Avalanche Forecast

Issued: Dec 6th, 2014 8:30AM

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

rbuhler, Avalanche Canada

Purcells.

New wind slabs may be a concern in exposed terrain. Persistent slabs remain a concern anywhere that did not avalanche last week. If you observe any new activity, please send us an email at forecaster@avalanche.ca

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A weak ridge of high pressure will bring dry conditions and some sun for Sunday. On Monday, the pattern changes to a strong SW flow which will persist for several days. Freezing levels will rise to around 1500m on Monday and as high as 2500m on Tuesday. Scattered precipitation is expected for Monday and Tuesday and alpine winds are expected to be moderate-strong from the SW.

Avalanche Summary

Avalanche activity has diminished, but it would still be possible for the weight of a person or sled to trigger a persistent slab, with big consequences.

Snowpack Summary

Surface layers consist of variable wind slabs and dry snow. Below this you may find a hard rain crust. In the Golden area this crust exists up to around 1600m, whereas in the south it is up to 2000m or higher. In total, last week's storm produced slabs up to 1m thick in the north of the region and around 60cm thick in the south. This slab sits on the mid-November weak layer (surface hoar, facets, and/or a crust). Below this you will likely find a 15-20cm thick layer of sugary facets, which is sitting on a solid rain crust from early November. The reactivity of these layers may be slowly diminishing, but they still warrant cautious consideration. Snowpack tests are getting hard pops and drops results, indicating the potential for large propagation and large avalanches.

Problems

Persistent Slabs

The chances of triggering a persistent slab have decreased, but the consequences are still high. Any slopes that did not avalanche during the last storm cycle should still be considered hazardous.

Avoid common trigger zones including thin snowpack areas, near rocky outcrops, and steep alpine slopes.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Wind Slabs

New snow and moderate winds have likely created wind slabs in leeward features in wind exposed terrain.

Use ridges or ribs to avoid pockets of wind loaded snow.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Dec 7th, 2014 2:00PM