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Archived

Avalanche Forecast

Dec 27th, 2013–Dec 28th, 2013
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Confidence

Good

Weather Forecast

Saturday: Mainly dry with broken skies, winds moderate to strong from the northwest and alpine temperatures -7.Sunday: Light snowfall, alpine temperatures -9, winds light to moderate from the west and southwest.Monday: Light flurries, alpine temperatures -10, light winds from the west.

Avalanche Summary

The deep persistent slab problem continues to be reactive in the past 3 days up to size 3 with larger triggers such as explosives. 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. Average snowpack depths at treeline elevations are 100-130 cm. 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.

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

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 5