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Avalanche Forecast

Archived

Dec 8th, 2022–Dec 9th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Columbia, South Columbia, Blue River, Clearwater, Clemina, Jordan, North Monashee, North Selkirk, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, Retallack, Valhalla, Whatshan.

Conditions are more complicated than what meets the eye. Fresh wind slabs formed at upper elevations. Riders may be drawn to more sheltered areas around treeline to avoid these wind slabs, but should consider that this is where the persistent slab problem has been most problematic to date. Keep your terrain choices conservative and don't let good riding lure you into more hazardous terrain.

Confidence

Moderate

Avalanche Summary

Over the past couple days several size 1 to 2 wind slab avalanches were reported in the region . These avalanches were generally in treeline and alpine terrain on northerly aspects. Some of these avalanches have failed on the mid november surface hoar layer. Many backcountry users have reported observing whumpfing and shooting cracks which are signs of instability.

Snowpack Summary

Recent new snow, about 30cm, has been redistributed by moderate winds forming wind slab. 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 50 to 90cm deep, a layer of surface hoar, crust, and faceted crystals is the persistent layer of concern. This layer has been most reactive at treeline between 1700-2200 m, but it was also observed as low as 1450 m and widespread whumpfing and cracking was reported throughout the region.

Snowpack depths range from 70 cm at treeline to 170 cm in the alpine, with wind-loaded areas exceeding 200 cm.

Weather Summary

Thursday Night

Around 5cm of new snow expected. Moderate southwest winds with a low of -10 at 1800m.

Friday

Mostly cloudy with a trace of new snow expected. Light to moderate southwest winds with a high of -8 at 1800m.

Saturday

Cloudy with up to 5cm of new snow. Moderate southerly winds in the morning becoming light in the afternoon. High of -7 at 1800m.

Sunday

Flurries in the morning bringing trace amounts of new snow and then clearing in the afternoon. High of -5 at 1800m. Light winds.

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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.