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Avalanche Forecast

Archived

Nov 27th, 2019–Nov 28th, 2019

Alpine
Natural and human triggered avalanches likely.
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

South Rockies.

An intense storm has created very dangerous avalanche conditions on the eastern slopes of the Rockies.

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to the extreme variability of wind effect on the snowpack.

Weather Forecast

WEDNESDAY NIGHT: Scattered flurries with another 5-15 cm of low density snow, 50-80 km/h wind from the east, alpine temperatures drop to -20 C.

THURSDAY: Flurries ease off throughout the day but still may deliver another 5-10 cm of snow in the morning, clearing skies in the afternoon, 30 km/h wind from the east, alpine high temperatures around -15 C.

FRIDAY: Mostly sunny, light wind from the northeast, alpine high temperatures around -15 C.

SATURDAY: Sunny, light wind, alpine high temperatures around -10 C.

Avalanche Summary

Natural and human triggered avalanches will remain likely on Thursday. The combination of strong wind and at least 30-60 cm of new snow will create the potential for storm slab, wind slab, and dry loose avalanches on the eastern slopes of the Rockies. We have not yet received any reports of avalanches in the region, but observations are very limited this time of year and the sheer amount of new snow suggests avalanches will remain very likely.

Snowpack Summary

An intense winter storm has delivered 30-60 cm of low density snow to the eastern slopes of the Rockies (and little to none in BC). Another 0-30 cm is possible over Wednesday night and into Thursday morning as the storm tracks east. Strong wind from the northeast has likely created extra deep deposits and hard wind slabs in open terrain, while other areas may be scoured down to rocks and old crusty snow. The new snow has fallen on a highly variable early season snowpack. Some alpine terrain already had 50-100 cm of snow while other alpine terrain features and lower elevations have had no snow prior to this storm. In areas that had prior snow, there could be a crust in the snowpack that could act as a sliding layer for the snow above it.

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.