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Avalanche Forecast

Archived

Mar 11th, 2023–Mar 12th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

Assess snow stability as you transition into wind-affected terrain and monitor how new snow is bonding to old surfaces.

Minimize time traveling on slopes below cornices. In shallow snowpack areas, a cornice fall could trigger a deep persistent slab avalanche.

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. No significant avalanches were reported since then.

Snowpack Summary

Snow arriving Saturday night and into Sunday will be falling on a sun crust on solar aspects. New and old wind slabs can be found near ridge crests in the alpine and treeline. These slabs sit on a variety of surfaces including sun crusts, facets, and previously wind-affected terrain. These recent winds have also formed large cornices. Around 20 cm of soft snow can be found in sheltered terrain.

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. This layer remains a concern in shallow snowpack areas.

Weather Summary

Saturday Night

Mostly cloudy, 5 to 10 cm accumulation in the northwestern sections, winds south 20 to 25 km/h, treeline temperatures -8 °C.

Sunday

Mostly cloudy, 5 cm accumulation, winds south 20 km/h gusting to 40, treeline temperatures -5 °C with freezing levels to 1300 m.

Monday

Cloudy, 10 to 20 cm accumulation, winds southwest 25 km/h gusting to 45, treeline temperatures -7 °C with freezing levels at 1200 m.

Tuesday

A mix of sun and cloud, trace accumulation, winds southwest 20 km/h gusting to 40, treeline temperatures -10 °C.

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.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Closely monitor how the new snow is bonding to the crust.

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.

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.