Boletín de aludes

South Coast Inland

Feb 24 – 25, 2020Avalanche Canada
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Archivado · caducó 7 years ago

Peligro de aludes

Wed
Thu
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Lo esencial

Recent snow rests on a weak layer so it may take longer than usual to bond to old surfaces and will likely remain reactive to human traffic. Continue to make conservative terrain choices while storm snow settles and stabilizes.

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely - Very Likely
    Tamaño
    1–2

    20-40 cm of recent snow is settling into reactive storm slab over a weak interface consisting of surface facets, surface hoar or sun crusts (aspect/elevation dependent). Storm slabs will be deepest where strong southwest winds have loaded lee terrain features in alpine and exposed treeline areas. A forecast switch in wind direction from south to northwest Monday will mean wind loading on a variety of aspects.

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2.5–3.5

    In the north of the region (e.g. Duffey, Hurley, Goldbridge), a buried weak layer lingers at the base of the snowpack. The most likely place to trigger this layer is in shallow and rocky terrain. We doubt that the new loads from the present storm will be sufficient to induce pervasive avalanche activity on these layers, but as is typical with deep persistent avalanche problems, there is uncertainty.

Weather Forecast

Sunday night: Around 15 cm new snow in the south of the region, trace in the north. Strong northwest wind. Freezing level dropping from 1000 m to valley bottom.

Monday: Mix of sun and cloud. Moderate northwest wind. Freezing level 800 m.

Tuesday: Mix of sun and cloud. Moderate to strong southwest wind. Freezing level 1000 m.

Wednesday: Mix of sun and cloud. Light to moderate southwest wind. Freezing level 1400 m.

Avalanche Summary

Natural storm slab and loose dry avalanches to size 1.5 were observed in the north of the region Saturday.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Snowpack Summary

20-40 cm of recent snow sits over a layer of widespread surface facets, surface hoar in sheltered areas or sun crusts on solar aspects. Recent avalanche activity indicates a poor bond at this interface. In the alpine and exposed treeline, recent snow has been redistributed by strong southwest to northwest wind, loading deep deposits into lee features.

In the north part of the region (e.g. Duffey/Hurley/Goldbridge), a deep instability exists in the snowpack, consisting of a weak basal facet-crust complex. Sporadic avalanche activity on this layer is keeping it on our radar, with the latest report described here. In the south of the region, including the Coquihalla and Manning areas, there are no concerns about deeply buried weak layers.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.

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