Avalanche forecast

Kootenay Boundary

Mar 3 – 4, 2016Avalanche Canada
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Avalanche danger

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

Storm slabs are highly reactive to human-triggering and conservative terrain selection remains critical for the next few days. Extra caution is required on south-facing slopes in the afternoon if the sun pokes out.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    An old weak layer down 80-100cm has been dormant recently but could wake up with substantial warming, sun, or new load. Heavy triggers such as cornice falls or smaller avalanches have the potential to step down to this layer.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    Recently formed storm slabs overlie a touchy weak layer and are primed for human-triggering. Particularly touchy wind slabs have formed in leeward features from recent strong SW winds.

Confidence

High

Weather Forecast

FRIDAY: Cloudy with sunny breaks and a chance of flurries late in the day. Freezing levels reaching 1800-2000 m late in the day with moderate to strong southwesterly ridgetop winds. SATURDAY: Periods of snow bringing another 5-15cm. Freezing levels steady around 2000-2200 m with strong southwesterly ridgetop winds. SUNDAY: Periods of snow. The freezing level is around 1600-1800 m and ridge winds ease to light and variable.

Avalanche Summary

On Wednesday there was a report of a size 2.5 avalanche that was remotely triggered by a group on a ridge. This avalanche occurred in the northern part of the region on a NE aspect. In addition, there were reports of numerous size 1.5-2 natural storm slab avalanches and several size 2 explosive triggered storm slabs. These were on a variety of aspects between 1900 and 2100 m elevation. The slabs were releasing on the late-February crust/surface hoar layer down 30 cm.

Snowpack Summary

Recent storm accumulations varied widely across the region, but were generally highest around Nelson where up to 45cm of new snow was reported. Significant wind transport has been noted so expect to find deeper, more destructive slabs in exposed lee terrain. The new snow overlies a new layer of well-developed surface hoar (up to size 20mm) which is very reactive to human triggers. This layer is widespread above 1700m except on south aspects where the interface was cooked by the sun and now exists as a buried crust. 80-100cm below the surface you will likely find the mid-February crust/facet/surface hoar layer. Although this layer has become less likely to trigger, avalanches failing at this interface could be large and destructive.

Regions covered