Avalanche forecast

Kootenay Boundary

Apr 7 – 8, 2016Avalanche Canada
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Avalanche danger

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

Freezing levels remain above the mountain tops. Failing cornices could trigger large avalanches running to valley bottoms. Watch out for what's above your head.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    If the sun is shining, cornices present a significant hazard. Even if they don't trigger a slab avalanche when they fall onto a slope, they have a nasty habit of running surprisingly long distances.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Changes can be rapid, sometimes significant change is possible in a matter of minutes, certainly within an hour or two.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely
    Size
    3–6
    Rapid warm ups can awaken dormant weak layers deep in the snowpack.

Confidence

High

Weather Forecast

FRIDAY: Freezing levels soar to 3500m, sunny, light southwest ridgetop winds that rise to strong Friday night out of the northwest. SATURDAY: Freezing levels remain around 3000m, sunny, light southwesterly ridgetop winds. SUNDAY: Freezing level 3000m, sunny, light southwesterly ridgetop winds.

Avalanche Summary

No new avalanches were reported in this region on Wednesday. However, I expect to see widespread natural loose wet avalanche activity on Thursday when the recent storm snow is heated by solar radiation and rapidly rising freezing levels.

Snowpack Summary

Cornices are large, fragile, and could trigger deep slab avalanches that run to valley bottoms. Monitoring the overnight freeze of the snow surface is very important during the spring.  If the snow surface does not freeze overnight or if the crust is only a few cm thick, the effect of daytime heating and solar radiation will weaken the snowpack much more quickly than it would if there is a well frozen thick crust.  This is because the crust must first melt before the sun can weaken the snowpack. Deeply buried weak layers in the mid snowpack and near the ground still have the potential to wake up and become active with a rapid warm up. While unlikely, releases on these deeply buried weak layers would result in very large avalanches. Glide cracks are widespread, active, and best avoided. Low elevation and thin snowpack areas have become isothermal, meaning the snowpack is 0 degrees Celsius throughout. An isothermal snowpack is more prone to full depth wet slab avalanches during the heat of the day.

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