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Avalanche Forecast

Archived

Feb 11th, 2021–Feb 12th, 2021

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

That layer is still a player! Conservative trip plans are the best way to manage the combination of a persistent avalanche problem and extreme cold weather. Read more about these tricky moderate conditions in this forecaster blog.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

THURSDAY NIGHT - Mostly clear / light to moderate north east wind / alpine low temperature near -28

FRIDAY - Cold, a few clouds / light north east wind / alpine high temperature near -18

SATURDAY - Increasing cloud / light to moderate north east wind / alpine high temperature near -20

SUNDAY - Overcast / light southerly wind/ highs near -15

Avalanche Summary

On Wednesday there was a size 1.5 skier triggered avalanche that failed on the late January surface hoar/facet layer. It was on a south east facing slope in the Tunnel Creek area. See MIN

On Tuesday there were a couple of smaller skier triggered avalanches, but of note was a remote triggered size 2 on Mt. Fernie (suspected surface hoar). Also on Tuesday, explosive control yielded wind slab avalanche results up to size 2.

February has been a busy one for avalanche activity with human triggered avalanches going back over a week that are too numerous to list. Do some research and check out the MIN reports in our region, click here.

Many thanks to the community for sharing information through the Mountain Information Network!

Snowpack Summary

Recent northerly and shifting winds have reverse loaded features; slabs may be found in open terrain on a variety of aspects. Surface faceting and surface hoar growth is occurring with clear nights and frigid temperatures.

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 it is touchiest on northerly and easterly aspects, but don't let your guard down elsewhere.

Below 1600 m a hard melt-freeze crust is underneath 20-40 cm recent snow. 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.
  • Be aware of highly variable recent wind loading patterns.
  • 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.

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.