Avalanche Forecast

Issued: Dec 19th, 2016 4:00PM

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

max darrah, Parks Canada

Jasper.

Things have changed significantly in the last 48 hours. Intense South West winds have redistributed cold dry snow and created a touchy windslab condition.

Summary

Weather Forecast

The calm and very cold weather of the last 2 weeks is over. Milder temperatures expected, with strong SW winds and steady precipitation (25cm possible by Friday in the Columbia Icefield area).

Snowpack Summary

Significant change in the last 48 hours due to intense SW winds and ridge top transport of faceted snow. Expect new wind slabs in lee areas and cross loaded gullies. Suspect surface hoar (Dec 11) in sheltered NE aspects around treeline (2100-2300m). Nov crust is now on the surface in scoured areas and as deep as 1m+ on lee aspects.

Avalanche Summary

Numerous natural wind slabs to sz 1.5 observed today, particularly in alpine gulley features and steep NE aspects. We expect that natural activity was fairly widespread in these types of terrain features, but become quickly obscured and re-loaded. Of note, one size 2 with impressive propagation (~250m) observed on Parker slab, NE, at 2200m.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

48 hours of intense ridgetop transport due to strong SW winds has created new windslabs, reactive to skier traffic. Numerous natural avalanches were observed from a variety of aspects, particularly alpine gulley features and planar NE slopes.

Be aware of the potential for wide propagations due to the presence of hard windslabs.Watch for whumpfing, hollow sounds, and shooting cracks.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

The depth of this crust is now highly variable, and may as deep as 1m in lee areas that have received significant loading due to strong SW winds. Careful evaluation of this interface is essential with this new loading pattern.

Be cautious in shallow snowpack areas where triggering is more likely.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Dry

Although there has been extensive scouring, the weak facets will likely continue to shed from steep rocky terrain.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 20th, 2016 4:00PM