Avalanche Forecast

Issued: Mar 21st, 2012 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs, Storm Slabs and Deep Persistent Slabs.

Avalanche Canada pmarshall, Avalanche Canada

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.

Summary

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.

Problems

Wind Slabs

An icon showing 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

An icon showing 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

An icon showing 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

Valid until: Mar 22nd, 2012 9:00AM

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