Bruce Temper, Director of the Utah Avalanche Center, recently cited this avalanche information resulting from new research into avalanche accidents. These numbers are heavy, shocking, and crucial. Please read them all, let them soak in, and use this information when you are in avalanche terrain.
1. 47% of avalanche deaths occur when conditions are reported as “considerable.” Most weekend warrior backcountry skiers back off on their plans in avalanche danger points to high and extreme zones, but “considerable” conditions are harder to predict, and where almost half of all avalanche deaths occur. While the majority of ski tours that take place under these conditions will have a happy outcome, skills such as safe route-finding, keeping a handle on group dynamics, and knowing how to undertake a rescue and find buried victims is of paramount importance.
2. 49% of avalanche deaths in the U.S. are now snowmobilers. With the development of high-powered lightweight snow machines that are able to effortlessly glide over untracked snow, the number of snowmobilers heading into the backcountry is increasing each year. Route-finding, avalanche safety, and rescue skills are every bit as necessary, and a combination of the sled’s weight and motor power can trigger weak layers in the snowpack. Many snowmobilers utilize the same safety measures and carry the same technical gear (ABS-style “avalanche bags”, 457 kHz beacons, along with shovels, probes, and other rescue items) as backcountry skiers, but sleds can cover a lot of ground and generate a false sense of security.
3. 74% of all human-triggered slides occur on slopes between 34 and 45 degrees. Slopes in this range would generally be rated as upper intermediate or advance runs at a ski resort; in short, they’re the perfect pitch for powder skiing. Throughout the winter, snowfall will build up in layers with each passing storm. On steep slopes, fresh snow will slide during a storm and natural storm-cycle avalanches will reduce risk. On flat slopes, there simply won’t be enough pitch to trigger weaknesses in the layers. In this critical 34-to-45-degree zone, the weight of a passing skier or snowmobile will be just enough to cause a slope to collapse. Proceed with caution — even when in the trees.
4. Terminal velocity of an avalanche reaches over 150 kilometres per hour (93mph). That’s a lot faster than the speed limit on our provincial highways. If you think you can outrun an avalanche, well, you’re crazy. The air blast alone from the natural forces unleashed will knock you over and debris will almost instantly bury you.
5. Wind can deposit snow 10 times faster than actual snowfall from storms. Most weather systems involve both precipitation and high winds. Wind will drive snow into sheltered parts of the mountain in many different directions during a storm and deposit significantly more snow in places such as gullies and on leeward slopes.
Bruce Tremper Bio:
Bruce has been the Director of the Forest Service Utah Avalanche Center since 1986. Bruce grew up in the mountains of western Montana where his father taught him the basics of avalanches at the age of 10. After a successful 15-year ski racing career, he did avalanche control at Bridger Bowl Ski Area in Montana, earned a Masters Degree in Geology from Montana State University, studying under the well-known avalanche scientists Dr. John Montagne and Dr. Bob Brown. He then took over as the Director of Avalanche Control at Big Sky Ski Area in Montana and worked as a backcountry avalanche forecaster for the Alaska Avalanche Center. Bruce has been featured in a number of national and international television documentaries about avalanches including those produced by National Geographic, Discovery Channel and PBS as well as appearing on a number of national network news programs. Bruce wrote the book “Staying Alive in Avalanche Terrain,” published by Mountaineers Books, now in its second edition. – Utah Avalanche Center