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Avalanche Forecast

Archived

Feb 24th, 2022–Feb 25th, 2022

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

Regions

Cariboos.

Yellow means caution ! Wind slabs are still reactive to human triggering on all aspects, and buried surface hoar layers remain suspicious on open slopes. Make sure to read the section Avalanche Problems.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

The ridge of high pressure will keep the region dry and cold, with the potential for lingering valley cloud and an alpine temperature inversion on Friday and Saturday. The next storm is expected for the weekend as a shift in the weather pattern will occur.

Thursday night: Clear skies. Patchy valley cloud. Alpine temperatures around -20 C. Moderate to strong northwesterly winds.

Friday: Mix of sun and clouds. Lingering valley cloud. Alpine temperatures around -12 C. Light to moderate northwesterly winds.

Saturday: Cloudy with light snowfall. Freezing level rising to 1000 m. Alpine temperatures around -8C. Strong southerly winds.

Sunday: Snow 5-10 cm. Freezing level rising to 1200 m. Alpine temperatures around -6 C. Strong to extreme southerly winds.

Avalanche Summary

On Wednesday, a storm slab avalanche was accidentally human-triggered on a short, steep treeline slope that was previously skied. 

Earlier this week, shifting arctic winds have redistributed the storm snow into wind slabs and several natural avalanches occurred. Evidence of a widespread natural avalanche cycle from the last weekend’s storm is still visible.

As the last storm added load to the snowpack, the mid-January weak layer began to "wake up". In the neighboring region of North Colombia, large cornice-triggered natural persistent slab avalanches on an east aspect at treeline were reported. 

Snowpack Summary

Last weekend's storm brought 20-80 cm of new snow accompanied by southwesterly winds. Recent northeasterly has created a heavily wind-affected surface in exposed areas and redistributed storm snow into wind slabs in lee areas. Below ~1200 m the majority of the precipitation fell as rain, with 10-20 cm of snow now overlying a thick melt-freeze crust. 

Up to 120 cm now overlies a weak layer formed in mid-February. This layer is comprised of surface hoar in sheltered areas, a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline. Reports suggest that in many areas, the storm snow is bonding poorly to this firm layer.

The late-January surface hoar/crust layer is now down 50-150 cm in the snowpack. During last weekend's snowfall, there was reactivity on this layer in the neighbouring Colombia regions. This layer may also be a concern in the Cariboos with a similar upper snowpack composition.

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Closely monitor how the new snow is bonding to the old surface.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.

Problems

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.

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.