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Avalanche Forecast

Archived

Feb 20th, 2022–Feb 21st, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal.

Soft snow will be vulnerable to the wind and sun on Monday. Watch for fresh wind slabs forming as strong outflow winds cross- and reverse-load atypical terrain features. Steep south facing slopes that don't see wind may be prone to solar triggered point releases.

Confidence

Moderate - Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

Sunday night: Clearing, light to moderate northwest wind, low of -12, freezing level dropping to valley bottom.

Monday: Sunny, strong outflow winds, alpine high of -10.

Tuesday: Increasing cloud, outflows easing to light northwest wind, alpine high of -8.

Wednesday: A mix of sun and cloud, moderate northwest wind, alpine high of -6.

Avalanche Summary

On Saturday, a remotely triggered size 2 was reported in this MIN. A few skier triggered size 1s and an explosive controlled size 2 were also reported.

During the storm on Thursday and Friday, avalanche activity was predominantly natural wet loose and wet slab avalanches size 1-2. Skier and explosive triggered storm slabs were also reported size 2.

 

Snowpack Summary

30-50 cm of recent snow has been wind affected at upper elevations. At mid elevations, it may contain a thin rain crust. Below 1300 m, a surface crust has formed over moist snow.

The recent snow sits over a 10-30 cm thick rain crust which effectively caps the underlying snowpack, making human triggering of avalanches on deeper weak layers very unlikely. However, cornice failures may still have potential to trigger these deeper weak layers, resulting in very large avalanches.

Terrain and Travel

  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.