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Avalanche Forecast

Archived

Feb 17th, 2018–Feb 18th, 2018

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

Regions

Sea To Sky.

Fresh storm slabs will be reactive, especially in wind-affected terrain. Use extra caution around steep unsupported terrain features.

Confidence

Moderate -

Weather Forecast

SUNDAY: Gradual clearing and cooling as Arctic air pushes into the region, moderate to strong northeast wind and alpine high temperatures around -15 C.MONDAY: Sunny, moderate northeast wind, alpine high temperatures around -14 C.TUESDAY: Mostly sunny, light wind, alpine high temperatures around -12 C.

Avalanche Summary

Preliminary reports from Saturday indicate storm slabs were reactive to skier and explosive triggers, producing mostly small slabs (size 1) and one larger slab (size 2) in lee terrain.Several large cornices collapses were reported last week. One resulted in a fatal accident in the Callaghan area on Saturday. A snowmobiler was parked 7-10 m back from the edge of a corniced ridge when a large chuck broke off and took the rider down the slope. See here for a full report. Cornices grew larger with Saturday's storm.

Snowpack Summary

25-40 cm of fresh snow sits above variable interfaces including hard wind-affected snow in exposed terrain, a hard crust below 1900 m, and a sun crust on south-facing alpine slopes. Deeper deposits of storm snow exist in lee and cross-loaded alpine terrain. The mid-January crust is now buried beneath 150-200 cm of settled snow, but a heavy trigger such as a cornice fall could potentially wake up this layer. The lower snowpack is generally strong and well-settled.

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.

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.