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Avalanche Forecast

Archived

Dec 14th, 2021–Dec 15th, 2021

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

Regions

Little Yoho.

There is uncertainty regarding wind slabs in the alpine due to minimal observations. Benign weather and a dive in temperature Thurs/Fri will continue to improve conditions.

Weather Forecast

Light snowfall associated with cloud and moderate west wind is expected over the next 2 days. Alpine temperatures are expected to drop into the -20 range on Thursday.

Snowpack Summary

20-30 cm of low density snow surface snow is bonding well with only limited windslab development at treeline and the low alpine. Our concern is growing for weaknesses developing above the Dec 2 rain crust, now buried 60-80 cm at treeline elevations (below 2250). Watch carefully as this weakness develops into an avalanche problem in the coming days.

Avalanche Summary

No new natural avalanches have been reported. Both LL and SSV ski areas report windslabs up to size 1 in their alpine areas.

Confidence

The weather pattern is stable on Tuesday

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.