ski into the mountains, dig snow pits and gather detailed measurements on snow depth, density, temperature, and stability that go into their avalanche warnings posted daily on the Internet, outside ranger stations, and at trailheads.

“Avalanches don’t just happen randomly,” said Eric White, a ranger based in Mount Shasta City, Calif., who patrols the Shasta-Trinity National Forest. “In about 90 to 95 percent of avalanche accidents the victim or someone in their party starts the slides. Because of that, if we can learn a little about avalanches and hone some of the observation skills we can travel more safely.”

According to statistics kept by the U.S. Forest Service National Avalanche Center in Ogden, Utah, eight deaths this winter were in Washington, five in Colorado, four each in Wyoming and California, three each in Montana and Utah, and one each in North Dakota, New Hampshire, and Wyoming.

Nine were snowmobilers, eight skiers, six climbers or hikers, five snowboarders, one snowshoer, and one was shoveling off a roof.

Doug Abromeit, director of the National Avalanche Center, has no solid figures on how many people ski and snowmobile in avalanche country, but figures the number is rising, because manufacturers are selling more gear, trailhead parking lots are full, and there are new magazines dedicated to backcountry skiing.

So what’s driving the boom?

“These days you are lucky to get one untracked line at a major ski area,” Abromeit said. “Two, I think there’s just the adventure of getting away from crowds, getting out on your own, ski mountaineering.”

More snow, too

And there has not only been a lot of snow, but it has fallen under conditions that have made it unstable in many regions, he said.

Avalanches occur when a cohesive slab of snow – think of cement – separates from an unstable layer of snow below it – think of a pile of potato chips – on a steep slope. They can be triggered naturally when the weight of the slab reaches a critical point, or by the weight of a skier or snowmobile.

To find that unstable layer, White digs down about four feet into the snowpack on a steep untracked slope overlooking a mountain lake in the Shasta-Trinity National Forest. He takes temperatures every six inches or so, looking for differences. He also cuts through the snow with a plastic card, feeling for changes in resistance, and pokes the snow layers with his fingers and fist. He takes samples at different levels and weighs them on a fish scale, and notes the size and shape of the snowflakes.

Finally he takes his snow saw and cuts out a big block of snow uphill from his pit, climbs onto it with his skis, and jumps up and down with increasing force until it breaks. It’s an avalanche test called the rutschblock, after the German word for slide.

An eye on flakes

New methods are being developed.

Mark Stoelinga, an assistant professor at the University of Washington, has a team of researchers in the Cascades who go out in snowstorms with microscopes to document what kind of snowflakes are falling every 15 minutes through the storm. He wants to see if the shape of the snowflakes – there are 80 different kinds – is a factor in avalanche conditions.

Avalanches rarely happen in ski areas, because the ski patrol controls them with explosives, White said. Most victims are skiing out of bounds from a ski area or head into the backcountry with at least some of the gear and training they need to be safe.

The problem, said White, is people are often so excited about new snow that they ignore the five classic danger signs: recent avalanches, “whoomphing” sounds or shooting cracks coming from the snow while moving along moderate slopes, recent or current heavy snowfall, high winds that pack snow into slabs on lee slopes, and rapidly warming weather or rain.

McCarthy, an environmental activist from Portland, Ore., sheepishly counts himself among those who ignored the signs.

When he went skiing with a group of friends on Jan. 9, 2005, in the Trinity Alps Wilderness of Northern California, he had read books on avalanche danger, and carried a beacon so he could be found in the snow, plus a probe and shovel to find others.

“It was a big powder day, and we all let ourselves be convinced it was safe,” McCarthy wrote in a report for the Forest Service.