Avalanche Forecast

Archived

Dec 20th, 2025–Dec 21st, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

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

Strong winds will help build fresh slabs as flurries accumulate through Sunday.

Expect to find the deepest and most sensitive slabs in lee and cross-loaded features.

Confidence

Moderate

Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Avalanche Summary

On Friday, explosives triggered size 1-2 storm slab avalanches, which failed about 20-40 cm deep within the recent storm snow. The few size 2 avalanches were triggered in steep, wind-loaded lee features.

On Thursday, avalanche control work triggered reactive slabs in wind-loaded, northerly terrain, up to size 1.5. Riders found reactive slabs in the immediate lees of ridgetop features, up to size 1.

Snowpack Summary

Strong southerly winds have left a variety of surfaces - wind slabs and loaded pockets in lee features, scoured rock in open terrain, and storm slabs and softer snow in sheltered areas.

Approximately 30 to 60 cm of wind-affected storm snow has accumulated through this week, and covers a melt-freeze crust is present at elevations of 2200 m and below. The depth of this crust is highly variable due to extensive recent wind transport.

A crust with associated facets, formed in mid-November, is buried an estimated 80 to 150 cm deep. This layer remains a concern in alpine terrain where it has not been capped by a strong overlying crust.

Weather Summary

Saturday night
Cloudy. 5 to 10 cm of snow. 30 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Sunday
Cloudy. 10 to 30 cm of snow. 40 km/h south ridgetop wind. Treeline temperature -3 °C.

Monday
Cloudy. 20 to 40 cm of snow. 30 km/h south ridgetop wind. Treeline temperature -5 °C.

Tuesday
Mostly cloudy. 15 to 25 cm of snow. 30 km/h south ridgetop wind. Treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Storm slab size and sensitivity to triggering will likely increase through the day.
Minimize exposure during periods of heavy loading from new snow and wind.
Be especially cautious as you transition into wind-affected terrain.
Be careful with wind-loaded pockets, especially near ridge crests and rollovers.

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.

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.