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Avalanche Forecast

Archived

Mar 2nd, 2023–Mar 3rd, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Friday will be a game of convective precipitation roulette. If it's snowing hard in your local area, treat avalanche danger as HIGH. Regardless of the weather, storm slabs are already deep and will remain reactive. Stick to conservative terrain and avoid overhead hazard.

Confidence

Moderate

Avalanche Summary

Preliminary observations from the storm include natural size 2-3 south of the Skeena as well as natural and skier triggered loose dry out of steep terrain. Explosive work near Stewart produced up to size 2.5.

Prior to this storm, storm and wind slabs were reactive. In the past few days, we've had reports of naturals size 2-3 and skier triggered storm slabs up to size 2, some remotely triggered from a distance.

Snowpack Summary

40-60 cm of new snow has been loaded into leeward terrain features at wind-exposed elevations, while remaining soft and fluffy in sheltered areas.

A layer of small surface hoar or facets is now buried over 80 cm deep. A facet/crust layer formed in late January exists around 150 cm deep. Large avalanches were suspected to have run on this layer over a week ago.

The lower snowpack is generally well consolidated but as you move further inland where the snowpack is thinner, basal instabilities linger.

The total height of snow in the alpine varies between 450 cm near the coast and 250 cm further inland.

Weather Summary

A cool, unstable airmass produces convective precipitation over the region. This means localized snowfall amounts that can vary widely. This airmass is forecast to migrate south of the region by the end of Friday.

Thursday night

5-20 cm of new snow. Strong southwest wind. Alpine low -10 ºC.

Friday

1-10 cm of new snow. Light to moderate southwest wind. Alpine high -8 ºC.

Saturday

Mostly sunny. Moderate to strong easterly wind. Alpine high -8 ºC.

Sunday

Mostly sunny. Light to moderate easterly wind. Alpine high -12 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be careful to keep storm day fever from luring you out into bigger terrain features.
  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be aware of the potential for large, destructive avalanches due to the presence of deeply buried weak layers.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.