Avalanche Forecast

Issued: Dec 24th, 2016 4:00PM

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

jonas hoke, Parks Canada

Waterton Lakes.

More snowfall followed by strong to extreme winds will continue to add complexity to an already weak and variable snowpack. It's a good time for conservative terrain use. JH

Summary

Weather Forecast

Sunday: A building ridge causes flurries to taper off, with some afternoon sun possible. -15, light winds.Monday: Return of the Westerlies! Expect: racing clouds, strong Westerly winds, blowing snow, and slightly rising temperatures (-11).Tuesday: Continued Zonal flow but with some embedded fronts: Strong Westerly winds, snowfall (5-10cm), and -9.

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

Explosives control work at neighboring avalanche operations has been producing large avalanches daily 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 on Friday.

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.

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

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.

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

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Dec 27th, 2016 4:00PM