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Archived

Avalanche Forecast

Dec 8th, 2019–Dec 9th, 2019
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
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Banff Yoho Kootenay.

The Nov crust/facet layer is becoming reactive and was the sliding layer in several large avalanches across the forecast region today. Although natural activity has tapered, human triggering remains real.

Weather Forecast

Continued NW wind in the moderate range is expected overnight. Temperatures should remain seasonal in the -10 range. Minimal snow and mixes of sun and cloudy periods for the next few days.

Snowpack Summary

40-60+ cm of snow has fallen in the last 4 days. A storm slab has formed at treeline and above. Below the storm slab, the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust exists up to 2500m and 30 cm up from ground. Snowpack depths at treeline are 80-130 cm and deeper in lee areas.

Avalanche Summary

A skier accidental size 2.5 was reported in West Bowl at Lake Louise today. The snowboarder was able to ride off to the side. This avalanche slid on the Nov crust layer. Sunshine Patrol also reported some very large explosive controlled avalanches in the Delirium Dive today up to size 3. These slides also ran on the Nov layer.

Confidence

Due to the number and quality of field observations on Sunday

Avalanche Problems

Storm Slabs

40-60 cm of recent snow and wind have formed a storm slab in many open areas at treeline and in the alpine. Human triggering of this slab will remain likely though natural avalanche activity will slow down.

  • Use caution in the alpine and treeline. Storm snow is forming reactive slabs.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1.5 - 2.5

Deep Persistent Slabs

As of today, large avalanches were reported as initiating on the Nov crust/facet layer and stepping down and gouging to near ground. Some were triggered with large loads (explosives) and one was triggered by a snowboarder on an adventure.

  • Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 3