Bulletin d’avalanche

South Columbia

Mar 9, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Storm slabs are primed for people triggering large avalanches, and have the potential to step down to deeper persistent weaknesses resulting in very large and dangerous avalanches.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–3
    A persistent weakness buried last week has the propensity to propagate slab fractures into large and dangerous avalanches. Deeper persistent weakness area also waking up in some parts of the region with isolated, but massive, recent avalanches.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    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.

Weather Forecast

THURSDAY: A mix of sun and cloud with flurries during the day, and a stronger system moving in late in the day.FRIDAY: Cloudy with 15-20cm of fresh snow accompanied by moderate SW winds. Alpine temperatures reaching -5 C.SATURDAY: A mix of sun and cloud with flurries bringing another 2-5 cm. Light to moderate SW winds and alpine temperatures around -5 C.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Avalanche Summary

Reports from Tuesday include numerous natural dry loose avalanches and one storm slab up to Size 2 within the recent storm snow. Skiers also triggered a couple Size 1 soft slabs in steep alpine terrain and a few cornices also fell off. On Sunday and Monday we had reports of natural, skier and snowcat triggered storm and wind slab, and dry loose avalanches up to Size 2. Of note were 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. Subsequent explosives control on Monday produced a Size 3 from the hang fire.

Snowpack Summary

Around 60-100cm of settled storm snow from the past week 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 at all elevations with multiple weaknesses within and under this recent storm snow. 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 solar aspects, and spotty surface hoar on shaded aspects. This layer 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. Its reactivity has been especially prominent over the crust at lower elevations.

Régions couvertes