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Avalanche Forecast

Archived

Jan 11th, 2024–Jan 12th, 2024

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 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

Blue River, Clearwater, Premier, Clemina, North Monashee.

The arctic air is here. Dial back trip plans to easier, shorter days and watch for unusual wind loading patterns from north winds. See our Forecasters' Blog for more on managing the cold.

Confidence

Moderate

Avalanche Summary

Wednesday avalanche reports documented a natural storm slab cycle averaging size 1-2, with a few size 2.5 avalanches. During the day, storm snow was very reactive to rider traffic including a size 1.5 avalanche, 70 cm deep, remotely triggered by skiers on a treeline ridge above the slope. Most slab avalanches were 50-70 cm deep and many reportedly ran on a layer of surface hoar buried Jan 4.

Snowpack Summary

Roughly 30-40 cm of new snow fell in the region Monday night through Tuesday. It buried moderately wind-affected snow in exposed areas at higher elevations and otherwise added to about 50 cm of recent storm snow. All this snow collectively overlies a variety of old surfaces, but sheltered terrain where it may overlie preserved surface hoar is the most concerning. It overlies a crust below about 1600 m.

Two additional surface hoar layers in the top 2 m of the snowpack are diminishing in importance. The deeper of the two likely has a robust crust above it below treeline. The depth of the snowpack varies greatly throughout the region and weak basal facets are present at the base of the snowpack.

Weather Summary

Thursday Night

Mainly cloudy. Variable northwest alpine wind 5-25 km/h. Treeline temperature dropping below -35°C.

Friday

Sunny. North alpine wind 10-20 km/h. Treeline temperature -35°C.

Saturday

Sunny. Variable alpine wind 5-10 km/h. Treeline temperature -30°C to -35°C.

Sunday

Increasing clouds. Northwest alpine wind 20-30 km/h. Treeline temperature -30°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.

Problems

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.

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.