Archived

Avalanche Forecast

Dec 27th, 2016–Dec 28th, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

Regions: South Rockies.

Watch for signs of fresh wind slabs, such as stiff or slabby snow or blowing snow at ridgetops. If you've been out in the mountain please share your obs on the Mountain Information Network (MIN).

Confidence

Moderate - Due to the number and quality of field observations

Weather Forecast

WEDNESDAY: Cloudy with isolated flurries, 40-60 km/h west winds, alpine temperatures around -12C.THURSDAY: 5-10 cm of new snow, 50-80 km/h southwest winds, alpine temperatures around -10C.FRIDAY: Mix of sun and cloud, 30-50 km/h northwest winds, alpine temperatures around -12C.

Avalanche Summary

On Tuesday, ski cutting produced a size 2 wind slab in the most recent storm snow. Natural loose dry avalanches up to size 1.5 have also been reported out of steep terrain the past few days.Fresh wind slabs will be the primary concern on Wednesday, as strong winds will dramatically redistribute the new low density snow. Larger avalanches releasing on deeper persistent weak layers remain possible to trigger, particularly in shallow or previously wind-affected terrain.

Snowpack Summary

5-10 cm of fresh low density snow is being redistributed by strong winds and likely forming touchy wind slabs in the lee of ridgetops. 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. Below treeline, the snowpack is very shallow and early season hazards such as stumps, rocks, and open creeks are still a major concern.

Avalanche Problems

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: Likely

Expected Size: 1 - 2

Persistent Slabs

Weak faceted snow exists in the lower snowpack and may be possible to trigger in thin snowpack areas and 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

Expected Size: 2 - 3