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Avalanche Forecast

Archived

Jan 18th, 2022–Jan 19th, 2022

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

Regions

Kootenay Boundary.

Be mindful of a deep persistent slab problem, which is very difficult to forecast. Use caution on shallow snowpack areas and thin to thick steep rocky zones. 

Confidence

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

Weather Forecast

TUESDAY NIGHT: Cloudy, light northwest wind, treeline temperatures around -3 C, freezing level lowering at valley bottom.

WEDNESDAY: Cloudy with sunny periods, light northwest wind, treeline temperatures around -6 C, freezing level at valley bottom.

THURSDAY: Snow 10-15 cm, moderate southwest wind, treeline temperatures around -5 C, freezing level rising to 1000 m.

FRIDAY: Mainly sunny, moderate northwest wind, treeline temperatures around -4 C, freezing level rising to 1000 m.

Avalanche Summary

No new avalanches were reported in the last 24h.

During the warm previous storm, mid-last week, a large widespread avalanche cycle occurred with most avalanches releasing within the storm snow and some on Jan 11 surface hoar layer. Strong solar radiation and warm temperatures were also at play after the storm, producing numerous avalanches at all elevations and scouring avalanche paths to the ground in places.

We have not heard reports of persistent slab avalanches for the last 10 days, when we saw numerous sizes 2 to 3 avalanches releasing on the early December facet/crust layer. Although the activity on this layer has tapered off, it still remains a concern as it is extremely difficult to forecast.

Snowpack Summary

Strong winds have redistributed the dry alpine snow, leaving variable wind slabs on specific terrain features. Around 1900 m and below, a crust is now capping the dense 10-30 cm of dense snow which has settled significantly with the past mild temperatures. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Below the recent snow, a layer of feathery surface hoar and melt-freeze crusts are found with decreasing reactivity. Lower elevations have gone through a melt-freeze cycle with past freezing level up to 1500m.

The early December crust/facet layer has been responsible for sporadic but very large, persistent slab avalanches over the past month. The crust is now buried 120-200 cm deep except in thin, wind-affected areas near ridgetops where most of the recent avalanches have been triggered.

Terrain and Travel

  • Conditions may have improved, but be mindful that deep instabilities are still present.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.