Avalanche Forecast

Issued: Jan 1st, 2015 7:40AM

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

pgoddard, Avalanche Canada

Purcells.

Conditions are variable across the region. Cautious route-finding and conservative decision-making are essential.

Summary

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

Snowfall is expected to increase overnight and into Friday (5-10 cm by Friday afternoon). Winds are forecast to be moderate from the SW to NW. Freezing level at valley bottom. Snowfall becomes light on Saturday before a second pulse of snow arrives late on Sunday.

Avalanche Summary

Explosives control on Tuesday produced several avalanches up to size 3. Some of these failed on persistent weak layers, while others only involved surface snow. Natural wind slabs were also observed near ridge tops over the last couple of days.

Snowpack Summary

Variable wind slabs exist in some areas. A spotty thin layer of surface hoar was buried on December 27th by about 5-10 cm of light dry snow. As more snow accumulates, this interface could become one to watch. A persistent surface hoar/crust weak layer from mid-December is now down about 40-60cm. Recent snowpack tests show moderate pops-type results here, indicating the potential for avalanches to propagate on this layer. This persistent slab problem is reasonably widespread across the region and is not expected to improve quickly. A deeper crust/facet layer which formed early in the season may still be triggerable from thin or rocky snowpack areas.

Problems

Persistent Slabs

A buried surface hoar/ crust layer demands respect. It has been easy to trigger persistent slabs with light loads (like a person). This layer is down about 30-50 cm in most areas, but may be deeper where wind slabs have developed.

Stick to small features with limited consequence and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Wind Slabs

Recent strong winds have left wind slabs behind on a variety of slopes. These may become hidden under a dusting of new snow.

Choose well supported terrain without convexities.>Use ridges or ribs to avoid pockets of wind loaded snow.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Jan 2nd, 2015 2:00PM