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Avalanche Forecast

Archived

Jan 20th, 2021–Jan 21st, 2021

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

Regions

South Coast Inland.

Isolated wind slabs and large overhanging cornices may remain triggerable by humans. Give cornices their space when travelling on ridgetops and check your line for pockets of wind slab beneath ridge crests and on steep roll-overs.

Confidence

High -

Weather Forecast

Wednesday night: Partly cloudy, light wind, freezing level valley bottom.

Thursday: Mix of sun and cloud, light wind, alpine high around -8.

Friday: Sunny, light wind, alpine high -12.

Saturday: Sunny, light wind, alpine high -12.

Avalanche Summary

On Tuesday, we received report of a thin wind slab size 1.5 triggered naturally in a confined treeline feature. Cornice falls in the northern parts of the region have been reported over the last few days. Many of them triggered wind slab avalanches up to size 2 in the slopes below. None of these large loads triggered deep persistent layers.

Snowpack Summary

In the south of the region, fluctuating freezing levels during the last storm have resulted in a crust to ridgecrest. At upper elevations, 5-10 cm of dry snow has been blown around by the wind, exposing the crust in some areas and building wind slabs on top of it in others. The lower snowpack is well settled.

In the north, upper elevations are extensively wind affected. A widespread surface crust exists below 1600 m. Remnants of a melt-freeze crust from early December may be found around 200 cm deep in the snowpack. It has been most prevalent northwest of Pemberton where large avalanches failed on this interface earlier this month. Recent reports and snow profiles suggest that this layer is decomposing and/or bonding to surrounding snow and trending dormant... for now at least.

Terrain and Travel

  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Pay attention to isolated alpine features as well as cross-loaded features at treeline.
  • Cornices often break further back than expected; give them a wide berth when traveling on ridgetops.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.