Avalanche Forecast

Issued: Dec 29th, 2016 5:20PM

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

jfloyer, Avalanche Canada

South Rockies.

Fundamentally weak snow exists in this region. A cautious approach to travel is required to remain safe at this time.

Summary

Confidence

High -

Weather Forecast

FRIDAY: Dry with some sunny spells. Winds mostly light westerly. Treeline temperatures around -6C. SATURDAY: Dry with some sunny spells. Ridgetop winds 20-40km/h from the southwest. Temperatures around -8C.SUNDAY: Light snow in the morning, 5-10 cm. Winds becoming moderate northeasterly. Temperatures around -14C.

Avalanche Summary

A large human-triggered avalanche was reported from Corbin yesterday on a wind affected slope in an area where weak facets were present. While technically this area is in the Lizard/Flathead area, I feel as though it is indicative of conditions in the South Rockies region. Where you get a combination of weak sugary snow lower in the snowpack and a supportive upper slab, conditions are ripe for avalanches to be human-triggered at this time.

Snowpack Summary

Up to 20 cm of fresh low density snow has been redistributed by mainly southwesterly winds and forming wind slabs in the lee of ridgetops. In general, there is very little structure to the snowpack, with low density new snow sitting over soft, sugary facets. Travel is very challenging as a result. A variable interface that formed during the cold snap in early December can be found buried 30-50 cm deep. This interface consists of weak faceted (sugary) snow and preserved surface hoar in sheltered areas. The interface is likely most reactive in wind-affected terrain where it is covered by hard wind slabs. 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. Hazards such as stumps, rocks, and open creeks are still a major concern.

Problems

Persistent Slabs

Where denser snow overlies weak, sugary snow below, there is the potential to trigger large, dangerous avalanches.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Danger spots are where denser snow overlies weak, sugary snow below.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Expect steady strong winds to redistribute loose 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

Possible

Expected Size

1 - 2

Valid until: Dec 30th, 2016 2:00PM