Bulletin d’avalanche

South Columbia

Dec 29 – 30, 2017Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Sun
Mon
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Points saillants

Another snowfall overnight Friday into Saturday will continue to test the strength of buried weak layers. Adopt a conservative approach in the coming days.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–3
    A weak layer of surface hoar buried 50-80 cm deep has potential to produce large avalanches where the overlying snow has settled into a cohesive slab.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2
    30 to 50cm of low density new snow has accumulated in the region the past 2 days. Where accumulations are higher expect the new snow to sluff and gather mass in steep terrain. West and northwest winds have created soft windslabs in alpine lees.

Avalanche Summary

Recent reports are limited to both natural and human triggered loose dry and very soft storm slab avalanches in steep terrain to size 1.5 and 2. A report from just northeast of Nakusp on Monday shows a size 2 persistent slab release on a north aspect at 1800 metres. Expect continued potential for triggering loose dry avalanches in steep terrain and consider the potential to trigger persistent slabs as the load continues to increase on top of the mid December persistent weak layer.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

SATURDAY: 10-15cm overnight Friday into Saturday then cloudy with isolated flurries / Light to moderate northwest wind / Alpine temperature -14 SUNDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -10 MONDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -5

Snowpack Summary

25-50cm of low density new snow from the past 2 days has buried a recently formed layer of weak feathery surface hoar and/or sugary facets. A layer buried mid-December that consists of surface hoar, sun crust and/or sugary facets is now down approximately 60-100cm.The bond at this old snow interface is of critical importance in areas where the overlying snow has consolidated into a slab. The most concerning areas are those that saw pronounced surface hoar development before the storm, such as sheltered areas at and below treeline, sheltered northerly aspects in the alpine, or anywhere the surface hoar formed on top of a sun crust. Recent snowpack tests show wide ranging reactivity on this weak layer but suggest that it may be most reactive on northerly aspects.A rain crust that formed in late November is now buried 100-140cm deep. Recent evidence from the North Columbia region suggests it may be reactive in steep, variably loaded terrain features in the alpine.

Régions couvertes