Bulletin d’avalanche

Lizard-Flathead

Dec 29 – 30, 2021Avalanche Canada
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Archivé · expiré 5 years ago

Danger d’avalanche

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

Westerly winds overnight are expected to form reactive wind slabs on lee features at treeline and above.

 Keep in mind that cold temperatures significantly increase the consequence of even minor injuries in the backcountry. 

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Possible - Likely
    Taille
    1.5–3

    Forecast strong westerly winds Wednesday night are expected to form fresh wind slabs on lee features at treeline and above.

  • Persistent Slabs

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

    A persistent slab problem formed by a crust down 50-150 cm has created a low likelihood, high consequence scenario that is difficult to forecast.

    Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with isolated flurries; 0-3 cm / Strong west wind / Low of -23

THURSDAY: Mix of sun and cloud / Light west wind / High of -17

FRIDAY: Sunny / Light variable wind / High of -19

SATURDAY: Mix of sun and cloud / Strong northwest wind / High of -18

Avalanche Summary

Numerous natural and explosive triggered storm slab and dry loose avalanches up to size 2.5 were reported at all elevations on Monday.

Additionally, an explosive triggered size 3 persistent slab was reported in the alpine. The avalanche failed on the crust formed in early December which is down 50-150 cm.

Snowpack Summary

Recent winds have created wind slabs on a variety of aspects and created a lot of variability in the upper snowpack.

A crust from early December is now 90-150 cm below the surface, and is found up to 2400 m. A layer of weak facets (sugary snow) has been reported above and below this crust. This is the layer of concern in our persistent avalanche problem, recent snowpack tests are generally showing hard results on this interface.

The lower snowpack consists of a variety of early-season crusts and mainly moist snow. Snowpack depths range from 100-250 cm at treeline elevations and taper quickly below 1800 m.

Terrain and Travel

  • 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.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.

Régions couvertes