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Avalanche Forecast

Archived

Feb 22nd, 2023–Feb 23rd, 2023

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 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.

Regions

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

Storm and wind slabs continue to be reactive. Cold weather increases the consequence of any incident.

Confidence

Moderate

Avalanche Summary

Widespread storm slab and wind slab avalanche activity occurred on Tuesday, mostly releasing within Monday night's storm snow. The avalanches were on all aspects and within all elevation bands and were generally small to large (size 1 to 3).

Numerous naturally triggered large to very large (size 2.5 to 3.5) persistent slab and deep persistent slab avalanches were observed on Monday and Tuesday. They occurred on all aspects between 1700 and 2700 m.

Looking forward, we suspect that storm and wind slab avalanches will continue to be triggerable by riders as all the recent snow slowly bonds to the snowpack. Triggering deeper layers remains possible, particularly on shallow, rocky slopes.

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 hosts various old layers of surface hoar, facets, and melt-freeze crusts that are gaining strength and bonding to the snowpack. Periodic reports of large avalanches on these layers are a reminder of the complicated snowpack in this region.

A layer of large and weak facets that formed in November is found near the base of the snowpack. The layer is slowly gaining strength but sporadic and very large avalanches continue to provide evidence that this layer cannot be trusted.

Weather Summary

Wednesday Night

Partly cloudy with no precipitation, 20 km/h east wind, treeline temperature -23 °C.

Thursday

Mostly clear skies with no precipitation, 20 km/h east wind, treeline temperature -22 °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.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Good day to make conservative terrain choices.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • 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.

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.