Bulletin d’avalanche

North 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 50-80 cm deep has potential to be reactive in areas where the overlying snow has settled into a cohesive slab.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    1–2
    30 to 50cm of low density new snow has accumulated in the region the past 3 days. 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 west wind / Alpine temperature -10 TUESDAY: Mix of sun and cloud / Light to moderate west wind / Alpine temperature -5, possible temperature inversion WEDNESDAY: Cloudy with sunny breaks / Light to moderate west wind / Alpine temperature -1, temperature inversion

Avalanche Summary

Reports from the past 3 days show several natural storm snow avalanches to size 2 at tree line and in the alpine on all aspects during the storm. There have been a several reports of remotely (from a distance) triggered persistent slab avalanches to size 2 on west, south and northerly aspects between 1400-1800m. Consider the potential to trigger persistent slabs as the recent storm snow settles more rapidly on top of the mid-December persistent weak layer with gradually warming temperatures in the coming days.

Snowpack Summary

30-50cm of low density new snow 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 50-70cm.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 80-120cm deep. A report from last week in the southwest end of this region suggests it may be reactive in steep, variably loaded terrain features in the alpine.

Régions couvertes