Avalanche Forecast

Issued: Jan 21st, 2015 8:26AM

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

rbuhler, Avalanche Canada

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.

Summary

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.

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

Valid until: Jan 22nd, 2015 2:00PM