Boletín de aludes

South Coast

Dec 25 – 26, 2021Avalanche Canada
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Archivado · caducó 5 years ago

Peligro de aludes

Mon
Tue
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Lo esencial

Choose mellower, low consequence slopes. This storm system keeps on giving, and reactive slabs require extra time to bond with the snowpack when temperatures are colder. 

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    2–3

    Low freezing levels mean that the snow could be deeper and take more time that usual to bond to the rest of the snowpack. Keep an extra eye out for signs of instability today. 

    Continued snow and moderate to strong southwesterly winds are building storm slabs that may be reactive to riders. 

    These slabs may become less reactive as they settle after the storm, and as temperatures get colder, but give them some time to bond to the rest of the snowpack. 

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Moderate snowfall continues as temperatures drop. Enjoy the cold, dry, holiday pow!

Friday Night: Overcast. 0-10 cm of snow expected. Light southwest winds. Freezing level falling to between 250m and 0 m.

Saturday: Overcast. 10-15 cm of low density snow expected. Moderate southwest winds trending to strong south at higher elevations. Freezing level falls to sea level. 

Sunday: Mostly cloudy with possible sun in the afternoon. 2-4 cm of snow expected. Light to moderate southeast winds. Temperature @ 1500 m dropping to around -15 C.

Monday: Clear overnight, mostly cloudy through the day. Possible trace of snow expected. Moderate to strong northwest winds. Temperature @ 1500 m around -15 C.

Avalanche Summary

Here is a great Mountain Information Network (MIN) post from Friday morning in the Mt. Seymour area. It reported the overnight snow sliding in steeper areas on a rain crust from Thursday. As more snow fell through the day and overnight, the storm slabs may get bigger and could avalanche on slopes that are less steep.

This MIN post, and this one, from later in the day, do seem to follow that trend.

On Wednesday in the North Shore Mountains, a few natural and skier triggered wet loose avalanches were reported to size 1, running on a crust from December 21.

Snowpack Summary

20-30 cm of low density snow overlies 20-40 cm of snow that fell Tuesday and Wednesday with generally strong southwest winds. Expect the wind transported snow to be deeper and more reactive on leeward slopes.

This Mountain Information Network (MIN) post from near Mt. Seymour shows that snowfall amounts could be variable across the region. 

The storm snow sits on a variety of snow surfaces: variable wind slabs and hard wind-scoured surfaces in terrain exposed to the wind, and preserved powder and possible surface hoar (mostly reported in the north of the region) in sheltered areas. 

In the north of the region, a concerning layer of facets (sugary snow) can be found down 100-200cm over a crust that formed in early December. This layer seems to have become dormant, but was most recently reactive in thinner snowpack areas near ridge tops, where the facets are more developed and where the crust layers are more accessible to the weight of a person or machine. This problem is particularly hard to predict and tricky to manage. Get more details and photos in our forecaster blog. 

Terrain and Travel

  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Use small low consequence slopes to test the bond of the new snow.
  • Even a small avalanche can be harmful if it pushes you into an obstacle or a terrain trap.

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