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Archived

Avalanche Forecast

Dec 22nd, 2011–Dec 23rd, 2011
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
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
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.

Avalanche danger is expected to increase throughout he weekend.

Confidence

Fair - Intensity of incoming weather is uncertainfor the entire period

Weather Forecast

Friday: Light snowfall in the morning with only a couple of centimetres expected in the Duffey Lake area, but possibly 10-15cm in Coquihalla Pass. Freezing levels around 1000m and moderate southwesterly winds before precipitation picks up, winds increase and freeing levels rise in the evening. Saturday: Another 10-15cm (Duffey) and 20-25cm (Coquihalla) late in the day is expected to add to the 15cm (Duffey) to 30cm (Coquihalla) of new snow already on the ground. Freezing levels as high as 1500m and strong westerly winds. Sunday: Continued moderate snowfall and moderate to strong southwesterly winds, with freeing levels back below 1000m.

Avalanche Summary

Fresh wind slabs and cornices are sensitive to human-triggers and could produce avalanches up to size 2.

Snowpack Summary

Dribs and drabs of new snow, in the Coquihalla area, with associated winds are keeping wind slabs fresh and poorly bonded, but also keeping recent persistent weak layer development and distribution to a minimum. While in the Duffey Lake area, wind-exposed slopes are predominately scoured and pressed, with pockets of hard wind slab. Buried surface hoar and/or facets persists 10 or so centimetres below a weak rain crust on sheltered treeline slopes and below, where recent compression tests on a northerly aspect at 1750m produced easy sudden results down 20cm on surface hoar as large as 15mm. Check out the Forecaster's Blog link below for a discussion on incremental loading of potentially persistent weak layers. The mid and lower snowpack are generally well-settled and strong, but recent reports suggest basal facets create a deep persistent slab problem that deserves caution in shallow snowpack areas on planar rocky slopes.

Avalanche Problems

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: Possible

Expected Size: 1 - 3