Bulletin d’avalanche

Kootenay Boundary

Apr 15 – 16, 2012Avalanche Canada
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Archivé · expiré 14 years ago

Danger d’avalanche

Tue
Wed
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
3 · Marqué
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Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely
    Taille
    3–6
    A crust that developed in late March is now buried down close to a metre. Strong solar radiation and daytime warming may cause avalanches to step down and propagate on this layer causing large destructive avalanches.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–5
    Loose wet avalanches are expected during periods of daytime warming and during periods of rain showers. Overnight freezing above about 1200 metres should develop a hard crust that may deteriorate during the heat of the day.

  • Wet Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    3–7
    Wet slab avalanches are expected during periods of daytime warming and during periods of rain showers. Overnight freezing above about 1200 metres should develop a hard crust that may deteriorate during the heat of the day.

Confidence

Fair - Freezing levels are uncertain on Monday

Weather Forecast

The freezing level is forecast to drop down to about 800 metres on Sunday night, and then rise to about 1800 metres on Monday. Monday should start out with mostly clear skies. The wind is expected to build out of the west during the day on Monday and some light precipitation is forecast by Tuesday morning. Another weak ridge of high pressure is forecast to move into the interior ranges on Tuesday that should end the precipitation, but probably won't dry most areas up enough to see the sun. Gusty westerly winds are expected to develop overnight and rain showers and flurries should start by mid-day and continue into Wednesday night.

Avalanche Summary

Spring conditions exist in the region. Exposure to the sun, warm temperatures, and periods of rain are the most likely factors to influence the avalanche danger. If the temperatures go below freezing overnight, strong crusts should develop that are likely to hold the snowpack together. If the sun shines for a few hours, the crusts may break down quickly and moist surface snow avalanches may start running naturally. Continued warming from more sun, rain, or no overnight freeze, may cause surface avalanches to step down and trigger deeper wet slab avalanches. Prolonged warming may cause very deep releases on weak layers that were deposited early in the season, or on depth hoar that developed during the winter. It is important to monitor the temperature and the freezing levels as they may change rapidly from day to day.

Snowpack Summary

As we transition into spring the surface layers have a great deal of influence on the snowpack. When there is a solid re-frozen surface crust, travel is fast and easy, and the snowpack is held together by the surface cap. Any deeper persistent weak layers are unlikely to fail until the surface cap breaks down from daytime heating. When there is no crust, any deeper weak layers may fail depending on the amount of heat and the triggering force that is applied. If it cools off and snows, new snow and windslabs may not bond well to the hard spring crusts.

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