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Avalanche Forecast

Archived

Dec 12th, 2022–Dec 13th, 2022

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

Moyie, St. Mary.

Large avalanches have been reported from our nearest neighbours. We should suspect similar conditions in our zone.

Watch for signs of instability like natural avalanches, whumpfing, and shooting cracks as you travel through the terrain. You can also read our latest blog for advice on how to manage this problem.

Confidence

Low

Avalanche Summary

No new avalanches have been observed or reported in this region. However, note that we have had very few field observations. Not having reports of avalanches does not mean that they are not happening or are likely to happen. There have been numerous large avalanches reported in regions all around ours that failed on wind slabs and on buried weak layers.

Please consider filling out a Mountain Information Network report if you are heading to the backcountry.

Snowpack Summary

At just below the treeline the total snowpack ranges between 80 and 120 cm. The top 20 to 30 cm is fairly light fresh snow that has been added incrementally over the last four days. On the west, north, and east aspects this snow sits on wind slabs. There were scattered reports of finding the lighter snow sitting on a buried layer of surface hoar in sheltered terrain and a sun crust on south-facing slopes.

A concerning layer of surface hoar from mid-November is buried down up to 40 to 60 cm. This layer could become more reactive as slab properties above it increase with new snow and wind.

Much of our region's snowpack is speculated at this time and information has been extrapolated from surrounding regions and modeling.

Weather Summary

Monday Night

Clear, no accumulation, winds northeast 15 km/h, temperature -8 C at 1500 m.

Tuesday

A mix of sun and cloud, no accumulation, winds northwest 10 km/h, temperature -6 C at 1500 m.

Wednesday

A mix of sun and cloud, trace accumulation, winds northwest 15 to 20 km/h, temperature -5 C at 1500 m.

Thursday

Sunny with cloudy periods, no accumulation, winds northwest 10 to 25 km/h, temperature -10 C at 1500 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

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.

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.