Archived

Avalanche Forecast

Mar 25th, 2013–Mar 26th, 2013

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

Regions: Glacier.

Avalanche danger will increase through the day on solar aspects. Avoid exposure to cornices and slopes that have been receiving direct sun.

Weather Forecast

Lots more sun is forecast for today and Tuesday. Cool temps are helping to reduce solar effects; alpine temps should stay below -10. Light alpine winds are forecast, but down-flow winds off glaciers are creating areas of windeffect. Freezing levels and alpine temps will start to rise over the next 3 days. Increasing cloud is expected on Wed.

Snowpack Summary

On steep, solar aspects the surface becomes moist and loose with warming, freezing into a crust overnight. 25cm of dry snow exists above 1400m elsewhere. Tests on surface hoar/crust layers in the top 1.5m indicate that they may be triggered by large loads (like cornices) in some areas (most likely on solar aspects). The snowpack below is strong.

Avalanche Summary

Yesterday, skiers triggered a size 2 on a W aspect at 2585m at 2pm. The avalanche failed on surface hoar sitting on a sun crust. The slab was 25cm deep, 100m wide and 120m long. Tragically, one person was fatally buried 1.9m deep. Natural avalanches were triggered on solar aspects and large cornice failures were reported throughout the Selkirks.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Cornices

Look up lots today and avoid slopes with cornices above them. Cornice failures are expected due to daytime warming or by people traveling along ridges. A section of cornice hurtling down slope is a real concern, it may also trigger slab avalanches.

Do not travel on slopes that are exposed to cornices overhead.Stay well to the windward side of corniced ridges.

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Persistent Slabs

Slopes receiving direct sun become more reactive during the day with warming. This is especially likely on steep solar aspects where buried crusts exist. Solar triggered avalanches are most likely around exposed rocks and may trigger deeper slabs.

Minimize exposure to sun exposed slopes when the solar radiation is strong.Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

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

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Wind Slabs

Isolated wind slabs in the alpine and near ridge crests have surprised a few skiers. These likely exist in steep, aggressive terrain where even a small avalanche could have severe consequences.

Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 2