Avalanche forecast

South Columbia

Jan 23 – 24, 2015Avalanche Canada
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Avalanche danger

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

Snow, rain, warm temperatures, and high winds are expected to initiate avalanches in this region.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    2–6
    A weak layer comprising of feathery surface hoar crystals and on south aspects a crust is buried between 40 and 60 cm below the surface. This layer was active during the last storm cycle and is likely to respond again to additional loading.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely - Certain
    Size
    2–5
    New snow or rain with high winds and warm temperatures will release avalanches from sufficiently steep terrain in a number of places.

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    A weak layer buried mid-December is still producing dangerous avalanches over a month after it was first buried. Particularly for slopes around treeline, there is a danger for a small avalanche to step down to this layer increasing the consequences.

Weather Forecast

A warm, wet storm is expected to bring 15-20 cm/mm snow/rain on Friday night and a further 10-20 cm/mm on Saturday. Freezing levels are expected to rise to around 2000 m on Saturday. On Sunday, a further 10-15 mm rain is expected on all but the highest peaks, with freezing levels rising to around 2400 m. On Monday, light residual rain, with freezing levels remaining high. Strong southwest winds are expected throughout the period.

Confidence

Good

Avalanche Summary

Forecast snow, rain, warm temperatures and high winds are a recipe for an avalanche cycle, especially when you throw in a couple of prominent weak layers. I anticipate an active cycle this weekend. Previous avalanche activity during and after the last storm system was widespread, with avalanches releasing up to size 3.5 on a variety of aspects and elevations.

Snowpack Summary

Moist new snow and rain forecast for this weekend will fall on a moderately dense upper snowpack. A weak layer that comprises feathery surface hoar crystals up to 15 mm lies buried between 30 and 50 cm below the surface, and may sit above a crust, particularly on south-facing slopes. This "mid-January" weak layer is widespread and has been the main focus for recent avalanche activity and I anticipate it to be active through the weekend as it is loaded by new snow and rain.The still problematic mid-December surface hoar/crust layer is now buried anywhere from 90 to 130 cm below the surface and continues to produce clean shears at and below treeline. Avalanches were reported to have stepped down to this layer during and after the most recent storm cycle. With additional loading and warm temperatures, I'd continue to treat this layer with respect and suspicion, particularly in the 1600-1900 m elevation band. A release on this layer would have very high consequences.

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