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Avalanche Forecast

Archived

Dec 23rd, 2019–Dec 24th, 2019

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

Regions

Cariboos.

The recent snow added load to buried weak layers and may still be reactive to human triggers. Conservative terrain selection is recommended.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT - Mainly cloudy / southeast wind, 10-30 km/h / alpine low temperature near -11

TUESDAY - Mainly cloudy / south wind, 10-30 km/h / alpine high temperature near -10

WEDNESDAY - A mix of sun and cloud / light northwest wind / alpine high temperature near -9

THURSDAY - A mix of sun and cloud / light southwest wind, 20-50 km/h / alpine high temperature near -8

Avalanche Summary

There is a notable weak layer of surface hoar that is down 40-100 cm and human triggering remains likely. Treat this layer with caution and choose conservative terrain.

On Sunday, there were reports of numerous natural and explosives triggered avalanches up to size 2.5

On Saturday, there were a few reports of natural and human triggered avalanches up to size 2. Check out this MIN report detailing the touchy conditions found in the Allan Creek area on Saturday.

On Friday, there were a few reports of natural and human triggered avalanches. Check out this great MIN report from Allan Creek that outlines reactive storm slab conditions. Here is another great MIN report about similar conditions further north in the region.

Snowpack Summary

The Cariboos have seen up to 70 cm of new snow over the past week, with most of it falling between Thursday afternoon and Saturday morning.

40-100 cm of snow is now sitting on a widespread layer of feathery surface hoar crystals. This layer has been responsible for several recent avalanches in the region. There is some uncertainty as to whether or not this layer will gain strength in the near future and so it should be treated with caution.

A weak layer formed in late November is now buried around 1 m or more below the surface. This is the layer of concern relating to the persistent slab avalanche problem. The weak layer may present as surface hoar, a crust, facets or a combination, depending on elevation and aspect.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • Storm slabs in motion may step down to deeply buried weak layers resulting in very large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.