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Avalanche Forecast

Archived

Feb 23rd, 2021–Feb 24th, 2021

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

Regions

Northwest Coastal.

The next storm starts impacting the region Tuesday afternoon. Danger remains elevated as slabs from both the previous storm and incoming storm will likely be triggerable by riders.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Clear skies, 30 km/h northwest wind, alpine temperature -9 C.

WEDNESDAY: Increasing clouds with afternoon snowfall, accumulation 5 to 10 cm, 60 to 90 km/h southwest wind, alpine temperature -6 C.

THURSDAY: Cloudy with snowfall, accumulation 30 to 50 cm, 80 km/h west wind, alpine temperature -6 C.

FRIDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 40 to 60 km/h northwest wind, alpine temperature -8 C.

Avalanche Summary

A natural avalanche cycle was reported across most of the region during the intense stormy conditions on Sunday and Monday. The avalanches were mostly large (size 2 to 3) and found at all elevation bands. This MIN shows excellent photos of slab avalanches around treeline elevations, potentially releasing on the surface hoar described in the Snowpack Summary.

Looking towards Wednesday, natural avalanche activity is expected to taper but human-triggered avalanches will remain likely to be triggerable by riders in avalanche terrain.

Snowpack Summary

Over 100 cm of snow fell on the weekend above around 800 m, which formed reactive storm slabs. Another 20 to 30 cm of snow fell to near valley-bottom on Monday and Tuesday. Wind slabs were formed in exposed terrain at treeline and alpine elevations from strong southwest wind. All of this snow may not bond well to previous surfaces buried mid-February, which may include:

  • Hard wind-affected snow, particularly in exposed alpine and treeline terrain,
  • Weak and feathery surface hoar in sheltered areas, with the most suspect elevation bands being lower alpine, treeline, and within openings below treeline,
  • A 20 to 40 cm thick layer of sugary faceted grains that developed during cold periods, and/or
  • A hard melt-freeze crust below treeline.

The mid-pack has been reported as being well-settled. There are presently no deeper concerns.

Terrain and Travel

  • Choose conservative terrain and watch for clues of instability.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Give the new snow several days to settle and stabilize before pushing into bigger terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

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.