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Avalanche Forecast

Archived

Feb 21st, 2022–Feb 22nd, 2022

Alpine
Natural avalanches possible, human triggered probable.
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

North Columbia.

Storm slabs may remain reactive to human triggered where they bond poorly to the underlying hard surface. 

Watch for fresh wind slabs forming as northerly outflow winds cross- and reverse-load atypical terrain features. 

Confidence

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

Weather Forecast

Bundle up in your warmest gear, arctic air is here! 

Monday Overnight: Clear skies. Alpine temperatures around -25 C. Light to moderate northeasterly winds. 

Tuesday: Cold and clear. An alpine high of -20 C. Light northeasterly winds.

Wednesday: Mainly cloudy with light snowfall. Winds shifting northwest and strengthening moderate to strong. Alpine temperatures rising to -15 C.

Thursday: Partially cloudy, light flurries. Light to moderate northwest winds. Alpine temperatures around -15 C.

Avalanche Summary

Sunday was an active day for avalanche activity! Numerous human-triggered storm slabs and wind slabs were reported at all elevations throughout the region, with many of these avalanches failing on the mid-February drought layer. Several natural wind slab, storm slab, and dry loose avalanches occurred, some as a result of cornice failures. 

Also on Sunday in the north of the region, a cornice-triggered storm slab avalanche stepped down to the mid-January interface on an east aspect in the alpine, reminding us that this layer is still with us and has the potential to be triggered with larger loads. 

During the peak of the storm on Saturday, numerous natural and human-triggered storm slabs were reported on all aspects due to rapid loading. Larger natural and human-triggered wind slab avalanches were reported in wind-loaded terrain in the alpine and treeline. Several natural dry loose avalanches were reported out of steep terrain on all aspects. 

Explosive control last week initiated some larger persistent slabs up to size 3. 

Snowpack Summary

Last weekend's storm brought 20-80 cm of new snow accompanied by southwesterly winds. 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 the mid-February drought layer. 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. 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 not been reactive to skier traffic in the past week but continues to show reactivity in snowpack tests. With a significant amount of new snow, this layer could start to 'wake up' or be triggered from a large load like a cornice fall or a shallower slab avalanche stepping down to this layer. 

The facet/crust layer that formed in early December is now buried around 150 to 250 cm. Human triggering of this layer is unlikely, except perhaps on a re-loaded bed surface or in a shallow snowpack area. This layer may become a concern during periods of warming or heavy loading. 

Terrain and Travel

  • Closely monitor how the new snow is bonding to the old surface.
  • 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.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.