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Avalanche Forecast

Apr 17th, 2013–Apr 18th, 2013
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
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
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: Purcells.

If you have any snowpack or avalanche observations, feel free to send them to forecaster@avalanche.ca. We'd love to hear from you.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

Thursday: Overcast. Light precipitation amounts. Ridgetop winds light-moderate from the West. Freezing levels rising to 1900 m. Friday: Overcast. Light precipitation amounts. Ridgetop winds moderate from the West. Freezing levels 1900 m. Saturday: Overcast. Light-moderate precipitation amounts. Ridgetop winds light- moderate from the NW. Freezing levels 1600 m and falling to valley bottom overnight.

Avalanche Summary

On Tuesday, a natural size 2 cornice fall was reported from an East aspect at 2400 m. This failure occurred under the influence of the sun and did not pull a slab on the slope below. In the adjacent region a size 2 slab avalanche was skier triggered on a NW aspect at 2500 m. The hard slab failed 3 m above the skier. There were no injuries. On Sunday, a naturally triggered size 2.5 slab failed on a buried crust. In Glacier National Park, skiers triggered a size 3 slab on a buried crust on an east aspect in the alpine on Monday.

Snowpack Summary

Recent storm snow and variable winds have formed wind slabs at treeline and above. Cornices on ridgelines have grown large, and pose a threat to slopes below.A weak interface buried early April is down about 60-120 cm and consists of a crust on solar aspects, and surface hoar on high-elevation northerly aspects. The slab above this interface may be reaching it's tipping point with additional loading from forecast snow and wind.

Avalanche Problems

Wind Slabs

Wind slabs exist on a variety of aspects at treeline and above. Cornices have grown large. Be aware of overhead hazard and stay back on ridgelines.
Avoid freshly wind loaded features.>Travel on ridgetops to avoid wind slabs on slopes below.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

A weak interface buried in the upper metre of the snowpack can create surprisingly large avalanches. It's been reactive in nearby regions, and remains a concern with professionals. Be cautious in alpine terrain.
Be aware of thin areas that may propagate to deeper instabilites.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 6