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Avalanche Forecast

Archived

Dec 13th, 2021–Dec 14th, 2021

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 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.

Regions

Kootenay Boundary.

Avoid wind effected terrain in the treeline and alpine. New snow and variable wind direction could make for a challenging wind slab problem.

Confidence

High -

Weather Forecast

Monday night: freezing levels will rise to 1100m. Winds will be strong from the South. Up too 20mm with the largest amounts in the Rossland range.

Tuesday: High of -6 at 1700m. 5cm of new snow with variable winds. Winds will start out early in the morning as moderate from the Southwest and become light from the West as the day progresses.

Wednesday: trace amounts of snow with light Southwest winds. Temperature at 1700m -6.

Thursday:Trace amounts of new snow with a high of -7 at 1700m. Winds becoming moderate from the Northwest. 

Avalanche Summary

Storm slabs remained reactive to explosive control on Sunday. Most results were on North aspects In treeline and above.

One skier controlled wind slab size 1.5 was reported on a North aspect at 2200m.

Snowpack Summary

Up too 20mm of precipitation is expected for the region Monday night. This will fall as snow in the treeline and alpine but likely as rain in the lower elevations. Winds will be variable starting Monday night and continuing to shift through Tuesday. Wind slab could form on all aspects in the treeline and alpine.

The defining feature of the snowpack is a prominent and widespread crust that now sits 40-70 cm below the surface. In many places, overlying snow is well-bonded to the crust but in others, including Kootenay Pass, 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. 

Snow depths are roughly 80-140 cm at treeline throughout the region.

Terrain and Travel

  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Avoid lee and cross-loaded terrain.
  • Be aware of highly variable recent wind loading patterns.
  • 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.