Archived

Avalanche Forecast

Apr 21st, 2013–Apr 22nd, 2013

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

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: Glacier.

The Winter Permit System is no longer in effect.

Weather Forecast

An ridge of high pressure with arctic air should keep things cool and mostly dry through tomorrow, with increasing sun. Dry conditions should persist, but a gradual warming trend through the week will bring freezing levels up to 2000m by Wednesday. Winds will pick up again tonight; increasing to moderate NW'ly for the outlook.

Snowpack Summary

Rain to 1900m turned to snow early Saturday. Above 1900m up to 20cm of snow overlies a variety of surfaces including crusts, surface hoar and moist isothermal snow. SW winds loaded lee slopes but have backed off overnight. The April 3rd crust is down around 50-60 cm. Snow below treeline is isothermal, but cooler temps are holding it together.

Avalanche Summary

Recent avalanches have mostly been skier triggered in extreme alpine terrain. Last week, there were two skier accidental's: A size 3.0 on the east face of Mt Swanzy, depth 100cm, 150m wide, suspect April 3 crust. Skiers were not involved. A size 2.0, Forever Young couloir, ran to 2/3 fan. Skier got taken down to the fan before self arresting.

Confidence

Avalanche Problems

Wind Slabs

Moderate to strong S-SW winds have transported the new snow; forming deeper pockets of windloaded snow and isolated windslabs on lee features. They are especially likely in the alpine where winds were highest, and may bond poorly where crusts exist.

Avoid traveling on ledges and cliffs where small avalanches may have severe consequences.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3

Storm Slabs

20cm of new snow above 1900m may bond poorly to the various surfaces below. Use your ski pole to feel for buried crusts or windslabs; and use snowpack tests to assess how reactive the interface is.

Dig down to find and test weak layers before committing to a line.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 2

Persistent Slabs

Large avalanches failing on deeper weak layers are still being human triggered, as was demonstrated Monday. Recent wind and new snow have increased the slab overlying these layers.

Be aware of thin areas that may propogate to deeper instabilites.Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely

Expected Size: 2 - 3