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Archived

Avalanche Forecast

Dec 21st, 2020–Dec 22nd, 2020
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
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
2: Moderate
The avalanche danger rating at treeline will be moderate
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
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Little Yoho.

Avalanche Control is planned for Mt. Stephen, Mt Field and Mt. Dennis on Tuesday December 22. No access to these areas!

Weather Forecast

An early christmas present of 15-20 cm has started to fall as I write this bulletin. This is forecast to fall with mostly light southerly winds which will switch to north and become strong at the tail end of the storm. Tuesday looks cool with clearing skies. Wednesday and Thursday look sunny and cold with lows near -20 and increasing alpine winds

Snowpack Summary

30-60cm over the last week have been redistributed by strong west winds forming windslabs in exposed alpine and treeline areas. The Dec 13 and Dec 7 sun crust/surface hoar/facet layers are down ~ 35cm and ~65cm respectively. The Nov crust/facets sit at the bottom of the snowpack and are generally well bonded. Height of snow at tree line is 80-150cm

Avalanche Summary

A field trip to treeline on Mt Field today revealed a less touchy snowpack than expected. No new avalanches seen and surprisingly no whumphing or reactivity on steep rolls TL and BTL. However, the Dec. 13th surface hoar layer was found in a test pit at 1950 m and produced an ECTP 26 result down 65 cm on well preserved 3-5 mm surface hoar.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Persistent Slabs

The new load will likely awaken the Dec. 7th surface hoar/facet/sun crust layer which is down 30 -70 cm in this area and is fairly widespread. Reign in your terrain choices!

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Storm Slabs

15-20 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 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

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