Avalanche forecast

Kootenay Boundary

Jan 20, 2018Avalanche Canada
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Archived · expired 9 years ago

Avalanche danger

Sun
Mon
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Recent loading from new snow and wind are adding to an already complex snowpack with several buried weak layers. Best to stick to simple terrain with no overhead hazards until the snowpack adjusts.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3.5
    The snowpack is complex and has produced very large and destructive avalanches on up to four separate weak layers buried 50 to 130cm below the surface. Expert level knowledge and experience is required to safely venture into the backcountry.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2.5
    Recent wind and storm snow has formed cohesive slabs above the most recent crust/surface hoar layer. If triggered these slabs have shown the potential to step down to one or more deeper weak layers buried in the snowpack.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

TONIGHT: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 700 m.SATURDAY: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -4. Freezing level 1000 m.SUNDAY: Snow. Accumulation 10-20 cm. Ridge wind strong, south. Temperature -4. Freezing level 1200 m.MONDAY: Flurries. Accumulation 2-5 cm. Ridge wind moderate, southwest. Temperature -5. Freezing level 1000 m.

Avalanche Summary

On Thursday explosive control work produced numerous size 1.5-2 storm slab avalanches as well as a size 2.5 and a size 3 that stepped down to the mid-December layer on north to northwest aspects above 2000 m. Ski cutting also produced numerous size 1-1.5 on all aspects from 1500-2100 m.Wednesday there were reports of a skier accidentally triggering a size 1 wind slab on an east aspect at 2000 m that is suspected to have failed on the most recent January 16th surface hoar layer, as well as a very large whumpf on a northeast aspect at 1800 m that is believed to have been associated with the mid-December layer.On Monday there were reports of two skier accidentals triggered on a northwest aspect between 1980-2000 m. The first was a size 1.5 and the second, triggered about thirty minutes later, was a size 2. A natural size 2 loose wet avalanche was also report on a southwest aspect at 2100m, as well as numerous explosive triggered size 2-3.5 slab avalanches running on weak layers deep in the snowpack.

Snowpack Summary

The snowpack is complex with several buried weak layers of concern that remain active and have produced several recent, large and destructive avalanches.Approximately 20-30 cm of storm snow now covers the January 16th surface hoar/ crust layer. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below the January 16th layer lies the January 5th interface which also consists of a crust/surface combination and is buried 50-90 cm below the surface. The spooky mid-December surface hoar layer is now 100-140 cm below the surface. This spooky interface continues to produce sudden snowpack test results and is most pronounced at treeline, but is also present below treeline. Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets. In shallow, rocky terrain the mid-December surface hoar and the late November crust seem to be reacting together which is a volatile combination.

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