Avalanche Forecast

Issued: Dec 24th, 2018 3:22PM

The alpine rating is considerable, the treeline rating is considerable, 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 and generally require patience and conservative terrain choices. Check out the new Forecaster Blog for a great explanation on how to best manage a persistent slab problem. Click here to read the blog.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY NIGHT: Cloudy with clear periods. Light south wind. Freezing level valley bottom.TUESDAY: Mix of sun and cloud. Light west wind. Freezing level valley bottom.WEDNESDAY: Cloudy with isolated flurries, trace accumulation. Light southwest wind. Freezing level valley bottom.THURSDAY: Mix of sun and cloud. Light southwest wind. Freezing level valley bottom.

Avalanche Summary

On Sunday, explosives and skier traffic triggered wind slab avalanches to size 2. Several explosives triggered avalanches to size 2.5 were reported in the region on Saturday. One natural size 2 avalanche that was triggered by a cornice was reported in the region on Friday.

Snowpack Summary

On Sunday, strong to extreme winds redistributed recent snow and formed wind slabs. 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.Pay attention to overhead hazards like cornices which could trigger persistent slabs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Wind Slabs

Strong to extreme winds have redistributed recent storm snow.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Valid until: Dec 25th, 2018 2:00PM