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Avalanche Forecast

Archived

Mar 1st, 2023–Mar 2nd, 2023

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
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.

630 am update: New snow and wind are forming reactive storm slabs. Stick to simple, low angle, wind sheltered terrain free from overhead hazard.

Confidence

Moderate

Avalanche Summary

Storm and wind slabs have been reactive recently. 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.

Looking forward, we are expecting a widespread natural cycle with potential to step down to buried weak layers, possibly resulting in very large avalanches.

Snowpack Summary

30-60 cm is forecast to fall by the end of Thursday. The new snow is likely being wind loaded into lee terrain features at wind-exposed elevations, while falling light 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 juicy northwest flow will deliver the bulk of the snowfall and strongest wind from this system overnight Wednesday. On Thursday, the unstable, convective airmass following in the wake of the cold front will bring locally variable snowfall through the day, tapering overnight and clearing on Friday.

Wednesday night

20-40 cm of new snow. Strong southwest wind peaking in the early evening. Alpine temperatures around -8ºC.

Thursday

5-20 cm of new snow. Moderate southwest wind. Alpine high -10 ºC.

Friday

A mix of sun and cloud. Light to moderate westerly wind. Alpine high -10 ºC.

Saturday

Mostly sunny. Light to moderate easterly wind. Alpine high -8 ºC.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid exposure to overhead avalanche terrain during periods of heavy loading from new snow, wind or rain.
  • Choose simple, low-angle, well supported terrain without convexities.
  • Be careful to keep storm day fever from luring you out into bigger terrain features.
  • Storm slab size and sensitivity to triggering will likely increase through the day.
  • 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.