There has been some recent information resulting from new research into avalanche accidents by Bruce Temper, Director of the Utah Avalanche Center. These numbers are heavy, shocking and crucial. Please read them all, learn understand and use the information while on Avalanche terrain.
1). 47% of avalanche deaths occur when conditions are reported as ‘considerable’ Most weekend back country 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 US are now snow mobilers. With the development of high powered lightweight snow machines that are able to effortlessly glide over un-tracked snow, the number of snow mobilers heading into the back country is increasing each year. Route-finding, avalanche safety, and rescue skills are are every bit as necessary, and a combination of the sled’s weight and motor power can trigger weak layers in the snow pack. Many snow mobilers 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 back country 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 advanced 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 avalanche 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 kilimetres per hour (93mph). That’s a lot faster than the speed limit than the speed limit on our 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.