Avalanche Forecast

Issued: Dec 26th, 2018 3:00PM

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

dsaly, Avalanche Canada

South Rockies.

Persistent slabs are tricky to manage. Avalanche activity is receding, but if triggered, an avalanche falling on the persistent weak layer could have serious consequences. Read the latest Forecaster Blog on the persistent slab problem here.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

WEDNESDAY NIGHT: Cloudy with isolated flurries, trace accumulation. Light northwest wind. Alpine low of -12C.THURSDAY: Mix of sun and cloud. Light northwest wind. Alpine high of -11C.FRIDAY: Mix of sun and cloud. Light increasing to moderate west wind. Alpine high of -10C.SATURDAY: Cloudy with sunny periods and scattered flurries, accumulating up to 5 cm. Moderate west wind. Freezing level rising to 1200 m.

Avalanche Summary

On Sunday, explosives and skier traffic triggered wind slab avalanches to size 2. On Saturday, explosives triggered avalanches on the persistent weak layer to size 2.5. One natural size 2 avalanche that was triggered by a cornice was reported in the region on Friday.Information in this region is limited. Post your observations to the Mountain Information Network here.

Snowpack Summary

Strong to extreme winds have redistributed new snow in the alpine and treeline, stripping areas exposed to the wind and creating hard wind slabs in wind-loaded terrain. In total, 60-90 cm of recent snow has formed a slab that sits on a persistent weak layer of facets (sugary snow) that formed during the dry weather in early December. Though avalanche activity on this layer has slowed down in recent days, it may still be easy for humans to trigger avalanches on this layer in certain terrain features. Steep features where the underlying ground cover is smooth, places where the snowpack depths are variable, and large convex features are some of the more likely places to trigger this layer.The lower snowpack has a weak structure composed primarily of facets. It is likely that an avalanche triggered on the persistent slab would step down to the lower facets, resulting in a full depth avalanche.

Problems

Persistent Slabs

60-90 cm of snow sits on a weak layer of facets (sugary snow). The snow below this layer consists primarily of facets all the way to the ground. Avalanches triggered on this layer will likely step down to the ground, resulting in large avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3.5

Wind Slabs

Watch for slabs in lee features, cross-loaded terrain, and open areas.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 27th, 2018 2:00PM