Bulletin d’avalanche

Northwest Inland

Mar 23 – 24, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

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

Forecast snowfall amounts are uncertain for Wednesday night and Thursday. If more than 10cm falls, the avalanche danger may be higher than posted.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2
    Continued light snowfall and strong southwest wind are forecast to form new wind slabs at treeline and in the alpine. Wind slabs may be especially reactive due to underlying hard surfaces.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–5
    Some cornices are the size of a bus, and will continue to grow with forecast snow and wind. Cornice collapses in the region continue to trigger large avalanches on the slope below.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–6
    A few persistent weaknesses exist in the mid snowpack (see snowpack description). These potentially destructive layers may become reactive with spring warming or with a large trigger such as a cornice fall.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Thursday

Weather Forecast

Generally light snowfall (5-10cm) is expected on Thursday. A dry ridge should develop on Friday bringing mainly clear skies while overcast conditions are forecast for Saturday. Ridgetop winds should be moderate from the southwest on Thursday and then become light for Friday and Saturday. Daytime freezing levels are forecast to hover between 1100 and 1200m for the forecast period.

Avalanche Summary

In recent days a natural cornice fall triggered a size 3 slab avalanche in the southwest corner of the region. The avalanche occurred on an east aspect in high alpine terrain and stepped down to a few persistent weak layers from January and December. This avalanche demonstrates how a cornice fall can trigger layers that may otherwise be difficult to trigger. New wind slab activity is expected in response to new snow and strong winds on Wednesday and Thursday morning.

Snowpack Summary

As of Wednesday morning, up to 5cm of new snow had fallen with moderate to strong southerly winds. At treeline and in the alpine small wind slabs are expected to have formed. These wind slabs overlie a variety of surfaces which include a hard crust on solar aspects above 1300, moist or refrozen snow on all aspects below 1300, and settled wind slabs in exposed high elevation terrain. A layer of surface hoar from early March can be found down 50-70cm but only seems to be a problem for the northern half of the region. Professional operators are still tracking two deep weak layers from early-January and early-February which can be found down about 1m or more. These layers are generally dormant but could wake up with substantial warming or a heavy trigger (like a cornice fall). Basal facets exist in most areas and have recently been reactive in the north of the region

Régions couvertes