Avalanche forecast

Kootenay Boundary

Jan 26 – 27, 2015Avalanche Canada
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Avalanche danger

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

Strong solar radiation may result in large natural avalanches releasing down to a deeply buried weak layer.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Persistent weak layers that were touchy during the recent storm may continue to be released by large additional loads, or by moist or wet avalanches in motion.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Moist or wet loose snow is expected to continue to release from light additional loads, or from strong solar radiation on Southerly aspects. 

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    Record breaking warm temperatures and extremely high freezing levels may result in deeply buried weak layers reacting to large loads like cornice falls or from light loads in thin snowpack areas.

Avalanche Summary

Moist or wet loose snow avalanches have been reported from several areas up to size 2.0 over the past few days during the warming event. On Saturday a skier triggered a size 2 persistent slab which failed on the mid-December layer. This was a surprising result because it was on a well-supported, concave terrain feature (which had also been heavily skied).

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Record warming on Monday should cool slightly on Tuesday as the ridge of high pressure begins to break down. Expect high overcast skies with periods of sunshine on Tuesday combined with moderate Southwest winds and freezing levels slowly descending from 3000 metres to around 2500 metres. High overcast is forecast for Wednesday with light winds and freezing levels around 1600 metres. The freezing levels should drop down to valley bottoms by Thursday morning. Expect valley cloud and a high overcast layer during the day on Thursday.

Snowpack Summary

10-40 cm rapidly settling recent snow overlies various surfaces including surface hoar, a thin crust, or a settled slab. Warm temperatures are affecting the surface layers and turning them moist or wet. Warming may also change the persistent slab properties such that triggering is more likely. The mid-Jan surface hoar layer is down about 20-60 cm. These large, well-preserved surface hoar crystals sit on a thin crust up to about 1900m on north aspects and all the way to ridgeline on south aspects. A deeper crust/surface hoar combo buried in mid-December is typically down 80-120cm and has produced some large avalanches recently. With the unusually warm temperatures and known weak layers in the snowpack, it's a good time to do some investigative digging and venture gently.

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