Avalanche forecast

South Columbia

Feb 20 – 21, 2013Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    New wind slabs are expected to develop on Thursday with light snowfall and moderate winds. These new wind slabs may hide older wind slabs that formed a few days ago.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–6
    There are older layers of buried surface hoar and crusts that are unlikely to be triggered by the weight of a skier or sledder, but may be triggered by large additional loads like cornice fall or a slab avalanche in motion.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    This storm slab is expected to continue to be reactive to the weight of a skier/rider where it overlies a weak layer of surface hoar and sun crusts that was buried on February 12th.

Confidence

Fair - Intensity of incoming weather is uncertain on Friday

Weather Forecast

Thursday: Light snowfall intensifying in the evening / Moderate southwest winds / Freezing level at 900mFriday: Heavy snowfall / Strong southwest winds / Freezing level at 1000mSaturday: Light snowfall / Moderate northwest winds / Freezing level at 700m

Avalanche Summary

Recent explosives control produced slab avalanches to size 2.5. The avalanches occurred on a variety of aspects at treeline and in the alpine and are suspected to have ruin on the February 12th interface. A recent natural cornice fall also pulled out a size 2 slab on the slope below.

Snowpack Summary

Variable amounts of low density snow add to the recent storm slab that is between 20-50 cms across the region. These light accumulations may overlie wind slabs which formed a few days ago in the alpine and at treeline. The recent storm slab is expected to remain reactive where it is sitting on the weak surface hoar layer that was buried on February 12th. The recent storm slab has also been reactive on Southerly aspects where a sun crust formed during the period from February 8th-11th. Future loading on the recent storm may cause another cycle of natural activity, or an increased sensitivity to human triggers. There are older weak layers that are now buried down around 60-80 cms and also at about 110 cms. These layers have been unlikely to trigger by skiers, but they may still be sensitive to large loads like avalanches in motion or cornice fall.

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