Avalanche forecast

Kootenay Boundary

Feb 8 – 9, 2015Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

The snowpack will need time to adjust to the heavy load of the new snow, and rain saturation at lower elevations. Very large avalanches are still a concern. Conservative terrain selection remains critical.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    Buried persistent weak layers in the mid snowpack may be over-loaded by the new storm snow. Any avalanche on these deeper layers would be large and destructive.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–5
    Deep, dense and destructive storm slabs have formed at upper elevations. Human triggering will remain a concern, especially due to a recently buried crust/ surface hoar layer.

  • Wet Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Continued rain at lower elevations may result in destructive wet slab avalanches running to valley bottoms. Loose wet avalanches are also a concern in steep terrain.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Monday

Weather Forecast

The pineapple express will bring continued precipitation until Monday. On Tuesday and Wednesday a warm dry ridge of high pressure will develop. Monday: Up to 15cm of snow at higher elevations / Strong southwest winds / Freezing level at 1800m Tuesday: Mix of sun and cloud / Light northwest winds / Freezing level at 1800m Wednesday: Mix of sun and cloud / Light West winds / Freezing level at 1800m

Avalanche Summary

Over the last few days there was a widespread natural avalanche cycle to size 3. Most of the avalanches were storm slabs which formed in response to new snow and wind. At lower elevations, a couple of wet slabs to size 3 were observed. With forecast weather storm slab avalanches will remain a concern with the potential to step down to deeper persistent layers. Loose wet and wet slab avalanches will also remain likely.

Snowpack Summary

Heavy precipitation over the past few days has resulted in deep and dense storm slabs above about 1800m. At lower elevations heavy rain has saturated the snowpack. Moderate to strong southwest winds have shifted the new snow accumulations into much deeper deposits in exposed lee terrain. Weaknesses are expected to exist within the new storm snow as well as on a hard melt freeze crust which exists up to 80cm below the surface. This crust, which formed at the end of January, is reported to have weak overlying surface hoar and should be treated with caution.Deeper in the snowpack the mid-January surface hoar remains a concern. It can be found down 60-120 cm across the region, but in most places it is about one metre down. In some locations it has reportedly gained quite a bit of strength, but elsewhere it is still producing "sudden" failures in snowpack tests. The mid-December surface hoar layer is now 80 to 140cm below the surface and has become unlikely to fail. The current storm pattern should be a good test to see if it will become active again.

Regions covered