Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Apr 15th, 2023–Apr 16th, 2023

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Coastal, Kitimat, Nass, Rupert, Seven Sisters, Shames, Stewart, Howson, Ningunsaw.

Numerous large persistent slab avalanches have been triggered by riders this past week.

Conservative terrain selection is critical, choose only well-supported, low-consequence lines.

Confidence

Moderate

Avalanche Summary

Numerous naturally triggered small (size 1) loose dry and wind slab avalanches were reported at upper elevations on Friday.

Two persistent slab avalanches were reported northwest of Terrace on Wednesday. A skier triggered size 2 on a north aspect in the alpine and a size 2.5 on an east aspect in the alpine that was triggered by solar radiation. Both failed on a layer of weak facets and/or surface hoar down 40-50 cm.

A fatal avalanche occurred north of Stewart on Tuesday. It was a skier-triggered size 3 persistent slab avalanche that occurred on a northeast aspect in the alpine.

Two additional skier-triggered size 2-2.5 persistent slab avalanches were also reported on northerly aspects at treeline and above on Tuesday. The depth of the weak layer was around 60-80 cm.

Snowpack Summary

5-20 cm of new snow and strong south wind have formed fresh wind slabs reactive to human triggers on lee features at treeline and above.

Two buried weak layers are down 40-120 cm deep in most areas. They include facets and surface hoar in shaded areas, and a melt-freeze crust elsewhere. Numerous human triggered persistent slab avalanches have occurred on these layers this week.

The mid and lower snowpack are considered generally strong and well-bonded. In the far northern reaches of the region, basal facets may exist which are currently considered inactive. This layer may become active with abrupt changes to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged warming.

Weather Summary

Saturday Night

Mostly cloudy with flurries; 3-10 cm / 20 km/h south ridgetop wind / Temperature at treeline around -5 C / Freezing level valley bottom

Sunday

Mostly cloudy with isolated flurries; 0-5 cm / 20 km/h southeast ridgetop wind / Temperature at treeline around -4 C / Freezing level 1100 m

Monday

Mix of sun and cloud / 10 km/h south ridgetop wind / Temperature at treeline around -4 C / Freezing level 1100 m

Tuesday

Mix of sun and cloud / 10 km/h northwest ridgetop wind / Temperature at treeline around -3 C / Freezing level 1200 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • 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 failure may trigger large avalanches.

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.