Avalanche forecast

Cariboos

Apr 20 – 21, 2012Avalanche Canada
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Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    New wind slabs have formed and reactivity may persist, especially where windslabs overlie crusts. Watch for triggering in gullies, behind ridgecrests and over steep rolls.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Snow stability can deteriorate very quickly with spring temperatures. Watch for loose wet avalanches on steep terrain, especially if the sun is shining.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    2–6
    Buried crusts will provide an ideal sliding layer for wet slabs, especially on sun-exposed slopes. Warmer temperatures at lower elevations are also a contributing factor. Spring temperatures will also promote glide crack activity.

Weather Forecast

Saturday: Mostly clear skies / light southwest winds / freezing level at 1900m Sunday: moderate precipitation intensifying to heavy overnight / strong southwesterly winds / freezing level at about 1900m Monday: moderate precipitation / strong southwesterly winds / freezing level at about 2200m

Avalanche Summary

A fairly widespread natural windslab avalanche cycle to size 2 took place on Friday in response to localized heavy loading on Thursday evening. I expect ongoing storm snow activity with a shift to more widespread wet snow instabilities with warming forecast for the weekend.

Confidence

Fair - Intensity of incoming weather is uncertain

Snowpack Summary

On Thursday, moderate to locally heavy accumulations formed wind slabs at treeline and above on a variety of temperature-affected surfaces that include well settled powder, wet grains and crust sandwiches. Rain has continued to penetrate and weaken the isothermal snowpack at lower elevations. The mid-February buried surface hoar layer is down about 140-220 cm, although avalanches releasing on this layer represent an extremely low probability-high consequence scenario. Cornices in the region are very large. With spring temperatures, and direct solar radiation these are more likely to become weak and fail. They could provide a large enough trigger to release deep layers on slopes below. Average snowpack depth in the alpine remains in the 3 m range. For more information on Spring Conditions and ways to mitigate risk, please visit the new Forecasters Blog Post.

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