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Avalanche Forecast

Archived

Feb 19th, 2022–Feb 20th, 2022

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

Regions

Northwest Inland.

Wind slabs likely remain triggerable in steep or convex terrain features and near ridgetops.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Saturday night: Mostly cloudy, a trace of snow, moderate northwest wind, freezing level dropping to valley bottom.

Sunday: A mix of sun and cloud, light northwest wind, high of -4.

Monday: Sunny, moderate northeast wind, high of -13.

Tuesday: Increasing cloud, flurries, strong northwest wind, high of -12.

Avalanche Summary

Natural and skier triggered wind slabs were reported up to size 1.5 on Thursday. On Friday, a single skier triggered size 1 wind slab was reported on a wind-loaded convexity near ridgetop at treeline.

Snowpack Summary

10-20 cm of recent snow sits over a 10-20 cm thick, supportive rain crust. At upper elevations the recent snow has been extensively wind affected, with exposed windward features scoured down to the crust. Below 1300 m, moist surfaces will refreeze as temperatures drop this weekend. 

The thick rain crust effectively caps the underlying snowpack, making human triggering of avalanches on weak layers deeper in the snowpack very unlikely. Large cornice failures may still have potential to trigger these deeper layers.

Terrain and Travel

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
  • 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.