Avalanche Forecast

Issued: Mar 22nd, 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, Loose Wet and Deep Persistent Slabs.

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Mainly sunny and mild weather is expected through the weekend. The freezing level should be near valley bottom overnight and rise to 1200m Friday and 1500m on Saturday and Sunday. Ridge top winds are generally light from the south.

Avalanche Summary

Wednesday was a very active day in the Coquihalla Pass. Explosive control produced several Size 4 avalanches running full path and taking out extensive mature timber, and numerous Size 2-3 avalanches. A few large natural avalanches were also observed in lee terrain. Explosive control on the Duffy Lake road on Wednesday results in one Size 2.5 slab avalanche on a SW aspect and many large black holes with no result.

Snowpack Summary

Solar aspects will likely go through a melt-freeze cycle with a frozen surface overnight becoming moist throughout the day. Snowfall amounts over the past few days have varied significantly throughout the region with southeast areas (Coquihalla) receiving up to 60cm of new snow, while places like the Duffy Lake have seen considerably less. Expect 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

Likely - Very Likely

Expected Size

2 - 5

Loose Wet

An icon showing Loose Wet
Loose wet avalanches are likely in steep south-facing terrain during the day. These heavy wet slides could step down and trigger deeper slab avalanches.

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

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

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 23rd, 2012 9:00AM