Avalanche Forecast

Issued: Dec 21st, 2020 4:21PM

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

Ian Jackson,

Email

Avalanche control on Mt. Stephen, Mt Field and Mt. Dennis in Little Yoho. No access to these areas on Tuesday Dec. 22.

Summary

Weather Forecast

An early christmas present of 15-40 cm has started to fall as I write this bulletin. The highest amounts are on the south and east sides of the bulletin area. Mostly light S winds switching to N becoming strong at the end of the storm. Tuesday: cool with clearing skies. Wed and Thurs: sunny and cold with lows near -20 and increasing alpine winds

Snowpack Summary

30-60 cm over the last week have been blown into windslabs in the alpine and down into tree line from strong West winds. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 35cm and ~65cm respectively. The decomposing Nov crust/facets sits at the bottom of the snowpack. Height of snow at tree line is 80-150cm.

Avalanche Summary

Minimal activity in the Lake Louise Ski Hill area but Sunshine Village ski patrol had some notable observations. A size 2.5 -3 was triggered with explosives in the "Wheelers" path above the ski out which stepped down to ground (2m in spots) and ran full path. They also reported a size 1.5 failing on surface hoar down 50 cm BTL in the Wild West area

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

An icon showing Storm Slabs

15-40 cm is expected overnight Monday. We expect this to slide easily until it has had time to settle. These storm slabs could potentially trigger the deep persistent or persistent slab problem.

  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

The new load will likely awaken either the Nov. 5th facet/crust layer at the bottom of the snowpack or the Dec. 7th surface hoar/facet/sun crust layer ~50cm down. Stay out of avalanche terrain!

  • Avoid avalanche terrain.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Loose Dry

An icon showing Loose Dry

With the incoming snow, loose dry avalanches will run in gully features and steep terrain.

  • Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 1.5

Valid until: Dec 22nd, 2020 4:00PM