Bulletin d’avalanche

South Coast

Feb 9 – 10, 2016Avalanche Canada
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Archivé · expiré 11 years ago

Danger d’avalanche

Thu
Fri
Alpin
3 · Marqué
Limite forestière
2 · Modéré
Sous la limite
2 · Modéré
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Points saillants

Destructive persistent slab avalanches remain a concern in the north of the region. Extra caution is required in the Duffey Lake, Birkenhead and Hurley areas.

Problèmes avalancheux

  • Cornices

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–4
    Cornices are huge and have become weakened by recent warming and solar radiation. They can be destructive by themselves, and may also become the trigger for a large slab avalanche on the slope below. Use extra caution around ridge crests.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Unlikely - Possible
    Taille
    3–6
    In the north of the region, persistent weaknesses continue to produce large and destructive avalanches in higher elevation terrain. Although the likelihood of triggering a persistent slab is dropping, the consequences could be severe.

  • Loose Wet

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    Freezing levels will remain high on Wednesday and loose wet avalanches may still be triggered in steep terrain. Use extra caution if the sun makes an appearance.

Confidence

Moderate - Freezing levels are uncertain on Wednesday

Weather Forecast

On Wednesday expect mainly overcast skies. On Wednesday night and Thursday the region may see 3-5cm of moist snow at higher elevations with similar amounts accumulating again on Friday. On Wednesday the freezing level should drop from about 2800m to 2000m, and should remain at that elevation for the rest of the forecast period. Ridgetop winds should remain mainly moderate from the southwest.

Avalanche Summary

On Sunday, a size 3 persistent slab avalanche was triggered naturally in the Birkenhead Lake area. The aspect and elevation are unknown; however, the mid-January surface hoar was the likely culprit. This speaks to the ongoing touchy persistent slab problem in the north of the region. On the same day, 2 people were partially buried and 1 person was fully buried in a size 2.5 slab avalanche on a south-facing alpine feature in Marriott Basin. The exact failure plane of the slide was unknown, but warming was thought to have played a major role in initiating the human triggered avalanche. Hats off to everybody who pulled-off a successful rescue. Check out the great Mountain Information post for more details. On Monday, widespread loose wet avalanche activity to size 3 was observed in steep, sun-exposed terrain. The gradual cooling trend will make heat-induced surface avalanches less likely; however, very large persistent slab avalanches are still possible in the north of the region.

Snowpack Summary

Extremely high freezing levels and solar radiation have left most surfaces moist or wet. This warming has also had a significant destabilizing effect on the snowpack. Cornices are reported to be huge and collapse has become more likely with daytime warming. About 50-80cm below the surface, you'll likely find a rain crust which formed on January 28th. This crust is widespread and exists up to about 1900m. Previous wet and heavy storms have likely flushed out the deeper mid-January surface hoar in the south of the region; however, this weakness which lies between 60 and 130cm below the surface is still reactive at higher elevations in the Duffey, Hurley and Birkenhead areas. This layer continues to produce sudden results in snowpack tests and has been responsible for recent destructive avalanches.

Régions couvertes