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Avalanche Forecast

Archived

Jan 28th, 2020–Jan 29th, 2020

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

Regions

Kootenay Boundary.

Natural avalanche activity may have subsided, but storm slabs remain sensitive to human triggering especially on steep, unsupported features.

Confidence

High -

Weather Forecast

Tuesday night: Mostly cloudy. Light northwest winds. Alpine low -4 C. Freezing level 1000 m.

Wednesday: Flurries bringing 5-10 cm new snow. Southwest winds building to strong. Alpine high -3 C. Freezing level 1300 m.

Thursday: Mix of sun and cloud. Moderate southwest winds building overnight, becoming extreme at ridgetop. Alpine high -1 C. Freezing level 1300 m.

Friday: Broken cloud with flurries bringing 5-15 cm new snow. Moderate southwest winds. Alpine high +2 C. Freezing level rising to 2200 m by evening.

Avalanche Summary

On Sunday and Monday, storm slabs were reactive to skier traffic up to size 1.5 on north to east aspects in the alpine. Natural storm slab activity has tapered since the weekend but a few have been observed up to size 2 out of steep, unsupported headwalls as recently as Monday. 

On Monday, two deep persistent slab avalanches were reported in shallow snowpack areas on southwest aspects around 2000 m, with crown depths of 1 m or greater. A size 1.5 was vehicle triggered above a cut bank. A size 2.5 was remotely triggered by a skier in a thin to thick snowpack area. 

Snowpack Summary

At upper elevations, recent snow has settled into a storm slab amid mild temperatures. Around treeline, the upper snowpack contains several crusts from recent warm temperatures and rain events, some observed as high as 2100 m. 

A layer of surface hoar is buried 80-120 cm below the surface in sheltered areas around treeline. Weak basal facet/crust layers are particularly noteworthy in the western Boundary area. Both of these layers have been trending less reactive over the past two weeks.

Terrain and Travel

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.

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.