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Archived

Avalanche Forecast

Nov 28th, 2020–Nov 29th, 2020
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
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
3: Considerable
The avalanche danger rating in the alpine will be considerable
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

Regions: Banff Yoho Kootenay.

Strong to extreme winds have and will continue to keep the alpine hazard elevated for the next few days, as uncertainty surrounds the extent and sensitivity of newly formed wind slabs.

Weather Forecast

A mix of sun and cloud for Sunday as the winds are forecasted to increase throughout the day, 30-80km/hr at ridge top from the South West. Temperatures will range from -2 to -7. Monday could see another 2 - 5cm of snow, strong to extreme winds and a slight cooling trend.

Snowpack Summary

10cm of recent snow and strong Westerly winds suspected to be building wind slab in the alpine down to tree line. The Nov 5 facet/crust combo is down 50-80 cm and producing variable test results, but 'sudden' in fracture character. This crust extends up to 2500 m on N aspects and higher on solar aspects. Snow depths at treeline are 70-130 cm.

Avalanche Summary

Evidence of natural avalanche activity within the past 36hrs up to size 2 (mainly sz 1-1.5) observed and reported throughout the forecast region consisting of cornice failures, wind slabs and loose dry sluffing.

Confidence

Avalanche Problems

Wind Slabs

Recent snow and increasing South West winds is expected to continue the wind slab development in the alpine and down to tree line.

  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

The Nov 5 crust has facets growing above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. New load from recent winds may make this layer more sensitive.

  • Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
  • Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3