Avalanche Forecast

Issued: Mar 25th, 2013 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

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

Summary

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

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

Valid until: Mar 26th, 2013 8:00AM