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Avalanche Forecast

Archived

Jan 22nd, 2020–Jan 23rd, 2020

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 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.

Triggering storm slab avalanches will become more likely as snow accumulates throughout the day.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

WEDNESDAY NIGHT: Cloudy and light flurries, moderate wind from the southwest, alpine temperatures drop to -5 C.

THURSDAY: Flurries increasing intensity throughout the day with 10-20 cm of new snow, moderate wind from the southwest, freezing level up to 1500 m with alpine high temperatures around -2 C.

FRIDAY: Scattered flurries with 5-10 cm of snow, light to moderate wind from the southwest, freezing level around 1500 m with alpine high temperatures around -2 C.

SATURDAY: Cloudy with light flurries, light wind from the southwest, freezing level around 1500 m with alpine high temperatures around -2 C.

Avalanche Summary

The incoming storm will form fresh slabs at higher elevations. Between Monday and Wednesday there have been a few reports of small (size 1) skier triggered avalanches in steep terrain and larger (size 2) explosive triggered storm slab avalanches on all aspects at treeline elevations. No persistent slab avalanches have been observed in the past week, suggesting they are becoming less likely to trigger.

Snowpack Summary

Another 10-20 cm of new snow on Thursday will bring a total of 15-30 cm of snow above a thin crust layer that formed on Monday. Strong wind from a variety of directions has created variable surface conditions in open terrain. 

There are two layers of surface hoar found around 70 to 130 cm below the snow surface that have been an issue in steep, sheltered, and shallow rocky areas. The base of the snowpack in many parts of the region consists of weak faceted crystals and crusts. Recent observations suggest these persistent weak layers are becoming less reactive.

Terrain and Travel

  • Watch for avalanche hazard to increase throughout the day.
  • Be aware of the potential for large avalanches due to the presence of buried weak layers.

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.