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Avalanche Forecast

Archived

Dec 18th, 2011–Dec 19th, 2011

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

Kootenay Boundary.

Confidence

Good - -1

Weather Forecast

Monday: Clear and sunny during the day becoming cloudy later on. Alpine temperatures around -6C, although mild local inversions are possible, raising alpine temperatures slightly. Light northwesterly winds. Tuesday: Light snow - around 3cm with moderate to strong northwesterly winds. Temps falling to around -10C. Wednesday: Dry and sunny. Light northerly winds. Temps around -10C.

Avalanche Summary

A small (size 1) avalanche was ski cut near Nelson on Saturday on a NW aspect at 2000m. The failure plane was approximately 15 cm deep.

Snowpack Summary

10-15 cm low density snow sits above a weak layer of well developed surface hoar. At present, the snow above this weak layer is not sufficiently deep and has not yet consolidated into a cohesive slab to set up the structure required for slab avalanches. Bear in mind, however, as more snow is added to the snowpack and the processes of settlement the uppre snowpack, the more likely slab avalanches become. We typically see dangerous slab avalanches start to occur when the depth to the weak layer reaches approximately 40 cm. Below the surface issues, the mid pack is strong. The basal snowpack layers are faceted. However, we have not had reports of instabilities affecting the lower layers in this area.

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.