Avalanche Forecast

Issued: Dec 20th, 2016 4:00PM

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

garth lemke, Parks Canada

Jasper.

Three days of strong SW winds have changed the landscape. Cautious route finding and conservative decisions are called for.

Summary

Weather Forecast

Moderate to Strong SW winds will continue through Wednesday night and maybe 5-10cm of snow by Thursday morning. The Icefields area may get 10-20cm by Friday. Temperatures will hover around -10 to -15.Â

Snowpack Summary

Strong SW winds and ridge top transport of faceted snow has occurred for the past 72 hours. Expect new wind slabs in lee areas and cross loaded gullies. Suspect surface hoar (Dec 11) in sheltered NE aspects around treeline (2100-2300m). Nov crust is now on the surface in scoured areas and as deep as 1m+ on lee aspects.

Avalanche Summary

Tuesday's patrol noted a size 1.5 slab 100m below the crevasse rescue wind lip on parkers ridge. It was 80m wide and 40cm deep. Monday was noted numerous wind slabs to sz 1.5 in alpine gulley features and steep NE aspects. We expect thatÂ these types of terrain features will be re-loaded with the current strong winds.

Confidence

Wind effect is extremely variable

Problems

Wind Slabs

72 hours of intense ridgetop transport due to strong SW winds has created windslabs. Numerous natural avalanches were observed from a variety of aspects, particularly alpine gulley features and planar NE slopes.

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.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

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

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Be cautious in shallow snowpack areas where triggering is more likely.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Loose Dry

Although there has been extensive scouring, the weak facets will likely continue to shed from steep rocky terrain.

Avoid travelling on ledges and cliffs where sluffing may have severe consequences.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 21st, 2016 4:00PM