Avalanche Forecast

Issued: Nov 25th, 2013 8:28AM

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

Avalanche Canada bcorrigan, Avalanche Canada

Email

Purcells.

This forecast has been prepared with limited observation data. If you're out in the field, please send information to:forecaster@avalanche.ca

Summary

Confidence

Poor - Due to the number and quality of field observations

Weather Forecast

Continued mild temps for the forecast period.  No precipitation in sight for the next 3 days. Warm air aloft will slowly be replaced by more seasonal cooler temps in the next few days.

Avalanche Summary

No recent avalanche activity has been reported. Skiers or sledders might trigger this deep weak layer although no recent reports of activity have been received. The likelihood of triggering is decreasing, however the consequences could be huge.

Snowpack Summary

Snowpack depths at tree line hover between 70-100 cm, and 100 to 120 cm in the alpine, except in heavily wind loaded locations.  A surface hoar layer has been identified at other locations in the Columbia ranges between 60and 120 cm from the surface and appears to be drainage specific.  So far it's not been reported in the Purcells. If you've found it, please let us know.Deeper in the snowpack near the base is a melt-freeze / rain crust that formed in October. This is generally found 70-110 cm down, with facetted (sugary) crystals above and below that are poorly bonded. The crust/ facet combo may be more predominant on Northerly aspects and allow for wider propagations, especially in places that have smooth ground cover (glacier ice, grassy slopes, rock slabs etc.).Snowpack conditions may change and deteriorate if temperatures rise in the alpine.

Problems

Wind Slabs

An icon showing Wind Slabs
The likelihood of triggering a wind slab is becoming more remote as the snowpack settles and bonds, but the consequences of a large avalanche event remain high.
Assess start zones carefully and use safe travel techniques.>Use caution in lee areas in the alpine and at treeline. Recent wind loading has created wind slabs.>The new snow will require several days to settle and stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

An icon showing Persistent Slabs
The location of this crust-sugar snow layer varies greatly throughout the Columbia mountains. It has been reported on the ground in the south, and 20 to 40cm up from the ground in the north.
Be aware of the potential for large, deep avalanches due to the presence of buried crust/ facet combo.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Nov 26th, 2013 2:00PM

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