Avalanche Forecast

Issued: Apr 22nd, 2012 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Loose Wet, Wet Slabs and Deep Persistent Slabs.

jlammers, Avalanche Canada

Purcells.

Summary

Confidence

Good

Weather Forecast

Scattered cloud is forecast for Monday with the possibility of light rain in the afternoon, particularly in the north of the region. Ridgetop winds are expected to be light to moderate from the southwest with freezing levels sitting at about 3100m.

Avalanche Summary

Numerous point releases and slab avalanches to size 2.5 were observed running within the recent storm snow on Saturday. There will be ongoing to wet snow instabilities on Monday with forecast freezing levels.

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 over the weekend. 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.

Problems

Loose Wet

Loose wet snow avalanches are expected with continued warming on Monday. 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 continued warming on 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 on deep persistent weaknesses that developed earlier in the winter are unlikely, but the probability will increase as warm temperatures persist and there is no overnight freeze.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Valid until: Apr 23rd, 2012 9:00AM