Archived

Avalanche Forecast

Dec 30th, 2018–Dec 31st, 2018

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Rockies.

Shifting winds will have set up a complicated pattern of wind-affected slopes in exposed areas.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

SUNDAY NIGHT: Dry with clear periods.MONDAY: Dry with a mix of sun and cloud. Light southwesterly winds. Treeline temperatures around -12C.TUESDAY: Dry with a mix of sun and cloud. Light westerly winds. Treeline temperatures around -12C.WEDNESDAY: Dry with a mix of sun and cloud. Moderate southwesterly winds. Treeline temperatures around -5C.

Avalanche Summary

Several loose dry avalanches and a few small (size 1) storm slab avalanches were triggered (ski cut) in this region on Sunday.

Snowpack Summary

The upper snowpack consists of hard wind slabs on north aspects, scoured and a shallower snowpack on south aspects, and a mixed bag of lower density snow in more sheltered areas. In total, 60-90 cm of December snow has formed a slab that sits on a persistent weak layer of facets (sugary snow) that formed during the dry weather in early December. This layer is most likely to be triggered on steep features where the underlying ground cover is smooth, areas where the snowpack depths are variable, or on large convex features.The lower snowpack has a weak structure composed primarily of facets over a crust on the ground. It is very likely that an avalanche triggered on the persistent slab would step down to the lower facets, resulting in a full depth avalanche.

Avalanche Problems

Wind Slabs

Strong winds have set up wind slabs in exposed areas. Winds initially blew from the southwest and then switched to the northwest making for a potentially complicated wind-loaded pattern.

Be cautious as you transition into wind affected terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

60-90 cm of snow sits on a weak layer of facets (sugary snow). The snow below this layer consists primarily of facets all the way to the ground. Avalanches triggered on this layer will likely step down to the ground, resulting in large avalanches.

Avoid steep convexities or areas with a thin or variable snowpack.Be wary of slopes that did not previously avalanche.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 2.5