Boletín de aludes

Northwest Inland

Feb 18 – 19, 2021Avalanche Canada
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Archivado · caducó 6 years ago

Peligro de aludes

Sat
Sun
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
2 · Moderado
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Lo esencial

Strong southwest wind is in the forecast. The wind will transport the 5-10 cm new snow falling throughout the day and form fresh reactive wind slabs in lee terrain features in the alpine and at treeline. 

Problemas de aludes

  • Wind Slabs

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

    The wind is forecast to shift to southwest overnight and increase to strong. The wind will form fresh wind slabs in the alpine and at exposed treeline throughout the day where soft snow is available for transport. 

    Recent shifting winds have created wind slabs on multiple aspects and all elevations. Older wind slabs may still be triggered by humans, especially where they sit on a weak faceted crystal layer.

    The strong southwest winds will contribute to cornice growth.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Increasing cloud coverage, south wind increasing from light to strong, temperature low -15 C.

THURSDAY: Cloudy, 5-10 cm new snow, strong southwest wind, temperature high -8 C.

FRIDAY: Cloudy, 5 cm of new snow, strong southwest wind, temperature high -4 C.

SATURDAY: Cloudy, 5-10 cm of new snow, strong southwest wind, temperature high -4 C.

Avalanche Summary

A couple natural wind slab avalanches up to size 2 and a few small wet loose avalanches out of steep solar aspects were observed on Wednesday. On Tuesday several small dry loose avalanches were reported as well as natural wind slab avalanches up to size 2 in the southwest of the region.

Wind slabs have been reactive to human triggering in wind loaded and cross loaded features over the weekend. Most ski cut results have been of size 1 to 1.5. On Saturday hard wind slabs were easy to trigger in the Crater Lake area as evidenced by this MIN.

In the Babine area a field team noted numerous size 1-2 wind slabs in the alpine on Saturday from the past 36 hours. They also posted this MIN from the Onion. This is in line with other avalanche observations from the outflow wind cycle like this size 2 near Miller Creek.

In the southwest of the region, two natural cornice triggered avalanches of size 2.5 and size 3 were reported on Friday and Sunday. They probably released during the outflow wind cycle.

Snowpack Summary

10-15 cm of soft snow overlies hard slabs, scoured slopes and sastrugi where outflow effects have been the strongest. In sheltered areas, the cold temperatures promoted surface faceting. The late January interface is down 30-50 cm consisting of isolated surface hoar in sheltered locations, and previous wind affected layers in exposed areas. On solar aspects, a buried sun crust can be found in places as well.

The lower snowpack has two decomposing crust layers. The upper crust is 70-140 cm deep and continues to show occasional hard, sudden results in snow pits. The deeper crust at the bottom of the snowpack is more prevalent in shallow snowpack ranges. These deep persistent layers seem to be dormant 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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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