Avalanche Forecast

Issued: Nov 29th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs, Deep Persistent Slabs and Loose Dry.

Ian Jackson,

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Avalanche Control is planned for the Sunshine Road on Nov. 30th. No access to Mt Bourgeau or Eagle Mountain zones.

Summary

Weather Forecast

Temperatures will cool Mon night, but then warming as the next storm arrives. Winds will rise to strong to extreme from the west and freezing levels are forecasted to be in the 2000m range. Models are forecasting ~20 cm by end of Tues, ~ 60 cm by end of Wed, and another ~ 10 cm as the system passes and cools on Thurs. Rain in valley bottoms.

Snowpack Summary

30-60 cm of snow in the last storm is reacting as a storm slab in alpine and treeline terrain. The Nov 15 crust is below this and present below 2100 m. The Nov 5 crust/facet layer exists near the ground. Snowpack depths at tree-line average 80-110 cm. Lower elevation snow (below ~ 1500 m ) is rain- soaked.

Avalanche Summary

Natural activity to size 3 as a result of the weekends storm was observed on Monday. Results from avalanche control in Kootenay showed touchy storm slabs at treeline and in the alpine with higher elevation avalanches stepping down to the deep persistent layer. At lower elevations, (below ~ 1700m), these were entraining loose wet snow.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Storm Slabs

An icon showing Storm Slabs

Recent new snow has created storm slabs that have been failing naturally and with explosives. The incoming storm will add load and make this worse. Treat all avalanche terrain with caution.

  • Watch for surface cracking and stiffer surface layers of snow. Avoid wind loaded terrain.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

With a significant new snow load we expect to see larger and more frequent avalanches occur on the basal crust and facets. These avalanches have sporadically been running full path so minimize your exposure to overhead hazards.

  • Be aware of the potential for full depth avalanches due to deeply buried weak layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Loose Dry

An icon showing Loose Dry

With up to 20 cm of new snow forecast by the end of Tuesday, we may see new loose dry avalanches running.

We are also using this problem to represent loose wet avalanches: At lower elevations, rain may create loose wet avalanches in steep terrain.

  • Use extra caution on slopes if the snow is moist or wet.
  • Be careful of loose dry sluffing in steep, confined or exposed terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Nov 30th, 2021 4:00PM