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Archived

Avalanche Forecast

Dec 27th, 2014–Dec 28th, 2014
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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.

A persistent weak layer of buried surface hoar is the sliding layer for human triggered avalanches. This problem results in the avalanche danger staying up at Considerable for the forecast period.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Flurries or light snow is expected to continue overnight and during the day on Sunday with total accumulations around 5 cm combined with light winds and alpine temperatures around -15. Gradually clearing skies during the day on Monday as cold arctic air moves in from the North and alpine temperatures drop down to about -25. Continued cold and clear on Tuesday.

Avalanche Summary

No natural avalanches reported. Explosives control work resulted in avalanches up to size 2.5 that appear to have run on the mid-December surface hoar that is buried down 40-60 cm.

Snowpack Summary

Storm snow totals 30-70 cm above a very touchy surface hoar layer that was buried mid-December. Below 2100 m this storm slab sits on a thick, solid crust/ surface hoar combo and has been acting as the perfect sliding layer. This persistent slab remains touchy to the weight of a skier or rider, especially in wind effected areas. A hard rain crust with facets from early November is buried over 1 m down and has recently been reactive with larger loads (explosives and smaller avalanches) especially in the Northern part of the region where the snowpack is thinner.

Avalanche Problems

Persistent Slabs

Thin windslabs and recent storm slabs may be sitting on a weak layer of surface hoar and/or a crust. This problem may persist through the Holiday season.
Use conservative route selection, dig down and test weak layers before committing to anything. >Stick to simple terrain, small features with limited consequence and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Shallow snowpack areas may continue to have concerns for deeply buried crusts with facets at the interface.  Large triggers like storm slab avalanches in motion may step down to near the ground where this problem exists.
Conditions may be worse in the north of the region, so get to know your local snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6