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Avalanche Forecast

Archived

Dec 1st, 2020–Dec 2nd, 2020

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

Regions

Kootenay Boundary.

The snowpack doesn't respond well to rapid change. The impact of the afternoon sun and warm temperatures could bump up the avalanche danger in the alpine. Watch for signs of instability and be conservative with your terrain selection.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

Wednesday: Sunny with some cloudy periods. Ridgetop winds light from the southwest and alpine temperatures + 5 degrees. Freezing levels 2500 m.

Thursday: A mix of sun and cloud. Ridgetop winds light and alpine temperatures near + 4 degrees. Freezing levels 3000 m.

Friday: A mix of sun and cloud. Ridgetop winds light and alpine temperatures + 2 degrees. Freezing levels 3200 m.

Avalanche Summary

No recent avalanche observations.

With sun and warming at upper elevations, I suspect we'll start to see some natural avalanche activity. Use extra caution with changing conditions.

Our eyes and ears in the mountains are limited at this time of year and may continue this winter due to fewer professional observations. If you see anything (or don't) while out in the field, please consider sharing via the Mountain Information Network (MIN). Photos are especially helpful! Thank you so much for all the great MINs submitted so far!

Snowpack Summary

Wind and small inputs of snow have formed wind slabs on a variety of aspects at upper elevations. In more sheltered areas, recent snow may rest on a couple of layers of surface hoar 5-10 cm and 15-25 cm below the surface. Forecast sun and alpine temperature inversions may have the greatest impact on the upper snowpack, showing signs of instability. Snow surfaces may become moist and/ or wet when it's warm then re-freeze overnight.

Treeline snowpack depths sit around 100 to 150 cm in the north and 50 to 100 cm in the south of the region. 

Melt-freeze crusts from mid-and early-November are generally found 30 cm below the snow surface and 30 cm up from the ground, respectively. While they are still showing results in snowpack tests, most reports indicate that the bonds at the interfaces with these crusts are improving.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Extra caution for areas experiencing rapidly warming temperatures for the first time.
  • Be aware of the possibility for full depth avalanches due to deeply buried weak layers.
  • Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.