Avalanche Forecast

Archived

Dec 23rd, 2020–Dec 24th, 2020

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

Cariboos.

A buried weak layer has produced recent avalanche activity. The best approach is to select conservative terrain at this time.

Confidence

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

Weather Forecast

WEDNESDAY NIGHT: Mostly clear skies, light southwest wind, alpine temperature near -12 C.

THURSDAY: Mainly sunny, light southerly wind, alpine temperature near -4 C with a chance of a weak temperature inversion.

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

SATURDAY: Mainly cloudy with scattered flurries, light west wind, alpine temperature near -7 C.

Avalanche Summary

On Monday there was a report of a human triggered avalanche that was suspected to have run on buried surface hoar. The MIN report can be view here.

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 last week 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. The distribution of this layer is variable. In some areas it's surface hoar and in others it may be surface hoar on top of a crust and in others it is very hard to find if it exists at all. 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, a crust that was buried in early November can be found. 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.