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Avalanche Forecast

Archived

Feb 23rd, 2018–Feb 24th, 2018

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

Regions

Kootenay Boundary.

New and old wind slabs exist in lee features. Watch for signs of avalanche activity and locally unstable snow, such as whumpfing and shooting cracks.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

SATURDAY: Early-morning snowfall, accumulation 2 to 5 cm, then clearing to a mix of sun and clouds, light to moderate northwesterly winds, alpine temperature -12 C, freezing level 500 m.SUNDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, moderate to strong southwesterly winds, alpine temperature -10 C, freezing level 800 m.MONDAY: Mostly sunny, light westerly winds, alpine temperature -10 C, freezing level 800 m.

Avalanche Summary

Numerous wind and storm slabs were triggered by skiers and explosives on Thursday.  They were small to large (size 1 to 2), 10 to 30 cm deep, between 1900 and 2100 m, and on all aspects.  A cornice also released naturally and did not trigger a slab below.On Wednesday, a few small slabs (size 1) were triggered by skiers on southerly to easterly slopes between 1600 and 2100 m.  They were 30 cm deep in steep and wind-loaded terrain.  Sluffing was also noted in steep terrain.

Snowpack Summary

Around 5 to 10 cm of storm snow fell with strong southwesterly winds, producing slabs on all aspects with deeper deposits in lee features.  This snow fell on previously wind-affected surfaces. The new snow may not bond well to these surfaces and could be reactive to both natural and human triggers.  Deeper in the snowpack, variable surface hoar, faceted grains, and crusts exists around 30 to 50 cm deep, which are showing to be reactive to human traffic.Weak layers that formed in January and December are gradually gaining strength. The layers include several surface hoar and facet layers buried 1-2 m below the surface and a crust/ facet interface near the base of the snowpack. No avalanches have been reported on these layers for the past two weeks and snowpack tests are showing improved bonding. Despite these signs, avalanche professionals are still treating these layers with respect and being cautious around shallow start zones and in big avalanche paths.

Problems

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.