Bulletin d’avalanche

Kootenay Boundary

Mar 3 – 4, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

Mon
Tue
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–5
    Generally lurking below ridgecrests, behind terrain breaks, and in gullies. Wind slabs are very touchy and continued strong winds over the forecast period is expected to overload weaknesses.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–6
    Persistently weak buried surface hoar demands continued diligence and conservative decisions. The potential for remote triggering, step down avalanches, and wide propagations, makes this weakness particularly tricky to predict.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    Touchy weaknesses within and under the recent storm snow are expected to become more reactive with warm temperatures and new snow load.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Monday

Weather Forecast

An "almost pineapple" weather pattern is setup across the province, and while the neighboring regions to the north receive the full brunt of the firehouse, the northern track of the jet leaves the South Kootenays with very little precipitation. SUN: FZLVL stays near 1500m, all day. Less than a mm of water is expected. 2km Winds; Mod SW decreasing throughout the day. MON: FRLVL lowers to 1200m. 10 - 15cm of snow is expected above 1200m, light rain below. Winds strong/extreme W, SW during daylight hours. Tue: A ridge of high pressure slides into the region bringing more seasonal cool temperatures, high solar & light winds.

Avalanche Summary

Two significant human triggered avalanches occurred on Thursday, before we had much wind or significant warming. 1. A group of sledders triggered a size 2.5 avalanche below treeline near 1700m in a moderately angled cutblock, resulting in a full burial. That same day, a snowboarder in the Nelson backcounty triggered a size 3.0 avalanche below treeline, SE aspect, 84cm in depth, 400m wide, running full path to the valley bottom. The snowboarder was able to cut out of the slide early and was unharmed. On Friday a group remote triggered a size 2.5 avalanche from 30m away on a SE facing slope near 2000m in the Slocan. The crown depth was 90cm, failing on the early Feb. SH. Sluffing was less of an issue Friday as storm snow settled out a bit.

Snowpack Summary

20-40cm of new snow is sitting on the Feb. 29 interface which consists of surface hoar on shady aspects and a thin sun crust on south aspects. A weak storm snow interface of well-preserved stellars is down approximately 50-60cm and reactive to human triggers on steep shady (cold) slopes at and below treeline. However the main snowpack feature of concern continues to be the surface hoar buried mid-February, which is now down 70-120cm and still giving sudden snowpack test results. This persistent weakness is susceptible to remote triggering and has the ability to propagate in low angled terrain, and the overlying slab structure creates the potential for step-down avalanches. Although generally getting deeper and harder to trigger, avalanche professionals throughout the region continue to treat this weakness with caution.

Régions couvertes