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Archived

Avalanche Forecast

Dec 18th, 2011–Dec 19th, 2011
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

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.

Avalanche Problems

Wind Slabs

Winds shifted recently from SW to NW. As a result, watch for old wind slabs on north through east aspects and fresh wind slabs on east through south aspects.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2