Avalanche Forecast

Archived

Dec 12th, 2025–Dec 13th, 2025

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Sea To Sky, Brandywine, Garibaldi, Homathko, Spearhead, Tantalus.

Concern remains for alpine north through east-facing, wind-loaded slopes, where both wind slabs and persistent slabs have been most reactive.

Confidence

Moderate

Avalanche Summary

Numerous size 1 to 2.5 explosive, natural and human-triggered slabs and cornices were triggered in the Whistler/ Blackcomb area throughout the storm cycle this week. A few of these slabs stepped down to the Mid-November crust up to 1 m deep, setting off very large avalanches. Most of these avalanches released in high alpine leeward north through east facing features.

We expect to see more avalanches like these as the next storm arrives.

Snowpack Summary

Saturday is bringing us a bit of a lull before the next big storm blows in Saturday night. Keep an eye out for lingering wind slabs on leeward north and east-facing terrain. These wind slabs also have some isolated potential to step down to a deeper persistent weak layer.

In the alpine, a persistent weak layer formed in mid-November lies 60–120 cm deep, depending on the aspect. This layer is a hard crust with weak facets both above and below it. Some recent slabs have stepped down to this persistent weak layer, creating larger-than-expected avalanches.

A melt-freeze crust or moist snow may be found on the surface below approximately 1700 m. The snowpack rapidly diminishes below 1100 m.

Weather Summary

Friday Night
Cloudy. 5 to 10 mm of precipitation as snow or rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 1700 m.

Saturday
Mostly Cloudy. 2 to 5 mm of rain at treeline. 30 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level rising to 2500 m.

Sunday
Cloudy. 30 to 40 mm of precipitation as snow or rain at treeline. 40 km/h south ridgetop wind. Treeline temperature -1 °C. Freezing level 1500 m.

Monday
Cloudy. 80 to 105 mm of rain at treeline. 50 km/h south ridgetop wind. Treeline temperature 3 °C. Freezing level 2200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid freshly wind-loaded terrain features.
Use ridges or ribs to avoid areas of wind-loaded snow.
Avalanche activity is unlikely when a thick melt-freeze crust is present on the snow surface.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.