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Avalanche Forecast

Archived

Dec 8th, 2019–Dec 9th, 2019

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

Regions

South Rockies.

Avalanche danger will remain elevated as the snowpack adjusts to the weight of the new snow.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

SUNDAY NIGHT: Clear with cloudy periods, 30-50 km/h wind from the northwest, alpine temperatures drop to -12 C.

MONDAY: Mix of sun and cloud, 30-50 km/h wind from the northwest, alpine high temperatures around -8 C.

TUESDAY: Mix of sun and cloud, 30-50 km/h wind from the west, alpine high temperatures around -8 C.

WEDNESDAY: Mix of sun and cloud, 30-50 km/h wind from the southwest, alpine high temperatures around -6 C.

Avalanche Summary

On Saturday there were a few small human triggered wind slab avalanches (size 1) and one large explosive triggered avalanche (size 3). The explosive triggered avalanche ran on an early season crust and traveled over 500 m down the slope. While human triggering an avalanche this size remains unlikely in the short term, these results are indicative of persistent weak layers lingering in the snowpack that could become more reactive with additional loading.

Snowpack Summary

20-30 cm of fresh snow is settling into a storm slab at upper elevations and being blown around by wind. Crust layers from November and October can be found deeper in the snowpack (check out this MIN report from Mear Lake). These persistent weak layers could become more reactive when loaded by new snow or wind. Snowpack depths range between 50-100 cm at higher elevations and taper rapidly below treeline.

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.