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Avalanche Forecast

Archived

Dec 22nd, 2020–Dec 23rd, 2020

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

Cariboos.

40 to 60 cm of snow now rests on a buried weak layer which has recently resulted in large avalanches. Take a look at this example. It's good time to adopt a conservative approach to selecting terrain. 

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

TUESDAY NIGHT: Broken cloud cover, moderate northwest wind, alpine temperature near -12 C.

WEDNESDAY: Scattered cloud cover, light to moderate west wind, alpine temperature near -3 C with potential for a light alpine temperature inversion.

THURSDAY: Mainly sunny, light southerly wind, alpine temperature near -2 C with potential for a light alpine temperature inversion.

FRIDAY: Mix of sun and cloud, light southwest wind, alpine temperature near -5 C.

Avalanche Summary

There was a smattering of reported natural and human triggered avalanches on Saturday throughout the region with humbling photos of large avalanches. The MIN posts from the weekend really tell the story, you can view them all here. This observation from Sunday on a north facing slope looks to be failing on the mid December surface hoar.

Snowpack Summary

A steady stream of storms over the past week has resulted in 30 to 65 cm of light density new snow across the region with areas to the east around Blue River getting the larger amounts. Southwest winds have built slabs in lee features at upper elevations.

An active weak layer is now down 40 to 70 cm below the surface. In some areas it's surface hoar and in others it may be surface hoar on top of a crust. The bond at this interface is poor and avalanches have recently failed on this interface in the east the region. 

Near the base of the snowpack is a crust that was buried in early November. This crust likely has weak facets associated with it. There have been no recent avalanches reported on this layer, though it may be possible to trigger from shallow, rocky terrain.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Use careful route-finding and stick to moderate slope angles with low consequences.

Problems

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.

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.