Archived

Avalanche Forecast

Mar 6th, 2013–Mar 7th, 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

1: Low

The avalanche danger rating below treeline will be low

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

1: Low

The avalanche danger rating below treeline will be low

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

1: Low

The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

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.

Avalanche 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