Boletín de aludes

Northwest Inland

Feb 2 – 3, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

Thu
Fri
Alta montaña
2 · Moderado
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Lo esencial

Wind slabs at upper elevations continue to be touchy to skier and rider triggers, especially where they sit above a buried surface hoar/ crust layer.

Problemas de aludes

  • Wind Slabs

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

    Moderate southerly wind will redistribute the recent snow and form fresh wind slabs in lee terrain in the alpine and at exposed treeline. Wind slabs will be particularly reactive anywhere they overlie surface hoar that was reported to be widespread in many sheltered areas. Loose dry avalanches (sluffs) are likely in steep and wind-protected areas. They might run longer and grow larger than expected. 

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the limited number of field observations.

Weather Forecast

Tuesday: A mix of sun and cloud with isolated flurries. Ridgetop wind light from the northeast. Alpine temperatures near -13 and freezing levels valley bottom. Possible alpine temperature inversion.

Wednesday: Mix of sun and cloud. Ridgetop wind 15-35 km/hr from the southwest. Alpine temperatures near -9 and freezing levels in the valley bottom.

Thursday: Snow 5-10 cm. Ridgetop wind strong from the southwest and alpine temperatures rising to -3. 

Avalanche Summary

A few small loose dry avalanches (sluffs) were triggered by skiers and released naturally on northern aspects in the alpine in the last couple of days (see this valuable MIN report). 

Sporadic deep persistent slab avalanches were reported 2-3 weeks ago (triggered with heavy loads such as explosives and cornices), but deeper weak layers appear unreactive under the current conditions.

Snowpack Summary

10-30 cm recent low density snow has buried surface hoar, which was reported as widespread below treeline and isolated at sheltered treeline and alpine locations. A buried sun crust can be found on steep solar aspects underneath the new snow. The new snow sits on widespread wind-pressed and scoured surfaces. A thick crust exists near the surface below 1000 m. 

The lower snowpack has two decomposing crust layers that have been causing a deep persistent slab problem for most of the past month, however no notables in the past 2-3 weeks. The upper crust is 70-140 cm deep in the Smithers area and continues to show occasional hard sudden results in snow pits. The deeper crust at the bottom of the snowpack continues to be a problem in shallow ranges like the Babines. These layers should be unreactive under the current conditions, but shallow rocky slopes should still be carefully assessed and approached with caution. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Watch your sluff: it may run faster and further than you expect.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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