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Archived

Avalanche Forecast

Dec 28th, 2011–Dec 29th, 2011
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Kootenay Boundary.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Wednesday night: 10-15cm. Moderate to strong west to south-west winds. Freezing level lowering to 1300m.Thursday: Light snowfall. Light-moderate north-westerlies. Freezing level around 900m.Friday: Moderate to heavy snow. Strong south-west winds. Freezing level around 1000m. Saturday: Light flurries. Cooling temperatures. Light north-westerly winds.

Avalanche Summary

We are now in an avalanche cycle with numerous natural and human-triggered avalanches occurring, reported as up to size 2.5. Many of these are failing on the mid-December surface hoar, mostly on north through east aspects from 1500m to the peaks. A skier remotely triggered an avalanche from 50m away and in many places shooting cracks and whumphing are further indicators of a very touchy, unstable snowpack.

Snowpack Summary

The snowpack is in a very touchy state. 30-50cm of storm snow has built up over a weak old snow surface. The storm snow has turned into a soft slab due to warming. South-west winds have led to the development of wind slabs on lee slopes. The surface hoar layer buried in mid-December is now under 45-70cm of snow and is highly reactive. It is well-preserved with 10-15mm crystals and exists into alpine start zones (although it's probably best preserved in sheltered areas near treeline). The mid-pack is generally well settled. Facets exist at the base of the snowpack.

Avalanche Problems

Wind Slabs

Be alert for wind slabs below ridge crests, behind terrain features, and in cross-loaded gullies.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Storm Slabs

Recent snow has fallen with a warming trend. This is likely to have created slab conditions within the new snow. A storm slab could step down to a persistent weak layer, creating a large avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

Enough snow has built up above a very touchy buried surface hoar layer that we are seeing many avalanches fail on this layer.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 2 - 5