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Archived

Avalanche Forecast

Dec 30th, 2018–Dec 31st, 2018
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

A significant storm Saturday has left fresh new windslabs and produced an avalanche cycle. Natural avalanche activity seems to have tapered off with light winds and cold temps but human triggering will remain a concern.

Weather Forecast

As ridge forms, light North winds are bringing cold, dry air to the region through the first few days of the week.

Snowpack Summary

15- 30 cm of snow quickly formed windslabs as it arrived with Strong SW winds Saturday. Below this, through most of the region, a 40-60cm stiff slab sits on a weak base of facets and depth hoar. Deeper snowpack areas display stronger base layers , but have a 60-80cm slab over top of the Dec10 surface hoar/facet layer that remains of concern.

Avalanche Summary

A road patrol in Kootenay today found limited evidence of a mid-storm cycle to sz 2.5 in steep treeline terrain. Saturday,  avalanches from Mt Fairview hit Lake Louise and  Surprise Pass ran. Lake Louise Ski area reported a sz 3 slab on Unity Peak 450m wide, and size 2 slabs in both Semicircular Bowl and Redoubt Bowl running mid-storm Saturday.

Confidence

Due to the number of field observations

Avalanche Problems

Deep Persistent Slabs

A stiff slab overlying a  weak lower snowpack comprised of facets and depth hoar can be found in most areas of the region (generally central and eastern) where  a shallow snowpack exists. Give this weak snowpack some time to adjust to the storm load.
Be wary of slopes that did not previously avalanche.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 3

Wind Slabs

Strong SW winds blew mid-storm on Saturday creating touchy new slabs. While the cold temperatures that have followed can be expected to diminish the sensitivity of these slabs, they certainly deserve some respect for the next little while.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2.5