Avalanche Forecast

Issued: Mar 12th, 2012 10:17AM

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

Avalanche Canada pgoddard, Avalanche Canada

Summary

Confidence

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

Weather Forecast

Tuesday: Light to moderate snowfall continues. Moderate south-westerly winds. Freezing level around 500m.Wednesday: The next storm pulse arrives with moderate to heavy snow. Freezing level rising to 1000m. Strong south to south-westerly winds.Thursday: Heavy snow. Freezing level rising to 1500m. Strong south-westerly winds.

Avalanche Summary

A few cornice-triggered and small skier-triggered slabs in the size 1-2 range have been reported since it began snowing on Friday. Earlier in the week, warming prompted a widespread natural cycle in the Coquihalla and skiers triggered very touchy persistent slabs at low elevations. An unnervingly large natural avalanche cycle occurred last weekend, with slabs up to size 4.5 propagating 2-3km along ridgelines and stepping down to the mid-February layer. Similar avalanches are possible as storm loading continues this week.

Snowpack Summary

Strong winds and new snow are expected to create wind slabs and storm slabs which are likely to fail in steep terrain, and could overload persistent weak layers. Persistent weak layers are variable in distribution across the region. A hollow series of poorly-bonded crusts was reported on southerly aspects in the Duffey Lake and Chilcotin regions last week, which may have healed somewhat with dramatic warming at the end of last week. A lower weakness comprising surface hoar, facets and a crust, has produced whumpfs and sudden planar ("pops") results in snowpack tests. It is still is a key concern for step-down avalanches in many parts of the region. It is especially prevalent on south-facing slopes above treeline, and all slopes below treeline.

Problems

Wind Slabs

An icon showing Wind Slabs
New and old wind slabs exist on a variety of slopes. Very strong wind speeds may have created wind slabs unusually low on the slope. Large cornices also threaten some slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 5

Storm Slabs

An icon showing Storm Slabs
Storm slabs have been building deeper with each successive weather system. Initial reports indicate a weak interface in the recent storm snow. Be cautious with sluffing in steep terrain as well.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 6

Persistent Slabs

An icon showing Persistent Slabs
Continued diligence and conservative decisions are necessary. The potential for cornice triggers, remote triggering, step down avalanches, and wide propagations makes this problem particularly tricky to manage.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

4 - 8

Valid until: Mar 13th, 2012 9:00AM

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