Avalanches are the dark side of winter. How can such beautiful landscapes--snow-draped peaks, shadowed cornices, sparkling alpine bowls--be so dangerous? How is it possible that an innocent excursion outside the ski area's boundary ropes to enjoy an afternoon of untracked powder can be a form of Russian roulette? For as long as people have lived in mountains, avalanches have been a problem, and avalanche danger has been something to try to understand, predict, and avoid. At ski areas, thankfully, the problem has been solved. Avalanches and avalanche awareness are the responsibility of the ski patrol, not of the individual skier. And these patrollers have paid their dues. They attend special avalanche courses. They study the weather, carefully plotting each winter's worth of wind, temperature, humidity, and snowfall on comparative charts. They spend hours digging snow pits, studying different snow strata under a glass. They are constantly studying, testing, learning ... and setting off avalanches, before they can trap skiers. American skiers are safe from avalanches, period. That is, as long as they stay within the ski boundaries and obey all the warning signs the patrol has put up.
But some skiers are particularly attentive to the siren call of adventure beyond the ropes. Ski areas occupy only a fraction of the skiable terrain in the West. And every season hundreds--no, thousands--of skiers succumb to the temptation of untracked slopes outside the ski areas. How to do this and stay safe? How to make sure you won't become an avalanche victim?
I'm going to share a few tips, rules of thumb that have kept me out of avalanche trouble in almost 30 years of mountaineering, skiing, and backcountry skiing. But first a caveat. Safety in the mountains, especially in avalanche country, is a matter of knowledge and judgment, not ignorance and luck. If you are interested in skiing away from ski areas into untracked, untamed, wild snow, then you too should start studying. Read a serious manual like the Forest Service Avalanche Handbook. Take an avalanche safety course that offers hands-on practice digging snow pits to analyze snow stability. (Such courses are offered in many mountain ski-resort communities; they don't cost much, and they can save your life.) Spend a few extra dollars to purchase the essential, minimal avalanche safety gear: transceiver radio beacons (or "beepers") for each skier, for the quick location of someone swept away in an avalanche; plus shovels and ski poles that double as probe poles. Learn how to use them, and don't leave them at home when you head off for an out-of-area ski adventure. In a word, don't rely on my advice or anyone else's when it comes to avalanche danger. Take the subject seriously, learn all you can, and develop your own backcountry judgment.
What I can tell you is this: Avalanche hazard is generally much higher in the dry, cold climate of the Rockies than it is in the damper, warmer climate of coastal ranges. A high hazard from brittle, ready-to-fracture slabs of snow can persist for weeks in the backcountry of Colorado or Wyoming. But in California's High Sierra, and in the ranges of the Pacific Northwest, acute avalanche danger is highest for 24 hours after a storm; it declines rapidly thereafter. Ski a few days after a storm and the odds, at least, are with you.
Perhaps the first rule of backcountry skiing is this: Don't ski it alone. Three skiers represent a minimum safe party. If you have doubts about a slope, ski it one at a time, with the rest of the group watching from a safe location. But if a slope really makes you nervous, trust your gut instincts; don't ski it. Hike back out, if you must, rather than ski a suspect slope when that little voice inside you is crying out: Don't do it!
Slopes 30 degrees or steeper are always suspect, but luckily there's an enormous amount of great skiing (most skiing, in fact) on slopes less than 30 degrees in pitch. Different ski areas have different policies about your using their lifts to get high on the mountain and then taking off for the backcountry; some facilitate it, some forbid it. Nowadays, for example, many Colorado ski areas have specially marked gates for skiers who want to exit the area and access the untracked, but also unpatrolled, national forest slopes beyond. If your thoughts are pulling you in that direction, I suggest you talk to a ski patroller first. Ask who is responsible for avalanche control at the area, and ask those patrollers about the backcountry conditions and snow stability. They'll know, and they'll tell you.
In winter, the greatest danger is from slab avalanches: consolidated sheets of snow that slide as a block on a weak underlayer. In spring, loose slides of wet, soggy snow from a point source are more common. In spring, too, the assessment of a slope's safety or risk is much easier. If the snow is firm enough for good skiing, it is probably safe from avalanches. When it gets soggy and unpleasant to ski in the afternoon--watch out!