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Avalanche Forecast

Archived

Mar 3rd, 2021–Mar 4th, 2021

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

Regions

Kananaskis.

Rapid warming with the first pulse of spring are reaching the forecast area over the next 48hrs. Anything rapid is rarely good and we expect natural avalanche activity to increase on Thursday especially on solar aspects. If the sun is intense we may see danger trend to HIGH. 

Confidence

Moderate -

Weather Forecast

Overnight lows are forecast to reach around -6C then tomorrow will be the first big warm weather pulse of the spring! Freezing level is expected to climb to 2200m with day time highs around +2C. Combine this with some clear skies and we are in for a warm day on Thursday. This rapid change will likely have an impact on the snowpack and possibly trigger a natural avalanche cycle .  

Avalanche Summary

There were a few new avalanches noted in the Aster lake area today with a sz 2.5 down 80cm, 200m wide that ran over 200m down the NE face of Northover Peak. We suspect that this was the Jan 29th interface. There was also an older slide (+24hrs) on a SE aspect of Mt Lyautey that started as an initial windslabs then stepped down to the basal facets running onto Aster lake (suspect sz 2).  

Skiers in the Engadine Burn area also reported a Skier accidental on a SW aspect in 30+ deg terrain at treeline that they estimated to be a sz 1 failing down 40-50m. 

Overall, seem over the past few days there has been a slow steady increase in avalanche activity related to the arrival of the warmer weather and the previous strong winds.  

Snowpack Summary

Recent snow from earlier in the week is settling. This snow is overlying a windslab down 10-20cm that was seeing some isolated cracking today in the Aster lake area. Deeper in the snowpack there are two layers that we are following closely. The Feb 19th Facets down 40-60cm and the Jan 29th interface down 60-100cm. Windslabs (buried and near the surface) in the upper snowpack are likely to step down to one of these layers that are within the top meter. These layers are subtle at treeline but very pronounced in the Alpine. Dig down and assess these layers. Forecasters today avoided big slopes in the alpine due to windslabs over these interfaces. Moist snow was also found up to 2000m by midday.  

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid lee and cross-loaded terrain.
  • Pay attention to isolated alpine features as well as cross-loaded features at treeline.
  • Be alert to conditions that change with elevation and sun exposure.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet

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.

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.