Bulletin d’avalanche

South Columbia

Jan 1, 2018Avalanche Canada
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Archivé · expiré 9 years ago

Danger d’avalanche

Tue
Wed
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

There has been a noticeable increase in persistent slab avalanche activity over the last two days. This suggests the load sitting over persistent weak layers has reached a critical level. 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 60-100 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
    Possible
    Taille
    1–2
    40 to 70cm of low density new snow has accumulated in the region last week. Where accumulations are higher expect the new snow to sluff and gather mass in steep terrain. West and northwest winds have created windslabs in alpine lees.

Confidence

Moderate - Freezing levels are uncertain on Wednesday

Weather Forecast

MONDAY:  Mix of sun and cloud / Light northwest wind / Alpine temperature -9 TUESDAY: Mix of sun and cloud / Light to moderate northwest wind / Alpine temperature -4, possible temperature inversion WEDNESDAY: Cloudy with sunny breaks / Light west wind / Alpine temperature -1, temperature inversion

Avalanche Summary

Recent reports show numerous natural and human triggered loose dry avalanches in steep terrain to size 1.5 and natural storm slab avalanches to size 2 in the alpine and at tree line. There have been several reports of persistent slab avalanches naturally, skier and remotely triggered to size 2 on north and east aspects between 1500 and 2200m. Consider the potential to trigger persistent slabs on top of the mid December persistent weak layer as the temperature rises and the storm snow begins to settle and consolidate more rapidly in the coming days.

Snowpack Summary

40-70cm of low density new snow from last week 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 mid-December, 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