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Avalanche Forecast

Archived

Dec 19th, 2019–Dec 20th, 2019

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

Regions

Cariboos.

Storm slabs are widespread and are expected to be reactive. Avoid avalanche terrain in the alpine, including exposure from above. Choose very conservative terrain as human triggered avalanches are likely.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system. Forecast snowfall amounts are uncertain.

Weather Forecast

THURSDAY NIGHT - Flurries, 10 cm / southwest wind, 50-70 km/h / alpine low temperature near -9

FRIDAY - Flurries, 5-10 cm / southwest wind, 40-60 km/h / alpine high temperature near -6 / freezing level 1200 m

SATURDAY - Flurries, 5-10 cm / southeast wind, 10-20 km/h / alpine high temperature near -6 / freezing level 800 m

SUNDAY - Cloudy with sunny periods / southeast wind, 20-30 km/h / alpine high temperature near -8

Avalanche Summary

Natural avalanche activity is expected to taper off somewhat, though natural avalanches are still possible. Human triggered avalanches remain likely.

Heavy snowfall likely resulted in a cycle of natural avalanches on Tuesday and Wednesday, leaving storm slabs very reactive to human triggering. Observations were limited on Tuesday and Wednesday due to poor visibility.

Snowpack Summary

A continuous wave of storms has delivered anywhere from 30-60 cm of snow to the Cariboos over the past few days. 50-90 cm of recent snow now sits above a widespread layer of large, feathery surface hoar crystals. New snow is expected to continue to accumulate and consolidate above this layer over the next few days, maintaining a high likelihood of human-triggered avalanches.

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. Below this, a variety of crusts from late October are buried deeper in the snowpack.

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.