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Archived

Avalanche Forecast

Jan 21st, 2015–Jan 22nd, 2015
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
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

Regions: South Rockies.

Winds slabs remain a concern in the alpine and exposed areas at treeline. Persistent slab avalanches may still be possible in some areas with a heavy trigger or thin-spot triggering.

Confidence

Fair - Due to the number of field observations

Weather Forecast

A mix of sun and cloud is expected for Thursday and Friday with freezing levels around 1500m and moderate-to-strong alpine winds from the SW. Unsettled conditions are forecast for Saturday with a mix of sun and cloud, light flurries, strong SW winds in the alpine, and freezing levels climbing to over 2000m.

Avalanche Summary

On Tuesday, explosives triggered 3 persistent slabs up to size 2. These released on the mid-Dec layer down 40-60cm. They were all on east aspects around 2000m elevation. On Monday, explosives triggered a size 2.5 deep persistent slab on the early-Nov layer near the ground. This was on an east aspect at 1700m in the Harvey Pass area. Natural avalanche activity is generally not expected on Thursday. Human-triggering remains a concern, especially in wind loaded areas and steep unsupported terrain features.

Snowpack Summary

10-20cm of snow fell last weekend. Moderate-to-strong SW wind has and will continue to redistribute snow in the alpine and will continue to load leeward features. The storm snow buried a layer of surface hoar and/or a crust that exists in many places up to 1900m. At higher elevations the new slow fell on widely wind affected surfaces. The mid-December crust layer is down 40-80cm. In many places this crust is overlaid by facets and/or surface hoar. In areas where the overlying slab is thick and cohesive, large avalanches remain possible on this interface. Closer to the ground a crust/facet interface that formed in November is generally dormant.

Avalanche Problems

Wind Slabs

Moderate-to-strong SW winds continue to load leeward features in the alpine and isolated areas at treeline.
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 - 3

Deep Persistent Slabs

Two weak layers should remain on your radar as they have both recently produced avalanches. The mid-Dec layer is in the middle of the snowpack and the Nov layer is near the ground. Thin-spot triggering or avalanches stepping down are both possible.
Avoid convexities or areas with a thin or variable snowpack where triggering could be more likely.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5