Avalanche Forecast

Archived

Jan 10th, 2024–Jan 11th, 2024

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 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 arriving. Dial back trip plans to easier, shorter trips and watch for unusual wind loading patterns from north winds. See our Forecasters' Blog for more on managing the cold.

Confidence

High

Avalanche Summary

Tuesday was likely a busy day for natural and human-triggerable avalanches as moderate to heavy snowfall and elevated winds affected the region.

A size 2 (large) deep persistent slab was triggered from a 20 m distance in the Clemina alpine on Sunday on a NE aspect. It was 70 cm deep, failing at the base of the snowpack. This highlights the problematic basal snowpack structure in the region.

Aspects lee to north winds are a concern for the most recent or new wind slab formation.

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 elevation 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

Wednesday night

Clearing, still mainly cloudy. Northwest alpine wind 5-15 km/h. Treeline temperature -16°C.

Thursday

Mainly sunny or thin overcast. Northeast wind 10-25 km/h, increasing overnight. Treeline temperature -29°C.

Friday

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

Saturday

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

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Wind slabs are most reactive during their formation.
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 aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

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.