Avalanche Forecast

Issued: Mar 6th, 2013 9:30AM

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

jlammers, Avalanche Canada

Sea To Sky.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Thursday: Trace amounts of new snow / Light northwest winds / Freezing level at 1200mFriday: Mix of sun and cloud / Light north winds / Freezing level at 1500mSaturday: Clear skies / Light northwest winds / Freezing level at 1400m

Avalanche Summary

Explosives control continued to produce results up to size 3 on Sunday. There were a couple reports of skier triggered avalanches up to size 2 on Monday, primarily from northeast through southeast aspects in the alpine.

Snowpack Summary

The snow surface consists of surface hoar, a sun crust, faceted snow, or thin soft wind slabs depending on aspect and elevation. Below this the recent storm snow (70-120 cm) continues to settle and strengthen. Snowpack tests are still giving generally moderate shears at various density changes within the storm snow, but triggering these instabilities has become more difficult. A weakness of surface hoar and/or a crust exists near the base of the storm snow (now 1-2 m deep). This layer was the culprit in most of the large avalanches that occurred last weekend. This layer could still be triggered in shallow rocky areas or by large triggers like a cornice fall. I would suggest avoiding any large slope that did not release during the latest avalanche cycle. Below this weakness the snowpack is strong and well settled.

Problems

Persistent Slabs

A buried persistent weak layer of surface hoar (shady slopes) or a sun crust (sunny slopes) is now down 100-200 cm. It may be possible to trigger this layer in steep rocky terrain. The resulting avalanche could have serious consequences.

Conditions have improved, but be mindful that deep instabilities are still present.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 6

Wind Slabs

Thin wind slabs exist on a variety of aspects at and above treeline. Watch for cross-loading in gully features.

Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Cornices

Cornices have grown large and weak in recent storms. Daytime warming could be enough to cause cornices to fail.

Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 7th, 2013 2:00PM