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Avalanche Forecast

Archived

Feb 23rd, 2020–Feb 24th, 2020

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

Regions

Kootenay Boundary.

The new snow rests on a weak layer so it may take longer than usual to bond to old surfaces and will likely remain reactive to human traffic. Uncertainty about reactivity of buried weak layers is best managed through conservative terrain choices at this time.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

Sunday night: Flurries bringing up to 10 cm. Moderate northwest wind. Freezing level 800 m.

Monday: Morning flurries bringing a trace of new snow. Moderate northwest wind. Freezing level 1200 m.

Tuesday: Mix of sun and cloud. Light to moderate northwest wind. Freezing level 1200 m.

Wednesday: Mix of sun and cloud. Light to moderate northwest wind. Freezing level 1500 m.

Avalanche Summary

Reports from Sunday consisted of loose dry sluffs and soft slab avalanches limited to size 1 easily triggered by skier traffic and running on the surface hoar/crust bed surface.

Snowpack Summary

10-20 cm of recent snow is settling into a storm slab over a layer of widespread surface facets, surface hoar in sheltered areas or sun crusts on solar aspects. In the alpine and exposed treeline, recent snow has been redistributed by strong southwest to northwest wind, loading deep deposits into lee features.

An older layer of surface hoar now sits 30-50 cm deep. This weak layer produced significant avalanche activity focesed in the east of the region last week. While it is likely bonding over time, there is uncertainty around remnant reactivity. The remainder of the snowpack is well settled.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Uncertainty is best managed through conservative terrain choices at this time.

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.