Avalanche Forecast

Issued: Dec 4th, 2018 4:05PM

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

kdevine, Avalanche Canada

South Columbia.

Two buried weak layers in the snowpack appear to be gaining strength, but don't forget about them just yet. Be skeptical of large treeline features, steep south facing slopes and large, rocky alpine bowls.

Summary

Confidence

Moderate - Due to the quality of field observations

Weather Forecast

TUESDAY NIGHT - Clear periods / light to moderate northerly winds / alpine temperature near -12WEDNESDAY - Sunny with cloudy periods / light easterly winds / alpine high temperature near -10THURSDAY - Sunny with cloudy periods / light southerly winds / alpine high temperature near -8, low temperature near -11FRIDAY - A mix of sun and cloud / light to moderate southerly winds / alpine high temperature near -6, low temperature near -8

Avalanche Summary

Explosives continue to trigger avalanches to size 1.5 in the region.One size 2 skier triggered avalanche was reported to have run on the surface hoar layer at 2450 m on a northwest aspect on Dec 1Several large, notable avalanches that were reported in the last 10 days in the region are listed below:On December 1 a natural size 3 slab avalanche was seen on Mt. Begbie (east to northeast aspect above 2000 m). It is likely that this avalanche was initiated by a large trigger such as a rock or cornice fall, and that it ran on the October crust.On November 29 an explosives triggered size 2.5 avalanche ran on the October crust on a north to northeast aspect at 2300 m.On November 24 a human triggered size 3 avalanche was reported in the region. This avalanche likely ran on the October crust, as it was reported as a full depth avalanche. Two reports on this avalanche can be found on the Mountain Information Network. MIN

Snowpack Summary

35-65 cm of snow sits on a layer of surface hoar (weak feathery crystals) and sun crust on steeper south facing slopes. The surface hoar is mostly found at treeline, but it may be found in sheltered alpine areas. At the base of the snowpack is a crust that formed near the end of October. This crust is associated with weak, faceted (sugary) snow and has shown some reactivity in the region. This layer is most prominent in the alpine but may exist into upper treeline elevations as well.Snowpack depths taper quickly with elevation, many areas have over 200 cm in the alpine, between 100-170 cm at treeline, and 10-100 cm below treeline.

Problems

Persistent Slabs

35-65 cm of snow sits on a layer of surface hoar (weak feathery crystals) and sun crust on steeper south facing slopes. It is likely that this layer will be most reactive in areas where wind loading has promoted slab development.

Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

A crust at the base of the snowpack will result in large avalanches if triggered. Smaller avalanches, cornice and/ or rockfall may have the potential to trigger to this layer.

Avoid alpine bowls with a thin or variable snowpack.Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Dec 5th, 2018 2:00PM