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Archived

Avalanche Forecast

Dec 5th, 2021–Dec 6th, 2021
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
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

Regions: Banff Yoho Kootenay.

The current avalanche hazard fits the definition of Moderate, however our main concern is with full depth avalanches failing on the basal facets which could  result in high consequences if triggered. Thinner snowpack areas seem the most problematic.

Weather Forecast

A cooling trend will continue into Monday with evening lows dropping to -20 C near valley bottom. Ridge winds will be light to moderate from the NW for the next few days with a mix of sun and clouds and no new snow expected. 

Snowpack Summary

Last weeks storms brought up to a meter of settled snow at higher elevations with wind effect in open areas. Periods of rain as high as 2200 m formed a crust which is down 5-30 cm depending on elevation. The lingering Nov 15 interface is down 50-100+ cm and the Nov 5 crust/facet layer is found near the ground. 90-200 cm of snow at treeline.

Avalanche Summary

No new natural avalanches were observed today. One significant skier accidental size 3 with a sympathetic size 2+ avalanche were triggered on Lipalian Mtn and failed on the basal facets. This thinner snowpack area with variable snow depths, cross loading by the wind and steep rolls is the type of terrain we are most concerned with at this time.

Confidence

Due to the number of field observations

Avalanche Problems

Deep Persistent Slabs

We continue to see occasional high consequence avalanches on the Nov 5 crust/basal facets in specific terrain features. Some slabs have initiated on this layer, while others were "step down" avalanches triggered as wind slabs or cornices hit them.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.
  • Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Wind slabs can be found in exposed treeline and alpine areas. These have not been as reactive over the last couple days but are worth paying attention to in steep lee or cross loaded features.

  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2.5