Bulletin d’avalanche

Northwest Coastal

Nov 22 – 23, 2015Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Tue
Wed
Alpin
Sans niveau
Limite forestière
Sans niveau
Sous la limite
Sans niveau
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Points saillants

Given the very limited information on hand for this bulletin, I would tread cautiously and take the time to gather snowpack information as I go. As always, we would love for you to submit any observations from your day to the MIN.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    New snow and extreme winds on the weekend have formed destructive wind slabs, especially in the north of the region where storm totals were the greatest. Watch for wide propagations, especially in the lee of ridgecrests and terrain breaks.

Confidence

Poor - Due to the number of field observations

Weather Forecast

Lingering cloud may persist on Monday, but a general clearing trend is expected for the forecast period as a cool ridge of high pressure sets up over the region. Ridgetop winds should remain northerly, peaking on Monday at about 80kmh, then decreasing somewhat on Tuesday and Wednesday. Ridgetop temperatures should remain between -12 and -17 for all three days.

Avalanche Summary

In the north of the region on Saturday, explosives avalanche control produced several wind slab avalanches up to size 2.5 on north and east facing terrain above 1400m. At least one of the avalanches stepped down to a crust/facet interface 100cm below the surface. The newly formed storm slab may remain ripe for human triggering for the next few days, especially in areas where persistent weak layers exist.

Snowpack Summary

Reactive wind slabs have likely formed throughout the region in response to Friday and Saturday's snowfall, warm temperatures and extreme westerly winds. At lower elevations, precipitation fell as rain and the surface now exists as a refrozen crust. The new wind slabs are likely most destructive in the north of the region where storm accumulations totaled around 30cm and ridgetop wind speeds peaked at 130 kmh. The reactivity of these new wind slabs will likely change with elevation and underlying snowpack structure. Due to limited observations, I have very little confidence in what that underlying structure may be, although faceting, crusts and surface hoar development have been reported from various parts of the region. If I were traveling in the mountains, I'd maintain an investigative approach and dig down to test for weak layers before committing to a slope. If you've been in the mountains, please share your observations on our Mountain Information Network.

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