Avalanche forecast

South Columbia

Feb 25 – 26, 2013Avalanche Canada
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Avalanche danger

Wed
Thu
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–6
    Numerous large avalanches are failing on a weak and reactive layer of surface hoar which now lies up to 100cm below the surface. Triggering this weakness may result in surprisingly large avalanches.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–5
    Snow and wind on Sunday night adds to an ongoing storm instability. Watch for increased slab reactivity in wind-affected terrain. In sheltered areas, the new snow may also react as a loose dry avalanche.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Tuesday: Light snowfall / Light northwest wind / Freezing level at 900mWednesday: Light snowfall/ Light west winds / Freezing level at 900mThursday: Light to locally moderate snowfall/  Moderate south winds / Freezing level at 800m

Avalanche Summary

On Sunday a skier remotely triggered a size 2 slab avalanche from 40 metres away. The avalanche, which occurred on a north aspect at 2000m, failed on the February 12 surface hoar. On Monday numerous deep size 2 avalanches were triggered off small rolls in a popular sledding area. These avalanches were also triggered on the February 12th surface hoar. These events speak to the touchy nature of the persistent avalanche problem. I would expect human triggering at this deep persistent interface to be a very real possibility throughout the week.

Snowpack Summary

Moderate to locally heavy snowfall on Sunday adds to ongoing potent storm instabilities which seem to be most reactive as a wind slab in exposed terrain or as loose snow in more sheltered areas. A weak surface hoar layer which was buried on February 12th now exists up to a metre below the surface in many places. The touchy and destructive nature of this persistent weakness remains a primary concern for professionals in the region. This interface has also shown reactivity on southerly aspects where a sun crust also exists. The mid to lower snowpack are generally strong and well settled. I anticipate significant cornice growth with the current weather pattern, and expect them to be weak and potentially destructive.

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