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Archived

Avalanche Forecast

Dec 7th, 2021–Dec 8th, 2021
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Kootenay Boundary.

Danger is gradually increasing as snow accumulates above a slippery crust, especially on wind-loaded slopes near ridges.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

A cold front will bring gusty winds and 5-20 cm of low density snow on Wednesday. 

TUESDAY NIGHT: Cloudy with some light flurries and 1-5 cm of snow by the morning, moderate wind from the southwest with some gusts to 50 km/h, treeline temperatures around -8 C.

WEDNESDAY: Flurries bring 5-15 cm of low density snow, moderate to strong wind from the west, treeline temperatures around -8 C.

THURSDAY: Mostly cloudy, no precipitation, light wind from the west, treeline temperatures around -10 C.

FRIDAY: Mix of sun and cloud, no significant precipitation, light wind from the southwest with some moderate gusts, treeline temperatures around -10 C.

Avalanche Summary

Recent avalanche activity has been limited to small sluffs (aka loose snow avalanches) running above the shallowly buried crust. Over the weekend there was one explosive triggered storm slab in an open bowl involving a deeper pocket of snow above the crust.

Be on the lookout for this low density snow becoming a more cohesive slab above the crust, especially in wind-affected areas.

Snowpack Summary

Expect more snow to accumulate over the widespread crust on Wednesday. By the end of the day there will likely be 20-40 cm of low density snow above the crust in sheltered areas, while strong wind will likely form wind slabs at upper elevations. The bond of the new snow to the crust is suspect.

The snowpack structure is relatively simple beneath the crust. At upper treeline elevations, the total snow depth is 60-120 cm with a few crusts in the lower snowpack. Below treeline, the snowpack is much thinner and a relatively uniform layer of frozen crusts.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Use ridges or ribs to avoid areas of wind loaded snow.
  • Closely monitor how the new snow is bonding to the crust.
  • Avoid areas where the snow feels stiff and/or slabby.

Avalanche Problems

Wind Slabs

A frontal system crossing the region will form unstable wind slabs on Wednesday. These conditions will most likely be found on the leeward side of ridges. The snow could be poorly bonded to the underlying crust.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2