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Avalanche Forecast

Archived

Jan 16th, 2022–Jan 17th, 2022

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

Regions

South Columbia.

New snow and wind are forming fresh, reactive slabs in lee terrain features at upper elevations. Be prepared to dial back your terrain choices if you see signs of instability such as shooting cracks or recent avalanches.

Confidence

Moderate - Uncertainty is due to the track & intensity of the incoming weather system.

Weather Forecast

Sunday night: Snowfall 5-10 cm, moderate SW wind, freezing levels around 600 m.

Monday: Snowfall 5-10 cm, moderate SW wind, freezing levels reaching around 1000 m.

Tuesday: A mix of sun and cloud, light variable wind, freezing levels near valley bottom. 

Avalanche Summary

On Saturday, small wind slabs on E-NE aspects in the alpine were reactive naturally and to ski cuts

A warm storm on Wednesday and Thursday last week triggered a widespread natural avalanche cycle up to size 3.5 (very large) at upper elevations. At lower elevations, loose wet activity was widely observed. By Friday, natural storm slab activity had largely tapered in size and number, but explosive control work continued to produce results up to size 2.

As of Saturday, observations continue to roll in from throughout the region of several persistent slab avalanches on the early December layer, suspected to have run during the warm storm Wednesday/Thursday. These avalanches are generally around 2100 m, size 2.5-3.5 (very large), 100-150 cm deep and on NE-NW aspects.

Snowpack Summary

New snow falls over 25-50 cm of well settled snow from the previous storm, possibly a layer of surface hoar crystals in sheltered areas, and/or a thin breakable crust which was observed as high as 1800 m in the Selkirks and into the alpine in the Monashees.

A couple of layers of weak facets and/or surface hoar that were buried earlier in January now sit 25-50 cm and 60-90 cm deep.

The early December crust/facet interface is now typically down 80-140 cm, but as deep as 200 cm in wind loaded terrain. It consists of faceted grains above a decomposing crust formed by the Atmospheric River rain event at the end of November. There has been avalanche activity on this layer as recently as recently as Friday in the region. Heavy triggers like natural cornice falls and storm slab avalanches may still have potential to step down to this layer resulting in very large avalanches. 

This video from our field team provides some additional insight into the snowpack in the south of the region. 

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.