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Avalanche Forecast

Archived

Feb 15th, 2021–Feb 16th, 2021

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

Regions

Lizard-Flathead.

Slabs sitting on surface hoar and sugary, faceted crystals still get triggered by humans, especially at the treeline/alpine interface. Continue to use conservative decision-making! Wind slabs on multiple aspects are preserved for human triggering due to the cold temperatures.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Mostly cloudy, trace of new snow, light westerly wind, temperature low -16 C.

TUESDAY: Sunny with cloudy periods, trace of new snow, moderate west wind, temperature high -10 C.

WEDNESDAY: Mix of sun and cloud, trace of new snow, light westerly wind, temperature high -6 C.

THURSDAY: Mix of sun and cloud, trace of new snow, light westerly wind, temperature high -5 C.

Avalanche Summary

On Monday, skiers triggered a size 1 avalanche in the alpine from a short distance away. On Sunday skiers triggered avalanches up to size 2.5 on open features at the treeline/alpine interface in the Lizard Range and Tunnel Creek. These failed on the late January persistent surface hoar layer (see this MIN as an example). 

Despite the lack of snow, there has been an increase in activity on the persistent weak layer. On Thursday and Friday there were human and remote triggered avalanches up to size 2 reported. Locations like Mount Fernie, 2000, Liverwurst and McDermid were a few location examples. Some avalanches were triggered from a distance away. 

February has been a busy one for avalanche activity with human triggered avalanches going back well over a week that are too numerous to list. Do some research and check out the MIN reports in our region when planning your trip, you can read them here.

Snowpack Summary

Surface faceting and surface hoar growth is promoted by clear nights and frigid temperatures. Below 1600 m a hard melt-freeze crust is underneath 20-40 cm recent snow. 

A persistent weak layer lurks 30-70 cm below the surface. In some places it consists of surface hoar, in other places just facets, or crust/facet combinations. This weak interface has been responsible for the majority of recent avalanches. 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.

A solid mid-pack sits above a deeply buried crust and facet layers near the bottom of the snowpack (150-200 cm deep), which is currently unreactive. 

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid terrain traps such as gullies and cliffs where the consequence of any avalanche could be serious.
  • 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.

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.