Avalanche Forecast

Issued: Dec 26th, 2018 4:00PM

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

jasper snow safety, Parks Canada

Jasper.

Avoid placing yourself under any terrain with cornices overhead as several failures have occurred producing large avalanches. Good skiing can be found at sheltered treeline locations.

Summary

Weather Forecast

Thursday and Friday will be light snow, sun and cloud, alpine temperature -10, overnight lows -17, and light SW winds.Â A detailed mountain weather forecast is available from Avalanche Canada.Â

Snowpack Summary

Last weeks storm snow is providing support underfoot. Snow conditions at treeline is variable from powder in sheltered areas, to slabs and sastrugi in exposed locations and near ridge crests. The Dec. 11th persistent weak layer is buried 50-100cm. The deep persistent weakness lingers near the ground in the depth hoar and facets.

Avalanche Summary

No new avalanches were noted on Wednesday's patrol. Last weeks storm initiated several deep releases from the alpine up to size 3. They appear to have been triggered by cornice failures from South Easterly facing slopes. It is likely these occurred at the interface of last weeks snow and then stepped down to the basal weakness.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Persistent Slabs

The new snow from last week is settling and the interface with the old snow surface, buried up to a meter deep, is strengthening. Large triggers such as cornices have produced several releases since the last storm.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The base of the snowpack is weak and facetted. Likely trigger locations are around rocks, where cold air can penetrate to the base of the snowpack, and shallow snowpack locations.

Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3

Wind Slabs

Winds have abated on all but the highest ridge tops where slabs will be at their most developed.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2.5

Valid until: Dec 27th, 2018 4:00PM