Winter Safety: “A” is for Avalanche

November 7, 2016

By Forest McBrian

Photo at right: Ian Nicholson, a member of the professional observer team for Northwest Avalanche Center (NWAC), observes the condition of the snow near the Phantom Slide of Mt. Snoqualmie, Snoqualmie Pass, Washington. Photo by Dallas Glass


The word avalanche evokes the sinister, unpredictable side of the mountains, and for many it is the simple reason that hiking remains a summertime activity.

However, the sports of skiing, snowboarding, snowshoeing, climbing and snowmobiling are all growing in popularity — proof that Pacific Northwest winter enthusiasts are not willing to give up their love affair with nature during the months when the mountains are covered in snow.

Winter mountain recreation can be fun and deeply rewarding, yet requires skill and knowledge.

What is An Avalanche?

An avalanche is simply snow moving on the surface of the earth under the influence of gravity. Avalanches can be big or small, travel fast or slow, and occur in a variety of conditions. Often referred to as slides or sluff, they can happen anytime, even on sunny cold days or rainy warm spring mornings.

Movies and television shows often portray the main hazard of an avalanche as getting buried in an icy grave and suffocating. Snow traveling at high speeds is usually the consistency of liquid concrete mixed with trees and boulders, traveling through forest glades and sometimes over cliffs. Over half of avalanche fatalities in North America are due to blunt-force trauma rather than asphyxiation.

An avalanche below Liberty Bell in North Cascades National Park covers State Route 20. Photo by Cliff Schwab, courtesy of Washington State Department of Transportation

Where Do Avalanches Take Place?

Avalanche terrain typically occurs on snowy slopes with a 30-degree angle or higher. The slopes tend to be wide open, with few trees, hills or other obstacles to impede the movement of snow.

An avalanche “path” is often visible as a treeless swath down the side of the mountain. Many avalanche paths include a flatter area at the downhill end where avalanche debris continues to slide for a distance.

Most ski areas have avalanche terrain, and it is no coincidence that these are the type of slopes many skiers like to ride. But the snow on steep slopes in a ski area is controlled because ski patrol takes measures to all but eliminate avalanches in-bounds. It’s important to realize that outside the ski area boundary, and beyond human control, snow behaves differently.

Being able to identify avalanche terrain in the mountains is a fundamental skill taught in basic avalanche courses, and it helps outdoor enthusiasts stay in tune with the landscape.

When do Avalanches Take Place?

The timing of avalanches revolves around snow conditions, which are notoriously fickle. A snowy slope might be reasonably safe to travel in the morning and very dangerous in the afternoon. It all depends on the snowfall, wind speed and direction, temperature, and other less obvious factors.

Discerning stable snow from unstable snow is very difficult, sometimes even for the experts. When in doubt, it’s best to opt for safer terrain. Learning what constitutes “safer” in a given set of conditions is the hard part.

Where Can I Learn More?

Available throughout the winter and spring, local avalanche forecasts are produced by the Northwest Avalanche Center (NWAC), a cooperative effort of the U.S. Forest Service and a community supported non-profit.

To learn more about avalanches, attend a free, 1.5-hour Avalanche Awareness program sponsored by NWAC. For anyone planning to travel in avalanche terrain — and that includes anyone who skis, snowboards, snowshoes, snowmobiles, or climbs ice — the NWAC strongly recommends a three-day Level 1 avalanche course.


Northwest Avalanche Center:

Forest McBrian is the Education and Operations Manager at the Northwest Avalanche Center. An International Federated Mountain Guides Associations (IFMGA) certified mountain guide, he has climbed and skied with his guests in the North Cascades, Alaska, the Alps, and Norway. This article appears courtesy of the Northwest Avalanche Center.