Avalanche Forecast

Issued: Dec 23rd, 2015 7:13PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Don't let powder euphoria override your judgement - think carefully before entering big slopes, or traveling above terrain traps. Buried wind slabs and a weakening buried crust may both make slopes difficult to evaluate.

Summary

Weather Forecast

An Arctic front slowly slips over us tomorrow, bringing flurries tonight & tomorrow. Most models predict 3 - 5cm of snowfall. Some periods of Moderate W winds at ridges. Already cool temperatures will fall sharply late tomorrow. For Friday, expect an improvement in the weather, and temperatures in the -8 to -14 range. Saturday is looking clear.

Snowpack Summary

Up to 20cm of low density snow has fallen since Dec 20 with Light NE winds, before a period of Moderate NW wind yesterday evening. This has buried wind slabs formed by previous strong SW winds. Below this is the Dec 9th crust (down 40-80cm), which has become a concern as a potential weak layer. Two more crusts exist in a strong lower snowpack.

Avalanche Summary

One large slab avalanche failed naturally within the last 24 hours, on an open slope at Treeline elevation on the Eastern aspect of Mt Rowe. Also, several size 1 loose snow avalanches, both natural and human triggered have been observed over the past two days.

Confidence

Due to the number of field observations

Problems

Wind Slabs

The existing Wind Slabs are variable in size and distribution. Watch for new wind slab development if forecast periods of Moderate Westerly winds eventuate.

The recent snow is now hiding windslabs that were easily visible before the snow fell.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

A large natural slab avalanche was observed today, that may have released at a buried crust from early December. For now, it is unclear if this will remain an isolated event, or if this layer is becoming more sensitive to loads.

Be aware of the potential for wide propagations.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Dry

Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Dec 26th, 2015 4:00PM