Avalanche forecast

Kootenay Boundary

Jan 25 – 26, 2015Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

It's too warm for winter. Eye the snowpack with suspicion until the weather returns to normal.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    Warm temperatures may increase the reactivity of persistent slabs and storm slabs, which overlie a touchy weak layer of buried surface hoar.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–3
    Very warm temperatures and a chance of sun are expected to weaken the surface snow and create loose wet avalanches in steep terrain. Wet slabs are also possible, especially at low elevations where the snowpack is becoming saturated.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    3–6
    People are still triggering large avalanches  on a weak layer buried about a metre down. The very warm temperatures may increase the sensitivity of this problem. They could also be triggered by smaller avalanches stepping down, or cornice fall.

Confidence

Fair

Weather Forecast

Temperatures remain unseasonably warm through Monday, with the freezing level climbing to 3300 m. On Tuesday, the freezing level begins falling towards 2000 m. Light rain or snow is possible overnight Tuesday/Wednesday. Winds are moderate SW, easing to light SW by Tuesday evening.

Avalanche Summary

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). A couple of naturally-triggered size 1.5 storm slabs were also observed. At low elevations, several loose wet avalanches failed in steep terrain. Earlier this week, several deep persistent slabs were triggered by skiers, remotely and naturally.

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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