Avalanche Forecast

Issued: Dec 28th, 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.

mark herbison, Parks Canada

Jasper.

Strong southwest winds have loaded leeward terrain and gully features. Natural avalanches observed up to size 2.5 in the Alpine.Hard wind slab or a shallow weak snowpack exists Tree Line and above. Soft snow found in sheltered areas Below Tree Line.

Summary

Weather Forecast

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

Snowpack Summary

Strong 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 faceted and weak.

Avalanche Summary

Recent avalanche activity up to Sz 2 on N-NE-E terrain below ridgeline, ~2400m running 300m and 50m wide on average. Also saw numerous Sz 2.5 on westerly terrain in steep, rocky, cross loaded terrain between 2400-2700m, 50cm deep, 50-80m wide and running up to 400m.

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.

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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 29th, 2016 4:00PM