Archived

Avalanche Forecast

Jan 10th, 2014–Jan 11th, 2014

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

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

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

1: Low

The avalanche danger rating below treeline will be low

Regions: South Coast.

The forecast snow will be a significant test for weak layers buried deep in the snowpack and will likely cause a natural cycle of deep large avalanches.

Confidence

Fair

Weather Forecast

Tonight and Saturday:Â Heavy to very heavy snowfall tonight will continue into Saturday /Â Strong to extreme southwest winds / Freezing level 1200mSunday: Moderate snowfall in the north of the region, locally heavy precipitation in the south / Strong to extreme southwest winds / Freezing levels between 700 and 1000mMonday:Â Cloudy with scattered flurries or rain / Strong to extreme southwest winds / Freezing levels between 1500 and 2000m.

Avalanche Summary

A size 2 deep persistent slab avalanche was reported on Blackcomb Mountain on January 8. This slide was accidentally triggered by a snowcat and released on facets near the ground. Check out Waynn Flann's blog for photos and more information. Two size 2 slab avalanches (human triggered and natural) were observed in Marriott Basin in the Duffey Lake area last weekend. No injuries were reported. The avalanches occurred around 2100m on south-facing terrain. Both were thought to have ran on a crust/facet interface. Check out our Incident Report Database for more details. These incidents highlight the potential for large, full depth avalanches with additional load of heavy snow forecast for the weekend.

Snowpack Summary

Around 20-30 cm of new snow overlies a variety of old surfaces which may include surface hoar in sheltered terrain, wind-pressed snow in exposed areas, or a crust on previously sun-exposed slopes. Recent moderate S-SW winds have produced new wind slabs in exposed lee terrain and cross-loaded features. In the north of the region, recent storm snow is sitting on a weak layer of buried surface hoar which formed in early December. Facets from December's cold snap also seem fairly feature of the snowpack in this part of the region. In some areas, these facets may co-exist with a crust. In shallow snowpack areas, the facets may exist at ground level. These persistent weaknesses will likely wake-up with new snow forecast heading into the weekend.Snowpack depths at treeline range from 140-190 cm in the south of the region, and from 80- 130 cm in the north of the region.

Avalanche Problems

Storm Slabs

Storm slabs continue to build. Watch for reactive wind slabs to form in exposed north and east facing terrain at and above treeline.

Avoid open slopes with any steepness over 30 degrees.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 4

Deep Persistent Slabs

The shock of the forecast heavy snowfall could overload buried week layers in an unusually thin snowpack, particularly in the north of the region. This has the potential to cause very large destructive avalanches.

It is a good time to stay within the boundaries of a ski resort.>Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 3 - 6