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Avalanche Forecast

Archived

Dec 11th, 2022–Dec 12th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Columbia, South Columbia, Clemina, Esplanade, Jordan, North Monashee, North Selkirk, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Whatshan.

Continue to make conservative terrain choices while storm snow settles and stabilizes. Though natural avalanche activity has tapered off the risk of humans triggering avalanches remains.

Confidence

Moderate

Avalanche Summary

On Saturday numerous storm slab avalanches were observed up to size 2 on an interface within the storm snow and on the Dec 5 surface hoar. Whumpfing and cracking were observed throughout the region.

Friday two remotely triggered size 2 persistent slab avalanches were reported failing on the persistent weak layers buried mid November. Activity occurred from 1800-2300 mostly in sparsely treed terrain.

Snowpack Summary

Moderate southwest ridgetop winds have redistributed 40 - 50 cm of storm snow into deep pockets at higher elevations. On south facing slopes this new snow has fallen on a sun crust and in sheltered terrain it sits over a layer of surface hoar.

Buried 60 to 90cm deep, a persistent layer of surface hoar, crust, and faceted crystals is the primary concern within the snowpack. This layer has been most reactive at treeline between 1700-2200 m, but it was also observed as low as 1450 m and on all aspects.

Snowpack depths are highly variable and range from 90cm at treeline to 200cm in the alpine in wind-affected locations.

Weather Summary

Sunday Night

Mainly cloudy with isolated flurries. Light northerly ridge winds. Alpine temperatures, high of -5. Freezing levels drop from 900 m to valley bottom overnight.

Monday

Mix of sun and cloud with isolated flurries. Light northerly ridge winds. Alpine temperatures, high of -8. Freezing levels rise to 700m in the southern part of the region.

Tuesday

Mainly sunny with a few clouds. Light to moderate easterly ridge winds. A weak alpine inversion brings alpine temperatures around -4 while the valley bottom remains -10.

Wednesday

Mix of sun and cloud with isolated flurries. Light to moderate northerly ridge winds. Alpine temperatures, high of -9.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Give the new snow time to settle and stabilize before pushing into bigger terrain.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.