Avalanche Forecast

Issued: Feb 18th, 2018 4:00PM

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

Tim Haggarty, Parks Canada

Jasper.

The persistent slab problem continues to make it difficult to travel in avalanche terrain with any degree of confidence. Be wary of any avalanche terrain that does not show signs of having already avalanched particularly at, and just above, treeline.

Summary

Weather Forecast

Light north winds will continue as will the cold temperatures with alpine lows near -25C and daily highs near -18C. While no snow is expected for most of the week, a fair amount of cloud can be expected for the period.

Snowpack Summary

Around 15cm over the last week, and large amounts of 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.

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

Due to the number of field observations

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 - Likely

Expected Size

1 - 3

Wind Slabs

While the winds are now starting to back off, they blew hard, and from a variety of directions all week. Fresh windslabs that are hard in the alpine and exist well into treeline areas 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: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Valid until: Feb 19th, 2018 4:00PM