Avalanche Forecast

Archived

Jan 8th, 2018–Jan 9th, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Cariboos.

New snow is falling on numerous weak layers and will likely be reactive to natural and human triggers. Storm slabs have the potential to step down and trigger deeper persistent weak layers. Conservative terrain choices are recommended.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

TUESDAY: Cloudy with light flurries, accumulation 5-10 cm, light to moderate westerly winds, alpine temperature dropping to -10 C over the day, freezing level below valley bottom.WEDNESDAY: Partly cloudy with intermittent flurries, light to moderate southwesterly winds, alpine temperature near -14 C, freezing level below valley bottom.THURSDAY: Partly cloudy with intermittent flurries, light westerly winds, alpine temperature near -10 C, freezing level below valley bottom.

Avalanche Summary

Storm slab avalanches were reported on Saturday, being triggered naturally and by skier activity. The slabs were small to large (size 1 to 2) and generally observed around treeline and alpine terrain with depths of about 20 cm. One release occurred in a loaded lee slope near ridgetop.Please share your observations through the Mountain Information Network.

Snowpack Summary

20-40 cm of new snow fell on surface hoar in sheltered slopes and a sun crust on steep solar aspects and may not bond well to them. The snow also fell with moderate southwesterly winds in the alpine, which likely produced small wind slabs in lee features.The new snow could create a dangerous slab above buried weak layers. Numerous persistent weak layers exist deeper in the snowpack. Dry snow overlies three layers composed of weak and feathery surface hoar, with the deepest layer (December 15) buried 40 to 70 cm. This layer is shallower in the north of the region and deeper in the south of the region. The weak layer is found most often at treeline and below treeline. As the snow above the weak layers becomes more cohesive and forms a slab, the setup has the potential to create easily-triggerable destructive slab avalanches. Snowpack test results in this MIN post show that this layer could be reactive.Deeper in the snowpack at depths of about 70 to 100 cm, a rain crust from November is producing variable snowpack test results, from sudden fracture characters to no result. This layer is considered dormant but could be triggered where the snowpack is thin.

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.