Bulletin d’avalanche

South Rockies

Dec 29 – 30, 2014Avalanche Canada
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Archivé · expiré 12 years ago

Danger d’avalanche

Wed
Thu
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Strong northwesterly winds will continue to form hard wind slabs. If the snow feels hollow, or drum-like, wide propagations are possible.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–3
    Between 15 and 30 cm of low-density snow has been shifted by strong southwest winds into hard wind slabs. Forecast northwesterly winds will also redistribute the surface snow, adding to the complexity of the wind slab problem.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–4
    A crust which formed in December should remain on your radar. Not much is known about its distribution in the South Rockies. However, in neighboring regions it has produced large avalanches. Dig down and test weak layers before committing to a line.

Confidence

Poor - Due to the number of field observations

Weather Forecast

The dry ridge of high pressure will persist bringing mainly clear skies for the entire forecast period. Ridgetop temperatures should hover around -23 for each day, while ridge top winds will be mainly moderate from the northwest.

Avalanche Summary

Wind slabs to size 2.5 were observed in high elevation terrain in the south of the region on Saturday. In one reported case, a wind slab in motion stepped down to the buried December crust. Since then, observations have been very limited. With forecast northwest winds, we could see a new round of wind slab activity as surface snow gets redistributed onto south-facing slopes.

Snowpack Summary

On the surface, up to 30cm of low-density snow exists. In the alpine and at treeline, strong to locally extreme winds have been conducive to blowing this snow into stiff and reactive wind slabs in exposed lee areas. 50 - 70 cm below the surface (more in wind affected areas) you may find a crust which formed in December. The crust, which may have surface hoar on top of it, may extend into the alpine to at least 2100 m. Where the crust exists, it may be bridging triggers from penetrating to deeper persistent weaknesses that formed earlier in the season. However, on high alpine slopes above where the rain crust formed, or in areas where rain didn't occur, deeply buried facets may still be susceptible to triggers.

Régions couvertes