Avalanche experts are warning of the extreme dangers of unstable snowpacks following several deadly slides in the US backcountry.

These warnings follow a series of tragedies that underscore how quickly a recreational outing can become fatal. Understanding the triggers of these events is essential for survival in mountain wilderness areas.

In the Lake Tahoe region of California, a group of 15 people was swept away by a slide on a Tuesday. Reports on the death toll vary, with some sources stating at least eight people died [1], while others report nine fatalities [2]. Search and rescue teams recovered six people [2], and one person remains missing [2].

Similar dangers were documented in the backcountry of Anchorage, Alaska, in early 2025. In that incident, three skiers are believed dead [3] after being buried under snow nearly 10 stories deep [3].

Simon Trautman, a director for the U.S. Ski & Snowboard Association, said the window for rescue is small. "You have about 20 minutes to live," Trautman said [1]. This 20-minute mark is the critical threshold before the chances of survival are cut in half [1].

An avalanche occurs when three specific conditions align: an unstable snowpack, a slope steep enough—typically greater than 30 degrees—and a trigger [4, 5]. Triggers can include a single skier, strong winds, or additional snowfall [4, 5]. When these factors meet, the snowpack can no longer support its own weight, resulting in a sudden, massive descent of snow, ice, and rock [4, 5].

Experts emphasize that the combination of steep terrain and heavy winter snowfall creates the highest risk for these events [4]. Without proper equipment and training, victims buried deep in the snow have little hope of self-extrication.

“"You have about 20 minutes to live"”

The disparity in fatality rates between the Lake Tahoe and Alaska incidents illustrates that while burial depth varies, the time-to-rescue remains the primary determinant of survival. The reliance on a narrow 20-minute window means that without immediate peer rescue or advanced beacons, the probability of death increases exponentially regardless of the slide's scale.