Avalanche Forecast

Archived

Jan 24th, 2025–Jan 25th, 2025

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Regions

Yukon, Tutshi, Wheaton, White Pass East, White Pass West.

Very large avalanches remain possible due to a deeply buried weak layer.

Strong wind continues to build slabs.

Confidence

Moderate

Avalanche Summary

On Tuesday, there were two very large (size 3) avalanches triggered by cornices falling on a slope and triggering a weak layer, suspected to be the early December crust.

On January 15th, a very large persistent slab avalanche was remotely triggered (MIN report).

Snowpack Summary

Exposed terrain has been heavily wind-affected. In sheltered areas, there is 20 to 30 cm of settling soft snow.

A weak layer of facets and a crust from early December is buried 80 to 140 cm deep. This layer exists on all aspects up to around 1700 m and produced large avalanches last weekend.

Check out this recent ACMG Mountain Conditions Report for more on the persistent weak layer problem.

Weather Summary

Friday Night

Mostly cloudy. 40 to 60 km/h southwest ridgetop wind. Treeline temperature -7 °C.

Saturday

Cloudy. 40 to 60 km/h southwest ridgetop wind. Treeline temperature -5 °C.

Sunday

Cloudy with up to 5 cm of snow. 50 to 70 km/h southwest ridgetop wind. Treeline temperature -4 °C.

Monday

Cloudy with 5 to 20 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -3 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for large avalanches due to buried weak layers.
Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Cornice failures could trigger large and destructive avalanches.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.