Avalanche forecast

Kootenay Boundary

Jan 22 – 23, 2016Avalanche Canada
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Avalanche danger

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

The recent heavy load of new snow with wind will keep the hazard high for the next few days.A Special Public Avalanche Warning is in effect for this region.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    The January surface hoar layer may become reactive with heavy loading from new snow and/or rain. An avalanche on this layer has the potential to be large and destructive.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–4
    The storm slab will continue to build with incoming precipitation . Extreme caution should be used, especially in areas with heavy loading of new snow and wind. Below treeline, rain soaked snow may be extremely touchy

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Continuing snowfall Friday through late Saturday will bring 10 to 20cm of new snow to the forecast region. A developing ridge should allow for mainly sunny skies on Sunday, although close to the US border there may be continued precipitation.  Ridge top winds should be light and southwesterly through the weekend. Freezing levels may climb as high as 1700m by late Friday, and then drop to about 1000m for the rest of  the weekend.

Avalanche Summary

Reports from yesterday tell of avalanches up to size 2.5 with explosives, and several skier controlled and skier accidental avalanches up to 1.5 have been reported. In some cases, avalanches were triggered within the storm snow and then stepped down to the early January surface hoar layer. With forecast snow and wind, storm instabilities are expected to continue. Continued loading will also add mass and sensitivity to the deeper early January persistent weak layer. As the overlying slab gets thicker, avalanches at this interface will become larger and more destructive.

Snowpack Summary

Moderate snowfall and strong ridge top winds are expected to form new storm slabs at all elevations on Friday. 50-85 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, appears to be variably reactive. Test results suggest an improving bond at this interface, however, reports of remotely triggered avalanches and whumpfing show this layer to be sensitive to light loads in many areas. I would be increasingly wary of this potentially destructive layer at treeline and below, where it has been reactive on all aspects. Up to 120cm below the surface, a melt freeze crust from December is still producing significant results in snowpack tests. No recent avalanches have been reported at this interface,  however, it is worth keeping an eye on with forecast warming and continued storm loading. Below this, the snowpack is generally well settled and strong.

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