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Avalanche Forecast

Archived

Dec 9th, 2021–Dec 10th, 2021

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

Regions

Little Yoho.

Winds will increase later on Friday as a storm makes its way into the Rockies for Saturday. Watch for slowly increasing hazard due to wind transported snow later in the day.

Weather Forecast

A NW flow will keep the temperatures cool on Friday with a warming trend and more snow expected on Saturday. Temperatures at treeline on Friday in the -10 to -15 C range and moderate winds from the NW. Some flurries expected overnight Thursday and into Friday. Saturday looks like a potentially big snowfall.

Snowpack Summary

5-20 cm of new snow over the last 36 hrs makes for 15-30 cm of soft surface snow above the Dec 2 rain crust. This crust disappears between 2100-2250 m. At treeline and above, moderate winds are developing soft slabs in immediate leeward slopes. The weak Nov 5 crust/facet interface is present near the ground.

Avalanche Summary

Ski cutting and explosive work at the local ski areas produced wind slabs from size 1-.5 on Thursday. No new natural avalanches were reported or observed but visibility was limited. The last significant skier triggered avalanche was a skier accidental size 3 triggered on Lipalian Mountain (near Lake Louise) on Sunday.

Confidence

Forecast snowfall amounts are uncertain on Saturday

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.