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Avalanche Forecast

Archived

Apr 8th, 2023–Apr 9th, 2023

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

Regions

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

As storm snow continues to build, step back into conservative terrain. Reactive storm slabs are forming at all elevations.

A weak layer buried late March came alive on Friday, head to low angle terrain free from overhead hazard to minimize your exposure.

Confidence

Moderate

Avalanche Summary

On Friday numerous persistent slab avalanches were reported near Stewart on the March 31st buried weak layer. Natural, rider triggered and remote avalanches were triggered to size 2.5. Activity occurred on all aspects and elevations. A wind slab reported in this area on a northeast facing slope stepped down to this weak layer as well.

On Thursday operators reported loose wet activity at low elevations where temperatures remained warm. Natural and rider-triggered avalanche activity was reported within the recent storm snow, mostly to size 1, with larger results produced by explosive control methods in heavy snowfall areas.

Snowpack Summary

Recent snowfall totals may reach 50 to 80 cm in coastal areas, and taper as you move inland where about 30-50 cm of snow has fallen over the week. This continues to be redistributed by southerly winds into wind slabs on north-facing slopes. This sits over wind-affected surfaces or a crust on south-facing slopes that extends into the alpine, or weak facetted crystals.

A weak layer buried at the end of March sits 50-80 cm deep in most areas (potentially over 1m deep in immediate coastal terrain). It includes facets and surface hoar in shaded areas, and a melt-freeze crust elsewhere. This layer has shown limited reactivity within the past week.

The mid and lower snowpack are considered generally strong and well-bonded. In 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

Friday Night

Mostly cloudy with 5-15 cm of snow. Moderate southerly winds. Freezing levels around 800 m.

Saturday

Cloudy with strong to extreme southerly winds. Snow intensifies with 15-40 cm possible. Higher amounts favor typical coastal terrain. Freezing levels around 1000 m.

Sunday

Cloudy with strong to extreme southerly winds. Another 15-30 cm of snow is possible. Freezing levels around 1000 m.

Monday

Cloudy, light snowfall with strong southerly winds. Freezing levels around 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • Be carefull around freshly wind loaded features.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.