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Avalanche Forecast

Archived

Feb 24th, 2023–Feb 25th, 2023

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

Regions

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, Shuswap, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Wind slabs are the primary concern, but lingering storm slabs may still exist in wind-sheltered terrain.

Confidence

Moderate

Avalanche Summary

Over the past few days we received reports of many natural, explosive, and human-triggered storm slab and wind slab avalanches. The storm slab avalanches were generally releasing within the storm snow since Tuesday or about 100 cm deep at the base of the snow that accumulated last weekend. Wind slab avalanches were occurring on all aspects in wind-exposed terrain where recent strong wind redistributed the storm snow. Avalanches were most often at treeline and alpine elevations and were mostly small to large (size 1 to 2.5).

Clear skies from the past few days allowed for observations of many deep persistent slab avalanches as well as explosive control missions, which produced large to very large (size 2 to 3.5) avalanches. They were on all aspects and between 2200 m and 2800 m in elevation. Although many of the avalanches occurred in unrideable terrain, they are evidence that the layer is still triggerable. Riders should continue to avoid thin snowpack areas, which are often found near ridgelines.

Snowpack Summary

Stormy conditions return on Saturday, bringing snow and southwest wind that could form new wind slabs in wind-exposed terrain. The snow will overly storm slabs that formed from Tuesday's 20 to 50 cm of snow and wind slabs that formed from sustained northeast wind.

Around 80 to 100 cm of snow may rest on a small layer of surface hoar crystals that was buried mid-February. This layer is most likely found around treeline elevations in areas sheltered from the wind. The remainder of the mid-pack is generally strong.

A layer of large and weak facets that formed in November is deeply buried, found near the base of the snowpack. The likelihood of human triggering this layer is currently low given its depth. However, it is still best to avoid steep, thin, rocky slopes near ridges at alpine and upper treeline elevations.

Weather Summary

Friday Night

Cloudy with snowfall, accumulation 1 to 3 cm, 20 to 40 km/h southwest wind, treeline temperature -17 °C.

Saturday

Cloudy with snowfall, accumulation 5 to 10 cm with local enhancement possible, 20 to 40 km/h south wind, treeline temperature -15 °C.

Sunday

Cloudy with snowfall, accumulation 15 to 30 cm, 20 to 40 km/h southwest wind, treeline temperature -13 °C.

Monday

Cloudy with snowfall, accumulation 5 to 10 cm, 20 km/h southwest wind, treeline temperature -12 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • 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.