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Archived

Avalanche Forecast

Dec 1st, 2020–Dec 2nd, 2020
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Banff Yoho Kootenay.

Climbers/skiers take note - the upper elevation temperatures rise to above 0C tonight, and up to 5 C tomorrow causing a bump up in hazard. We expect increased avalanche activity, particularly on steep solar aspects.

Weather Forecast

Tonight a temperature inversion establishes with temperatures at 2000 m and above rising to +5C tonight and through tomorrow.  The rise in temperature together with sunny skis will cause existing layers to become more sensitive to triggering or produce natural avalanches on Wednesday.  Temperatures will cool Thursday late afternoon.

Snowpack Summary

Variable surface conditions exist with hard wind slabs in exposed locations and softer snow in more sheltered areas. The Nov 5 facet/crust combo is down 50-80 cm and producing variable test results, but can be 'sudden' in character. This crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-130 cm.

Avalanche Summary

No avalanche activity reported Tuesday. There have been a few isolated larger avalanches in the last week on deeper layers including a size 2.5 avalanche on the W aspect of Dolomite Peak on Sunday in a cross loaded gully feature and a couple deep avalanches on steep glacier features. Warm air aloft & sunny skies Wed may cause activity to increase.

Confidence

Avalanche Problems

Wind Slabs

Wind slabs exist in exposed alpine areas from strong winds over the past week. Slabs may be more reactive with warmer temperatures and sun exposure if you are in steep lee loaded or cross loaded terrain.

  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

The Nov 5 crust has facets growing above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. We have seen a few isolated avalanches on this layer so use caution in large steep terrain features.

  • Be aware of thin areas that may propogate to deeper instabilites.
  • Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3