Avalanche Forecast

Issued: Jan 16th, 2013 9:12AM

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

pgoddard, Avalanche Canada

Purcells.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Thursday: Moderate W winds. Alpine temperature near -4. Freezing level is at valley bottom, with alpine inversions possible (parcels of warm air which could bring relatively warm alpine temperatures). Trace of snow.Friday: Light to moderate W winds. Alpine temperature near -9. No snow.Saturday: Light SW winds. Alpine temperature near -4. No snow.

Avalanche Summary

Several size 1-2.5 wind slabs were triggered naturally and by skiers on Tuesday and Wednesday. Cornice falls were also reported.

Snowpack Summary

Strong NW through SW winds have left wind slabs in many areas, even at treeline. Cornices are unstable in some places. Settled storm snow sits above surface hoar (found especially at and below treeline in sheltered areas), a sun crust (on steep S to SW -facing slopes) and facets. The distribution of these weaknesses is patchy, but where they exist, it may still be possible to trigger a large avalanche with the weight of a person or snowmobile. A strong mid-pack overlies a weak facet/crust layer near the base of the snowpack, which is now considered inactive.

Problems

Wind Slabs

Wind slabs may be found behind terrain breaks such as ridges and ribs. It may be possible for a wind slab to step down to a deeper instability.

Be cautious as you transition into wind affected terrain.>Be aware of the potential for wide propagations due to the presence of hard windslabs.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Persistent Slabs

Persistent weaknesses are variable in their distribution, but can still be triggered by the weight of a person or snowmobile.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Be cautious on steep southerly aspects, where a crust/facet layer may be most reactive.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Jan 17th, 2013 2:00PM