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Archived

Avalanche Forecast

Feb 5th, 2015–Feb 6th, 2015
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
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
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: Banff Yoho Kootenay.

We expect a natural avalanche cycle to start Friday and continue to Saturday night. Avoid avalanche terrain as conditions will change rapidly on Friday. Good ski conditions at lower elevations out of the wind. SH

Weather Forecast

Another 30-50cm is expected by Saturday night at treeline elevations. Alpine winds will be in the strong range and freezing levels to 1900m Friday.

Snowpack Summary

25-50cm of recent storm snow sits on a crust from January 30, which exists up to 2300m on all aspects (higher on solar aspects). In isolated locations this has been blown into soft slabs.Over the next two days this bond to the Jan. 30 interface will be critical. The basal depth hoar, facet layer may also be "woken up" with the additional load.

Avalanche Summary

One natural size 2 avalanche was observed on Mt. Redoubt near Lake Louise yesterday which stepped to the basal weakness, was 60 m wide and failed on the ground level depth hoar. Another group today triggered a size 2.5 which was almost 2m deep on a crossloaded treeline feature above Bow Summit.  Yikes!  This failed on the Basal facets/Depth hoar.

Confidence

on Friday

Avalanche Problems

Storm Slabs

Storm slabs will be rampantly forming and failing, especially at higher elevations. The bond to the Jan 30 interface and within the storm snow itself will be critical to monitor.
Avoid freshly wind loaded features.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Deep Persistent Slabs

The base of the snowpack remains weak due to basal depth hoar/facets. Additional snow load or a storm slab failure may trigger large to very large avalanches in thin snowpack areas. See forecast details for a photo example of this from today.
Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 3