Avalanche Forecast

Issued: Dec 28th, 2013 8:23AM

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

mbender, Avalanche Canada

Purcells.

Summary

Confidence

Good

Weather Forecast

Sunday: Another series of weather systems starts to affect the interior. Light flurries, alpine temperatures -8, winds light to moderate from the northwest.Monday: Light flurries, freezing level at 1200m, winds light northwest.Tuesday: Mainly cloudy with some sunny breaks. Alpine temperatures -6 and freezing level at 1200m.

Avalanche Summary

No new avalanches to report. Although there is no recent activity to report, rider triggering is possible especially in shallow snowpack areas like rocky outcrops or near small trees.

Snowpack Summary

Up to 25 cm of new snow from the past 5 days covers stiff, dense wind slabs in exposed lee terrain at and above treeline. In the upper 80 cm of the snowpack a couple persistent weak layers exist, comprising of surface hoar and a facet/crust combo. This interface has produced variable results with snowpack tests, and operators are keeping a close eye on them as the load above increases and/or a slab develops.A bigger concern, especially in the Northern part of the region where the snowpack is thinner and more variable is weak faceted and depth hoar crystals combined with a crust from early October. This is now down around 80-120 cm. This deep persistent weakness may be stubborn to trigger, especially in deeper snowpack areas, but the sensitivity to triggers likely increases in shallower locations, especially on steep, convex, north-facing slopes.

Problems

Wind Slabs

Recent moderate winds have created new windslabs in the lee of terrain features. A small wind slab release may be enough to trigger a deep weak layer, producing a large and destructive avalanche.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The sensitivity to triggers is increased in shallow locations, especially on steep, convex, north-facing slopes.

Be aware of thin areas that may propogate to deeper instabilites.>Caution around convexities or areas with a thin or variable snowpack.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 29th, 2013 2:00PM