Avalanche Forecast

Issued: Dec 13th, 2019 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low.

Avalanche Canada ahanna, Avalanche Canada

Caution areas of shallow snowcover in steep, rocky terrain. These are common trigger points for avalanches which can then propagate out into deeper snowpack areas and result in large avalanches.

Summary

Confidence

Moderate - Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

Friday Night: Clear periods, alpine low -9, light northwest wind.

Saturday: Mix of sun and cloud with isolated flurries, alpine temperature -7, light northwest wind.

Sunday: Mix of sun and cloud with isolated flurries, alpine temperature -10, light northwest wind.

Monday: Mix of sun and cloud, alpine temperature -10, light northwest wind.

Avalanche Summary

The south of the region has been reporting skier triggered loose dry avalanches in old, faceted snow up to size 1.5. A common theme surrounding recent avalanche activity is that avalanches are most often triggered in shallow snow in steep, rocky terrain, then propagating out into thicker snowpack areas, sometimes stepping down to deeper persistent weak layers.There have been numerous reports from the north half of the region of natural windslab and persistent slab avalanches averaging size 2, which follow this trend.

Snowpack Summary

So far this season's snowpack is shaping up to be quite complex with a high degree of variability even over short distances. Snow depth is highly variable with many thin, rocky areas where the snowpack is primarily composed of sugary facets and depth hoar. These are common trigger points for avalanches, which then propagate out into thicker snowpack areas.

Here's a general synopsis of the snowpack top to bottom: 

The key element of the upper snowpack is windslab in the alpine and treeline, especially in lee features such as ridge tops and gullies. 

The mid snowpack is characterized by layers of surface hoar crystals often in combination with crusts or other firm surfaces, which make for pretty classic sliding surfaces for overlying slabs.

The lower snowpack is composed of decomposing crusts, facets, and depth hoar. These very weak crystals supporting the weight of the snowpack are a major concern and are the basis for the deep persistent slab problem. Avalanches associated with this problem would be large, involving the full depth of the snowpack.

Valid until: Dec 14th, 2019 5:00PM