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Clear signs of unstable snow

The snowpack often displays visible, palpable and audible signs of unstable snow. These are warnings that indicate potentially dangerous conditions exist:

  • Whumpfing (the sound of snow collapsing) and cracking, especially shooting cracks. This suggests thick weak layers and cohesive slabs are primed for avalanches, given a sufficiently steep and open slope.
View larger image Cracks shooting across a slope
  • Recent avalanche activity suggests that slopes with similar characteristics in terms of elevation, aspect, incline, shape, etc. that have yet to produce avalanches are likely to be unstable.
View larger image Widespread persistent slab avalanche activity | Photo: M. Rasiah
  • Hollow sounds or sensations, like you’re walking on a drum. This suggests thin hard slabs with very little underlying support, and can indicate a thin snowpack area, where triggering is more likely, on an otherwise well covered slope that can produce a large avalanche. Take a look around, and if there are exposed rocks or trees scattered about, then you are likely in a thin snowpack area.
  • Difficult travel because you’re breaking trough heavy surface snow into underling light snow, which can also be felt by probing with a ski pole, ice axe, etc. This is also known as “up-side down snow”, because light snow on top is the right side up for good riding, and can indicate wind slabs or storm slabs that are primed for avalanches.
Common triggers