Lawinenlagebericht

South Columbia

Mar 18 – 19, 2016Avalanche Canada
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Lawinengefahr

Sun
Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Rising freezing levels over the weekend will increase the likelihood of large natural and human triggered avalanches. Avoid slopes with overhead exposure where falling cornices could trigger large avalanches.

Lawinenprobleme

  • Cornices

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible - Likely
    Größe
    2–5
    Daytime warming and solar radiation will promote large cornice failures which could, in turn, trigger a large avalanche on the slope below.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    3–6
    The late February layer is becoming less likely to trigger, but it continues to surprise riders with large avalanches. I'd aim for well-supported slopes without convexities, and be increasingly cautious as freezing levels increase.

  • Loose Wet

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely - Very Likely
    Größe
    1–4
    As the sun comes out, surface avalanche conditions will include a mix of wind slabs in high elevation lee terrain, and pushy loose wet activity on steep, sun-exposed slopes. Loose wet avalanches may also trigger deep and destructive slab avalanches.

Confidence

High

Weather Forecast

Another sunny day forecasted for Saturday with freezing levels rising to around 2000m. Cloudy skies are expected to return either Saturday evening or Sunday morning, but the exact timing of this is uncertain.  If it's cloudy Saturday night, the hazard will increase on Sunday due to lack of "crust recovery". On Sunday, freezing levels rise sharply to as high as 2500m with possible flurries in the afternoon. The unstable weather continues into Monday. Generally light southerly ridgetop winds are forecasted throughout the period.

Avalanche Summary

On Thursday, a skier triggered a size 2 slab avalanche on a north aspect at 2400m.  The weak layer buried in late February was the likely culprit of this avalanche.  Additionally, several naturally triggered size 2 slab avalanches were reported on a variety of aspects in the alpine. They generally started as smaller loose wet avalanches triggered by solar radiation that then stepped down to the persistent weak layer that was buried late February. Solar radiation and increasing freezing levels will be the main driver of natural avalanche activity in the coming days.

Snowpack Summary

At ridgetop, cornices are huge and could become increasingly touchy with forecast solar radiation. Expect old wind slabs on lee features at treeline and in the alpine to become more reactive with solar radiation. Sunny skies have likely promoted a melt-freeze cycle on sun-exposed slopes. 60-110cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried in late February, seems variably reactive. In other words, it's still touchy in some places while in other places it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential to produce very large avalanches. Below this interface, the snowpack is generally strong and well-settled.

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