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Avalanche Forecast

Archived

Feb 20th, 2023–Feb 21st, 2023

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

Regions

North Rockies, Kakwa, McGregor, Pine Pass, Tumbler.

Conservative terrain travel is warranted with touchy wind slabs and cold weather.

Confidence

Moderate

Avalanche Summary

Some small to large (size 1 to 3) wind and storm slab avalanches were observed on Sunday and Monday from recent storm snow. Check out the MIN for one notable avalanche observed on Saturday.

Looking forward, we anticipate that the storm snow will continue the bonding process to the snowpack. Wind slabs may continue to be reactive to human traffic. Cold weather should reduce the likelihood of avalanches in the coming days, though triggering deeper weak layers is always possible, where they exist.

Snowpack Summary

The region has received anywhere from 40 to 80 cm of recent storm snow, which was redistributed into wind slabs and large cornices. The wind was predominantly southwest but is switching to northeast, meaning that wind slabs may be found on all aspects.

The mid-pack is gaining strength and consists of rounding facets and decomposing melt-freeze crusts.

A weak layer of large and weak facets is found near the base of the snowpack. This layer is most likely to be triggered in thin, rocky alpine and upper treeline terrain.

Weather Summary

Monday Night

Cloudy with snowfall, accumulation 5 to 15 cm, 40 to 60 km/h northeast wind, treeline temperature -20 °C.

Tuesday

Mostly sunny skies with no precipitation, 40 km/h northeast wind, treeline temperature -25 °C.

Wednesday

Mostly sunny skies with no precipitation, 40 km/h northeast wind, treeline temperature -28 °C.

Thursday

Mix of sun and cloud with no precipitation, 40 km/h northeast wind, treeline temperature -30 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Wind slabs are most reactive during their formation.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.