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Archived

Avalanche Forecast

Jan 20th, 2012–Jan 21st, 2012
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
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
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: Kootenay Boundary.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Saturday

Weather Forecast

Saturday: 10-15cm of snow - Moderate to strong southwest winds - Freezing level at 1000mSunday: Some ridging in the morning with trace amounts of snow forecast for the afternoon - Light southwest winds - Freezing level trending from surface to 600m throughout the dayMonday: Light snowfall - Light to moderate west winds - Freezing level at 600m

Avalanche Summary

Ski-cut sluffs to size 1.5 were observed throughout the region on thursday. A few skier-accidental slabs to size 1.5 (30-50 cm crowns) were also observed in the Nelson area. Expect a spike in avalanche activity with Friday night/Saturday's forecast weather.

Snowpack Summary

Average treeline snow depths are nudging over the 2 m mark in this region. In the last seven days, between 40 and 80cm of cold, low density snow has fallen in this region, which has settled to create a storm slab 20-40 cm thick. Cold temperatures have kept the snow light and cohesionless in most areas, although friday night's forecast heavy snow, strong winds and rising freezing levels will add a new load to any buried weaknesses, and create a reactive "upside-down" snow pack.A crust now lies buried around 25-45 cm below the snow surface at elevations below 1900 m. Some areas reported this crust had a layer of surface hoar on it when it was buried. Occasional reports of small soft slab avalanches that have started to come in indicate this slab is starting to be become sufficiently cohesive to produce slab avalanches. There is a blog posting on the Forecaster Blog (link on the sidebar on the left) that discusses this issue in more depth. The mid-December surface hoar/facet persistent weakness, now down 70-120 cm, remains a concern only for very heavy triggers in thin slab areas.

Avalanche Problems

Wind Slabs

Forecast wind, snowfall and rising temperatures will create significant reactive wind slab development on cross-loaded and lee terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Storm Slabs

Forecast temperatures, wind and snow will add load and reactivity to a storm slab that has been developing throughout the week.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 6