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Avalanche Forecast

Archived

Dec 16th, 2025–Dec 17th, 2025

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

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Copious precipitation with balmy mid-mountain temperatures means certainty about dangerous avalanche conditions increases with elevation. Travel in the alpine is not recommended!

Confidence

Moderate

  • Forecast snowfall amounts are uncertain.
  • Uncertainty is due to rapidly fluctuating freezing levels.

Avalanche Summary

Last Wednesday, a size 3 avalanche stepped down to a persistent weak layer near Allison Pass. See photo captions for more details.

Although observations are scant, it's likely the atmospheric river caused more persistent slab activity where this layer exists up high, and wet loose activity everywhere else there is snow.

Looking forward, a switch to heavy snowfall at higher elevations should form a reactive storm slab problem for above-threshold areas on Wednesday.

Snowpack Summary

35 - 60 cm of new snow should accumulate above 1500 m by end-of-day Wednesday, mostly overnight, with amounts increasing with elevation. This will cover a rain-soaked snowpack that was 80 - 140 cm deep abefore the storm. There's not much snow below 1500 m.

A crust with facets, formed in mid-November, exists about 50 to 100 cm deep. Although all the rain ought to have cleaned out this problem where it existed, it's hard to gain total confidence in it with limited observations and as loading continues.

Weather Summary

Tuesday Night
Cloudy with increasing, warming precipitation bringing 30 to 50 cm of new snow to the alpine, diminishing with elevation with rain below about 1500 m. 50 km/h southwest ridgetop wind. Treeline temperature -2 °C. Freezing level 1400 m.

Wednesday
Cloudy with easing flurries bringing 5 to 10 cm of new snow. 40 to 60 km/h west ridgetop wind. Treeline temperature -5 °C. Freezing level 900 m.

Thursday
Mostly cloudy with wet flurries bringing about 5 cm of new snow to high alpine, light rain everywhere else. 40 to 60 km/h southwest ridgetop wind, increasing. Treeline temperature 2 °C with freezing level reaching 2000 m.

Friday
Mix of sun and clouds with scattered flurries and a possible few cm of new snow. 20 to 30 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 900 m.


More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Make observations and continually assess conditions as you travel.
  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.

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.