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Avalanche Forecast

Archived

Mar 8th, 2023–Mar 9th, 2023

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

Regions

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Lingering wind slabs may remain reactive to human triggers on a variety of aspects in the alpine.

Avoid travelling on slopes below cornices.

Confidence

Moderate

Avalanche Summary

A cornice triggered size 1.5 wind slab avalanche was reported on a northwest aspect in the alpine in the Duffey zone on Tuesday.

Additionally, there was a MIN report of a size 1 skier triggered loose dry avalanche in the alpine.

Snowpack Summary

Cornices are large and may fail with daytime heating.

Sun crust on sunny aspects. Recent southeasterly winds formed wind slabs on numerous aspects at treeline and above. These slabs sit on a variety of surfaces including sun crusts, facets, and previous wind effect.

The mid-snowpack is well consolidated.

This is not the case for the lower snowpack. There is a widespread weak layer of large sugary facets at the bottom of the snowpack. Recent avalanche activity on this layer has been confined to northern parts of the region in the Chilcotins.

Weather Summary

Wednesday Night

Clear skies / Light southeast ridgetop wind / Low temperature at treeline -11 C / Freezing level valley bottom.

Thursday

Mix of sun and cloud / Light southeast ridgetop wind / High temperature at treeline -3 C / Freezing level 1100 m.

Friday

Cloudy with isolated flurries; 0-3 cm / Moderate southeast ridgetop wind / High temperature at treeline -4 C / Freezing level 900 m.

Saturday

Mix of sun and cloud / Light southwest ridgetop wind / High temperature at treeline -2 C / Freezing level 1100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Avoid exposure to slopes that have cornices overhead.
  • Be alert to conditions that change with elevation and sun exposure.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.