Bulletin d’avalanche

Purcells

Mar 2 – 3, 2012Avalanche Canada
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Archivé · expiré 15 years ago

Danger d’avalanche

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

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Generally lurking below ridgecrests, behind terrain breaks, and in gullies. Fresh wind slabs are expected to be very touchy and continued strong winds over the forecast period is expected to overload weaknesses.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely - Very Likely
    Taille
    1–3
    Weekend conditions lend themselves to continued cornice development & with fluctuating freezing levels, I expect cornice fall, especially on Sunday. Cornice failure may act as a trigger for persistent slab avalanches

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    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.

Confidence

Good

Weather Forecast

An "almost pineapple" weather pattern is setup across the province, and while the neighboring regions to the north & west receive the full brunt of the firehouse the Purcells will likely see a more modest garden house amount. The latest model run show the Purcells receiving a bit more moisture than originally expected with slightly lower Freezing Levels (FZLVL). SAT: FZLVL will be on the rise, climbing to 1700 m by 4:00 pm. 11.7 SWE forecast, expect around 15 cm of snow above 1700m, rain below. 2km wind: West, Mod increasing to upper end of Mod throughout the day. SAT NIGHT: FZLVL drops to 1000m overnight. SUN: FZLVL near 1800m most of the day. 14.3mm SWE expected. MON: FRLVL slowly lowers throughout the day. 3.1mm SWE forecast. Winds initially Mod SW Tapering to Light W late in the day.

Avalanche Summary

Natural size 2.5, failing on mid Feb. SH in the north of the region. A few different remote triggered avalanches to size 1.5 on steep south facing slopes in the south of the region.

Snowpack Summary

A cohesive slab continues to settle over the mid-February surface hoar, which is generally down in the 40-55cm range. Recent reports include whumpfing and cracking, and moderate but sudden compression 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. Basal facets have only been reactive on steep, shallow, and rocky slopes, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.

Régions couvertes