Boletín de aludes

Lizard-Flathead

Dec 27 – 28, 2021Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

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

 Watch for newly formed and reactive wind slabs as you transition into wind affected terrain. 

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

Problemas de aludes

  • Wind Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1.5–2.5

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

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    2–3

    A layer of weak facets (sugary snow) can be found down 100-150 cm over a crust from early December. Large natural avalanches avalanches failing on this layer have been reported as recently as Friday, Dec 24. Additionally, some operators have reported that re-loaded bed surfaces (areas that have already avalanched this season) have become reactive with new loads, while deeper snowpack areas that did not previously avalanche remain dormant, furthering the complexity of dealing with a persistent weak layer.

Confidence

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

Weather Forecast

MONDAY NIGHT: Cloudy / Light to moderate west wind / Low of -23

TUESDAY: Cloudy with isolated flurries; 0-5 cm / Light to moderate west wind / High of -17

WEDNESDAY: Sunny / Light northwest wind / High of -19

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

Avalanche Summary

Several explosive triggered size 2 storm slab avalanches were reported in the alpine near Fernie on Sunday.

Expect dry loose avalanches (sluffing) running far and fast in steep terrain.

On Friday, 3 large (size 2-2.5) natural slab avalanches were reported, all failed on a persistent weak layer 100-200 cm deep, likely triggered by the new load of snow. Explosives also triggered large (size 2.5) storm slabs.

Snowpack Summary

Recent storm totals reached over 100 cm of low density snow. Reports indicate the recent snow buried a layer of surface hoar in some areas.  

Expect dry loose avalanches (sluffing) running far and fast in steep terrain.

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

  • Use small low consequence slopes to test the bond of the new snow.
  • Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

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