Avalanches in Colorado: How do they occur?

It's avalanche season in Colorado's high country, and with periods of warmer, dry weather between snowstorms, conditions are ripe for avalanches.

Several factors contribute to an avalanche, but the strength of the snowpack is at the core.

As snow falls in our mountains, it falls in layers. Each layer has different a different density, structure, and strength. The weaker the layers of snow, the more prone the slope is for an avalanche.

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The higher-risk slopes that are more prone to avalanches range from 35 to 45 degrees. Snow that falls on these slopes does not fall in slabs, rather it gradually slides. The slope's steep angle affects the gravitational force acting on the snow, which contributes to its movement when triggered.

Wind also contributes to the uneven distribution of snow on mountain slopes. The wind blows up the windward side, and down the leeward side of a mountain, and as it blows it carries some snow with it. That snow will unevenly fall on the leeward side which can weaken the snowpack.

Weather conditions play a critical role in the formation of an avalanche. Rapid changes in temperatures, especially warm temperatures can cause melting, which will weaken the snow layer. That melt can then re-freeze, and with more snow falling on top of that, the strength of the snowpack is further compromised. With the longer periods of dry and warm weather between snowstorms in the high country so far this season, the strength of the snowpack will be weaker.

An avalanche can be triggered by several different factors, including temperature changes, heavy snowfall, or human activity. Skiing, snowboarding, snowmobiling, or even the vibrations from construction and machinery can trigger an avalanche.

If you do plan on doing any backcountry skiing, snowboarding, or snowmobiling be sure to check for cracks in the snowpack and try to focus on areas that didn't receive that early-season snow. Avalanches are more common after a recent snowstorm, so if the weather has fluctuated between dry and warm to a snowstorm, be very mindful of where you choose to ski and snowboard.