Bulletin d’avalanche

Purcells

Feb 14, 2019Avalanche Canada
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Archivé · expiré 8 years ago

Danger d’avalanche

Fri
Sat
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Avalanche danger south of Cranbrook and south is CONSIDERABLE. Up to 40 cm of new snow fell on Tuesday in the most southern part of the region.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    1.5–2.5
    Two weak layers of surface hoar crystals are buried between 30 and 60 cm in the snowpack. The layers are most prominent around treeline and below treeline elevations.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2
    A storm slab problem is isolated to areas south of Cranbrook where up to 40 cm of new snow fell on Tuesday. Lingering windslabs at tree line and in the alpine may still be reactive in areas further north.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    2.5–3.5
    Particularly in thin snowpack areas, the base of the snowpack is composed of weak faceted grains and a crust. This layer has produced sporadic but very large avalanches. The probability of triggering this layer is low, but the consequences very high.

Confidence

Moderate -

Weather Forecast

WEDNESDAY Night: Clear periods, light southeast wind, alpine temperature -15 C.THURSDAY: Mix of sun and cloud, light to moderate southeast wind, alpine temperature -8 C.FRIDAY: Flurries, accumulation 5-10 cm , light to moderate southwest wind, alpine temperature -7 CSATURDAY: Flurries, accumulation 10-15 cm, moderate west wind, alpine temperature -8 C

Avalanche Summary

Recent activity on Monday and Tuesday includes a few naturally triggered wind slab avalanches in the alpine to size 1.5. A few large wind slab avalanches were observed in the region on Sunday, generally in alpine terrain and up to 60 cm deep.

Snowpack Summary

In much of the region 5-10 cm of recent snow sits above wind-affected snow and/or sugary facets. In the far south of the region (south of Cranbrook) 30-40 cm of new snow that fell Tuesday also sits above wind-affected snow or sugary facets. Beneath this lies two weak layers of surface hoar that were buried at the end of January and mid-January. These layers are around 30 to 60 cm deep. The mid-January layer may be associated with a melt-freeze crust on southerly aspects. These layers are most prominent at treeline and below treeline elevations.The base of the snowpack is composed of weak and sugary faceted grains that overly a melt-freeze crust. This weak layer has produced large and destructive avalanches that are sporadic in nature and very difficult to predict. It is most likely to be triggered from areas where the snowpack is shallow and weak. Rocky alpine bowls, ridge crests, and rocky outcroppings are some examples of terrain features to be wary of. See the Forecaster Blog here for more info on this problem.

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