Avalanche Forecast

Issued: Jan 8th, 2016 7:16AM

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

triley, Avalanche Canada

Purcells.

Watch for pockets of windslab in the alpine. We continue to be concerned about a weak layer of surface hoar buried down 40-60 cm. Dig down to evaluate if this condition exists in your area.

Summary

Confidence

High

Weather Forecast

Modified arctic air has drifted down from the north, pushed by light northerly winds and a noticeable absence of a jet stream. Valleys may continue to have low level clouds for the duration of the forecast period. Some thin high cloud may block the sun at times in the alpine, but generally the region should have broken skies for the next few days. There may be some very light precipitation in the form of flurries over the next few days, however at this time the region looks pretty dry until at least Wednesday. The colder arctic air is forecast to stay in the Rockies and further east. The north and east of the Purcells will probably see the coolest temperatures, but should not be much below -12 in the alpine. Winds are expected to remain light, but should become westerly sometime Saturday afternoon or evening.

Avalanche Summary

No new natural avalanches reported. Some sluffing reported in steep terrain.

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 continue to be reported in the alpine on various aspects due to changing wind directions. Wind slabs may be sitting on a weak layer of surface hoar and/or facets that was buried by light snow around the 4th of January.

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

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

We have not had any new reports of avalanches on this persistent weak layer of surface hoar that is buried down 40-60 cm. Professional operations continue to monitor this weak layer because the consequences of triggering are high.

Dig down to find and test weak layers before committing to a big line. >Avoid exposed alpine faces, especially in the north of 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.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 4

Valid until: Jan 9th, 2016 2:00PM