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Avalanche Forecast

Archived

Feb 20th, 2022–Feb 21st, 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 possible, human triggered probable.
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.

The north of the region was a hot spot for Saturday's storm. Continue to be conservative with terrain choices as storm slabs may still be reactive to human-triggering.

In the south of the region, the problem is likely more confined to a wind slab problem in lee areas.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region. 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! 

Sunday Overnight: Cloudy with light flurries, clearing into the morning. Light to moderate northerly winds. Alpine temperatures plummet to around -20 C.

Monday: Partially cloudy and cold. Light northerly winds. Alpine temperatures around -20 C.

Tuesday: Cold and clear. Light northerly winds. Alpine temperatures around -20 C.

Wednesday: Cloudy with light flurries. Light to moderate northwesterly winds. Alpine temperatures around -16 C.

Avalanche Summary

In the north of the region, a natural cycle likely occurred during the peak of the storm on Saturday afternoon. Numerous human-triggered storm and wind slabs were 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.

Explosive control last week initiated some larger persistent slabs up to size 3 on north-facing aspects at treeline.

Snowpack Summary

This weekend's storm brought 20-70 cm of new snow, with up to 100 cm now overlying the old, hard surface. This surface is a result of a period of high pressure in mid-February. The layer is comprised of facetted snow, 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. 

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 and is showing limited reactivity in snowpack tests. Although unlikely, the layer could 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

  • Be especially cautious as you transition into wind affected terrain.
  • 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.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Avoid exposure to overhead hazards when solar radiation is strong.

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.