Avalanche Forecast

Issued: Dec 25th, 2016 3:32PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs and Wind Slabs.

Avalanche Canada shorton, Avalanche Canada

Strong winds will increase the avalanche danger in the upcoming days.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

MONDAY: Cloudy with isolated flurries, west winds increasing throughout the day reaching 50 km/h in the afternoon and 80 km/h overnight, alpine temperatures around -12C.TUESDAY: Flurries with accumulations of 5-15 cm, 40-60 km/h west winds, alpine temperatures around -8C.WEDNESDAY: Mix of sun and cloud with isolated flurries, strong west winds, alpine temperatures around -10C.

Avalanche Summary

On Saturday, ski cutting produced size 1 loose dry avalanches in the new low density snow. Skiers in Kananaskis Country remotely triggered a size 2 avalanche from 35 m away on Friday. The avalanche was a wind slab over a weaker facets, which closely resembled snowpack conditions in the South Rockies.Triggering persistent slab avalanches on weak interfaces that formed in early December are the primary concern. Triggering these layer is most likely in wind-affected terrain where the weak layers are covered by hard wind slabs. In the southeast corner of the region, explosive results suggest there are also weak facets near the ground that may be possible to trigger from thinner snowpack areas.

Snowpack Summary

Recent flurries delivered 10-15 cm of low density powder. The fresh snow covers hard wind slabs from a storm last week. A variable interface that formed during the cold snap in early December can be found 20-40 cm under the new snow. This interface consists of hard wind packed snow in exposed terrain, weak faceted (sugary) snow, and feathery surface hoar up to 20 mm in sheltered areas. This interface will likely evolve into a lingering persistent slab problem as the recent storm snow settles into a slab. The snowpack is a generally weak and faceted below this interface, including another weak layer with surface hoar or facets that was buried in early December. Below treeline, the snowpack is very shallow and early season hazards such as stumps, rocks, and open creeks are still a major concern.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Weak faceted snow exists in the lower snowpack and may be possible to trigger in thin snowpack areas or on wind-loaded slopes.
Carefully evaluate and use caution around thin snowpack areas.Be aware of the potential for full depth avalanches due to deeply buried weak layers.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

An icon showing Wind Slabs
Expect increasing winds to redistribute the loose surface snow and form touchy wind slabs. If triggered, wind slabs may step down to deeper weak layers.
Avoid freshly wind loaded features.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 26th, 2016 2:00PM

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