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Avalanche Forecast

Archived

Dec 17th, 2025–Dec 18th, 2025

Alpine
Natural and human triggered avalanches likely.
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.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

*06:00 Update* The storm is underdelivering in the Whistler area but hazard will increase over the day. Stick to lower consequence terrain and avoid avalanche terrain in the alpine.

Confidence

Moderate

  • Forecast precipitation (either snow or rain) amounts are uncertain.

Avalanche Summary

Tuesday's reports were limited to ski cut and explosives-controlled slab and loose dry results to size 1.5 in the Whistler area. All ran on the new atmospheric river crust.

A wet slab avalanche cycle to size 3 was observed in the Whistler area after around 90 mm of rain below 2000 m. Monday morning, new size 1.5 wet loose releases were observed and explosives produced a size 2.5 wet slab.

Expect more active avalanche conditions with the next storm pulse.

Snowpack Summary

30 to 50 cm of new snow should accumulate Wednesday night through Thursday, with greatest amounts in the south of the region. Dangerous storm and wind slabs should form as a result.

The new snow will add to an existing 20 to 50 cm of storm snow from this week overlying crust and a wet snowpack from Monday's 2200 m freezing levels and heavy rain. The limited terrain above this elevation may have substantially greater accumulations.

A crust with facets, formed in mid-November, is buried an estimated 80 -150 cm deep. It may still exist as a problem in alpine locations where it hasn't been capped by a strong crust, particularly in thin-to-thick snowpack areas.

Weather Summary

Wednesday Night
Cloudy with increasing snowfall bringing 10 to 20 cm of new snow. 40 km/h south ridgetop wind. Treeline temperature -4 °C. Freezing level 900 m.

Thursday
Cloudy with continuing snowfall bringing 20 to 30 cm of new snow. 40 km/h south ridgetop wind. Treeline temperature -3 °C. Freezing level 1100 m.

Friday
Mostly cloudy with flurries bringing 10 to 20 cm of new snow, including overnight amounts. 30 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 800 m.

Saturday
Cloudy with flurries bringing 10 to 20 cm of new snow. 20 to 30 km/h southwest ridgetop wind, easing. Treeline temperature -5 °C. Freezing level 800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make observations and continually assess conditions as you travel.
  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Make conservative terrain choices and avoid overhead hazard.

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.