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Avalanche Forecast

Archived

Dec 3rd, 2019–Dec 4th, 2019

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, human triggered possible.

Regions

South Columbia.

New snow and wind! Expect to find more reactive deposits of storm snow around lee features and cross-loaded terrain.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

Tuesday night: Snow and flurries, 5-15 cm overnight. Alpine temperature -5 C, southwest wind, 30-50 km/hr.

Wednesday: Cloudy with scattered flurries, up to 10 cm through the day. Alpine temperature -5 C, west wind 25-30 km/hr.

Thursday: Mix of sun and cloud and isolated flurries, trace to 5 cm. Alpine temperature -8 C, southwest wind 10-25 km/hr.

Friday: Flurries, 5-15 cm. Alpine temperature -5 C, southwest wind 20-40 km/hr.

Avalanche Summary

On Tuesday, a natural avalanche cycle was observed in Glacier National Park. Numerous size 2 storm slab avalanches were observed on all aspects at 2200 m and above. Additionally, 2 size 3 storm slab avalanches were observed on a north aspect at 2165 m and a northwest aspect at 2400 m.

Explosives also triggered a size 3 storm slab avalanche on a north aspect at 2200 m along the Trans-Canada Highway corridor this afternoon.

Near Revelstoke, storm slab avalanches to size 2 were reacting easily to explosives, many occurring on north and northeast aspects from 1800-2300 m.

Snowpack Summary

Snowfall deposited upwards of 30-40 cm of snow by the end of Tuesday. Westerly winds have begun to redistribute new snow into lee features and cross-loaded terrain.

The new snow has fallen on a faceted upper snowpack and previously wind-affected surfaces. Below the 15-35 cm layer of old, wind-affected snow, a layer of surface hoar (feathery crystals) may be found in sheltered areas around treeline and below. In these areas old, stubborn wind slabs may still be reactive where they overly the weak surface hoar on a crust.

Snow depths range from 60-150 around treeline elevations. A variety of crusts from late October are buried deeper in the snowpack.

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.