Avalanche Forecast

Issued: Jan 12th, 2013 9:41AM

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

ghelgeson, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Sunday: Ridgetop winds light NW. Freezing level at valley bottom. No significant snowfall. 1500m temp: -10Monday: Mod/Strong W/NW winds at ridgetop. Freezing level at valley bottom. No significant snowfall.Tuesday: Freezing level rising to 2000m in the morning.

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. Windslabs 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.

Problems

Wind Slabs

Wind slabs are getting old and tired. Watch for small isolated wind slabs at ridgetop.

Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

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 avalanches due to the presence of buried surface hoar.>Be cautious with open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 13th, 2013 2:00PM