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Archived

Avalanche Forecast

Feb 20th, 2021–Feb 21st, 2021
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
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Banff Yoho Kootenay.

A significant storm will arrive Sunday. Expect conditions to change during the day. By Monday, a significant step back in terrain choice will be warranted.

Weather Forecast

Continued light snowfall overnight Saturday. Sunday, trace amounts of snow, up to 10 cm,  favouring the North part of the region will fall,  as a warm front arrives late in the day. Freezing levels will approach 1800m and alpine winds will reach 70-80km/h. A cold front Monday will bring 10-15cm of snow, peak winds and cooling as it sweeps N to S.

Snowpack Summary

Extensive wind effect with a few thin wind-slabs and fresh cornice growth developing in the alpine. At treeline and below the snowpack is well settled except the surface snow which is facetted and sluffs in steep terrain although wind effect is starting to creep down. A facet and sun crust layer buried Jan 27 persists at treeline down 30-40 cm.

Avalanche Summary

Moderate wind transport at ridge top led to a least one small cornice triggered avalanche in Kootenay NP  today. Sunshine Village reported working with fresh cornice growth and small fresh wind slabs at ridge crests and into  isolated treeline areas. Thursday, Sunshine triggered a very large cornice that initiated a size 2.5 persistent slab.

Confidence

Intensity of incoming weather systems is uncertain on Sunday

Avalanche Problems

Wind Slabs

Winds will be strong out of the west overnight Saturday and reach Extreme as the storm arrives Sunday. Expect the small wind-slabs in the alpine to develop further and extend to treeline elevations especially as fresh snow and warming temps are added

  • Pay attention to overhead hazards like cornices which could trigger slabs.
  • Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Storm Slabs

New snow, intense winds and warm temperatures associated with the storm arriving late Sunday will promote slab development at all elevations as snowfall continues through Tuesday. Expect the new slabs to be touchy over the current faceted surfaces.

  • The new snow will require several days to settle and stabilize.
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1 - 1.5