Boletín de aludes

Coquihalla

Mar 6 – 7, 2023Avalanche Canada
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Archivado · caducó 4 years ago

Peligro de aludes

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

Variable winds have created wind slabs on all aspects.

Seek out low-angle sheltered areas for the best riding.

Problemas de aludes

  • Wind Slabs

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

    Heavy snowfall last week has given the wind plenty of material to build wind slabs. Southwest winds associated with the storms have now shifted to the northeast. Expect reactive wind slabs on all aspects and at elevations lower than you would think.

    In many areas, this new snow may be bonding poorly to the underlying surface and storm slab reactivity may persist for longer than is typical.

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Unlikely - Possible
    Tamaño
    1.5–3

    A crust formed in mid-January can be found down 90 to 130 cm. In areas around the Coquihalla, facets can be found sitting on the crust. This layer is of greatest concern with large triggers, such as a cornice fall, or by first triggering a smaller avalanche that could step down to this interface.

Confidence

Moderate

Avalanche Summary

On Saturday, avalanche control with the use of explosives resulted in very large avalanches. These were storm, persistent, and deep persistent slab avalanches. They ranged in size from 3 to 4. They occurred on all aspects. Most were initiated in the alpine but ran to the valley bottom.

It is important to remember that this avalanche control is to help keep the highway safe for travel, not the backcountry. With the amount of snow that fell in our region over the last seven days and now the wind, you should expect to see natural and human-triggered reactivity.

Snowpack Summary

Moderate easterly winds may have started to redistribute the up to 100 cm that fell last week. New and old wind slab formations will have built wind slabs on all aspects and at elevations lower than what you would typically expect. Temperatures remain cool so much of this snow will take some time to settle. Southerly winds redistributed this new snow at higher elevations and in exposed areas creating reactive wind slabs. The new snow may have a poor bond to the underlying stiff wind slabs and faceted snow formed by recent cold temperatures.

A melt-freeze crust formed in mid-January is buried up to 170 to 190 cm deep in the alpine and at treeline. It is still a concern but it seems to be gaining strength.

Weather Summary

Sunday Night

Mostly cloudy with clear periods, trace accumulation focused in western areas, winds east 10 to 20 km/h, treeline temperatures -10 to -8 °C.

Monday

Morning sun with increasing clouds, 5 cm accumulation starting late in the day, winds northeast 10 to 15 km/h, treeline temperatures -8 °C.

Tuesday

A mix of sun and cloud, trace accumulation winds, south 15 to 20 km/h, treeline temperatures -6 °C, and freezing levels potentially reaching 1300 m.

Wednesday

Cloudy with sunny periods, trace accumulation, winds southeast 25 km/h gusting to 45, treeline temperatures -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

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