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Avalanche Forecast

Archived

Feb 19th, 2022–Feb 20th, 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.

Slabs may remain triggerable at upper elevations where dry snow has been wind loaded into leeward terrain features. Watch for signs of instability like cracking and recent avalanches.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Saturday night: Mostly cloudy with flurries up to 5 cm, moderate northwest wind, freezing level dropping to 500 m.

Sunday: A mix of sun and clouds with isolated flurries, light to moderate northwest wind, high of -2, freezing level 500 m.

Monday: Sunny, strong northeast wind, alpine high of -15, freezing level valley bottom.

Tuesday: Increasing cloud, light northwest wind, alpine high of -10.

Avalanche Summary

On Thursday and Friday, natural wet loose avalanches were reported up to size 2. Skier and explosive triggered storm and wind slabs were also reported size 2.

 

Snowpack Summary

30-50 cm of recent snow sits over a widespread 10-30 cm thick rain crust at all elevations. At upper elevations, the recent snow has been wind affected. At mid elevations, it may contain a thin rain crust. Below 1300 m, moist surfaces will refreeze as temperatures drop this weekend.

The thick rain crust beneath the recent snow 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

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be careful as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Start with conservative lines and watch for clues of instability.
  • Extra caution is needed around cornices under the current conditions.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.