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Avalanche Forecast

Archived

Feb 11th, 2020–Feb 12th, 2020

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

Purcells.

Little precipitation along with recent winds blowing from a variety of directions will keep wind slabs at upper elevations the main concern.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Tuesday Night: Cloudy with isolated flurries. Moderate northwest wind. Alpine high temperatures around -8.

Wednesday: Cloudy with sunny breaks. Light west wind. Alpine high temperatures around -5. Freezing level 1000 m

Thursday: Scattered flurries, accumulation 5 cm. Light to moderate southwest wind. Alpine high temperatures around -7. Freezing level 900 m

Friday: Mainly cloudy with isolated flurries. Moderate west wind. Alpine high temperatures around -6. Freezing level 1000 m

Avalanche Summary

On Monday there were reports from the central part of the region of two explosives triggered deep persistent avalanches size 2.5 and 3 running on north aspects in the alpine. One of these ran on facets sitting glacial ice.  

Sunday and Monday's reports also showed a few windslab avalanches running to size 1.5 in alpine terrain from a variety of aspects.

On Saturday there was a report of remotely triggered (from a distance) wind slab avalanche size 2.5 avalanche at 2350 m on a southeast aspect in the north of the region. The details can be seen in this MIN post. There were also reports of numerous loose dry avalanches running in steep terrain size 1-1.5.

Snowpack Summary

20-40 cm of snow accumulating through the last week sits over older wind-affected snow at high elevations, or over a widespread melt-freeze or rain crust with a variable upper extent of 1800-2000 metres in elevation. The recent snow has mainly shown reactivity where winds have had a chance to redistribute it into new slabs.

A weak layer of surface hoar may still be found about 90 cm deep around Golden and Kimberley, 50 cm deep around Invermere, and 130 cm deep along Kootenay Lake. Recent reports from the Golden area suggest a positive stabilizing trend. At lower elevations this layer has likely been bridged over by the above-mentioned crust.

The base of the snowpack contains basal facets. It remains possible to trigger these deep weak layers in shallow rocky start zones or from a heavy trigger such as a cornice fall. 

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.