Which statement best describes the timing statistic that 90% of human-triggered avalanches occur?

• A. They Happen During a Storm
• B. They Happen During or Within 24 Hours After a Storm
• C. They Happen At Night
• D. They Happen Only With Large Storms

Answer: (B)

The timing being tested is when human-triggered avalanches are most likely to occur, and the best answer shows that risk peaks during a storm and continues for about 24 hours after it ends. Storms load the snowpack with fresh snow, wind-deposited slabs, and sometimes rain or warming, creating unstable conditions and weak layers beneath the surface. This combination makes slopes prone to failure as the added weight stresses slabs that haven’t bonded well to the layers beneath. The highest danger window isn’t just the storm itself but the immediate day after, when the new snow is still accumulating and settling, and the weak interfaces are most vulnerable. After roughly 24 hours, conditions often begin to stabilize as the snowpack bonds and stresses redistribute, though new storms or warming can renew the risk. The other options don’t capture this critical timing pattern: storms create the loading and instability, but the risk isn’t limited to night or to only very large storms.