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Avalanche Forecast

Archived

Feb 23rd, 2023–Feb 24th, 2023

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

Continue to assess for slab properties within the recent snow, where storm and wind slabs will be most likely triggered. Cold weather increases the consequence of any incident.

Confidence

Moderate

Avalanche Summary

We continue to receive reports of many natural, explosive, and human-triggered storm slab and wind slab avalanches. The storm slab avalanches are generally occurring within the most recent storm snow since Tuesday or about 100 cm deep at the base of the snow that accumulated last weekend. Wind slab avalanches are occurring on all aspects in wind-exposed terrain where recent strong wind redistributed the storm snow. Avalanches are most often occurring at treeline and alpine elevations and are mostly small to large (size 1 to 2.5). We anticipate that similar avalanche activity will continue on Friday, since bonding of this snow will be slow with the cold weather.

Wednesday's clear skies allowed for observations of many deep persistent slab avalanches , which were large to very large (size 2 to 3.5). They were all naturally triggered, on all aspects, and between 2200 m and 2800 m in elevation. Many of the avalanches were triggered from rapid wind loading and from shallower avalanches stepping down to the basal facets. 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

Storm slabs formed from Monday night's 20 to 50 cm of snow. The snow fell with southwest wind which has now switched to easterly wind, meaning wind slabs may be found on all aspects.

Around 80 to 100 cm of snow may overly 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 strengthening.

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

Thursday Night

Clear skies with no precipitation, 10 to 20 km/h east wind, treeline temperature -23 °C.

Friday

Clear skies with no precipitation, 10 to 20 km/h west wind, treeline temperature -21 °C.

Saturday

Cloudy with snowfall, accumulation 5 to 10 cm, 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.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Good day to make conservative terrain choices.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • 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.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.