Avalanche forecast

Northwest Coastal

Mar 28 – 29, 2013Avalanche Canada
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Avalanche danger

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

Large natural and human-triggered avalanches have occurred on a persistent weakness buried on March 9th. Continued reactivity is expected on this layer throughout the weekend.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–6
    Large developed cornices loom over slopes. Forecast warming will increase the chances of failure with the potential to initiate large avalanches failing on the March 09 persistent weak layer.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–6
    In some areas the March 9th layer can be triggered from a distance, propagate across large distances and create surprisingly large avalanches.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Expect loose wet sluffs to trigger in the afternoon when the sun is at its strongest.

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

No precipitation is expected for the forecast period. Mainly clear skies are forecast for Friday and Sunday, although high cloud is expected on Saturday.Winds will be light from the west on Friday switching to light and northwesterly on Saturday and Sunday.Freezing levels will climb steadily from 1200m on Friday to about 2400m on Sunday.

Avalanche Summary

Natural slab avalanches up to 2.5 have been reported, likely failing on the March 9th layer. Loose wet sluffs up to 2.0 have also been reported. As well, a recent size 2.5 slab avalanche was remotely triggered by a skier in the Hidden Lake area near Shames. Once again, the March 9 surface hoar layer was the culprit. Nobody was caught in the slide.

Snowpack Summary

Recent snow has settled with the influence of warm temperatures and surface hoar is growing on shaded slopes. Solar aspects and lower elevation terrain are now well into a daily melt-freeze cycle. Wind slabs may be found at alpine and treeline elevations on many aspects due to variable winds. Between 50-75cm below the surface is layer of surface hoar buried on March 9th which is variably reactive. In some areas it is stubborn and requires a significant trigger, while in other areas the layer is well preserved and primed for human triggering with the potential for very large avalanches. Check out the Forecaster's Blog for related discussion. The mid snowpack is generally well settled and strong. Cornices are large and untrustworthy, especially when the sun is out.

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