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Archived

Avalanche Forecast

Jan 3rd, 2012–Jan 4th, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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: South Coast.

Confidence

Good - -1

Weather Forecast

Wednesday: 10-30cm of new snow with freezing levels around 1500m and strong southwesterly winds. Thursday: 5-10cm of new snow with freezing levels back to valley bottoms. Friday: Relatively dry and cold with freezing levels in valley bottoms.

Avalanche Summary

Three separate serious incidents occurred on Monday afternoon in the Duffey Lake and Southern Chilcotin areas, all of which had similar terrain characteristics with north through east facing steep treeline features. Two of the avalanches likely involved the mid-December persistent weakness, while the third was reported to have released on basal facets in a shallow snowpack area with a 50-75cm depth. All of the avalanches resulted in serious injury and at least two of them were human-triggered.

Snowpack Summary

Gusty winds are keeping wind slabs and cornices fresh and weak. Persistent weaknesses buried mid-December are primed for avalanches in the northern part of the region. Weak surface hoar is lurking generally down 50-70cm in sheltered treeline areas and below. In exposed treeline and alpine areas, weak facets with associated crusts are down generally 80-120cm, but wind-loading has resulted in highly variable slab thicknesses. Basal facets remain a concern in shallow rocky areas. Meanwhile in the Cascades, last weeks storm snow is generally well settled and right-side-up with mostly resistant shears on storm slab weaknesses in the top metre, but fresh wind slabs are touchy.

Avalanche Problems

Persistent Slabs

Primarily a concern in the northern part of the region. Persistent weaknesses are primed for human triggers, even on low-angled slopes, and slabs can propagate over large areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 2 - 5

Wind Slabs

Fresh wind slabs are lurking below ridgecrests, behind terrain features and in cross-loaded gullies.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4