Avalanche forecast

Northwest Coastal

Mar 16 – 17, 2012Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–4
    Winds at ridgetop are high enough to blow snow into wind slabs behind ridges and other terrain breaks in the alpine and at treeline.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–6
    Cornices are reported to be very large and potentially unstable at this time. A cornice fall could be destructive by itself, and may also act as a trigger on the slope below.

Confidence

Good

Weather Forecast

Generally settled weather with flurries possible throughout the forecast period, Saturday, Sunday and Monday. Winds generally light, initially from the southeast, becoming southerly on Sunday and Monday. Freezing levels going up to around 800 m during the day and dropping down to valley bottom each night.

Avalanche Summary

On Thursday, two natural slab avalanches were observed, one size 1.5 on a north aspect at 1250 m with a fracture line 40cm deep in the recent storm snow. The other was a glide release at 575m near Terrace caused by warm temperatures. Numerous wet loose avalanches were also observed. On Wednesday, a size 3 natural cornice failure was observed in the region on Wednesday.

Snowpack Summary

Sporadic strong and variable winds have redistributed moderate amounts of recent storm snow into wind slabs that most commonly exist in the lee of terrain features at treeline and in the alpine.In the northern part of the region two persistent weak layers are on the radar of some operators: Surface hoar buried at the beginning of March is as much as 70cm deep. The early February persistent weak layers (surface hoar, facets, crusts) are over a metre down. Although triggering persistent weaknesses has become less likely, persistent slabs would be destructive in nature, particularly below treeline on isolated and sheltered steep terrain where buried surface hoar may be preserved. Cornices in the region are reported to be very large and potentially unstable.

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