Avalanche Forecast

Issued: Mar 7th, 2013 9:19AM

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 - Timing or intensity of solar radiation is uncertain on Friday

Weather Forecast

Friday: Mix of sun and cloud / Light northwest winds / Freezing level at 1200mSaturday: Clear skies / Light northwest winds / Freezing level at 1500mSunday: Light snowfall / Moderate southwest winds / Freezing level at 1200m

Avalanche Summary

A couple of skier-triggered size 1 wind slabs were observed on Wednesday. The occurred on west/southwest facing terrain at treeline and above. The effect of the sun is somewhat uncertain on Friday/ Saturday. If it is strong, expect wet snow instabilities with the potential to trigger deeper persistent weaknesses.

Snowpack Summary

Light snowfall overlies wind slabs in exposed areas, surface hoar or facets in sheltered locations, or a sun crust on south facing terrain.Below the surface, recent accumulations of 70-120cm continue 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 in some locations). 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, especially with forecast solar warming. Below this interface, 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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 6

Wind Slabs

Thin wind slabs have been reactive on a variety of aspects at and above treeline.

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.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 8th, 2013 2:00PM