Loose dry avalanches, sometimes called point avalanches or sluffs, generally occur during or shortly after new snowfall and indicate that the new snow is settling and strengthening rather than forming a slab. They can be observed at all times of the year in the mountains, but happen most frequently during the winter snow season. They often fall as numerous small sluffs during or shortly after a storm, removing snow from steep upper slopes and either stabilizing lower slopes or loading them with additional snow. In the case of high mountain faces with large collection zones, a considerable amount of snow can be involved, leading to large, destructive wind-blast avalanches.
Although relatively small, dry loose-snow avalanches can easily dislodge you from a safe stance and take you for a ride over cliff bands or into a crevasse. Most winter ice climbers are familiar with fresh snow cascading down the climb from above; in these conditions you should be particularly careful when negotiating steep snow slopes between pitches. Snow falling from steep upper slopes can trigger persistent slab avalanches from the old snow layers.
Typical natural triggers are sluffs from steep ground above, rockfall and tree bombs. Loose snow avalanches are usually triggered at the point where the snow is initially disturbed (hence the term Point Avalanches). They can be triggered by riders or climbers traversing steep terrain and are often pulled loose when descending very steep terrain.
- Be cautious of sluffing in steep terrain until the surface snow has stabilized and be aware of terrain traps below.
- When descending large steep slopes, occasionally move across the fall line to avoid being caught by your own sluffs from above.
- Scramblers risk being carried over cliffs by small sluffs and ice climbers can be at risk from sunlit slopes above.