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Avalanche Forecast

Archived

Jan 3rd, 2021–Jan 4th, 2021

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

Regions

Lizard-Flathead.

Carefully evaluate your terrain choices, triggering storm slab avalanches remains a concern (especially at higher elevations).

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

SUNDAY NIGHT: Cloudy with some isolated flurries and up to 5 cm of snow, moderate west wind, temperatures drop to -8 C.

MONDAY: Cloudy with isolated flurries and up to 5 cm of new snow, moderate southwest wind, temperatures around -4 C.

TUESDAY: 10-20 cm of snow overnight then light flurries during the day, moderate west wind, temperatures around -6 C.

WEDNESDAY: Cloudy with some isolated flurries, moderate southwest wind, temperatures around -2 C.

Avalanche Summary

The storm over the weekend resulted in a widespread cycle of storm slab avalanches in the Fernie area. This included numerous size 2-3 explosive and naturally triggered avalanches. Some of these occurred on bed surfaces of previous avalanches that had been reloaded by strong winds redistributing new snow.

Storm slabs are likely stabilizing in the coming days, but are still a concern and should be considered when assessing steeper and wind loaded slopes.

Snowpack Summary

Saturday night's storm brought 20-30 cm of heavy snow that should stabilize relatively quickly, but could still be a problem in steep and wind affected terrain.

In the Lizard Range, a melt-freeze crust has been reported around 20 to 50 cm deep and up to an elevation of 1900 m. A few reports suggest that sugary faceted grains may exist around the crust but others indicate no weakness. It remains to be seen if this layer will become an avalanche problem.

Around 50 to 100 cm deep, weak layers of feathery surface hoar and/or faceted grains may overly a hard melt-freeze crust. This layer appears to be bonding in certain areas of the region but remains suspect where it is well preserved.

Terrain and Travel

  • Approach lee and cross-loaded slopes with caution.
  • Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

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.