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Avalanche Forecast

Archived

Dec 2nd, 2018–Dec 3rd, 2018

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.

We're on a positive track with last week's avalanche problems mostly stabilized, but you can likely still find trouble spots of wind slab and cornice in the alpine.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Sunday night: Cloudy with clear periods. Light northwest winds.Monday: Mainly sunny. Light northeast winds. Alpine high temperatures around -7.Tuesday: Mainly sunny with some valley cloud. Light northwest winds. Alpine high temperatures around -1 under a mild temperature inversion.Wednesday: Sunny. Light northeast winds. Alpine high temperatures around -1 under a mild temperature inversion.

Avalanche Summary

No new avalanches were reported over the weekend.Explosives control work in the Whistler area on Friday produced several size 1.5 cornice releases and one 20 cm deep size 1.5 storm slab. On Wednesday cornices were touchy; a size 1.5 cornice failure was initiated with a very light load. Control work produced storm slabs that averaged size 1.5 on a variety of aspects in the alpine. The outlier was a size 3 avalanche induced by control work on a north facing alpine feature which stepped down to the early November crust.Skies cleared on Tuesday, allowing some observation of avalanches that likely released at the height of the storm. A large (size 2.5) avalanche was reported on a northeast facing glacial feature between 2100 and 2200 m. The avalanche failed naturally with a crown up to 1 meter in depth. Another large natural avalanche (size 2) was reported from a north facing feature near 2000 m. Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

The storm from early last week brought intense precipitation that rain-soaked the snowpack up to about 1800 m and left 20 to 30 cm of wet snow in place up to 2000 m. Above 2000 m the storm produced around 60 cm of new snow. The upper 20 to 30 cm of this snow is reportedly dry in the alpine. Strong to extreme south winds during the storm left behind thick wind slabs and fragile new cornice growth in high elevation alpine terrain. Above 2000 m, 50 to 200 cm of snow now sits on the early November melt-freeze crust. This crust may be associated with weak faceted crystals in some places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

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.