Avalanche Forecast

Archived

Feb 26th, 2024–Feb 27th, 2024

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 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.

Dangerous avalanche conditions exist at higher elevations where new snow struggles to bond to surfaces below

Human triggering potential persists as natural avalanche activity tapers off

Confidence

Moderate

Avalanche Summary

No new avalanches had been reported in the region by 4 pm on Monday, however, operators who were in the field reported seeing signs of instability as they moved through the terrain, such as cracking and whumpffing. We expect users who head into the backcountry on Tuesday will see evidence of a natural storm slab avalanche cycle that occurred during the storm.

Snowpack Summary

Strong southwest winds have redistributed 25 to 50 cm of storm snow into wind slabs in lee terrain features at higher elevations. Recent snow overlies a variety of surfaces including surface hoar in sheltered terrain, and a crust on south-facing slopes. In exposed terrain at higher elevations, new snow covers old wind-affected surfaces.

A widespread crust is 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, human-triggering remains a possibility.

Weather Summary

Monday Night

Partly cloudy with 0 to 5 cm of snow. 10 to 25 km/h northwest ridgetop wind. Treeline temperature -12 °C. Freezing level drops to valley bottom.

Tuesday

Cloudy with 0 to 2 cm of snow. 25 to 40 km/h southwest ridgetop wind. Treeline temperature -13 °C. Freezing levels remain at valley bottom.

Wednesday

Cloudy with snow switching to rain in the afternoon, accumulation 10 to 20 cm above the rain-snow line. Freezing level rises to 1500 m. 60 to 80 km/h southwest ridgetop wind. Treeline temperature -1 °C.

Thursday

Cloudy with 10 to 20 cm of snow. 30 to 50 km/h southwest ridgetop wind. Treeline temperature -6 °C. Freezing level drops to 800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.

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.