Boletín de aludes

South Rockies

Feb 1 – 2, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

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

Moderate to strong southwest wind continues to form wind slabs in lee terrain features in the alpine and at exposed treeline. Hollow sounds, whumpfing and shooting cracks are all signs that the recent snow is not bonding well with old surface layers.

Problemas de aludes

  • Wind Slabs

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

    Moderate to strong southwest wind will continue to redistribute the new snow and build wind slabs in lee terrain features in the alpine and at exposed treeline (see this MIN report from Saturday). These slabs will be particularly reactive where they overlie surface hoar. It is uncertain how well the transported snow will bond with other old surfaces, for example hard wind affected layers. 

    Cornices might grow larger and become more fragile.

Confidence

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

Weather Forecast

SUNDAY NIGHT: Mainly cloudy with clear periods, up to 4 cm of snow, moderate to strong southwest wind, treeline temperature -6 C, freezing level at 1500 m.

MONDAY: Mix of sun and clouds, trace of new snow, moderate to strong southwest wind, treeline temperature -5 C, freezing level at 1900 m.

TUESDAY: Mainly cloudy, 10 cm new snow and 20 cm in the west of the region, moderate to strong southwest wind, treeline temperature -4 C, freezing level at 1700 m.

WEDNESDAY: Mainly cloudy, 5-10 cm new snow, light southwest wind, treeline temperature -10 C, freezing level at valley bottom.

Avalanche Summary

Several loose dry avalanches up to size 2 were reported in steep alpine and treeline terrain over the last few days. Small wind slab avalanches were triggered by skiers on Wednesday. 

Snowpack Summary

20-30 cm of recent snow buried surface hoar and old surfaces. On steep solar aspects a sun crust can be found underneath the new snow. In the alpine and upper treeline, the new snow sits on top of layers of hard wind slab, scoured areas, sastrugi and isolated pockets of soft snow. A hard thick crust is found up to 1900 m. 

A solid mid-pack sits above deeply buried decomposing crust and facet layers near the bottom of the snowpack (100-150 cm deep). Avalanche activity on these layers has been sporadic and mostly triggered by large loads such as wind slab avalanches and cornice falls. Though unreactive under the current conditions, steep rocky slopes and shallow snowpacks 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.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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