Avalanche Forecast

Issued: Dec 27th, 2016 6:05PM

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

jonas hoke, Parks Canada

Waterton Lakes.

You guessed it, snowfall and then extreme winds, and then snowfall. Watch for Wind Slabs low on the slope. The possibility also still exists to trigger persistent weaknesses in the mid to lower snowpack.

Summary

Weather Forecast

Wednesday: Strong Westerly wind, flurries, treeline highs of -12.Thursday: Strong West wind trending to Extreme, light snowfall possible in the afternoon, treeline highs of -7.Friday: Mix of sun and cloud, decreasing wind, treeline highs of -10.

Snowpack Summary

New snowfall is burying a variable snowpack with several layers of wind slab (from extreme West winds) at all elevations. In deeper snowpack areas, hard persistent slabs (from earlier SW winds) sit on a faceted mid and lower snowpack. In thin snowpack areas, several layers of hard wind slab are sitting on weak, large, developing depth hoar.

Avalanche Summary

Explosive control work at neighboring avalanche operations has been producing large avalanches in wind exposed terrain, especially in areas that were shallow prior to recent wind loading from the west.Shooting cracks and whoomphing were observed in pockets of hard wind slab over depth hoar in Eastern (shallow snowpack) areas.

Confidence

Problems

Persistent Slabs

Nearby operations have reported these failing in the middle of the snowpack, and in some cases stepping down to ground. They are most likely to be triggered in thin rocky areas, which are more widespread in the Eastern areas of the Park.

Be aware of the potential for wide propagations due to the presence of hard windslabs.Avoid convexities or areas with a thin or variable snowpack.

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

These are more widespread than usual, existing on most aspects and elevations due to the intensity of previous winds. They will be hard to spot under new snowfall. New Wind Slabs will build with forecast Strong Westerlies on Monday.

Watch for whumpfing, hollow sounds, and shooting cracks.Be careful with wind loaded pockets while approaching and climbing ice routes.

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 30th, 2016 4:00PM