Bulletin d’avalanche

South Coast Inland

Jan 7 – 8, 2021Avalanche Canada
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Archivé · expiré 6 years ago

Danger d’avalanche

Sat
Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Points saillants

Tuesday night's storm brought 15-20 cm of new snow combined with moderate to strong wind. As a result wind slabs at upper elevations are the main concern on Thursday.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1–2

    New snow combined with primarily southwest wind on Tuesday night has created new reactive wind slabs.

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible
    Taille
    2–3

    A couple of problematic layers may be found around 80 to 180 cm deep, including weak layers of surface hoar and faceted grains above a hard melt-freeze crust. With the addition of a significant load of new snow, large avalanches may run naturally on these layers. This problem seems to be most prevalent in the north of the region around Duffy Lake.

Confidence

Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Wednesday Night: Mainly cloudy, light to moderate southwest wind, alpine high -5.

Thursday: Mainly cloudy with sunny breaks, light southeast wind, alpine high -3 freezing level 900m.

Friday: Flurries, 3-5 cm, moderate southerly wind, alpine high -3, freezing level 1000 m.

Saturday: Mainly cloudy with sunny breaks, light south wind, alpine high -3, freezing level 1000 m.

Avalanche Summary

Reports from Wednesday include a human triggered size 2 storm slab avalanche at 2000 m on a north aspect in the Duffy Lake area. As well a few natural size 1-1.5 naturally triggered windslabs in the alpine. On Tuesday there was a size 2 persistent slab avalanche reported on Tuesday on Joffre Shoulder. See this MIN report for more details.

 

Over the weekend, a large natural storm slab avalanche cycle was observed up to size 3 in much of the region and up to size 4 near Pemberton.

Persistent slab avalanche activity has tapered significantly since the cycle early last week, but persistent slabs size 2-2.5 were still triggerable by explosives on weekend.

Snowpack Summary

Over 70 cm of recent snow in the past week has seen extensive wind affect at upper elevations, with scoured windward aspects, wind slabs in lee features and growing cornices at ridgetop. In sheltered areas below treeline, recent snow may be sitting on surface hoar. 

A melt-freeze crust from early December is found around 80 to 180 cm deep in the snowpack. This crust may have surface hoar or sugary faceted grains sitting above it. This persistent weak layer is most prevalent in the north (e.g., Duffey Lake, Hurley) and found to a lesser extent in the south of the region.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

Régions couvertes