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Avalanche Forecast

Archived

Jan 26th, 2023–Jan 27th, 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 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

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Significant snowfall accumulation is forecasted for our area in the next 36 hours.

Expect storm slabs to form and new snow to be transported by associated wind.

Keep terrain choices conservative during this time.

Confidence

Moderate

Avalanche Summary

Avalanche control with the use of explosives produced three size 1.5 avalanches from wind slabs in the Fernie area on Wednesday. Ski cutting on Monday and Tuesday yielded more size 1 avalanches also produced from wind slabs.

Sunday saw a cornice fail naturally but it did not trigger buried weak layers in this instance. Even so, it's a great reminder to be mindful and to practice avoidance of overhead hazards.

Although they have not produced avalanches in the last few days, a deep persistent slab problem still affects the region and should steer you away from thin or variable depth snowpack locations and shallow rocky start zones throughout the region.

Snowpack Summary

New snow will be falling on wind slabs about 1800 m. Below treeline a surface hoar layer will be getting buried in sheltered areas and on south-facing aspects, a melt-freeze crust can be found getting covered over.

A crust/facet layer, 2 to 15 cm thick at treeline is 50 to 90 cm below the surface. Where it's thickest, it caps the settled and consolidated mid-snowpack.

Another crust/facet layer is down 70 to 150 cm. Below this crust, the basal snowpack is weak and faceted. The total snowpack depth ranges between 90 and 250 cm.

Weather Summary

Thursday Night

Cloudy, 6 to 12 cm accumulation, winds southwest 20 to 30 km/h, treeline temperatures around -6 C with freezing levels getting up to 1300 m.

Friday

Cloudy, 5 to 10 cm accumulation in the morning with up to another 10 cm in the evening, winds north 20 km/h, treeline temperatures around -5 C.

Saturday

A mix of sun and cloud, trace accumulation ending in the morning, winds northeast 30 km/h, treeline temperatures dropping down to -20 C.

Sunday

Mostly sunny, possible trace accumulation, winds northeast 20 to 30 km/h, treeline temperatures getting down to -25 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid exposure to slopes that have 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.