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Avalanche Forecast

Archived

Feb 13th, 2021–Feb 14th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Rockies.

 

With continued reports of remote and rider trigged avalanches on the persistent weak layer, conservative decision making and careful route finding are ESSENTIAL. This layer has been most reactive at the treeline elevation on the BC side, but don’t let your guard down elsewhere.

Confidence

Low -

Weather Forecast

SATURDAY NIGHT - partly cloudy / light to moderate easterly wind / low -26

SUNDAY - Partly cloudy / light southerly wind / highs of -14

MONDAY - Overcast, trace of new snow / light south west wind / -12

TUESDAY - Partly cloudy, light westerly wind, high of -10

Avalanche Summary

There are recent reports in the South Rockies region of human triggered avalanches on a persistent weak layer of feathery surface hoar. One of the groups made a MIN report for us, check it out. There was also a report of a few natural cornice triggered avalanches in headwall features suspected from the last 36 hours.

Skiers triggered a large (size 2.5) avalanche on a south facing slope in K-Country (forecast region to the north of us) on Thursday. Facets over an old sun crust may have played a role. You can read the MIN report here.

Ski cuts have been producing small avalanches avalanche in reverse loaded terrain. 

Snowpack Summary

Variable winds have redistributed loose snow developing slabs in lee and open features. In sheltered zones the surface snow is becoming faceted and sugary.

A persistent weak layer lurks 40-65 cm below the surface. In some places it consists of surface hoar, in other places just facets, or crust/facet combinations. Reports suggest the surface hoar interface at treeline is the biggest repeat offender, and things have been most reactive on northerly and easterly aspects, but don't let your guard down elsewhere.

In most places 30-60 cm loose snow and soft slab overlies a handful of surfaces: wind affected snow at upper elevations and exposed terrain, softer snow in sheltered areas, and a crust on steep, solar slopes and below 1600-1900 m. 

A solid mid-pack sits above deeply buried decomposing crust and facet layers near the bottom of the snowpack. Though unreactive under the current conditions, steep rocky slopes and shallow snowpacks should still be approached with caution.

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • If triggered, loose dry avalanches may step down to deeper layers resulting in large avalanches.

Problems

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.