Avalanche forecast

South Columbia

Mar 11, 2017Avalanche Canada
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Avalanche danger

Sat
Mon
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Snow, wind, warming and sun-exposure will keep storm slabs touchy, and coupled with the potential for cornice triggers, the likelihood of massive deep persistent slabs is expected to increase.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Various persistent weaknesses strewn throughout the snowpack create the potential for large step-down avalanches. Warming and sun-exposure is expected increase the likelihood of these massive avalanches, especially with cornice-fall triggers.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–3
    Weaknesses within the recent storm snow are susceptible to human triggering. These storm slabs are particularly deep and touchy on slopes loaded by southerly winds and have the potential to step down to deeper persistent weaknesses.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

SATURDAY: A mix of sun and cloud with localized periods of intense sun-exposure and isolated light flurries. Increasing cloud with snow in the afternoon. Light becoming moderate SW winds. Freezing levels generally remaining in valley bottoms with alpine temperatures around -5 C.SUNDAY: Cloudy with 10-15cm of fresh snow by the morning and continued light flurries throughout the day. Light to moderate SW winds and freezing levels rising to 1500m for southern areas, but remaining near valley bottoms in the north.MONDAY: Mainly cloudy with another 5-10cm by morning and light flurries throughout the day. light to moderate SW winds and freezing levels rising to 2000m.

Avalanche Summary

Reports from Thursday include a few skier-triggered 10-40cm thick Size 1 storm slabs and loose dry sluffs, as well as two 50cm thick explosives-triggered Size 2's. A cornice also collapse naturally, but didn't trigger a slab on the slope below. Early reports from Friday morning suggested that a natural avalanche cycle was underway in response to lheavy loading from snow and wind.On Sunday and Monday we had reports of two very large natural deep persistent slab avalanches in the Selkirk mountains near Trout Lake. One was a 250 cm deep Size 3 on a north aspect on Sunday and the other was a 300 cm deep Size 4 on a southwest aspect on Monday that filled the creek at the bottom of the valley and ran 100m up the other side, both of which released on deeply buried old facets.

Snowpack Summary

Around 20-25cm of fresh snow has added to the 60-100cm of settled storm snow from the past week, which is bonding poorly to faceted snow, thin sun crust on steep southerly aspects, as well as more isolated small buried surface hoar. Southerly winds have formed touchy slabs with multiple weaknesses within and under this recent storm snow at all elevations . A persistent weakness buried mid-February is now down about 90-135cm and composed of a thick rain crust up to about 1800 m, sun crusts on steep southerly aspects, and spotty surface hoar on shaded aspects. This and deeper persistent weaknesses has seen a recent increase in more sudden snowpack test results and has been identified as a failure plane in a number of recent avalanches.

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