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Avalanche Forecast

Archived

Apr 10th, 2023–Apr 11th, 2023

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

Regions

West Purcell, Badshot-Battle, Goat, Kokanee, Retallack, Valhalla.

Forecasted weather will bring heavy precipitation and strong winds to much of our region and will increase the avalanche hazard.

The chance of avalanches is very likely today.

Make conservative choices and back off if you see signs of instability.

Confidence

Moderate

Avalanche Summary

Sunday saw an increase in avalanche activity as this most recent weather system touched down in our region. These avalanches were caused by wind slabs and storm slabs.

The wind slabs were triggered naturally, by ski cuts, and by cornice failure. They reached up to size two and were 35 to 40 cm deep when they started. All were in the alpine on a variety of aspects including cross-loaded terrain.

Snowpack Summary

By Tuesday evening up to 60 mm will have fallen in a 36-hour period. Due to recent high freezing levels much of this fell as moist heavy snow or rain. Expect wind slabs to have formed from southwest winds where snow was light enough to be transported.

On southerly aspects and below treeline, there is a widespread cust buried 30 to 50 cm down. On north-facing slopes at treeline and above there may exist a layer of faceted snow or surface hoar in shelter areas. Further down in the snowpack, around 60 cm, a surface hoar layer has been reactive to human triggering. This has occurred primarily in the Selkirks, on northeasterly slopes from 1700 m to 2100 m. Wednesday was the last day that there was any real activity on this layer but this storm may change that.

The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.

Weather Summary

Monday Night

Cloudy, 25 to 30 cm accumulation of wet snow, winds southwest 20 to 30 km/h gusting to 50, freezing levels cooling to 1600 m.

Tuesday

Cloudy, 20 to 30 cm accumulation, winds southwest 30 to 40 km/h, freezing levels 1500 m.

Wednesday

Cloudy with sunny breaks, up to 10 cm accumulation by morning, winds west 15 km/h, freezing levels starting at 500 m and climbing to 1500 m.

Thursday

Cloudy with sunny periods, trace accumulation, winds west 10 to 20 km/h, freezing levels climbing back up to 1600 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.
  • Caution around slopes that are exposed to cornices overhead.

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.