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Avalanche Forecast

Archived

Feb 15th, 2018–Feb 16th, 2018

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

Regions

Sea To Sky.

Wind slabs at higher elevations continue to be the main concern. Approach steep features cautiously.

Confidence

High - on Friday

Weather Forecast

FRIDAY: Trace to 5 cm of new snow by the morning then clearing throughout the day, moderate west wind, freezing level climbing to 1000 m with alpine high temperatures around -5 C.SATURDAY: Moderate snowfall with 15-25 cm throughout the day, strong southwest wind, freezing level up to 800 m with alpine high temperatures around -5 C.SUNDAY: Clearing and cooling with strong northeast wind and alpine high temperatures around -14 C.

Avalanche Summary

No new avalanches have been reported on Thursday (as of 4 pm). On Wednesday, a few small isolated size 1 storm slabs were reactive to skiers and few large (size 2-2.5) natural slab avalanches were reported in steep rocky terrain and lee features. Cornices were reactive to explosive triggers, some producing small slabs on the slopes below.Several large cornices have collapsed over the past 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. A similar incident occurred nearby the same day, but the person only suffered minor injuries. A collapsing cornice also triggered a large slab (size 3) on a north-facing slope west of Pemberton on the weekend. Fragile cornices continue to be a concern in the region.

Snowpack Summary

10-20 cm of light snow sits above a variety of old surfaces, including scoured crusty surfaces on south-facing alpine slopes, a melt-freeze crust up to about 1900 m, and old wind slabs on a range of aspects at high elevations. 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

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.