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Avalanche Forecast

Archived

Jan 14th, 2021–Jan 15th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Rockies.

Human triggered avalanches remain likely as strong winds are expected to form fresh slabs throughout the day. Look for low-angle, sheltered slopes for the best, and safest riding.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT - Mainly clear / light to moderate northwest wind / alpine low temperature near -6 

FRIDAY - Sunny with cloudy periods / strong west wind / alpine high temperature near -4 / freezing level 1500 m

SATURDAY - A mix of sun and cloud / light to moderate west wind / alpine high temperature near -7 

SUNDAY - Mainly cloudy with sunny periods and isolated flurries / strong west wind / alpine high temperature near -5

Avalanche Summary

With strong west winds in the forecast and a lot of fresh snow available to blow around, storm and wind slabs are expected to be easy to trigger on Friday, especially in wind loaded areas.

There was one size 3 persistent slab avalanche reported on an east aspect at 2400 m in the neighboring Waterton National Park region on Thursday.

There were several natural and explosives triggered avalanches up to size 2.5 reported in the region on Wednesday.

A large (size three) cornice triggered persistent slab avalanche was reported on a large south-facing alpine slope in the Crowsnest Pass area last Thursday. This avalanche failed on weak facets overlying a hard crust deep in the snowpack and is an example of the "low probability; high consequence" scenario that persistent slab problems often create. View the MIN report HERE.

Snowpack Summary

The region received 15-30 cm of new snow between Tuesday night and Wednesday with strong to extreme wind.

The lower snowpack consists of decomposing crusts and weak, faceted snow. In the Elk Valley, a decomposing surface hoar layer can be found around one of these crusts 60-120 cm below the surface. Avalanche activity on these layers in the lower snowpack has been sporadic, mostly triggered by large loads such as a wind slab avalanche, or a cornice fall. These deeper weak layers are most likely to be human triggered on steep, rocky slopes with a shallow or thin to thick snowpack.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded terrain features.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.