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Avalanche Forecast

Archived

Feb 23rd, 2022–Feb 24th, 2022

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

Regions

South Columbia.

Wind slabs have been reactive to human triggers in recent days. As you enter wind-affected terrain, watch for wind slabs on all aspects.

A developing persistent slab problem warrants caution on open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

The ridge of high pressure will rebuild on Thursday, with the potential for lingering valley cloud and an alpine temperature inversion on Friday and Saturday. 

Wednesday Overnight: Light snowfall. Alpine temperatures around -15 C. Light to moderate northwesterly winds.

Thursday: Cloudy with light snowfall, clearing in the afternoon. Alpine temperatures around -12 C. Light to moderate northerly winds.

Friday: Mainly clear, lingering valley cloud. Freezing level rising to 500 m. Alpine temperatures around -10 C. Light to moderate northwesterly winds.

Saturday: Increasing cloud cover, light snowfall in the afternoon. Freezing level rising to 800 m. Alpine temperatures around -6 C. Moderate to strong southwesterly winds.

Avalanche Summary

In the north of the region, a natural avalanche cycle occurred during the peak of the storm on Saturday afternoon. Reactivity persisted into Sunday, with numerous human-triggered storm and wind slabs reported throughout the day. In the south of the region, wind slabs were reactive to human triggering, with natural loose dry avalanches observed out of steep terrain in the alpine.

As this storm added load to the snowpack, the mid-January weak layer began to "wake up". Two human-triggered avalanches occurred on northerly aspects at or just above treeline and a large natural avalanche also occurred on a north-facing aspect at treeline. 

As arctic air invaded the province on Monday, strong northerly winds redistributed the storm snow into wind slabs on southerly aspects. A natural avalanche cycle occurred on southerly aspects as a result of this wind-loading. Several human-trigged wind and storm slab avalanches were also reported throughout the day. 

Snowpack Summary

Last weekend's storm brought 20-80 cm of new snow accompanied by southwesterly winds. The north of the region received highest snowfall amounts, with tapering amounts to the south. 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 80 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 mid-January surface hoar/crust layer is now down 50-150 cm in the snowpack. This layer has started to 'wake up' following last weekend's snowfall. See the avalanche summary for more details.

The facet/crust layer that formed in early December is now buried around 150 to 250 cm. This layer is currently considered dormant but could become active later this season. 

Terrain and Travel

  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Keep your guard up at lower elevations. Wind slab formation has been extensive.
  • Use small low consequence slopes to test the bond of the new snow.
  • Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

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.