Avalanche Forecast

Issued: Mar 12th, 2013 10:47AM

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

Avalanche Canada ccampbell, Avalanche Canada

Summary

Confidence

Fair - Intensity of incoming weather is uncertain for the entire period

Weather Forecast

Wednesday: Another 5-10cm of snow is expected with freezing levels rising as high as 1700m and extreme southwest winds. Thursday: 10-15cm of new snow, with freezing levels around 1800m and light to moderate southeasterly winds. Friday: Continued snowfall with another 5-10cm of accumulation, freezing levels remaining around 1800m and moderate southerly winds.

Avalanche Summary

Initial reports from Tuesday include numerous natural wet avalanches in the Coquihalla area involving saturated recent storm snow running on a crust. There was a report of a size 2 skier triggered slab avalanche on a steep southwest aspect in the Steep Creek area (Duffey Lake). This incident happened a few days ago, but highlights the lingering potential for triggering large slab avalanches.

Snowpack Summary

Approximately 10-20cm of new snow had already fallen by Tuesday morning and another 10-15cm is expected by the end of the day. This new snow is bonding poorly to the previous snow surface, which includes faceted snow, surface hoar, and/or a crust, but is most concerning where surface hoar is sitting on a crust on previously sun-exposed sheltered treeline slopes. Around a metre below the snow surface is a layer surface hoar buried on February 20th. Although this layer has a history of producing large avalanches, triggering this layer has now become difficult, and would most likely require a very large trigger on a steep, unsupported slope. Below this interface, the snowpack is strong and well settled.

Problems

Storm Slabs

An icon showing Storm Slabs
New snow is bonding poorly to the previous snow surface and continued loading is expected to overload this bond and possibly deeper persistent weaknesses. Wind is causing increased loading on exposed north through east aspects.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be cautious as you transition into wind affected terrain.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Mar 13th, 2013 2:00PM

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