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Avalanche Forecast

Archived

Mar 10th, 2020–Mar 11th, 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 possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Kananaskis.

Intense winds have added another generation of wind slabs. This is a good time to avoid the alpine and open features at treeline. Good skiing can still be found in sheltered areas.

Confidence

High -

Weather Forecast

Strong to extreme SW winds started on Tuesday and are expected to continue until Wednesday morning, only to diminish to 50km/hr from the West for the rest of Wednesday. Weather models are showing 10-15cm of snow by Wednesday morning with the rest of the day to be a mix of sun and cloud and a high of -9c.

Avalanche Summary

One size 2.5 slab avalanche was observed around 11am on Mount Lawrence Grassi which might have reached the Highline trail. Several other slabs were observed on Mount Rundle, west of EEOR. No other slides were observed along the Spray road but visibility was limited.

Snowpack Summary

Wind, wind and wind slabs.  

The forecasters on Tuesday noted strong to extreme SW winds creating intense loading in the alpine and on lee and cross loaded features at treeline. 10-15cm wind slabs at treeline were cracking and breaking with skier traffic. These new wind slabs are growing and are sitting on previous wind slabs from the weekend. It will take several days for all this to sort it self out and settle. Cornices are growing once again.

Terrain and Travel

  • Avoid freshly wind loaded terrain features.
  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Avoid lee and cross-loaded terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Extra caution is needed around cornices under the current conditions.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.

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.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.