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Avalanche Forecast

Archived

Feb 23rd, 2023–Feb 24th, 2023

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Winds will increase in strength through the day tomorrow, gusting to 80km/h in the alpine. Wind slabs will continue to pose a serious problem.

Confidence

Moderate

Avalanche Summary

The field team saw evidence of avalanches in the last 24h up to size 3. While the amount of activity is decreasing, natural and human triggering is still very possible.

One notable avalanche at Bow Summit ran onto the standard traverse track. See MIN.

Snowpack Summary

The recent storm snow continues to settle and feel the affects of the cold. Faceting of the upper snowpack was observed by the field team today as was extensive wind transport at ridge top elevations. Wind-slab's continue to develop at tree-line and into the alpine. These slabs have been formed primarily by north and east winds. These slabs are still reactive to human triggering. There are crusts in the middle of the snow pack and the base of the snowpack is still weak with basal facets. Test profiles done today are still producing sudden results in the basal facets.

Today's field team did a profile with a visiting forecasting team from Norway, which can be HERE.

Weather Summary

The next front will begin to move into the region tomorrow, slowly starting to warm temperatures up. Forecast highs in the alpine are between -15 and -20. As the front arrives, winds will shift to a southerly flow and increase in strength. Mainly clear skies tomorrow, with clouds developing in the afternoon. Friday night will be cold again before we break out of the cold snap on the weekend.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make conservative terrain choices and avoid overhead hazard.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Cornice failure may trigger large 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.

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.

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.