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Avalanche Forecast

Archived

Jan 24th, 2022–Jan 25th, 2022

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Columbia.

 Conditions may have improved, but be mindful that deep instabilities are still present. Avoid shallow or variable depth snowpacks and unsupported terrain features. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

MONDAY NIGHT: Partly cloudy / Light northwest wind / Low temperature -10 C / Freezing level dropping to valley bottom.

TUESDAY: Cloudy with sunny periods / Light southwest wind / High temperature -6 C / Freezing level around 700 m bottom.

WEDNESDAY: Cloudy with sunny periods / Increasing westerly wind gusting 40 km/h / High temperature -8 C / Freezing level at valley bottom.

THURSDAY: Mix of sun and clouds / Increasing southwest wind / High temperature -8C / Possible temperature inversion / Freezing level at valley bottom.

Avalanche Summary

On Sunday, numerous cornice falls were reported in the south part of the region, with some triggering storm slabs avalanches up to size 2. Wind slabs are still showing signs of reactivity throughout the region, producing large natural avalanches (size 2) as well as surprising human-triggered avalanches. In some cases, a weak layer of surface hoar was reported at the interface (down 30-60 cm).

During the warming event Saturday, explosives near the Trans Canada triggered very large avalanches (size 2.5-3.5) failing on the early December facet/crust layer. This included a historical size 4.5 avalanche which started at ridgeline, created new trim lines, and destroyed mature timber. 

The past week, numerous very large (size 2.5-3.5) deep persistent slab avalanches occurred in both the Selkirks and Monashees. These avalanches failed on the early December facet/crust layer, typically 100-150 cm deep. One notable pattern is that many of these avalanches released at relatively low elevations (1700 to 2000 m) in open clearings, burns, and slide paths. In many cases, they were triggered by smaller avalanches starting at higher elevations. This layer is likely to plague our snowpack for the remainder of the season and will be a low probability but extremely high consequence result if triggered.

Snowpack Summary

A variety of snow surfaces can be found: crusts at lower elevations and on solar slopes into the alpine, wind press and wind slabs in open and exposed terrain, and dense powder in sheltered areas. Surface hoar growth has also been reported.

The most recent snowfall covered a layer of surface hoar now down 20-30 cm, this interface was responsible for the most recent natural storm slab avalanches reported Jan 20-21. The top 50-100 cm of the snowpack has a variety of little layers that may or may not be a problem. These layers include surface hoar and crusts from January snowfalls and facets buried at the start of January. 

The primary weak layer that remains a widespread concern across the Columbia Mountains is a deeply buried crust/facet layer that formed in early December. It is typically down 100-150 cm, but as deep as 200 cm in wind-loaded terrain. There has been regular avalanche activity on this layer at all elevations for over a month, but we are now seeing decreasing evidence since the last warm event.

Terrain and Travel

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.