Avalanche forecast

South Columbia

Mar 13 – 14, 2016Avalanche Canada
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Avalanche danger

Tue
Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Spring "power flurries" may produce more snowfall than forecast. Pay close attention to how much snow falls in your area and select terrain accordingly.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Snowfall amounts are uncertain for Sunday night. Spring "power flurries" may produce significant snowfall and moderate winds may shift these accumulations into deep wind slabs in exposed lee terrain.

  • Cornices

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–5
    Large cornices loom over open bowls and alpine faces. Not only are massive cornice falls a hazard in themselves, but they can also act as a heavy trigger for slab avalanches on the slope below.

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    3–6
    A persistent weak layer continues to produce intermittent large avalanches. Although this layer is slowly becoming less likely to trigger, it has the potential to surprise with nasty consequences. I'd continue riding with a conservative mind set.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

On Sunday night and Monday morning expect 10-25cm of new snow and moderate southwest ridgetop winds. On Tuesday and Wednesday the region should see a mix of sun and cloud with generally light northwest winds. The freezing level should hover around 1400m for the forecast period. Note: Due to the convective nature of the Sunday night's weather pattern, the track and intensity of the precipitation is tough to pin down. There could be localized areas where snowfall total exceed 30cm.

Avalanche Summary

On Saturday quite a few size 1-2 storm slabs were observed failing naturally or by ski cutting. They formed in response to new snow and wind and were mostly triggered on north to northeast facing terrain at treeline and in the alpine. No new persistent slab avalanches were observed in the South Columbia region on Saturday; however, a few were noted in the size 2-3 range in the neighboring North Columbia and Kootenay Boundary regions sliding on the late February layer. They failed either naturally or under light loads on various aspects at treeline and in the alpine. This intermittent pattern is spooky, and sporadic persistent slab avalanches can be expected in the South Columbia region as well. With more snow and wind on the way, watch for new wind slab activity throughout the region on Monday.

Snowpack Summary

On Saturday and Saturday night highly variable amounts of new snow fell (10-47cm) throughout the region. Moderate ridgetop winds that developed at the tail end of the storm likely formed soft slabs in leeward terrain at treeline and in the alpine. 60-110cm below the surface you'll find a persistent weak layer comprised of surface hoar, facets and/or a thick crust. This layer, which was buried on February 27th, seems variably reactive. In other words, it's still touchy in some places while in other places it's really tough to trigger, and there's not much of a reliable pattern telling us what exact aspects are most suspect. I'd continue to be suspicious of steep, unsupported features at treeline and in the alpine as this layer has the potential for very large avalanches. Below this interface, the snowpack is generally gaining strength. At ridgetop, cornices are huge and potentially unstable.

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