Avalanche Forecast

Issued: Feb 20th, 2018 4:00PM

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

deryl kelly, Parks Canada

Jasper.

A stiff, persistent slab sitting over weak layers will continue to plague the back-country for the foreseeable future. The greatest concern is at, and just above, treeline however these slabs are represented at all elevations and on all aspects.

Summary

Weather Forecast

Cold arctic air dominating the region. Alpine high forecasted to be -22 for Wednesday with broken skies and light north winds. Brrr!

Snowpack Summary

15cm snow over the last week, and available snow from the previous storms, has been redistributed by strong winds from variable directions to build slabs and wind effect in open areas. A persistent slab sitting on three weak layers down 50 to 80cm can be found throughout the forecast region and has produced many large avalanches traveling full path

Avalanche Summary

No new avalanche activity observed or reported in the last week however an extensive cycle resulted when the persistent slab became overloaded with successive storms totalling 50cm each on January 30th and February 8th. Avalanches to size 3.5 were observed from most aspects and at most elevations with the majority of the action seen around 21-2500m

Confidence

Problems

Persistent Slabs

A stiff slab 50 to 90cm thick, sits over sun crusts on south and west aspects, Surface Hoar preserved at, and just above treeline and weak faceted crystals lurking in shallow snowpack features. This is a dangerous problem that is difficult to avoid.

Watch for whumpfing, hollow sounds, and shooting cracks.Use conservative route selection, stick to supported terrain features, avoid overhead hazards.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Wind Slabs

While the winds have abated, they blew hard, and from a variety of directions last week. Windslabs are hard in the alpine and they exist well into treeline areas. These can be expected to be be sensitive to skier triggering.

The best powder will be found in sheltered locations at or below treeline.If triggered the 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 - 2.5

Valid until: Feb 21st, 2018 4:00PM