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Avalanche Forecast

Archived

Dec 27th, 2019–Dec 28th, 2019

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

Hazard may be improving but keep in mind that potential size and consequences of human triggered avalanches remain high. Deep instabilities like this are difficult to assess from the surface, so let terrain selection be your solution.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

FRIDAY NIGHT: Mostly cloudy, alpine low -12 C, alpine wind moderate from the west.

SATURDAY: Mostly cloudy with isolated flurries, alpine high -7 C, alpine wind moderate from the west.

SUNDAY: Scattered cloud, alpine high -7 C, light variable wind.

MODAY: Scattered cloud, alpine high -7 C, alpine wind building to strong from the west.

Avalanche Summary

No new activity has been reported since Monday.

Last weekend, there were reports of numerous natural and explosive triggered avalanches up to size 2.5

Snowpack Summary

Moderate winds over the last couple of days are likely to have blown around some of the 40 to 70 cm from last weekend's storm, forming soft windslab in alpine lees. Anywhere from 40 to 100 cm of snow is now resting on a widespread layer of large, feathery, surface hoar which we're calling the "December 12th Surface Hoar." This layer was the culprit for the large natural avalanche cycle during and after last weekend's storm. Activity on this interface has likely tapered off, but there remains some uncertainty as to how quickly the snowpack is gaining strength.

A weak layer formed in late November is now buried around 1 m or more below the surface. This interface may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect.

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Caution around convexities or sharp changes in terrain.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avalanche hazard may have improved, but be mindful that deep instabilities are still present.

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.