Thirty people died in avalanches in the United States in 2023, making it a particularly deadly year. Heavy snowfalls and extended winter conditions across much of the country contributed to these numbers, but 27 people die in avalanches in an average year. Dozens more are injured. Many ski resorts purposefully trigger avalanches when conditions are dangerous in order to protect the skiers on their slopes, but no one purposefully triggers avalanches in the backcountry. Those who plan to recreate in the backcountry must be aware of conditions, have an understanding of snow science, and be prepared. 

First, a note on snow: snow falls when moisture in the air freezes and when the ground temperature is at or below freezing. Snowflakes themselves are flakes of crystallized ice, and snow on the ground is an accumulation of these packed ice crystals. The characteristics of this snowpack depends on a multitude of factors, including moisture content, temperature, depth, and weather. For example, in a storm with heavy winds the ice crystals tend to be smaller, broken up into bits that become more densely packed into drifts than they would on a still day, when the flakes fall in larger pieces and settle lightly. If snow remains on the ground the consistency changes through freeze-thaw cycles and it tends to grow more densely packed with time. Moisture content also affects the characteristics of snow. The Sawtooths tend to get a lot of dry snow, meaning it’s light and fluffy with a low moisture content and great for skiing! Moisture content of snow always depends on the storm and its duration, however, and sometimes we get heavy, wet snow, especially in warmer conditions in early winter or late spring. Think about how heavy snow can be to shovel some days when it seems lighter other days, or the difference between wet slush and light powder.

Where there is snow, there is avalanche danger. What changes are the conditions and likelihood of avalanche occurrences. Avalanches are usually caused by unstable snow conditions, which are in turn caused by weather, temperature, moisture content, and sun exposure–all of the factors that effect the characteristics of the snow itself. Snow is weighed down by gravity, so the more that piles up on a steep or vertical slope the more likely it is to succumb to gravity and fall. Gravity pushes the snow down into the ground, but also downslope. The steeper the slope, the more the gravity exerts downslope and the less stable the snow is. Avalanches can be triggered by movement, loud noises, wind, or rock and snowfalls.