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Avalanche Forecast

Jan 19th, 2012–Jan 20th, 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
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
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: South Columbia.

Confidence

Fair - Timing of incoming weather is uncertain on Friday

Weather Forecast

Friday: Moderate to heavy snowfall starting on Friday afternoon. 10-15cm, with 20cm+ expected on western slopes. Freezing level at valley bottom for most of the day. Winds increasing to strong westerlies by afternoon.Saturday: Snow continuing, with a further 10-20cm expected (most in the southern part of the region and on western slopes). Freezing level rising briefly to around 1000m on Saturday morning. Westerly winds.Sunday: Light snow. Freezing level valley floor.

Avalanche Summary

Several natural and human-triggered avalanches have been reported over the last few days. A wind event on Tuesday triggered slabs on exposed lee slopes. On Wednesday, skiers triggered size 1.5 slabs below treeline and observed natural and cornice-triggered events up to size2, mainly on north and east aspects in the alpine. Recent avalanches have mainly been running in, or at the base of, the storm snow.

Snowpack Summary

50-80cm of recent storm snow is slowly settling into a slab over variable surfaces including a rain crust and preserved stellar snow crystals. Recent winds have caused wind slabs to develop at treeline and above, and in openings below treeline. A surface hoar layer buried in mid-December is gaining strength, but professionals are still treating it with caution, as the consequences of an avalanche on this layer would be high. Occasional hard, planar results have been reported on this layer in snowpack tests. It's now down about 130cm in the snowpack and could potentially be triggered from a shallow snowpack area or by a very heavy load, like cornice fall or group of sledders.

Avalanche Problems

Wind Slabs

Variable winds have built slabs on many slopes. These can be found behind ridges and terrain breaks and in cross-loaded gullies. Recent low-elevation winds created wind slabs in openings below treeline.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Storm Slabs

Recent storm snow is reactive as a slab on steep or convex terrain. Incoming snow and warming will build further storm slab problems.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4