Bulletin d’avalanche

Kootenay Boundary

Feb 15 – 16, 2018Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Sat
Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré

Points saillants

Two incoming storms will elevate the danger. Continue to choose conservative terrain and limit your exposure during the storms.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2
    Wind slabs will continue to grow on Friday with strong west wind and 5-15 cm of new snow. Beware of an interface buried up to 30 cm below the surface that could support wide propagations.
  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2.5–4
    Several deeply buried weak layers exist in the snowpack. Although the likelihood of triggering a persistent slab is gradually decreasing, the consequences remain very high.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

FRIDAY: Flurries throughout the day with 5-15 cm of new snow and then clearing in the evening, moderate to strong west wind, alpine high temperatures around -6 C.SATURDAY: Another storm pulse brings 20-30 cm of new snow throughout the day, moderate southwest wind, alpine high temperatures around -4 C.SUNDAY: Lingering flurries with light east wind and alpine high temperatures around -15 C.

Avalanche Summary

Wednesday's storm produced a few small (size 1) skier-triggered slabs on north facing terrain at treeline elevations, while explosive control produced a few size 2 avalanches in wind-affected terrain.Last weekend, three large persistent slab avalanches (size 3) were reported on northeast aspects in the Valhallas. Two were triggered with explosive and the third was naturally triggered. These were large avalanches with fracture depths of over a metre. Natural activity on deeply buried weak layers has wound down recently, but human triggering remains a real concern.Expect the incoming snow to form reactive slabs as well as potentially stress deeper weak layers.

Snowpack Summary

Fresh slabs will grow with the incoming storms. A few interfaces buried 20-30 cm below the most recent snow could potentially support wide propagations in the fresh storm/wind slabs. This includes sun crusts on steep south-facing slopes, a rain crust below 1800 m, small surface hoar in isolated areas, and hard wind slabs at upper elevations. Fragile cornices may be found at ridgetop. We now have 1-2 m of settled snow sitting on three significant surface hoar/crust layers that were formed early to mid-January, and back in December. Near the base of the snowpack a crust/facet interface exists that will likely haunt us all season. These persistent weak layers that lurk within the snowpack have produced large and destructive avalanches. Although this activity has been diminishing gradually, recent activity and continued sudden snowpack test results have kept them a top concern in the region.The complex and widespread nature of our multiple overlapping persistent slab problems continues to demand respect and diligence from backcountry travelers in the region.

Régions couvertes