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Avalanche Forecast

Archived

Jan 22nd, 2021–Jan 23rd, 2021

Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
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

Sea To Sky.

It is generally a good travel habit to minimize exposure to slopes with cornices overhead and stay well back of them when travelling on ridges. And it's an especially good idea on days like Saturday, when cornices are big and solar radiation is strong.

Confidence

High -

Weather Forecast

Friday night: Clear, light wind, alpine temperature -3, freezing level valley bottom.

Saturday: Sunny, light wind increasing to moderate northwest in the evening, alpine high -4 and cooling, freezing level valley bottom.

Sunday: Flurries up to 5 cm, light west wind, alpine high -9, freezing level valley bottom.

Monday: Flurries up to 10 cm, light northeast wind, alpine high -11, freezing level valley bottom.

Avalanche Summary

Explosive control work targeting cornices on Thursday produced size 1.5 results and did not trigger slabs in the slopes below. This indicates an improvement in stability since last weekend, when similar work produced size 2 results, some triggering deep slabs on the rocky slopes below. 

Earlier this month, we saw significant deep persistent slab activity, both natural and human triggered. Deep glide cracks have also been observed previously but appear to be holding together in the cool temperatures.

Snowpack Summary

Extensive wind effect in the alpine includes scoured windward aspects and hard slabs in lee terrain. As wind slabs facet and lose cohesion in the cold temperatures, they have become largely unreactive. A widespread surface crust exists below 1900 m and on south-facing slopes.

Remnants of a melt-freeze crust from early December may be found around 200 cm deep in the snowpack. In thin rocky snowpack spots, it still shows some propagation and collapse to moderate to hard loading in the most recent snowpack tests. In thicker snowpack areas it has shown no results, and appears to be trending dormant... for now at least.

Terrain and Travel

  • Minimize your exposure time below cornices.
  • Cornices become weak with daytime heating or solar exposure.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

Problems

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.