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Avalanche Forecast

Archived

Apr 20th, 2022–Apr 21st, 2022

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, 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.

Regions

South Coast Inland.

Lingering wind slabs may remain reactive to human triggers below alpine ridgetops.

 Use ridges or ribs to avoid areas of wind loaded snow. 

Confidence

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

Weather Forecast

Wednesday night: Cloudy with isolated flurries (rain below around 800 m); 0-5 cm / Light southeast wind / Low of -5 / Freezing level 1100 m.

Thursday: Mostly cloudy with isolated flurries/ showers below around 1500 m; 0-3 cm / Light southwest wind / High of 3 / Freezing level 1800 m.

Friday: Mix of sun and cloud / Light northwest wind / High of 4 / Freezing level 1900 m.

Saturday: Mix of sun and cloud / Light southwest wind / High of 5 / Freezing level 1900 m.

Avalanche Summary

A small (size 1) wind slab avalanche that was remotely triggered by skiers below a ridgetop was reported on Tuesday. See MIN.

Additionally, a size 1.5 cornice failure was reported. The cornice did not trigger a slab on the slope below.

We currently have very limited avalanche observation data from this region.

Please consider posting your observations to the Mountain Information Network (MIN). Photos of current conditions and avalanches are the most helpful. 

Snowpack Summary

5-20 cm of recent snow and moderate southwest winds have formed wind slabs that may remain reactive to human triggers below alpine ridgetops.

The recent snow is sitting on a variety of hard snow surfaces, including crusts and wind scoured snow. Below this, there are several crusts in the upper snowpack, but they are unlikely to be a concern in most areas until the next significant warming event.

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Make observations and assess conditions continually as you travel.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.