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Avalanche Forecast

Jan 4th, 2012–Jan 5th, 2012
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
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

Regions: South Coast.

Confidence

Good - -1

Weather Forecast

Thursday: 5-10cm of snow with freezing levels in valley bottoms and light to moderate westerly winds. Friday: Generally dry with light westerly winds and freezing levels in valley bottoms. Saturday: light amounts of new snow possible with freezing levels in valley bottoms.

Avalanche Summary

A large widespread natural avalanche cycle is underway, but will probably taper off as the storm dissipates late Thursday, however fresh storm and wind slabs, as well as deeply buried persistent slabs will remain sensitive to human triggers. 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

As of Wednesday morning, over 30cm of new snow fell in the Duffy Lake area under strong southerly winds, with freezing levels generally below 1500m, but briefly peaking at 1800m. The Cascades were a dryer and warmer. Persistent weaknesses buried mid-December are primed for avalanches in the northern part of the region. Weak surface hoar is lurking generally down 60-90cm 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 triggering, even on low-angled slopes, and slabs can propagate over large areas.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 5

Wind Slabs

Heavy loading from wind is resulting in natural avalanche activity. Fresh wind slabs lurking below ridgecrests, behind terrain features and in cross-loaded gullies, will remain sensitive to human triggers after the storm dissipates.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Storm Slabs

Heavy loading from new snow and rain is resulting in natural avalanche activity. Storm slabs will remain sensitive to human triggers after the storm dissipates and avalanches have the potential to step-down to deeper persistent weaknesses.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 4