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Avalanche Forecast

Archived

Feb 5th, 2023–Feb 6th, 2023

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

Regions

Tumbler.

Reactive wind slabs may exist in wind-loaded terrain, but our primary concern rests with the potential for large deep persistent slab avalanches.

Conservative, low-consequence terrain selection continues to be your best defence.

Confidence

Low

Avalanche Summary

No new avalanches have been reported, but field information is very limited in this region.

We suspect recent storm snow and wind have created wind slabs in the alpine and treeline that may remain reactive to human triggering.

Our greatest concern lies with the potential for large natural and human-triggered deep persistent slabs. Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure. See more on the potential of triggering deeper weak layers in our latest Forecasters' Blog.

Snowpack Summary

Stormy weather over the past week has brought 20 cm of new snow to the region. This new snow was accompanied by strong southerly winds that have stripped exposed windward areas and deposited pockets of wind slabs in lee areas. The recent storm snow sits on previously wind-affected snow. Below this, a melt-freeze crust is found on sun-exposed slopes and everywhere below 1600 m.

Several crust/facet/surface hoar layers exist in the upper and middle portions of the snowpack. The most concerning persistent weak layer is at the base of the snowpack from large and weak facets formed in November. This layer is widespread and most likely problematic in steep, rocky alpine terrain.

In general, the snowpack is weak and shallow in this area with an average snowpack depth of 100 cm at treeline.

Weather Summary

Sunday Night

Mainly cloudy with clear periods and isolated flurries, trace accumulation. Alpine temperatures reach a low of -6 C. Ridge wind westerly 30-50 km/h. Freezing levels fell from 1500 m to 500 m.

Monday

A mix of sun and cloud with isolated flurries in the afternoon, 2-5 cm accumulation. Alpine temperatures rise to -4 C. Ridge wind southwest 40-60 km/h. Freezing level rises to 1500 meters.

Tuesday

A mix of sun and cloud with isolated flurries, trace accumulation. Alpine temperatures drop to -6 C. Ridge wind west 10-30 km/h. Freezing level drops to 1000 meters.

Wednesday

A mix of sun and cloud with isolated flurries, trace accumulation. Alpine temperatures rise to -7 C. Ridge wind southwest 40-60 km/h. Freezing level rises to 800 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.

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.