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Avalanche Forecast

Archived

Dec 17th, 2025–Dec 18th, 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 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

South Coast Inland, Birkenhead, Duffey, South Chilcotin, Stein, Taseko.

Accumulations on our new crust could reach tipping points on Thursday. Monitor the depth and reactivity of new snow as you travel and choose terrain defensively.

Confidence

Moderate

  • Forecast snowfall amounts are uncertain.

Avalanche Summary

No new avalanches were reported in the region Tuesday. In the adjacent Sea to Sky, ski cut and explosives-controlled slab and loose dry results to size 1.5 were running on the new atmospheric river crust.

On Monday, five natural releases in the size 2.5 to 3 range were reported on the Duffey. As was suspected with the earlier size 3's in the Hurley and Upper Lillooet, all failed on the mid-November crust.

Expect more active avalanche conditions with the next storm pulse.

Snowpack Summary

15 - 40 cm of new snow should fall Wednesday night through Thursday, with the greatest amounts expected northwest of the Duffey. Dangerous storm and wind slabs should form as a result, especially where accumulations are greater.

The new snow will add to an existing 20 to 50 cm of storm snow from this week overlying a new crust and the wet snowpack below from Monday's 2100 m freezing levels and heavy rain.

A crust with facets, formed in mid-November, was buried 50 to 100 cm before the storm. Recent very large persistent slab releases have failed on this layer and continuing loading prevents us from gaining full confidence in it.

Weather Summary

Wednesday Night
Cloudy with increasing flurries bringing 5 to 10 cm of new snow. 40 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 1100 m.

Thursday
Cloudy with increasing snowfall bringing 10 to 30 cm of new snow. 30 km/h south ridgetop wind. Treeline temperature -4 °C. Freezing level 1200 m.

Friday
A mix of sun and cloud with isolated flurries and 5 to 10 cm of new snow, including overnight amounts. 20 km/h south ridgetop wind. Treeline temperature -6 °C.

Saturday
Mostly cloudy with scattered flurries and 5 - 10 cm of new snow, including overnight amounts. 20 km/h southwest ridgetop wind. Treeline temperature -6 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Make observations and continually assess conditions as you travel.
  • Be especially cautious as you transition into wind-affected terrain.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.