Avalanche Forecast

Issued: Jan 21st, 2016 4:45PM

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

Ruari Macfarlane, Parks Canada

Waterton Lakes.

Friday is not the day to be pushing your limits. Stick to easily managed terrain. Conditions will improve by late in the weekend, but start small and build up, evaluating conditions critically as you go.

Summary

Weather Forecast

Strong-Extreme SW winds until Friday evening. A classic chinook...expect the highest windspeeds and freezing levels in the East of the Park. Temperatures may reach 5 degrees in town, and an Above Freezing Layer makes an appearance at treeline early Friday. 5-15cm of new snowfall by Friday evening. The weekend: cooler temperatures and light winds.

Snowpack Summary

Fresh wind slabs are building lee to Moderate - Strong SW winds, sitting atop harder, thicker wind slabs from strong SW winds several days ago. Down 40-50cm is a weak layer: Sun crust on solar aspects, and surface hoar on most non-solar slopes. This layer is producing mainly Moderate-Hard shears. Tests indicate limited propagation potential.

Avalanche Summary

Poor visibility is hampering avalanche observations. Cornices have grown, but proved stubborn to triggering when cut by forecasting staff at treeline elevation ridges. Cornice chunks and ski cutting produced only thin surface Wind Slab results in immediate lees and unsupported features, however areas of thicker buried Wind Slab were avoided.

Confidence

Due to the number of field observations

Problems

Wind Slabs

These Wind Slabs are widespread in exposed areas, and may also be found in isolated locations below treeline. Avoid obviously loaded slopes.

Avoid steep lee and cross-loaded featuresIf triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer that was buried in early January seems to be gaining strength, but this strength is being put to the test by wind loading, new snow and near-zero temperatures.

Choose conservative lines and watch for clues of instability.Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Jan 24th, 2016 4:00PM