Bulletin d’avalanche

Cariboos

Mar 28 – 29, 2012Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Fri
Sat
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    New wind slabs will build with forecast snow and mod-SW winds. These exist on lee slopes below ridgelines and behind terrain features. Cracking and/or whumphing felt below you is a good indicator of unstable, wind effected snow.

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–5
    Large cornices exist and may fail. Cornice fall could be detrimental in itself, stay well back on ridgelines, and slopes below. A cornice fall provides a large trigger, and could initiate an avalanche on the slope below.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    4–8
    A weak interface down 1-2 m remains concerning. While avalanches on this layer have become less frequent, those that do release are very large and destructive. The last incident occurred Saturday March 24th, don't rule it out yet.

Confidence

Fair - Due to variable weather conditions

Weather Forecast

A continued low over the Gulf of Alaska will whirl a series of convective and synoptic systems into the southern part of the province, bringing remnants of those systems to the northern regions. The bulk of the precipitation will arrive Thursday, with continued bands of fast moving clouds, light precipitation and sunny breaks later Friday into Saturday. Thursday: Snow amounts 10-20 cm. Ridgetop winds light from the SW, gusting into moderate. Alpine temperatures -3, freezing levels near 1500 m during the day then dropping to 1000 m at night. Friday: Snow amounts 5-10 cm. Ridgetop winds moderate from the South. Freezing levels near 1300 m, then falling to valley bottom at night. Saturday: Occasional light flurries and cloud cover. Sunny breaks expected with intense solar radiation during those times. Freezing levels are expected to 1000 m.

Avalanche Summary

Natural avalanche activity seemed to have tapered off, with the exception of active solar aspects in the afternoon. Numerous small loose wet avalanches were reported on Southerly slopes up to size 1.5. On Monday several large natural solar induced cornice releases were reported. These occurred on NW-NE slopes from 2000 m- 2400 m. To note, none of theses cornice falls stepped down to the deeply buried persistent weak layer. I wouldn't rule out the potential, as we saw that layer reactive only 4 days ago. Numerous loose wet avalanches were also reported on Monday on various aspects, running up to size 2. This could continue in your local mountains if the sun pokes through the clouds over the next few days. On Saturday three, size 3 natural avalanches were observed in steep, rocky, unsupported terrain. They occurred between 2000-2800m on north to east aspects and are suspected to have run on the February persistent weak layer.

Snowpack Summary

Recently formed variable wind slabs exist in the alpine, treeline, and open areas below treeline. These can be found on lee slopes, and behind terrain features. Over the past several days, spring-like conditions have influenced the snowpack. Solar radiation has led to moist surfaces on sun exposed slopes up to ridgetop, other aspects moist below 1500 m with crust recovery developing at night. Cornices have grown large and have become unstable; they may act as a large trigger on slopes below. A well settled, consolidated slab overlies a persistent weak layer that was buried in early February. Now 1-2 m below the surface, these weaknesses include surface hoar, facets or crusts. Concern still exists potentially for deep and destructive releases at this interface. This may be a low probability, high consequence problem that may require a large trigger.

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