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Avalanche Forecast

Dec 22nd, 2011–Dec 23rd, 2011
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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
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: Sea To Sky.

Avalanche danger is expected to increase over the weekend.

Confidence

Fair - Intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Friday: Light snowfall in the morning with 2-5cm expected. Freezing levels around 1200m and moderate southwesterly winds before precipitation picks up, winds increase and freeing levels rise in the evening. Saturday: Another 20-30cm late in the day is expected to add to the 15-25cm of new snow already on the ground. Freezing levels as high as 1700m and strong westerly winds. Sunday: Continued moderate snowfall and moderate to strong southwesterly winds, with freeing levels back around 1200m.

Avalanche Summary

Recent observations are limited to isolated human-triggered Size 1 fresh wind slabs. One was 20m wide by 20cm deep on a NE facing alpine slope.

Snowpack Summary

Alpine areas are wind-hammered with scoured and pressed surfaces, exposed crusts, and pockets of hard and soft wind slabs. Buried surface hoar and/or facets persists 10-20cm below a weak rain crust on sheltered treeline slopes and below. Recent compression tests on a treeline slope produced easy to moderate sudden collapse results down 65cm on on this weakness where it was wind-loaded. Watch this layer as it gets more load and a thick cohesive slab develops, particularly below treeline where the buried surface hoar is especially large. A strong mid pack overlies weak basal facets and depth hoar in shallow alpine areas. This deep persistent weakness may also deserve attention with more load.

Avalanche Problems

Wind Slabs

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

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3