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Avalanche Forecast

Archived

Jan 27th, 2021–Jan 28th, 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.
Below Treeline
Natural avalanches unlikely.

Regions

Kootenay Boundary.

Fresh storm slabs may become increasingly reactive throughout the day, especially in wind loaded areas. Watch for signs of instability such as whumfing, cracking, and recent avalanches.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

WEDNESDAY NIGHT - Flurries, 5-10 cm / moderate to strong south wind / alpine low temperature near -8 

THURSDAY - Flurries, 5-10 cm / moderate to strong south wind / alpine high temperature near -5

FRIDAY - Mainly cloudy with isolated flurries / light southwest wind / alpine high temperature near -5 

SATURDAY - Mainly cloudy with isolated flurries / moderate south wind / alpine high temperature near -7

Avalanche Summary

With continued snowfall through the day and strong winds expected, storm slabs could become increasingly reactive throughout the day on Thursday, especially in wind loaded areas.

A size 1 human triggered wind slab avalanche was reported on a northwest aspect at 2100 m near Whitewater on Sunday. 

Another size 1 human triggered wind slab avalanche was reported on a northeast aspect at 2000 m in the Five Mile Provincial Park area on Saturday. 

Snowpack Summary

10-20 cm of new snow is expected in the region between Wednesday night and Thursday afternoon, with moderate to strong south wind. 

One or more crusts may exist in the upper snowpack depending on elevation and area within the region. The uppermost crust extends up to around 2000 m. In higher terrain, 15-20 cm of snow may sit over a crust and/or large surface hoar crystals.

Another layer of surface hoar found 20-50 cm below the surface in isolated areas in the north and east of the region appears to be gaining strength but could become more reactive with some new snow in the coming days.

A couple of crusts surrounded by weak faceted grains are buried deep within the snowpack. The upper layer is 80 to 130 cm deep and the lower is near the ground. 

Terrain and Travel

  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

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.