Avalanche Forecast

Archived

Feb 24th, 2025–Feb 25th, 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 and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

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.

Reactive storm slabs are the main concern as stormy weather continues.

Be mindful that deep instabilities are present and have produced recent large avalanches.

Confidence

Moderate

Avalanche Summary

Numerous wet loose avalanches (up to size 2.5) were reported near Yak Peak on Sunday due to rapid warming. A natural size 3 persistent slab was observed in Allison Pass on Saturday. It occurred on a 37°, northeast-facing slope at treeline (1740m) and had a 240 m-wide crown fracture. Storm loading will increase the concern for this type of avalanche activity.

Snowpack Summary

20 cm of new snow overnight overlies 20 cm of moist snow in the upper snowpack. A weak layer of faceted snow or surface hoar is now buried 50 to 60 cm deep and present in higher elevations, particularly shaded terrain.

Storm loading has woken this layer up decisively in neighboring regions and produced a troubling size 3 avalanche in Allison Pass on Saturday. High-elevation rain brought moisture to the facet layer at treeline on Saturday, both a possible trigger and a suggestion that the layer may strengthen soon.

A crust from December exists buried 100 to 150 cm deep, with facets around it in shallow areas. Otherwise, the lower snowpack is strong. At lower elevations, the snow is wet, heavy and water-saturated.

Weather Summary

Monday Night

Cloudy with 5 to 10 cm of snow. 30 to 40 km/h south ridgetop wind. Treeline temperature stable around -2°C. Freezing level around 1200 m.

Tuesday

Cloudy with 15 to 20 cm of new snow. 30 to 40 km/h south ridgetop wind. Treeline temperature stable around -2°C. Freezing level around 1200 m.

Wednesday

Partly cloudy with isolated flurries. 20 km/h south ridgetop wind. Treeline temperature stable around +6°C. Freezing level rising to 2700 m.

Thursday

5 to 10 cm of wet snow or rain. 50 to 70 km/h southwesterly ridgetop wind. Treeline temperature 0°C. Freezing level lowering to 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Closely monitor how the new snow is bonding to the old surface.
Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Be aware of the potential for large avalanches due to buried weak layers.
Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.

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.