Bulletin d’avalanche

Northwest Inland

Feb 1 – 2, 2021Avalanche Canada
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Archivé · expiré 6 years ago

Danger d’avalanche

Wed
Thu
Alpin
2 · Modéré
Limite forestière
2 · Modéré
Sous la limite
1 · Faible
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Points saillants

Moderate southerly wind will form fresh wind slabs in lee terrain features in the alpine and at exposed treeline. These slabs will be particularly reactive where they overlie surface hoar.

Problèmes avalancheux

  • Wind Slabs

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

    Moderate southerly wind will redistribute the new snow and form fresh wind slabs in lee terrain in the alpine and at exposed treeline. Older wind slabs were formed on westerly aspects on previous days and may still be reactive and harder to recognize. Wind slabs will be particularly reactive anywhere they overlie surface hoar that was reported to be widespread in many sheltered areas. 

    Loose snow 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.

Weather Forecast

SUNDAY NIGHT: Cloudy, up to 6 cm new snow, moderate southwest wind, treeline temperature -10 C. 

MONDAY: Mainly cloudy, trace of new snow, light to moderate southerly wind, treeline temperature -8 C.

TUESDAY: Mainly cloudy, 2 cm new snow, moderate southerly wind, treeline temperature -12 C.

WEDNESDAY: Mix of sun and clouds, trace of new snow, moderate to strong westerly wind, treeline temperature -14 C.

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). Several large natural dry loose avalanches (up to size 2.5) were reported on Thursday. Fresh small wind slabs and small dry loose avalanches (sluffs) on steep alpine slopes were reported on Tuesday. 

Isolated large avalanches failed during the storm last weekend on buried surface hoar in the southwest of the region where snowfall amounts were on the higher end (up to 15 cm). 

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 scoured surfaces, older wind slabs in alpine and exposed treeline locations and open wind affected areas below treeline. 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. 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.

Régions couvertes