Avalanche Forecast

Issued: Jan 12th, 2015 8:13AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Persistent Slabs.

rbuhler, Avalanche Canada

South Columbia.

The mid-December weak layer remains reactive to human-triggering and continues to produce large, destructive avalanches. Stay disciplined and continue to seek out conservative terrain options.

Summary

Confidence

Fair

Weather Forecast

A ridge of high pressure continues to be the dominate weather feature for the next three days. Tuesday should see a mix of sun and cloud, freezing levels around 700m, and light NW alpine winds. On Wednesday, an above-freezing layer (AFL) of air will form over the interior. This layer is expected to sit between 2000 and 2500m elevation. Alpine winds should remain light from the NW and sky should be mostly sunny with cloudy periods. The AFL persists on Thursday but should break down by Thursday afternoon. Thursday should see a mix of sun and cloud, and alpine winds are forecast to be moderate from the SW. The next weather system is expected for Thursday night or Friday.

Avalanche Summary

On Sunday, several natural size 3 glide slabs were reported around Nakusp. These released on the ground with average depths of 2.5m. These were east aspect between 1200 and 2000m elevation. Also reported was a size 2 which was remotely triggered by a helicopter from 100m away. This occurred on a west aspect at 2200m and released down 1m on the mid-Dec layer. Finally, a snowcat intentionally started a size 2 avalanche by pushing snow over the edge of a ridge. This also released on the mid-Dec layer down 60-100cm and occurred on a NE aspect at 1900m. Natural activity remains possible on Tuesday, especially on sun exposed slopes. Human-triggered persistent slabs remain the main concern for the foreseeable future.

Snowpack Summary

A few centimeters of new snow fell over the weekend. Below this new snow is likely a breakable melt-freeze crust which exists below around 1800m on all aspects and on steep sun-exposed slopes at all elevations. Recent warm temperatures have aided in the settlement of the nearly week old storm snow. Down 80-140cm is the touchy mid-December surface hoar/crust layer which remains sensitive to human triggering. This persistent weak layer continues to produce widely variable results from very easy shears to no shear at all which isn't very confidence inspiring. The trend shows that easy to moderate sudden planar shears and the resulting human triggered avalanches are most likely at treeline or just below treeline.

Problems

Persistent Slabs

The persistent weakness buried mid-Dec is spotty in distribution and widely variable with regard to reactivity which makes management tricky. It remains most prevalent at and just below treeline where human triggered avalanches are most likely.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 13th, 2015 2:00PM