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Avalanche Forecast

Archived

Dec 6th, 2021–Dec 7th, 2021

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

Regions

Cariboos.

Avalanche danger will gradually increase in wind-affected terrain this week. There have been some reports of a localized dangerous weak layer in the Barkerville area. 

Confidence

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

Weather Forecast

MONDAY NIGHT: Clear skies, no precipitation, light wind from the west, treeline temperatures around -15 C.

TUESDAY: Increasing cloud with some light flurries in the afternoon, no significant precipitation, moderate wind from the southwest, treeline temperatures warming to -10 C.

WEDNESDAY: 5-15 cm of low density snow by the morning with some clearing skies in the afternoon, moderate wind from the west, treeline temperatures around -12 C.

THURSDAY: Partly cloudy skies, no precipitation, light wind from the west with some gusts to 40 km/h, treeline temperatures around -12 C.

Avalanche Summary

In most parts of the region there were no reports of avalanches over the weekend, however, one size 2 avalanche was triggered in a north-facing bowl in Barkerville. This avalanche is suspected to have occurred on a 50 cm deep surface hoar layer that our field team also observed in that area.

Otherwise, the only other recent reports are from Thursday Dec 2, when two very large (size 3) avalanches were reported in the Valemount - Blue River corridor. One failed naturally on a south aspect, and the other was triggered by a cornice collapsing on a north-facing slope. Both avalanches ran on the early season crust/facet layer that is 150-200 cm deep in this area.

Snowpack Summary

Pockets of wind slab are found in lee features at upper elevations, with fun powder in protected areas and depressions. Open areas and higher elevations are windswept and hold little fresh snow. The early December crust exists below 1800 m on all aspects and has 10-30 cm of low density snow above it.

The snowpack structure is generally strong and settled with an early season crust layer about 150-250 cm deep in the alpine. One potential exception is in the Barkerville area where there have been some reports suggesting a weak layer of surface hoar may be 50 cm below the surface. Extra caution should be taken in this area since little is known about this layer at this time.

Check out our latest Forecaster Blog here.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Caution around convexities or sharp changes in terrain.

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.