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Avalanche Forecast

Archived

Dec 23rd, 2018–Dec 24th, 2018

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

Regions

Little Yoho.

The natural cycle is tapering off, however, the weak layers in the snowpack are still reactive. Don't expect conditions to improve quickly and adjust your terrain decisions accordingly.

Weather Forecast

Lows in the mid teens are expected over the next few days. High overcast skies will at times produce very light amounts of snow (trace). Winds are dropping and it is expected to be calm on Christmas Day.

Snowpack Summary

An average 40-80 of recent storm snow with variable wind effect now sits over the Dec. 10 facet/surface hoar interface. This layer is producing snowpack test results in the hard range. In many areas the lower snowpack is weak with the October 26 depth hoar, facets and crust near the base. Snow pack depths range from 90-160 cm at ~2000 m.

Avalanche Summary

The natural avalanche cycle has started to taper off with the cooler temperatures. Large avalanches to size 3 have been noted in the last few days.

Confidence

Problems

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.