Avalanche Forecast

Issued: Dec 21st, 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 and Persistent Slabs.

deryl kelly, Parks Canada

Jasper.

Intense ridge top winds have scoured many areas at all elevations. Be very careful about getting pushed into dangerous cross-loaded or planar features where the wind slab is present.

Summary

Weather Forecast

Continued gusty SW winds at ridge top with snowfall forecasted but with little agreement from the weather models on timing and total accumulation. Potentially 4 to 8cms overnight. Cloudy with moderate (downright pleasant) temperatures.

Snowpack Summary

Strong SW winds and ridge top transport of faceted snow has occurred for the past 72 hours. 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

Continued isolated action on Dec.11 surface hoar. 1.5 slab 100m below the crevasse rescue wind lip on parkers ridge. It was 80m wide and 40cm deep. We expect that these types of terrain features will be re-loaded with the current strong winds.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

Intense ridgetop transport due to strong SW winds has created windslabs. 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

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 22nd, 2016 4:00PM