Bulletin d’avalanche

Purcells

Apr 21 – 22, 2014Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré

Points saillants

Avalanche danger will be greatest in the band at and above treeline where rain falls on previously dry snow which may lie above an older crust.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    Expect to see an increase in avalanche activity where rain affects previously dry snow. At higher elevations expect winds slabs will form on north aspects.
  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3
    Expect to see an increase in loose avalanche activity were the forecast rain saturates the upper snowpack
  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3–6
    The potential for very large deep slab avalanches needs to remain on your radar. Cornice fall, warming temperatures or a smaller wet or wind slab avalanche in motion could act as triggers.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Synopsis:  A southerly flow will generate widespread precipitation over the southern interior Tuesday and Wednesday before a weak ridge ushers in drier conditions on Thursday.  Temperatures will remain warm through the first part of the forecast period.Tonight and Tuesday:  Light to moderate precipitation - up to 15 cm of snow at upper elevations / Moderate south southerly winds / Freezing levels between 2000 and 2400m.Wednesday: Light flurries / Moderate westerly winds / Freezing levels falling to between 1500 and 1600mThursday: Sunny with cloudy periods and a chance of flurries /  Light southwesterly winds / Freeing levels around 2000m

Avalanche Summary

Small slabs have been recently triggered naturally and by skiers in areas where the upper snow is moist and sits above a crust.  At lower elevations and on solar aspects small to large loose wet avalanche continue to be triggered on steep slopes. Cornices collapses have been reported during periods of daytime warming. Occasionally these heavy triggers have caused large deep slab avalanches on the slopes below.

Snowpack Summary

Moist snow or a fresh crust may be found on the surface on slopes that have seen recent sun.  Between 10 to 30cm of snow overlies several widespread melt-freeze crusts on all but high elevation North aspects. Wind slabs can be found in lee features on N and E aspects in the Alpine.Several persistent weak layers still exist in the highly variable snowpack of the Purcells:-The mid-March sun crust/surface hoar layer down 50-80cm and the early-March crust/facet/surface hoar layer down around 80-120cm seem to be laying dormant for the time being.-The mid-February crust/facet/surface hoar combo is typically down 60 - 120cm. Direct triggering of this layer has become unlikely, however, cornice fall, a smaller avalanche in motion or prolonged warming may wake this layer up. The resulting avalanche would be very large and destructive.- Weak basal facets can be found in many areas, however triggering this layer is unlikely.

Régions couvertes