Bulletin d’avalanche

Northwest Inland

Feb 27, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

Mon
Tue
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible

Points saillants

Weak sugary snow in the bottom third of the snowpack continues to be a concern, as there is potential for large human triggered avalanches failing at this interface.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Changing wind directions Monday may form new wind slabs on south through southeast aspects. Old wind slabs may continue to linger on north through east aspects.
  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    2–4
    A lingering weakness at the bottom of the snowpack may remain sensitive to human triggering, especially in shallow snowpack areas.  Surface avalanches in motion also have the potential to step down and trigger deep persistent slabs.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Wednesday

Weather Forecast

Dribs and drabs of snow are expected for the first half of the week before the potential for a more significant system comes into play on Thursday.MONDAY: Scattered cloud cover, freezing level at valley bottom, light to moderate north/northwest wind, no significant precipitation. TUESDAY: Broken cloud cover, freezing level at valley bottom, moderate southwest wind, scattered snow showers. WEDNESDAY: Broken cloud cover, freezing level at valley bottom, moderate to strong southwest wind, 1 to 5 cm of snow. Visit avalanche.ca/weather for a more detailed mountain weather forecast.

Avalanche Summary

On Saturday wind slabs to size 1.5 were triggered by skiers on E aspects between 1600 and 1850 m. Previously, there was a report of a size 2.5 natural avalanche in the northern part of the region. This may have happened in the last 4 days and possibly failed on a persistent weak layer buried early february on a NW aspect in the alpine.

Snowpack Summary

10 to 20 cm of storm snow accumulating in the last week has been transported by the wind, and now sits on a variety of old surface conditions including isolated wind slabs, pockets of soft snow (5 to 10 cm deep), sun crusts, and surface hoar. A supportive rain crust exists below 1000 m. A layer of surface hoar that was buried on February 10th may exist 30 to 60 cm below the surface, but there's a fair bit of uncertainty regarding the reactivity and distribution of this layer. A stiff mid pack sits above weak sugary snow near the ground. Although possibly dormant, this basal weakness has the potential to produce very large destructive avalanches.

Régions couvertes