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Avalanche Forecast

Archived

Dec 9th, 2019–Dec 10th, 2019

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Little Yoho.

Enjoy the great snow but stick to more conservative terrain, minimize exposure to large slopes and avoid terrain traps for a few days. In many areas there is a significant slab over a weak base and it will take time for the snowpack to improve.

Weather Forecast

Continued NW alpine winds in the moderate range are expected overnight, increasing to strong on Tuesday. Temperatures should remain seasonal in the -10 range at treeline. Minimal snow, and a mix of sun and cloud for the next couple days.

Snowpack Summary

Moderate winds in the alpine creating small wind slabs. Recent storm snow has formed a slab at treeline and above. Below the storm slab, the snowpack structure is generally weak, consisting of facets and depth hoar. The Nov crust is present up to 2500m and ~30 cm up from ground. Snowpack depths at treeline range from 80-160 cm.

Avalanche Summary

Avalanche control on Sunday and Monday produced numerous size 2 and a couple size 3 avalanches. The largest slides were failing on the Nov crust and basal facets. A skier accidental size 2.5 occurred in West Bowl at Lake Louise Sunday. This avalanche also slid on the Nov crust layer. Natural avalanche activity has slowed, but not stopped.

Confidence

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.