Avalanche Forecast

Issued: Jan 27th, 2018 4:00PM

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

deryl kelly, Parks Canada

Jasper.

Forecast snow amounts for Sunday are light, and not expected to overload the persistent weakness. Watch for hidden hazards buried under the new fresh snow!

Summary

Weather Forecast

Sunday: cool temps with cloud and light flurries and 5cm new snow. Monday: temps will remain constant, around -9. Winds will be light SW with moderate to strong gusts. Up to 25cm has been forecast over the day Monday and into Tuesday!

Snowpack Summary

The persistent slab is made up of 3 weak interfaces, all in the top 30 to 50cm of the snowpack. Depth and distribution of these weak surface hoar/facet layers varies with the terrain, vegetation, and shelter; although it has consistently been found in sheltered features at TL and above. Windslabs continue to developed in open areas at TL.

Avalanche Summary

Avi control on Parkers Ridge Friday produced 2 large avalanches, size 2 and 2.5 on a N aspect running as the the persistent slab. Slope was hit with 17 explosive charges. The 18th shot, a large crown appeared up to 1.5m thick x 150m long x 300m wide and buried under 2m of debris for 150m. Interesting display of sensitivity and spacial distribution.

Confidence

Forecast snowfall amounts are uncertain on Monday

Problems

Persistent Slabs

This problem is made up of 3 significant interfaces in the top 30-50cm of the snowpack but may be seen deeper in wind loaded locations. These slabs have been active to skier testing and explosive control work producing a few very significant results.

Carefully evaluate terrain features by digging and testing on adjacent, safe slopes. Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

Last week's storm snow, combined with southwesterly winds, has built soft slabs in open features. These slabs failed when small sluffs, out of very steep lee terrain, hit the slope.

Be careful with wind loaded pockets while approaching and climbing ice routes.Be cautious as you transition into wind affected terrain.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 28th, 2018 4:00PM