Avalanche Forecast

Issued: Jan 5th, 2016 8:15AM

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.

triley, Avalanche Canada

Purcells.

New snow and wind are combining to build new wind slabs above weak layers of surface hoar and facetted loose snow. Recent sun crusts may act as an easy sliding layer on southerly aspects.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

A weak low pressure system is slowly moving from the southern interior towards the northwest. This system is difficult to forecast for snowfall amounts. Generally there is not a lot of moisture associated with this low pressure, however some areas may receive another 5-10 cm of light dry snow overnight and Wednesday. Freezing should remain at valley bottoms for the forecast period. Winds are expected to be light easterly for the forecast period.

Avalanche Summary

No new natural avalanches reported. Some loose snow avalanches up to size 1.0 continue to be reported from steep shaded aspects in the alpine.

Snowpack Summary

Light new snow falls have buried large surface hoar on all aspects at and below treeline and on shaded aspects in the alpine. Easterly winds associated with the new snow may have disturbed surface hoar in the alpine. New snow on southerly aspects may be sitting on a sun crust and/or surface hoar, providing an easy sliding layer. The new snow should be mostly unconsolidated except where it has been re-distributed by the wind. Fresh wind slabs may be sitting on 10-20 cm of facetted snow on all but steep solar exposed aspects. In the southern Purcells, (west of Kimberley), a prominent layer of buried surface hoar has shown to be reactive to human triggers. In this part of the region, it's buried down 40 cm with a cohesive slab above it. Shallow snowpack areas and moraine features may have weak facetted snow near the ground that will require time and some warming to strengthen.

Problems

Wind Slabs

Thin wind slabs may continue to develop due to forecast new snow and wind. Southeast winds may create some reverse loading in the alpine.

Use ridges or ribs to avoid pockets of wind loaded snow. >Be cautious as you transition into wind affected terrain. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Buried weak layers of surface hoar may be triggered by human activity. This problem is more likely in the area west of Kimberley, but may be found in shallow snowpack areas across the region.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved, especially in the south of the region.>Avoid exposed alpine faces, especially in the north of the region.>Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Jan 6th, 2016 2:00PM