Avalanche Forecast

Issued: Jan 12th, 2018 4:50PM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada cgarritty, Avalanche Canada

Very dangerous avalanche conditions will persist in the Cariboos - especially in the south of the region. A Special Public Avalanche Warning is in effect in this region.

Summary

Confidence

High -

Weather Forecast

Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Light to moderate southwest winds. Alpine high temperatures to -3, rising overnight.Sunday: A mix of sun and cloud with thicker valley cloud due to a temperature inversion. Light south winds. Freezing levels rising to 1700 metres with alpine high temperatures to +3. Cooler at lower elevations.Monday: A mix of sun and cloud with thicker valley cloud due to lingering temperature inversion. Moderate southeast winds. Freezing levels to 1700 metres with alpine high temperatures to +5. Cooler at lower elevations.

Avalanche Summary

Reports from the past couple of days include several Size 1-1.5 persistent slab releases that were triggered remotely (from a distance). With slab depths of 30-100 cm, both the January 5 and December 15 surface hoar layers were noted as failure planes. 'Step down' type releases were also observed. These reports all came from the south of the region.Considerably more avalanche activity has been reported from the adjacent North Columbias, where numerous persistent slabs and storm slabs have recently been observed running naturally and with remote triggers. Sizes have ranged from small to very large (Size 1-3) with slab depths from 30-100 cm. This activity has been observed on all aspects and elevation ranges, although the deeper releases running on the December 15 surface hoar have been focused at treeline and below.Conditions in the south of the Cariboo region are quite similar to those the North Columbias at the moment, so it is advised to consider activity in this neighbouring region as indicative of the potential that exists in the Cariboos.

Snowpack Summary

Recent storms brought 20-50 cm of new snow to the region. This snow sits on surface hoar on sheltered slopes as well as sun crust on steep solar aspects and the deepest accumulations exist in the south of the region. Shifting winds since the storm have redistributed loose snow into wind slabs on a variety of aspects around exposed terrain features.As the new snow continues to consolidate, it is forming a dangerous slab above several persistent weak layers that exist in the snowpack. The first of these is the surface hoar that existed at the old snow surface. Recent snowpack tests and avalanche activity show high reactivity at this layer. Below it, the December 15 surface hoar is now buried 50 to 80 cm deep. Reactivity at this layer has been gradually increasing and is most apparent at treeline and below. Both of these layers are buried deeper, show greater reactivity, and present greater danger in the south of the region. Deeper in the snowpack at depths of about 70 to 100 cm, a rain crust from November has shown less reactivity in recent snowpack tests. It is considered dormant but could be triggered in thin spots around variable snowpack areas in the alpine.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent snowfall in the south of the region has formed storm slabs over a touchy weak layer. Storm slab releases have been observed 'stepping down' to produce large avalanches. Wind slabs at higher elevations are a greater concern in the north.
If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.The recent snow sits on a persistent weak layer and will require more time than usual to stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer buried 40-70 cm deep is becoming increasingly reactive in many areas of the BC interior. This layer has produced numerous large avalanches and is an increasing concern in the Cariboos - especially in the south of the region.
Numerous large avalanches have run on this layer in well supported, treed terrain.Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Jan 13th, 2018 2:00PM