Bulletin d’avalanche

Kootenay Boundary

Mar 1 – 2, 2013Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Sun
Mon
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    2–6
    The presence of weak layers buried in the upper snowpack means there is a risk of triggering surprisingly large large slab avalanches. The weak layers may be more reactive with additional loading from new snow, wind and rising freezIng levels.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–4
    New snow and wind will continue to build touchy storm slabs on all aspects and elevations. Natural avalanches are likely and rider triggering is very likely, especially on lee slopes that have been wind loaded.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    Rising freezing levels in combination with new snow and rain may produce loose wet avalanches from steeper terrain features within the upper snowpack.

Confidence

Fair - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

Saturday: A ridge of high pressure over the Kootenay region eases precipitation to light amounts during the day and moderate amounts developing in the evening. Strong winds easing to moderate from the SW.  High diurnal temperature trends and freezing levels rising to 2200 m. Sunday: Light-moderate precipitation accompanied by moderate-strong ridgetop winds from the NW. Alpine temperatures near -7 and freezing levels falling to 900 m. Monday: No significant precipitation expected with ridgetop winds blowing light form the South. Alpine temperatures near -8, and freezing levels hovering around 1200 m in the afternoon.

Avalanche Summary

On Thursday natural slab avalanche activity occurred on SE aspects around 1800 m up to size 1.5. Throughout the region loose dry sluffing occurred from steeper terrain features on all aspects and elevations. I expect the avalanche activity has ramped up and will persist through the weekend with additional precipitation, rising freezing levels and strong ridgetop winds.

Snowpack Summary

In much of the region, up to 80 cm recent snow overlies weak interfaces buried in mid-February (mainly surface hoar/ sun crust layers). The storm slab above these interfaces has the potential for wide propagations and surprisingly large avalanches, especially where winds have shifted the snow into slabs in the lee of terrain breaks. A thin freezing rain/rime crust formed last Friday, which is now buried by about 20-40cm snow.In the Rossland Range, surface hoar which was buried mid-week is 20-35 cm down and exhibits easy, sudden results in snowpack tests. As more snow builds over this layer, it could become touchy.Older snowpack weaknesses buried in the upper snowpack (Feb 4th and Jan 23 surface hoar/facet/sun crust layers) are still being tracked by professionals. There is some potential for triggering one of these deeper layers with a large trigger like an avalanche in motion, or from a thin-spot trigger point. The lower snowpack is generally well settled.

Régions couvertes