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Avalanche Forecast

Feb 1st, 2012–Feb 3rd, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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: South Rockies.

Confidence

Fair - Freezing levels are uncertain for the entire period

Weather Forecast

On Wednesday the region may have seen the last drips and drabs of precipitation for a while. A strong ridge building from the western part of the province will bring dryer conditions for the forecast period. On Thursday ridgetop winds will be light from the NW; freezing levels may rise to 1200m and alpine temperatures steady near -5. Friday and Saturday mainly sunny as the ridge of high pressure holds true with freezing levels potentially reaching 1800-2000m.

Avalanche Summary

No new natural avalanches reported today. Our CAC field team did spend the day out, and investigated some natural slab avalanches that occurred on the 29/30th from Michel Ridge. All three slides were size 3 slab avalanches. One of the avalanches occurred on a East aspect, @ 1965m. The debris was 175m long x 20m wide, with an average depth of 2m. The avalanche consisted of a dense hard slab running on weaker facets below.

Snowpack Summary

Strong SW winds created stiff, yet reactive wind slabs on lee slopes. Cross-loading, and wind slabs are also found lower on the slopes and in unsuspecting terrain due to the strong push of the winds. Below 1700m a 4cm thick crust exists, I suspect it's from the rising freezing levels, and precipitation last Sunday. This crust is said to be supportive. Below this reports indicate the mid-pack to be fairly well settled. Deeper in the snowpack sits the mid-December surface hoar layer. This layer remains a concern for deeper releases. Basal facets and depth hoar also play a major role in this region. The average snowpack depth at treeline is 150cms.

Avalanche Problems

Wind Slabs

Stiff wind slabs have formed on North through East aspects. They may be found lower on slopes in unusual places due to the strong winds. Wind slab avalanches are likely reactive to rider triggers.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Deep Persistent Slabs

The probability of triggering this layer is low in most areas, but the consequences are high. A large avalanche on this layer could be very destructive.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 6