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Archived

Avalanche Forecast

Dec 10th, 2019–Dec 11th, 2019
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
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Banff Yoho Kootenay.

Lots of recent snow over a weak base, now being moved by west wind into reactive wind slabs. Stick to conservative lines and allow some time for the snowpack to adjust and bond.

Weather Forecast

Continued moderate West alpine winds are expected overnight and increase to strong on Thursday. This will add to existing wind slabs and keeping the alpine hazard at Considerable. Temperatures should remain seasonal in the -10 range at tree line. Minimal snow, and a mix of sun and cloud for Wednesday and up to 5 cm on Thursday.

Snowpack Summary

Moderate winds in the alpine are adding to the wind slabs problem in the alpine. Beneath the recent 40-60 cm of recent snow, the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust is present up to 2500m and ~30 cm up from ground. Snowpack depths at treeline range from 80-160 cm.

Avalanche Summary

Avalanche control today continues to produce windslab avalanches. Sunday and Monday's control produced up to size 3 avalanches with propagations across terrain features and stepped down to the Nov crust and basal facets. A skier accidental size 2.5 on the basal weakness occurred in West Bowl at Lake Louise Sunday.

Confidence

Avalanche Problems

Wind Slabs

Recent snow and wind have formed reactive wind in many open areas at treeline and in the alpine. Human triggering of this slab remains possible or even likely in some terrain, though natural avalanche activity has slowed down. 

  • Use caution in lee areas. Recent wind loading has created slabs over weaker snow.
  • Caution on open steep slopes at treeline that have been exposed to wind loading.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1.5 - 2.5

Deep Persistent Slabs

The recent snow sits over weak facet and crust layers. Numerous natural and explosive triggered avalanches up to size 3 have been observed on these weak lower layers in the past several days. Human triggering in steep terrain remains a real concern.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1.5 - 3