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Avalanche Forecast

Archived

Jan 19th, 2021–Jan 20th, 2021

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

Regions

Sea To Sky.

A windy night has likely resulted in fresh wind slabs reverse loaded into atypical alpine features. Watch for these pockets especially at ridge crests and on steep roll-overs.

Confidence

High -

Weather Forecast

TUESDAY night: Flurries, trace, strong to extreme ridgetop wind easing to light northwest, freezing level 500 m.

WEDNESDAY: Mix of sun and cloud, light ridgetop wind, alpine high -4, freezing level 800 m.

THURSDAY: Mix of sun and cloud, light wind, alpine high -7, freezing level 700 m.

FRIDAY: Sunny, light wind, alpine high -7, freezing level 500 m.

Avalanche Summary

A few small wind slab and wet loose avalanches were reported on Sunday and Monday. Explosive control targeting cornices on Friday and Saturday produced size 2 results, some triggering deep slabs on the rocky slopes below. 

There has been significant deep persistent slab activity this month. During a widespread avalanche cycle last week, several storm slabs stepped down to deeper weak layers resulting in very large (size 3-4) deep persistent slab avalanches (see these photos from Panorama Ridge). On Jan 9, a large (size 3) avalanche was remotely triggered by skiers on Cowboy Ridge near Whistler. The avalanche occurred on a north to northwest aspect at around 1900 m. The crown was up to 200 cm deep and was approximately 200 m wide. See this MIN for photos and more information. A similar avalanche was remotely triggered by skiers on a nearby westerly slope a few days before (see this MIN).

Snowpack Summary

Ski quality in the extensively wind affected alpine has been widely referred to as chalky. Soft snow may be found in sheltered areas around treeline. A widespread surface crust exists below 1900 m and on south-facing slopes.

Remnants of a melt-freeze crust from early December may be found around 200 cm deep in the snowpack. Several large natural and human triggered avalanches failed on this layer earlier this month. Recent reports and snow profiles suggest that it is decomposing and/or bonding to surrounding snow and trending dormant... for now at least.

Terrain and Travel

  • Be carefull around freshly wind loaded features.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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.