Archived

Avalanche Forecast

Mar 21st, 2012–Mar 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

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

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: South Coast.

Conditions vary greatly throughout the region with >60cm of new snow in the Coquihalla and much less further north. Local observations are crucial for safe backcountry travel.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Thursday: Cloudy with flurries - 2-5cm on average with more possible in the southeast corner. The freezing level rises to around 800-1000m during the day. Winds are light and variable. Friday: A mix of sun and cloud. Freezing level staying low near 800m. Winds remain light. Saturday: Mainly sunny and milder with the freezing level jumping to 1500m. Winds are light from the southeast.

Avalanche Summary

Currently the Coquihalla highway is closed for avalanche control. Areas north of Pemberton reported several skier controlled avalanches up to Size 1.5 within the recent storm snow (15-25cm crowns) on Tuesday. There was also one report of a larger avalanche in the South Chilcotin that may have failed on the mid-Feb persistent weakness.

Snowpack Summary

Conditions vary greatly throughout the region. Southeast areas (Coquihalla) have seen up to 60cm of new snow in the past 48 hours, while places like the Duffy Lake have seen considerably less. Expect new wind slabs to be deep in heavy snowfall areas and thin in other areas. Crusts down around 60cm can be found on solar aspects in the Duffey Lake, Chilcotin, and down closer to 1m in the Coquihalla. These exhibit moderate to hard, sudden results in snowpack tests. Deeper persistent weak layers are variable in distribution across the region. A crust/surface hoar/facet layer buried in early February, now down about 1.5m, is still is a key concern. It is especially prevalent on south-facing slopes above treeline, and all slopes below treeline. Although the likelihood of triggering this layer has decreased, the potential for surprisingly large avalanches remains. Cornices are reported to be very large and should be given a wide berth.

Avalanche Problems

Wind Slabs

Wind slabs are lurking behind ridges and terrain breaks. They may be hidden by new snow, making them hard to spot. Large cornices also threaten slopes below.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 2 - 6

Storm Slabs

Variable new and old storm slabs will be easiest to trigger on steep or convex terrain. Size and likelihood is much greater in the southeast section.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Deep Persistent Slabs

Persistent weaknesses, buried in February, still have the potential to create very large, destructive avalanches if triggered. Possible triggering mechanisms include a person/sled on a thin snowpack spot, cornice fall, or step-down avalanche.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 4 - 8