Huge turn in the waist powder in the backcountry

The snowfall this winter has been unusual, leading to a higher risk for avalanches in the U.S. and Canada. In the last two weeks alone, nine people have been killed in the U.S. and eight people (including two not yet found but presumed dead) in British Columbia, Canada.

Three U.S. deaths occurred in “safe” ski resorts, where the slopes are usually patrolled and fatal avalanches seldom happen.

Mark Moore, the director of the Seattle-based Northwest Weather and Avalanche Center, says the situation has made everyone very worried: this kind of problem has not occurred in ski resorts for many years.

Weathermen have described the unstable snow pack as similar to a brick resting on top of a pyramid of potato chips. The point is this: conditions are very dangerous.

The strange weather this winter has produced treacherous slopes covering an unusually broad stretch — Mammoth Mountain in Southern California to Mt. Baldy in Utah, to Crested Butte, Colorado to Jackson Hole, Wyoming and further northwards to Canada.

The first snowfall came in November, a comparatively dry month. Because the ground was still warm, the snow layer formed in large-grained molecules with cup-shaped facets that did not bond very well. The unusually thin layer of November snow was then covered by a thick layer of snow that came with fierce winter storms about two weeks ago. The thin layer was likely to crack easily under the weight of the heavier, wet December snow.

Another heavy snowfall, winter winds, or the added weight of people stepping on the snow — anything could easily set off the avalanche, which can move at speeds up to 80 miles per hour.

Ski resort operators are trying everything to assure safety on the slopes. Typically, the unstable snow may be induced to cascade safely down in a planned avalanche by setting off explosives — some dropped from helicopters, others fired by howitzers of Second World War vintage.

For intrepid skiers, though, the heavy snowfall speaks of fantastic skiing.

Safety Tips:

* Before heading out, check with the avalanche center in the locality (for directions, visit www.fsavalanche.com).

* Make sure to have a beacon, to transmit your location, and carry a shovel and probe for rescues.

* Avoid skiing into a potential avalanche path. This can have the following characteristics:

o Most (not all) avalanches happen during or soon after a storm, especially within the first 24 hours.
o Heavy snowfall, at least 1 inch per hour, produces a high risk for avalanches.
o Most (not all) avalanches occur on slopes of 30-45 degrees.
o The risk of avalanches increases when there are strong winds.
o In the middle of winter, north-facing slopes are more likely to slide than south-facing slopes.
o Leeward slopes are more likely to slide than windward slopes.
o Slopes with no trees are more likely to have an avalanche than forested slopes.