Avalanche forecast

Kootenay Boundary

Dec 21 – 22, 2014Avalanche Canada
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Avalanche danger

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

Touchy avalanche conditions are expected for the next few days. Buried weak layers exist, and can surprise with nasty consequences.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    2–5
    An avalanche on Sunday stepped down to deeply buried weak layers which formed in November. These destructive layers should remain on our radar as they could "wake-up" with large inputs such as a cornice fall or an avalanche in motion.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    The storm may have ended, but recently buried weak layers will continue to produce large avalanches in many areas. Conservative terrain selection will remain critical.

Confidence

Fair - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

On Monday a dry upper ridge will bring mainly sunny skies, light northwest winds and freezing levels at about 1000m. On Tuesday expect increased cloud and light snowfall as a pacific system moves eastward into the region. Snowfall will intensify on Tuesday night and Wednesday. With this system we can expect up to 30cm of snow, moderate westerly winds and freezing levels at about 1000m.

Avalanche Summary

Widespread natural and remotely triggered storm slab avalanches to size 2.5 were reported from the Rossland Range on Sunday. They occurred on a variety of aspects and elevations. The recently buried crust/surface hoar interface was the culprit in these avalanches. In one event, a remotely triggered storm slab in motion stepped down to the November crust/facet interface near the ground on a planar slope at 2100m.Looking forward, I would expect natural storm slab activity to taper-off. However, human triggered large avalanches will remain a real concern for some time to come.

Snowpack Summary

Up to 50cm of recent storm snow has been shifted by strong winds into much deeper deposits in exposed terrain. This new snow overlies a prominent surface hoar layer above a thick rain crust that extends as high as 2400 m. This crust/surface hoar interface is now reactive, as widespread whumpfing and cracking were reported from the Rossland Range. High elevation north aspect slopes do not have the rain crust, but are still reported to have buried touchy surface hoar. On these slopes, deeper facets or buried surface hoar from earlier in the month may also be lurking. At the base of the snowpack, a crust/facet combo has become less likely to trigger, although a recent avalanche indicates this destructive layer should still on our radar on steep, smooth terrain at treeline and in the alpine.

Regions covered