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Avalanche Forecast

Archived

Nov 30th, 2024–Dec 1st, 2024

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

Regions

Kananaskis, Bow Valley, Highwood Pass, North 40, Spray - KLakes.

A slight bump in the danger rating due to the increase in wind and the amount of snow available for transport.

Wind, Wind, Wind! The wind has shown up and is leaving its mark. Windward aspects are becoming scoured and lee features loaded. Caution when entering loaded aspects. Investigate for the presence of windslabs and their reactivity.

Confidence

Moderate

Avalanche Summary

During a field day to the Hero's drainage significant sluffing was observed off all steep cliffy terrain, On the drive along the Spray, there was evidence of a small Loose dry cycle that appeared to be about 12-24 hours old on steep alpine East faces,

Snowpack Summary

Saturdays field teams traveled through the Hero drainage and towards the purple bowl. On the traverse into the bowl we came across firm slabs that were directly under steeper cliff features. These were more likely spindrift slabs and they did not crack or fail like a windslab would. However the winds were howling and fresh windslabs are likely forming on lee and cross loaded features in Alpine and Treeline elevations. Below this the snowpack in this area was weak, unconsolidated and very thin.

Weather Summary

Saturday: The winds really picked up and are reaching further down into the terrain. Moderate to strong transport was observed off all ridge crests and cliff faces were constantly shedding snow. Temperatures reached -1 at the road elevation (1800m)

Sunday: Clouds with sunny periods, No precip expected. Winds will keep blowing from the West @ 25 km/h. Freezing levels are slowing rising to 1500-1700m over the next couple days.

3 observations from today:

  1. Moderate snow transport from Strong to Extreme West winds in the alpine.

  2. Driving back to Canmore, most trees along the road and hill sides are bare of snow now (evidence of winds in the valley).

  3. Spray lakes ice has thawed out by almost a km since Thursday. (warming temps) & white caps were visible on the open water (Wind).

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.