Bulletin d’avalanche

Northwest Inland

Feb 8 – 9, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Wed
Thu
Alpin
4 · Fort
Limite forestière
4 · Fort
Sous la limite
3 · Marqué
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Points saillants

Recent storm loading, buried weak layers, high freezing levels and solar radiation are a perfect recipe for widespread avalanche activity on Tuesday.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–4
    Newly formed wind slabs will likely remain sensitive to human triggering on Tuesday. Watch for increased reactivity in high elevation lee terrain.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–5
    Recent storm loading, solar radiation and skyrocketing freezing levels will increase the likelihood of waking-up deep and destructive persistent weak layers. Cornice falls triggered by solar radiation may also trigger a persistent slab avalanche.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–4
    Rising freezing levels and solar radiation on Tuesday will spark a round of loose wet avalanche activity on sun-exposed slopes. Loose wet avalanches may also step down to deeper, more destructive layers.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

Weather Forecast

On Tuesday expect mainly clear skies, moderate southwest ridgetop winds and freezing levels around 3000m. On Wednesday and Thursday the region should see light snowfall (3-5cm each day), strong southwest winds and freezing levels at about 1700m.

Avalanche Summary

In the Smithers area on Saturday there were reports of a few naturally triggered wind slab avalanches to size 2 on east and southeast aspects at about 1700m. On Monday, a natural avalanche cycle was also observed in the Howson Range on the west side of the region. Slabs were triggered by warming and were reported to be in the size 2.5-3 range with impressive propagation. Looking forward, solar radiation and skyrocketing freezing levels will likely spark a widespread round of loose wet avalanche activity on Tuesday. Warming will also promote cornice falls, wet slabs and persistent slab avalanches failing on deeper, more destructive weak layers.

Snowpack Summary

Light rain on Monday, and then rising freezing levels and solar radiation will likely leave most surfaces moist or wet on Tuesday. This warming will also have a significant destabilizing effect on the snowpack. Between 18 and 25cm of new snow fell on Sunday. Strong southwest winds have no doubt shifted these accumulations into reactive wind slabs in higher elevation lee terrain. These new accumulations have also added mass and reactivity to a developing slab which overlies buried surface hoar buried at the beginning of February. This layer was observed in the Hankin area and may exist in many other places. The early or mid January surface hoar layer is generally 50-80 cm deep, although it may be buried by well over 100cm of snow in the far west of the region. Observers have found this persistent weakness on all aspects and at all elevations. It consistently produces moderate "pops" results in snowpack tests. Below this, the Boxing Day surface hoar problem may also be lurking. The mid and lower snowpack is generally quite weak and faceted, especially in lower snowpack areas such as the Babines.

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