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 possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

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, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson, Kispiox, Ningunsaw, Ningunsaw, Ningunsaw.

Updated 7:24

Weak layers in the top meter of the snowpack remain rider and remotely triggerable.

Confidence

Moderate

Avalanche Summary

Natural, rider, and remotely triggered storm and wind slab avalanches size 1-2 were reported throughout the region over the past 3 days. On Sunday, explosive work produced wind slabs up to size 2.5.

Most of the recent avalanches were on north aspects at treeline and above. The failure plane has been predominantly facets under the recent storm snow, but in some cases slabs ran on a buried crust with crowns 50 to 100 cm deep.

Snowpack Summary

30 to 60 cm of recent snow has been redistributed by wind at upper elevations. It may take some time to bond to underlying snow, including facets and crusts as well as surface hoar in wind-sheltered terrain.

A thick crust with weak facets overtop was buried in early February and is now 50 to 100 cm deep. It has been a problematic layer for step-down avalanches.

Below, the mid and lower snowpack is generally well-bonded and strong.

Weather Summary

Colder end of forecast temperature ranges are for areas north of Stewart.

Monday night

Partly cloudy. 10 to 20 km/h northeast ridgetop wind. Treeline temperature -16 to -24 °C.

Tuesday

Mostly cloudy with 5-10 cm of snow. 30 to 50 km/h south ridgetop wind. Treeline temperature -12 to -16 °C.

Wednesday

Overnight flurries bringing 5-10 cm then a mix of sun and cloud. 20 to 40 km/h southeast ridgetop wind. Treeline temperature -5 to -12 °C.

Thursday

A mix of sun and cloud. 30 to 50 km/h southeast ridgetop wind. Treeline temperature -6 to -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Stay off recently wind loaded slopes until they have had a chance to stabilize.
If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Seek out sheltered terrain where new snow hasn't been wind-affected.

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.