Avalanche forecast

Kootenay Boundary

Feb 18 – 19, 2016Avalanche Canada
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Avalanche danger

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

You may be managing more than just the new snow. A reactive crust lies up to 70cm below the surface, and can produce surprisingly large avalanches.

Avalanche problems

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–4
    Recent stormy weather has encouraged cornice growth. Large and fragile cornices may be destructive by themselves, but they may also act as a trigger for a large avalanche on the slope below.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–4
    New snow and wind on Wednesday night and Thursday have added to a developing storm slab. Storm slab avalanches may be surprisingly large if they fail on a buried crust located up to 75cm below the surface.

Confidence

Moderate

Weather Forecast

Light flurries are expected on Friday, although a brief pulse will bring 10-15cm of snow to region on Friday night. Expect a mix of sun and cloud on Saturday with generally clear skies on Sunday. Ridgetop winds will be strong from the west with Friday night's system and then become mainly light for the weekend. Daytime freezing levels should hover between 1300m and 1500m for the forecast period.

Avalanche Summary

On Wednesday, a few skier triggered avalanches were observed in the size 1.5 to 2 range. These avalanches failed on the February crust interface mentioned in the Snowpack Discussion section. Of note, a size 2 slab avalanche northwest of Kaslo (in the South Columbia region) partially buried 2 people and completely buried another person. The avalanche, which failed on the early February interface, occurred on an east aspect at 1700m. Nobody was injured in the avalanche, but it points to the touchy conditions which also extend south into the Kootenay Boundary region. New snow and wind on Thursday and then Friday afternoon will deliver its own mix of wind slab activity, but it will also add to the likelihood and consequences of avalanches failing on the buried early February crust.

Snowpack Summary

On Thursday up to 20cm of new snow fell at treeline and in the alpine. Southwest winds have likely shifted these accumulations into wind slabs in lee terrain. Rain below 1700m continued to saturate the upper snowpack. 35-80 cm below the surface you'll find a hard melt-freeze crust which formed during the 2nd week of February. This crust is quite widespread and may co-exist with weak surface hoar or facets. This variably reactive interface is the critical layer to watch in the region as it has caught a few people by surprise in recent days. A few buried surface hoar layers exist in the top 100 cm in drier areas on the west side of the region near Rossland. In other areas the notable early January surface hoar layer is 80-130 cm deep and poses a low probability/ high consequence threat. It should remain on your radar, especially in thin snowpack areas and during periods of significant warming or rapid loading.

Regions covered