Bollettino valanghe

Kootenay Boundary

Mar 20 – 21, 2012Avalanche Canada
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Archiviato · scaduto 15 years ago

Pericolo valanghe

Thu
Fri
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Apri la mappa completa

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–4
    Fresh wind slabs are forming on exposed lee and cross-loaded features in response to new snow and loading by SW winds.

  • Cornices

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible - Likely
    Dimensione
    1–6
    Cornices are very large and may fail with daytime warming, especially with sunny breaks. There is potential for triggering deep slabs on underlying slopes.

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–7
    The deep nature of the mid-February surface hoar layer makes potential avalanches triggered on this layer large and destructive. Avoid thin snowpack areas where triggering is more likely.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Wednesday: Unsettled conditions with light convective flurries. Freezing level is around 1000m during the day. Winds are light from the S-SE. Thursday: Some uncertainty, but a weak system should give some snow - 5-15cm (greater amounts to the east). Freezing level steady around 1000m. Friday: A drier and sunnier day as a weak ridge builds in. Freezing level rising to 1500m during the day.

Avalanche Summary

We're still seeing almost daily reports of very large avalanches failing on the deeply buried mid-Feb surface hoar layer. The latest report is from the Lumberton snowmobile area in the East Kootenays. A snowmobiler accidentally triggered a very large (Size 3+) avalanche that resulted in a close call. Although triggering the deep persistent weakness is becoming less likely, if you do, the resulting avalanche could have fatal consequences.

Snowpack Summary

An additional 20-30cm of new snow on Tuesday with moderate to strong winds resulted in new wind slab formation in exposed leeward terrain. Several resistant shears have been noted in the storm snow. A sun crust on southern aspects and a spotty 2-6mm surface hoar on north and east aspects is down around 60-100cm. Below that, the more significant early February surface hoar is down 100-180cm. Snowpack tests show moderate to hard forces generating sudden planar shears on this layer. A melt-freeze crust, down 20-30cm, below 1800m provides some bridging to the layers below. Below the early February surface hoar layer, the snowpack is strong in most places. Cornices are very large and would act as a significant trigger for all the layers mentioned above if they drop.

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