Avalanche Forecast

Archived

Dec 15th, 2025–Dec 16th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

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 unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Up to 60 cm of new snow could arrive by end-of-day Tuesday if we see the high end of forecast amounts. Good news for the snowpack, but also a good day to avoid avalanche terrain!

Confidence

Moderate

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 new observations are scant, it's likely the atmospheric river has 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 Tuesday.

Snowpack Summary

30 - 60 cm of new snow should accumulate above 1500 m by end-of-day Tuesday, with amounts increasing with elevation. This will covering a rain-soaked snowpack that was 80 - 140 cm deep ahead of 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 much confidence in it with limited observations and as loading continues.

Weather Summary

Monday Night
Cloudy with easing flurries bringing 5 to 20 cm of new snow. 40 - 60 km/h southwest ridgetop wind, easing. Treeline temperature -4 °C. Freezing level falling to 1200 m.

Tuesday
Cloudy with increasing snowfall bringing 25 to 40 cm of new snow. 25 - 45 km/h southwest ridgetop wind, increasing. Treeline temperature -2 °C. Freezing level rising to 1500 m.

Wednesday
Mostly cloudy with easing flurries bringing around 10 cm of new snow after 30 to 50 cm overnight (rain below about 1500 m). 50 - 60 km/h southwest ridgetop wind, easing. Treeline temperature -4 °C. Freezing level 1200 m.

Thursday
Mostly cloudy. 5 to 10 mm of mixed precipitation (rain below about 1800 m). 40 - 70 km/h southwest ridgetop wind, increasing. Treeline temperature 2 °C. Freezing level peaking at 2100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.
Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.
Storm slab size and sensitivity to triggering will likely increase through the day.
Back off slopes as the surface becomes moist or wet with rising temperatures.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.