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Avalanche Forecast

Archived

Mar 4th, 2020–Mar 5th, 2020

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

Regions

Kananaskis.

New snow and persistent strong winds have raised the avalanche danger. Stick to conservative terrain and avoid overhead hazard.

Confidence

Moderate -

Weather Forecast

Thursday should bring a mix of sun and cloud with winds out of the SW at 80km/h. Temperatures are expected to reach -4 in the Alpine. Friday and Saturday look snowy with as much as 25cm falling over the course of those two days.

Avalanche Summary

Given the recent intense wind loading, there has been a surprising lack of natural avalanche activity. The snowpack is nearing a tipping point, and a natural avalanche cycle is expected to begin in the near future.

Snowpack Summary

Another 15cm of new snow in past 24 hours brings recent storm snow totals to near 45cm. Extreme westerly winds have stripped west aspects down to bare rock and redistributed significant amounts of snow on N, NE and E aspects. Expect extensive wind slab development on lee and cross-loaded features. These slabs could easily be 100cm deep in places. Human triggering is very likely and a natural avalanche cycle is a real possibility in the next couple of days.

Terrain and Travel

  • Avoid all avalanche terrain during periods of strong wind.
  • Be aware of the potential for large avalanches due to the presence of a deep persistent slab.
  • Minimize exposure during periods of heavy loading from new snow and wind.
  • Avoid lee and cross-loaded slopes at and above treeline.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.