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Archived

Avalanche Forecast

Mar 21st, 2012–Mar 22nd, 2012
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
4: High
The avalanche danger rating in the alpine will be high
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
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Be wary of any slopes receiving direct sun. Solar warming could trigger avalanches or weaken existing slabs.

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Thursday: Light snow. 5-10cm. Light to moderate south-west winds. Freezing level valley floor.Friday/Saturday: Clear and sunny. Light winds. Afternoon temperatures rising on sunny slopes, with the freezing level falling to valley floor at night.

Avalanche Summary

In the Dogtooth Range on Tuesday, a size 3 slab was triggered by a skier on a north aspect. It's suspected to have initiated on the February weakness, and stepped to ground. Two large slabs (size 2-2.5) also released naturally on north to north-east aspects, up to 1 m deep. There were two snowmobile-triggered size 3 avalanches in the southern Purcells near Kimberley (read more in 'related incidents'on this page). I'm concerned about strong solar warming on Friday and Saturday potentially triggering cornice fall or surface avalanches, which could step down to persistent weaknesses and create very large avalanches.

Snowpack Summary

Newly formed soft wind slabs were touchy on Wednesday in specific terrain. Deeper in the snowpack, the major concerns are the mid-February persistent weak layer, buried 1-2 m deep, and facets at the base of the snowpack. Neither of these has truly healed and sporadic very large avalanches continue to occur.

Avalanche Problems

Wind Slabs

Wind slabs can be found in the alpine and at treeline, behind ridges and terrain breaks. Large cornices are also looming and could trigger deep weak layers on the slope below.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Avalanches failing on a persistent weak layer are deep and destructive. Choose conservative terrain, as the consequences of triggering this layer could be huge.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 4 - 8