Avalanche Forecast

Issued: Feb 13th, 2015 8:51AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Cornices and Deep Persistent Slabs.

ccampbell, Avalanche Canada

South Rockies.

A Special Public Avalanche Warning is in effect for this region. The only worthwhile riding is likely on the least trustworthy slopes. Be circumspect on large steep alpine slopes.

Summary

Confidence

Good

Weather Forecast

Saturday: Cloudy with possible light snow. The freezing level lowers to around 1500 m. Winds are generally light from the W-NW. Sunday: Mainly cloudy with light snow. The freezing level is around 1200-1500 m. Monday: A mix of sun and cloud, and mainly dry. Freezing levels in valley bottoms with light variable winds.

Avalanche Summary

Reports from Thursday include two cornice-triggered that stepped down to a deep persistent slab on a hanging face. A couple of explosive-triggered storm and and wind slabs up to Size 2 were also reported, but ski-cutting produced no results.

Snowpack Summary

Recent reports suggest 10-50 cm thick hard wind slabs lurk below ridge crests and behind terrain features at treeline and alpine elevations; however, these seem to be generally well-bonded. In more sheltered areas, variable amounts of previous storm snow is sitting on a crust that formed at the end of January. Recent warm temperatures have softened the upper snowpack, reawakening deep persistent weaknesses in isolated areas. As temperatures continue to fluctuate and stress the snowpack, expect an increased likelihood of triggering large destructive avalanches in isolated areas (e.g. thin spots) with heavy triggers (e.g. cornice falls, stuck sleds spinning tracks, or groups of people).

Problems

Wind Slabs

Hard wind slabs may be stubborn to trigger, but they have a tenancy to propagate across entire slopes or pull into low angled terrain on ridge crests, catching people by surprise.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Be cautious as you transition into wind affected terrain.>Be careful with wind loaded pockets, especially near ridge crests and roll-overs.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Cornices

Cornices will likely become unstable with fluctuating temperatures. Not only are they a hazard in themselves, but they are also large triggers for deep slab avalanches on the slope below.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

Persistent weaknesses recently woke up with the warm temperatures and should be treated with suspicion until after things freeze up again. Although likely to need a large trigger, the potential consequences are dire.

Avoid steep convexities or areas with a thin or variable snowpack.>Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar or a facet/crust layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 14th, 2015 2:00PM