Avalanche forecast

South Columbia

Jan 27 – 28, 2015Avalanche Canada
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Avalanche danger

Thu
Fri
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Avalanche danger will drop as the temperature cools, however, a widespread melt-freeze crust will make for challenging riding.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    A layer of weak surface hoar siting on a crust is buried by 40 to 70 of moist snow has been responsible for most of the recent avalanche activity.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Unlikely - Possible
    Size
    3–6
    A deeper layer of surface hoar is still producing the occasional large avalanche given a large enough trigger in the right spot. It is especially a concern on open slopes around treeline. 

Avalanche Summary

As the temperature drops I expect that avalanche activity will slow down.   The recent snow, rain, and wind were a great test of buried persistent weaknesses in the snowpack and resulted in a widespread avalanche cycle.  The mid-January surface hoar layer has been responsible for the majority of the recent avalanche activity although there have been reports of occasional releases to ground or the mid December layer in the Selkirks.

Confidence

Fair

Weather Forecast

Freezing levels will continue to drop as a cold front moves across the province.  A ridge of high pressure will build over the coast Wednesday resulting in clear skies and light SW winds over the interior.  A weak front will move across the province on Friday and may produce isolated flurries.

Snowpack Summary

I suspect that freezing levels rose to about 2800m during the recent warm spell and that rain saturated the upper snowpack.  At upper elevations the surface is heavily wind affected.  A breakable crust already exists in the alpine and as the freezing level continue to drop down to the valley floor a widespread melt freeze crust will form on all aspects and elevations.  I suspect that at lower elevations warm moist snow may have destroyed the mid-January surface hoar layer.  Where it still exists it can be found down between 40 and 80 cm.  The midpack is broken by the mid-December surface hoar layer that is now 80 to 140cm below the surface.

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