Bulletin d’avalanche

Northwest Inland

Jan 30, 2017Avalanche Canada
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Archivé · expiré 10 years ago

Danger d’avalanche

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

Fresh storm slabs have formed after a stormy weekend and persistent snowpack weaknesses have yet to fully heal. Sustained strong winds will keep conditions touchy on Monday.

Problèmes avalancheux

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–3
    New snow and strong winds have formed a fresh storm slab problem. Choose supported, low angle terrain while the new snow stabilizes and maintain constant awareness of overhead hazard. Conditions will be especially touchy in wind-exposed areas.

  • Deep Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3
    New snow and wind have added load to weak, sugary snow at the bottom of the snowpack and potential exists for full depth avalanches. This problem may be more likely in shallow snowpack areas near Kispiox and in the north of the region.

Confidence

Moderate -

Weather Forecast

Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds moderate to strong from the northwest. Alpine temperatures of -11. Tuesday: A mix of sun and cloud. Winds light to moderate from the northeast. Alpine temperatures of -12 Wednesday: A mix of sun and cloud. Winds light from the east. Alpine temperatures of - 10.

Avalanche Summary

Stormy weather has been obscuring visibility of higher elevation avalanche terrain, but a natural cycle was at least audible and suspected to Size 3 in the Howson Range on Saturday. Warm valley temperatures also allowed a number of loose wet avalanches to be observed occurring at lower elevations on Friday. Aside from new storm slabs that have formed and become a problem in their own right, it should be noted that these slabs have introduced a new load above our deeper snowpack weaknesses, increasing their likelihood of triggering. It remains to be seen to what extent avalanche activity over Saturday and Sunday has involved these deeper persistent weaknesses, but sustained strong winds and a changing wind direction can be expected to promote instability over the short term.

Snowpack Summary

Stormy weather over Friday to Sunday morning has delivered anywhere from 30-60 cm of new snow to the region. Including snow from earlier in the week, 40-80 cm of storm snow now sits above a widespread rain crust up to about 1300 m. At treeline and above, the storm snow is settling above wind slabs that formed on lee and cross loaded features in days before the storm. Our new snow has effectively shifted this wind slab problem into a more generalized storm slab issue. Below our the storm snow forming the upper snowpack, several buried surface hoar layers can be expected roughly 50-100 cm deep. Before the storm, these layers had been yielding moderate to hard results in snowpack tests. Many areas have hard slabs in the mid snowpack above weak sugary snow near the ground. Triggering a deep persistent slab above this sugary snow will remain a low probability high consequence scenario for some time, with probability increasing as sustained strong winds redistribute loose snow and add load to specific areas of the snowpack.

Régions couvertes