Avalanche conditions: 'It's precarious'

After an unusually long mid-winter thaw compacted the season's early snowpack in the mountains, a steady stream of storms has piled up several feet of newer snow that could pose an avalanche hazard to backcountry travelers.

Potential problems can exist on any snow-covered slope, but some slope and snow conditions present greater potential danger.

Gabe Chladek, of Three Sisters Backcountry, lives in Sisters and operates the facilities for the Oregon Avalanche Institute and is a member of the American Avalanche Association. He routinely guides local backcountry experiences and is a certified avalanche course leader.

"I just came off a four-day course on Tam (McArthur) Rim," said Chladek last week during a brief stopover in the civilized world. "We saw several avalanches naturally release, and the avalanche danger is very high right now. Since mid-February, it (the snow) has been really, really active. Probably 10 feet of snow at the upper elevations, and the storm layers aren't bonding well."

That is the big indicator that avalanche watchers key in on. If different layers from different snowstorms are not sufficiently melded, the layers can more easily separate and slide apart, causing an avalanche.

Forest Service Trails Specialist Chris Sabo recently issued a bulletin for the Deschutes National Forest stating: "Backcountry travel in avalanche terrain warrants a word of caution! Buried ice layers, and the possibility that bonding between the new snow and hardened ice is weak, is a heads-up to backcountry snow riders."

Chladek explained the situation in more detail.

"Each one of those (snowstorms) occurs with different conditions, and the snow has different properties. Most of what we have now are characteristics that are not bonding well; so, we have a number of layers that are not bonded."

While an avalanche can occur on any slope, they more frequently occur on slopes between 25 and 65 degrees, with the most common range between 30 and 45 degrees. Less steep slopes can be more stable, and extremely steep slopes may slough snow continually, preventing large build-ups of snow. Still, whenever the danger of avalanche exists, Chladek recommends staying away from all slopes in excess of 30 degrees.

Trevor Miller is the president of the Central Oregon Avalanche Association and keeps a close eye on snow conditions at this time of the year.

"The avalanche environment is one that is ever changing," he said. "Hour by hour, day to day, risk and danger can change. It is important for backcountry users to have a working knowledge of indicators of avalanche danger and heed those signs on any particular outing."

Miller observed that, while many mountain communities have avalanche forecast centers, Central Oregon does not. As a result, he says, "it becomes even more important for users to have a good understanding of avalanche principles and rescue and carry the right tools - beacon, probe, shovel - and know how to use them if traveling in or through avalanche country."

It is also important for backcountry travelers to learn to recognize potentially dangerous situations. A convex contour on a slope profile can make the area more avalanche prone, while a concave surface may have the opposite effect.

In addition to slope, wind and snow conditions can play a big role in setting the stage for avalanche danger. For example, windswept slopes may be less prone to avalanche if falling snow is carried away. At the same time, when that snow is blown and transported to the lee side of a slope, even more snow may accumulate in those locations, exacerbating already unstable conditions.

Backcountry users should be alert to changing conditions and learn to recognize signs that lead to avalanches.

"Lots of variables are at play in the mountains this time of year," said Miller. "Fluctuating temperatures, new snow, lots of wind...all of which play a role in changing conditions and avalanche risk."

One sure method of developing avalanche savvy lies in recognizing areas where avalanches have occurred before. A steep slope, swept clean of trees, can be a likely sign of past and future avalanche activity. Areas studded with trees or rock outcroppings are indications of areas that are better equipped to anchor the snow in place.

The Forest Service reports that wind-transported snow loading has been a significant factor in recent days. Sabo reminds backcountry users to be responsible for their own safety and that of others. He stressed that travelers should also learn to make their own careful snowpack evaluations and safe route decisions. Whenever avalanche danger is high, travel is better directed to low-angle terrain that is also away from avalanche path runouts.

Offices of the Deschutes National Forest Service offer a free brochure entitled "Basic Principles to Avoid and Survive Snow Avalanches." At a minimum, winter backcountry users should be familiar with those principles. The brochure is available locally at the Sisters Ranger District office.

Websites for the American Avalanche Association (www.americanavalanche

association.org) and the Central Oregon Avalanche Association (www.co

avalanche.org) can also provide useful information and links to other sources, including opportunities for avalanche courses, such as those offered by instructors like Gabe Chaldek.

"It's been an interesting winter," said Chladek. "It's kind of precarious out there right now, so good judgment is really important."