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Archived

Avalanche Forecast

Jan 13th, 2013–Jan 14th, 2013
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
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
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

We should see a rapid increase in temperatures early this week, resulting in a spike in avalanche danger. Check out the latest forecasters blog for advice on how to manage these changing conditions.

Confidence

Good

Weather Forecast

Monday: A mix of sun and cloud. Freezing level is at valley bottom and alpine temperatures rise to -10. Winds are light from the north.  Tuesday: Mainly sunny with possible valley cloud. An above freezing layer will develop between 1200-1500 m. Winds are light to moderate from the north. Wednesday: Much the same as Tuesday - continued warm alpine temperatures and generally clear skies.

Avalanche Summary

The upper snowpack has tightened up with the cold temperatures and the time elapsed since the last storm. Overall numbers of avalanche observations have decreased, but the avalanches are getting more interesting/scary.  A group of skiers remotely triggered a size 2 avalanche from 70m away on a W facing aspect at TL Friday.  Explosive work in the region didn't produce much activity Friday. 

Snowpack Summary

40 - 90 cm of settled storm snow rests on the January 4th interface which consists of small facets, surface hoar (up to 12mm) in sheltered treeline and below treeline areas and sun crust on steep south and west facing slopes. The bonds at this interface are gaining strength but I still wouldn't bet the house on it. Recent tests on this interface show shears trending towards Resistant Planar. Professionals operating in the region are most concerned about slopes that have not yet avalanched. Wind slabs formed during the last storm are getting old and tired.The deep crust/facet combo from early November is till evident but it is inactive at this point. 

Avalanche Problems

Persistent Slabs

The 40 - 90 cm of storm snow has settled out nicely and the likelihood of triggering has greatly decreased. I suspect it's still possible to trigger an avalanche failing on the Jan. 4th interface in terrain that is steep rocky and/or convex.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 5

Wind Slabs

New wind slabs are likely in exposed lee and cross-loaded terrain from recent northerly winds. Old wind slabs lurk beneath, but triggering is less likely.
Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 4