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Avalanche Forecast

Archived

Feb 25th, 2021–Feb 26th, 2021

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

Regions

Northwest Inland.

20-30 cm of recent snow accompanied by strong to extreme wind has formed reactive storm slabs and wind slabs. Natural avalanche activity may taper off on Friday but skier and rider triggering is likely.

Fresh and reactive wind slabs will build throughout the day.

Confidence

Low - Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region. Uncertainty is due to the limited number of field observations.

Weather Forecast

Friday: A mix of sun and cloud with alpine temperatures near -10. Ridgetop wind strong from the northwest. Freezing level valley bottom.

Saturday: Cloudy with sunny periods and flurries. Alpine temperatures near -8. Ridgetop wind strong from the West and freezing level valley bottom.

Sunday: Snow 10-20 cm. Alpine temperatures near -5 and ridgetop wind strong to extreme from the southwest. Freezing level 900 m.

Avalanche Summary

No recent reports by Thursday afternoon, but I suspect a natural avalanche cycle may have occurred. 

We are still receiving reports of widespread avalanche activity that occurred earlier this week across the region, for example as described in this MIN as well as this MIN. We also heard of a deep persistent slab releasing out of treeline terrain on a north aspect near Ningunsaw.

Looking towards Friday, natural avalanche activity may taper but skier and rider triggering is likely. Strong winds may build fresh and reactive wind slabs. A conservative mindset is warranted and avoid slopes with any negative consequence, as triggering storm and wind slabs will remain likely.

Snowpack Summary

By Thursday afternoon the region received 20-30 cm of fresh snow. The new snow arrived with strong to extreme southwest to northwest wind. Reactive storm slabs likely exist in sheltered terrain and wind slabs in exposed terrain at high elevations. 

This snow will build on the 40 to 60 cm of snow that accumulated earlier this week. All of this snow overlies hard wind-affected snow in exposed terrain and weak, faceted snow or surface hoar crystals in sheltered terrain, suggesting it may take some time for the snow to bond to these surfaces.

Basal faceted snow remains part of the snowpack structure in much of the region. Once we see a substantial warm-up, we'll be thinking about the potential for the reactivation of basal layers.

Terrain and Travel

  • Travel in alpine terrain is not recommended.
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Choose conservative terrain and watch for clues of instability.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

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.

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.