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Avalanche Forecast

Archived

Dec 13th, 2021–Dec 14th, 2021

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

Regions

South Columbia.

Continually assess for changing snowpack conditions. Variable wind direction and the presence of a persistent weak layer make for challenging decision making. When in doubt choose conservative terrain.

Confidence

Moderate -

Weather Forecast

Monday night: 5cm of new snow expected with moderate Southeast winds. Low of -6 at 1600m.

Tuesday: up to 5cm of new snow with a high of -5 at 1600m. Winds will be light to moderate from the Southwest in the morning and from the West in the afternoon.

Wednesday: Trace amounts of new snow with moderate Southwest winds. High of -7 at 1600m.

Thursday: Up to 5cm of new snow with a high of -6 at 1600m. Winds becoming strong from the Northwest.

Avalanche Summary

On Saturday a skier controlled size 2.5 was reported in the Selkirks. This avalanche was on a East aspect at 2100m and ran on the early December crust/facet layer.

Wind slabs up to size 2 were reactive to ski cuts and explosives on Sunday. A limited natural avalanche cycle up to size 2.5 was reported to have run during the storm on Saturday. 

Snowpack Summary

15-30 cm of recent snow has seen redistribution by strong wind at upper elevations. 

The defining feature of the snowpack is a prominent and widespread crust that reaches as high as 2400 m in the alpine now sits 40-70 cm below the surface. In many places, overlying snow is well-bonded to the crust but in others, weak faceted grains have been observed growing above it around treeline. Snowpack models show the faceting process progressing quickly at this elevation, likely due to the amount of heat and moisture trapped by the crust. We will be closely monitoring this layer going forward. The snowpack structure is relatively simple beneath the crust, with treeline snow depths around 100-200 cm.

Terrain and Travel

  • Approach lee and cross-loaded slopes with caution.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent 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.