Avalanche Forecast

Issued: Dec 27th, 2016 4:00PM

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

max darrah, Parks Canada

Jasper.

Steady snowfall and strong winds will test the generally weak and shallow snowpack over the next 72hours. Be vigilant of changing conditions, especially new windslabs in cross loaded terrain.

Summary

Weather Forecast

Steady increase in snowfall towards the weekend, with weather models predicting between 15-30cm. Temperatures to remain fairly seasonal, ranging from -8C to -20C at treeline. Strong, gusty Westerly winds expected throughout the storm.

Snowpack Summary

Variable SW winds have built slabs in lee features and cross loaded gullies. Weak layers include; buried surface hoar (Dec 11) in sheltered NE aspects around treeline and the Nov 12 crust approximately 30cm from the ground. The snowpack is generally faceted and weak, and is beginning to slide naturally in lee terrain and steep Westerly aspects.

Avalanche Summary

Several new size 2 windslabs out of N to NE terrain around ridgelines (~2100m). These slides ran an impressive 300m, were 50m wide on average, but the sliding layer is unknown due to visibility. Numerous healthy avalanches up to size 2.5 were also observed on steep, Westerly terrain between 2500-2800m. These ran 400m, were 60m wide and 50cm thick.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

Strong winds have created a mosaic of snow depths across the landscape. These slabs will vary greatly in their sensitivity to triggering and requiring each slope to be evaluated carefully.

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, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

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

Carefully evaluate and use caution around thin snowpack areas.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 28th, 2016 4:00PM