Avalanche forecast

Kootenay Boundary

Jan 20 – 21, 2016Avalanche Canada
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Avalanche danger

Fri
Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Reports of whumpfing and remote triggering indicate a weak layer buried at the beginning of January may still be sensitive to light loads. Choose conservative terrain and watch for clues of instability.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Weather models indicate up to 15cm of new snow may fall on Thursday. Strong southwest winds are expected to shift these accumulations into touchy wind slabs in high elevation lee terrain.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible - Likely
    Size
    1–3
    Recent storm accumulations overlie a weak layer of surface hoar. Although this layer seems to be variably reactive, touchy conditions may exist in areas where the recent storm snow has settled into a cohesive slab.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

On Thursday expect steady snowfall with 5-15cm of new snow falling throughout the day. An additional 20cm may fall on Thursday night and into Friday with areas to the south of the region receiving the highest accumulations. Light snowfall is forecast for Saturday. Ridgetop winds will be strong form the southwest on Thursday and Friday morning, and will then drop to light for the rest of the forecast period. Freezing levels are expected to spike at about 1600m on Thursday and Friday, and then drop to about 1000m on Saturday.

Avalanche Summary

In the north of the region, a few recent persistent slab avalanches to size 2 were remotely triggered between 1600 and 1700m from a distances of about 5 metres. This demonstrates the sensitive nature of this instability in some areas. A skier also ski cut a size 1 persistent slab avalanche in the Kootenay Pass area. The early January surface hoar was the culprit in all of these events. New storm loading on Wednesday also produced explosive and human-triggered storm slab activity to size 2.5 on a variety of aspects in higher elevation terrain.

Snowpack Summary

Up to 15cm of new snow is expected on Thursday. Strong ridgetop winds are expected to form new wind slabs at treeline and in the alpine. 45-65 cm below the surface you'll find a weak layer of surface hoar and a hard crust on steep solar aspects. This layer, which formed at the beginning of January, seems variably reactive. Some test results suggest an improving bond at this interface while remote triggering and Mountain Information Network reports of whumpfing show this layer is still sensitive to light loads in some areas. I would be increasingly cautious in areas where the overlying slab is deep and has gained cohesion through wind pressing, warming, and/or settlement. The mid and lower snowpack are generally well settled and strong.

Regions covered