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Archived

Avalanche Forecast

Dec 21st, 2019–Dec 22nd, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
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
3: Considerable
The avalanche danger rating below treeline will be considerable
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.

Clearing skies and new snow will lure people back into the mountains, but stay out of avalanche terrain and away from the runouts of large paths.

Avalanche control on Mounts Whymper, Simpson, Wardle Sunday.  No activities there during that time. 

Weather Forecast

The end of the storm is coming Saturday night.  Temperatures will be in the -10C range Sunday, and winds will be light from the West with a few lingering flurries and cloud. Temperatures will continue to cool through the beginning of next week.

Snowpack Summary

30-70cm of warm, wet snow in the past 48hrs with moderate to strong S/SW winds.  Storm slabs have formed at all elevations and aspects. Below the new snow the snowpack structure is generally weak, consisting of facets and depth hoar and a Nov crust up to 2500m.  These weak layers are getting overloaded with all of the new snow. 

Avalanche Summary

Visibility has been very limited but there have been avalanches up to size 3 in various locations.  We suspect a good sized avalanche cycle is occurring.

Confidence

Due to the number and quality of field observations

Avalanche Problems

Storm Slabs

Storm slabs will be everywhere and will remain reactive while the snowpack adjusts to the new load.

  • Use caution in lee areas in the alpine and treeline. Storm snow is forming reactive slabs.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2.5

Deep Persistent Slabs

The weak, faceted mid and lower pack is overloaded by the new storm snow at all elevations.  Lots of uncertainty surrounds this layer, but if triggered it would result in a large avalanche. 

  • Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 2 - 3.5

Loose Dry

In the short term this will be a problem, especially in gully features and off of sidewalls.

  • 874
  • If triggered dry loose point releases can form deeper deposits in terrain traps.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2