Avalanche Forecast

Issued: Apr 5th, 2017 4:00PM

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

garth lemke, Parks Canada

Jasper.

Cautious route-finding and conservative decisions is critical the next few days. Thursday to Friday's precipitation will be rain at lower elevations raising the potential for loose wet avalanches below treeline locations.

Summary

Weather Forecast

Thursday to Friday freezing level may be 2200m, rain in valley bottom with possibly 15cm of snow in higher elevations by Friday afternoon. Winds may shift Easterly on Friday afternoon with a second pulse of precipitation. Possibly a slight cooling trend on Saturday.

Snowpack Summary

Good skiing between 1900-2400m in sheltered areas. Wind-slab along lee ridge-lines and cross-loaded gully features from strong SW winds. Mid-pack bridging basal weakness. Lower snowpack is weak with a combination of facets, Nov rain crust and depth hoar. Below tree line a supportive 20cm melt freeze crust sits above a weak facet layer to ground.

Avalanche Summary

Helicopter flight from Jasper to Sunwapta Resort to Maligne. No new avalanches noted on this flight and visibility was good but very windy at ridge-tops. Tuesday's Bald Hill patrol also did not note any new avalanches. Previous cornice and wind-slab failures have triggered the deep persistent slab resulting large full path avalanches.

Confidence

Freezing levels are uncertain

Problems

Wind Slabs

Expect wind-slab formation by current strong SW winds particularly off alpine ridges and cross-loaded gullies. If triggered, could step down to the deep persistent slab.

Be careful with wind loaded pockets while approaching and climbing ice routes.Use caution in lee areas. New snowfall mixed with wind loading will created slabs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Cornice failure is hard to predict but is more likely with inputs like solar radiation and wind-loading. Some very large cornices out there.

Give cornices a wide berth when travelling on or below ridges.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Deep Persistent Slabs

This problem is unlikely to disappear. It can be triggered by large loads like cornice fall or wind-slab avalanche. Human triggering is most likely from shallow spots or on steep unsupported slopes.

Be cautious in shallow snowpack areas where triggering is more likely.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Apr 6th, 2017 4:00PM