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Avalanche Forecast

Archived

Feb 8th, 2023–Feb 9th, 2023

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

Regions

North Rockies, Kakwa, McGregor, Pine Pass.

Continue to choose conservative terrain and watch for clues of instability as storm snow and strong winds continue to incrementally load the snowpack throughout the day.

Avoid lee and cross-loaded terrain. Minimize exposure to avalanche terrain during times of heavy loading from wind and new snow.

Confidence

Moderate

Avalanche Summary

On Tuesday, a skier accidental, size 1.5 storm slab avalanche was reported at 1500 m. A size 2, natural windslab avalanche was observed on a northwest aspect at 1400 m.

On Monday, a natural wind slab avalanche, size 2 was observed on a northerly aspect at 1900 m.

On Sunday, three very large natural avalanches were observed up to size 4. Two were size 3 persistent slab avalanches on steep north-facing aspects with 750 m wide crowns. A size 3.5-4 deep persistent slab avalanche was also observed. It is suspected this avalanche failed in depth hoar at the base of the snowpack.

See more on the potential of triggering deeper weak layers in our latest Forecasters' Blog.

Snowpack Summary

Flurries begin again Thursday morning building upon 60 to 110 cm of storm snow from the last week. The storm snow sits on previously wind-affected surfaces. 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 and upper treeline terrain.

Weather Summary

Wednesday Night

Partly cloudy. Ridge wind southwest 40-50 km/h. Alpine temperatures -10 C. Freezing level valley bottom.

Thursday 

Partly cloudy with scattered flurries, 5-10 cm through most of the region. Up to 20 cm accumulation in the Pine Pass area. Ridge wind from the southwest 50 km/h picks up to 70 km/h in the evening. Alpine temperatures rise to -3 C. Freezing level 1400 meters. 

Flurries continue through the night, 5-10 cm accumulation

Friday

Partly cloudy with isolated flurries, 5-10 cm accumulation. Alpine temperatures rise to -2 C. Ridge wind southwest 40-50 km/h. Freezing level 1300 meters. 

Saturday

Partly cloudy with isolated flurries, 5-10 cm accumulation. Alpine temperatures rise to -3 C. Ridge wind southwest 40-50 km/h. Freezing level 1000 meters. 

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.
  • Avoid all avalanche terrain during periods of strong wind.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.