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Avalanche Forecast

Archived

Apr 20th, 2022–Apr 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Moderate southerly winds have formed wind slabs that may remain reactive to human triggers on lee features at treeline and above.

 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 flurries; 5-15 cm (rain below around 800 m) / Moderate southeast wind / Low of -3 / Freezing level 1100 m.

Thursday: Cloudy with flurries; 3-10 cm (rain below around 1300 m) / Light south wind / High of 2 / Freezing level 1600 m.

Friday: Mix of sun and cloud / Light west wind / High of 3 / Freezing level 1800 m.

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

Avalanche Summary

Skier and snowmobiler triggered storm slab avalanches up to size 2 were reported on Tuesday. North and easterly aspects that had been loaded by the wind at treeline and above were the most reactive. See MINs Here and Here.

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

5-15 cm of new snow Wednesday night will add to the 35-55 cm of recent snow. Moderate southerly winds have formed wind slabs that may remain reactive to human triggers on lee features at treeline and above.

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 especially cautious as you transition into wind affected terrain.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Avoid exposure to slopes that have 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.

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.