Avalanche Forecast

Archived

Apr 16th, 2025–Apr 17th, 2025

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Northwest Coastal, Northwest Inland, Boundary, Stewart, Kispiox, Ningunsaw, Ningunsaw, Ningunsaw.

Very dangerous avalanche conditions are expected.

Avalanches may run into the valley bottom.

Confidence

Moderate

Avalanche Summary

On Tuesday, there were two large persistent slabs (size 2 and 3) in the alpine from northeast to northwest aspects. Failing on the March weak layers.

As well as several wind slabs to size 2, and numerous wet loose avalanches from solar slopes.

Large avalanches are expected to continue on Thursday. Potentially running below treeline to the valley bottom.

Snowpack Summary

Up to 40 cm of recent snow has fallen over various crusts which are found up to 1800 m, higher on sunny slopes. Southwest wind has redistributed soft snow in exposed areas, building slabs.

Three layers of note, currently exist in the mid-snowpack:

A layer of surface hoar and a crust that formed in mid-March is 50 to 80 cm below the snow surface.
Another layer of surface hoar that formed in early March buried 70 to 120 cm.
A layer of facets, surface hoar, and/or a crust from mid-February is buried 120 to 200 cm deep.

The remainder of the snowpack is well consolidated.

Weather Summary

Wednesday Night

Mostly clear skies. 10 to 20 km/h west ridgetop wind. Treeline temperature -3 °C.

Thursday

Mostly sunny. 20 to 30 km/h west ridgetop wind. Treeline temperature 0 °C. Freezing level rising to 3000m.

Friday

Cloudy with 5 to 10 cm of snow. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level 1100 m.

Saturday

A mix of sun and cloud with 5 to 10 cm of snow. 15 km/h southwest ridgetop wind. Treeline temperature -5 °C. Freezing level 1100 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Be aware of the potential for large, destructive avalanches due to deeply buried weak layers.
Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
Cornice failures could trigger large and destructive avalanches.
Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

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.

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.

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.