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Avalanche Forecast

Archived

Dec 2nd, 2020–Dec 3rd, 2020

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, 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 like rapid change. The avalanche danger remains elevated in the alpine due to sustained warm temperatures. Watch for signs of instability and be very conservative with your terrain selection. 

Confidence

Moderate -

Weather Forecast

Thursday: Mix of sun and cloud. Treeline temperatures near +1 and ridgetop wind light from the southwest. Freezing levels 1600 m.

Friday: Cloudy with sunny periods. Treeline temperatures near 0 and ridgetop wind light from the South. Freezing levels near 1400 m with a weak temperature inversion in the alpine.

Saturday: Mix of sun and cloud. Alpine temperatures near +3 and ridgetop winds remain light. Freezing levels 1400 m with an alpine temperature inversion. 

Avalanche Summary

On Wednesday, numerous loose wet avalanches were reported from NE slopes above 2000 m. These avalanches were up to size 1.5 with no significant propagation.

Have you been out and about in the mountains? If so please submit to the Mountain Information Network (MIN). It doesn't have to be technical it can be as simple as a photo. Photos are especially helpful! 

Sending a big thank you to the already submitted MIN's this season. Thanks everyone!

Snowpack Summary

It's a very dynamic period and the snowpack doesn't like rapid change.

Recent sun and warm air in the alpine on Wednesday likely had the greatest impact on the upper snowpack, showing signs of instability and promoting further slab development and cohesion. This may be most concerning where these slabs sit above an old thin crust on south aspects and feathery surface hoar crystals in wind-sheltered areas. 

Northerly aspects will likely see fresh wind slab development at upper elevations on leeward slopes and melt-freeze conditions may exist on most aspects at upper elevations. 

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

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 older reports indicate that the bonds at the interfaces with these crusts are improving, but a lot of uncertainty still exists with limited observations. Triggering a slab above this layer may be more likely on south-facing slopes and in shallow, rocky, snowpack areas in the alpine.  

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.