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Avalanche Forecast

Jan 21st, 2012–Jan 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
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
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
4: High
The avalanche danger rating below treeline will be high

Regions: Sea To Sky.

If heavy snowfall arrives during the day on Sunday, consider alpine terrain to be at High danger.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

Sunday: There will likely be some heavy snow showers during the day before a more organized band of heavy snow arrives in the afternoon/evening. Amounts of 20-30 cm are expected by Monday morning. Freezing levels should stay around 400 m with strong southerly winds during the day on Sunday. On Monday, unstable air will bring another 10-15 cm new snow. On Tuesday, another intense Pacific frontal system arrives, which could bring as much as 40 cm new snow. Freezing levels may go up to around 1500 m. Continued strong westerly/southwesterly winds.

Avalanche Summary

Several small (size 1) skier-triggered slab avalanches were reported in exposed lee terrain (wind slabs) and in a band between 1700 and 1800 m (storm slabs) on steep terrain on a variety of aspects. Explosives were able to trigger slabs to size 2 in the most recent storm snow. Avalanches did not appear to be stepping down to lower layers.

Snowpack Summary

A cohesive slab has formed on the snow surface in response to new snow amounts that varied between 20-40 cm. The underlying snow was cold and in places, a layer of low density snow has been preserved. Reports indicate it may be particularly reactive between 1700 and 1800 m, although I would be concerned about this interface on all steep terrain right now. A rain crust lies buried approximately 30-50 cm below the snow surface at lower elevations (up to around 1800 m). Reports indicate the bond at this interface is quite good, although the slick nature of the crust may still provide a sliding layer in some steeper locations. Previous concerns about deeper weak layers appear to have now diminished. Snowpack depths at treeline are in the region of 260 cm.

Avalanche Problems

Storm Slabs

Heavy amounts of storm snow have fallen on existing cold, low density snow. This has set up an unstable situation in the upper snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 5

Wind Slabs

New snow and strong winds will set up touchy new wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4