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Avalanche Forecast

Archived

Jan 23rd, 2023–Jan 24th, 2023

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

Regions

Banff Yoho Kootenay, Little Yoho, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Some small wind slabs to watch for in the alpine. The upper snowpack is slowly becoming more supportive and allowing for better travel, however, the lower snowpack remains weak and unsupported. Conservative terrain choices are still a good idea.

Confidence

Moderate

Avalanche Summary

On a flight Sunday, Visitor Safety observed a recent size 2 cornice triggered slab on the East side of Copper mountain. Ski hills reported ski cutting some small wind slabs in lee areas near ridge crests on Monday, and were still able to trigger a couple of size 2's at 2300 m with explosives on Sunday that scrubbed down to the ground in areas that were previously uncontrolled.

Snowpack Summary

Some small wind slabs in the alpine. At treeline 10-20 cm of recent snow sits over a spotty surface hoar/sun crust Jan 4 interface. The Dec 17 surface hoar/sun crust layer is down 25-50 cm, and generally not reactive. The Nov 16 deep persistent layer is down 40-90 cm and continues to produce sudden failures in snowpack tests. In areas west of the divide, these layers are generally deeper and more spread apart in the snowpack.

Weather Summary

Tuesday will see some light flurries in the morning, becoming a mix of sun and cloud in the afternoon. Alpine winds will start in the moderate to strong range out of the W, and decrease as they switch to NW in the afternoon. Alpine temperatures will range from -10 to -15°C.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.

Problems

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.

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.