Avalanche Forecast

Archived

Feb 28th, 2024–Feb 29th, 2024

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Coquihalla, Harrison-Fraser, Manning, Skagit.

Very dangerous avalanche conditions continue at all elevations. Avoid all avalanche terrain.

Natural and human-triggered avalanche activity remains likely.

Confidence

Moderate

Avalanche Summary

No recent avalanches have been reported in the region however poor visibility and high avalanche danger kept many users out of the backcountry on Wednesday.

We expect those who head into the backcountry on Thursday will see evidence of a widespread natural storm slab avalanche cycle that occurred during the storm.

If you do head out please consider reporting and observations and photos from your day to the Mountain Information Network.

Snowpack Summary

Up to 70 cm of storm snow overlies wind-affected surfaces and old wind slabs in exposed areas and 30 to 60 cm of settling snow in sheltered areas.

Multiple weak layers exist in the upper and mid snowpack. The most concerning weak layer is a widespread crust found down 60 to 100 cm, with weak, faceted snow immediately above it. This layer will need time to adjust to the new snow load. Although natural avalanche activity may taper out on this layer as the snow stops falling it will remain possible to human-trigger it for some time afterward.

Weather Summary

Wednesday Night

Cloudy with 25 to 35 cm of snow. 40 to 60 km/h southwest ridgetop wind. Treeline temperature -6 °C. Freezing level drops to 500 m.

Thursday

Cloudy with 5 to 15 cm of snow. 10 to 25 km/h southwest ridgetop wind. Treeline temperature -8 °C. Freezing level hovers around 500 m.

Friday

Partly cloudy with 1 to 2 cm of snow. 20 to 40 km/h south ridgetop wind. Treeline temperature -6 °C. Freezing level rises to 1000 m.

Saturday

Partly cloudy with 2 to 3 cm of snow. 20 to 40 km/h southeast ridgetop wind. Treeline temperature -6 °C. Freezing level rises to 1000 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.
Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.