Avalanche Forecast

Issued: Dec 26th, 2015 8:42AM

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

Avalanche Canada rbuhler, Avalanche Canada

New wind slabs are expected to build on Sunday at upper elevations. In isolated areas, the weak layer from early Dec may still be reactive.Continually assess local conditions as you travel and use extra caution in wind affected terrain.

Summary

Confidence

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

Weather Forecast

A weak storm system will result in snowfall Saturday night and Sunday. 2-6cm of new snow is expected by Sunday evening. Alpine winds are expected to be moderate to strong from the SW and treeline temperatures should be around -12C. On Monday, unsettled conditions are expected as the storm exits the region. Light intermittent snowfall is possible in the morning and sunny breaks are possible in the afternoon. Alpine winds should ease to light after the storm passes and treeline temperatures should remain around -12C. On Tuesday, a ridge of high pressure builds and sunny conditions are expected.

Avalanche Summary

On Wednesday, two skier accidental avalanches were reported in the Golden backcountry. The first occurred in the morning and was a size 2 wind slab avalanche which occurred on a northwest aspect at about 2400m. It was up to 50cm in depth and ran approximately 600m. The second occurred in the afternoon and was a size 2.5 wind slab at ridgetop. This also occurred on a NW aspect at 2400m elevation. This avalanche stepped down to a deeper layer lower down in the start zone, likely the early December interface. On Thursday, a large settlement was felt in a flat meadow in the Invermere backcountry. This occurred at 2200m in a below treeline terrain feature and the failure layer is unknown. No new avalanches were reported on Friday.  New wind slabs are expected to form during the weekend storm and may be sensitive to human-triggering on Sunday.

Snowpack Summary

20-30cm of low-density snow typically overlies a well-settled mid and lower snowpack. Surface hoar growth and near-surface faceting are both being reported on the snow surface. New wind slabs are expected to form this weekend as winds increase with the storm system. Between 40 and 100cm below the surface you'll likely find a weak layer which was buried in early December. Between 1400m and 1800m, this layer consists primarily of large surface hoar. At higher elevations, this layer consists of a sun crust, facets, and/or small surface hoar. This layer is still reactive in some snowpack tests and has produced a few human-triggered avalanches in the last week. The layer is creating a low probability, high consequence type of problem, especially in the north of the region. Below this layer, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

An icon showing Wind Slabs
New wind slabs are expected to form in leeward features at ridge crest as SW winds increase during the storm.
Make observations and assess conditions continually as you travel. >Use ridges or ribs to avoid pockets of wind loaded snow. >Be cautious as you transition into wind affected terrain. >

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A prominent layer of buried surface hoar can be found between 1400m and 1800m. A weak crust/facet/surface hoar layer is expected to still be reactive in isolated areas at higher elevations. Smaller avalanches may step down to these layers.
Conditions are greatly improved, but be mindful that persistent weak layers are still present. >Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 27th, 2015 2:00PM