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Archived

Avalanche Forecast

Apr 21st, 2012–Apr 22nd, 2012
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
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
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
Below Threshold
The avalanche danger rating in the alpine will be below threshold
Treeline
Below Threshold
The avalanche danger rating at treeline will be below threshold
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold

Regions: Purcells.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The region will see mostly scattered cloud on Sunday with the possibility of light rain on Monday. Freezing levels will sit at about 3000m for both days with moderate southwesterly ridgetop winds.

Avalanche Summary

Several size 2 point releases and slab avalanches were observed running within the storm snow on Friday. There will be a shift to wet loose and wet slab instabilities on Sunday and Monday as freezing levels rise.

Snowpack Summary

On Thursday night, light to locally moderate amounts of snow fell forming wind slabs that most likely settled considerably or turned to wet slabs with warming on Saturday. The recently fallen snow overlies well settled powder, melt-freeze crust sandwiches and wet grains. At lower elevations, warm temperatures continue to penetrate and weaken the isothermal snowpack. Deeper in the snowpack there are layers that may not be reactive with cooler temperatures, but should be on your radar as spring brings more prolonged periods of warm weather. These layers include near surface crusts, the early-February surface hoar (about 100-170cm down) and basal facets. Cornices in region are also large and will become weak with warm temperatures.

Avalanche Problems

Loose Wet

Loose wet snow avalanches are expected with warming forecast for the weekend. Watch for increased activity in steep, sun-exposed rocky terrain. Loose snow avalanches may entrain a great deal of mass and may trigger deeper weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1 - 5

Wet Slabs

With warming forecast for Sunday and Monday, wet slabs become more likely. A number of crusts in the upper snowpack may act as a suitable sliding layer for wet slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 5

Deep Persistent Slabs

Avalanches may release on the deeply buried weak layers from February or from depth hoar that developed early winter. The likelihood will increase if warm temperatures persist and there is no overnight freeze.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 7