Avalanche Forecast

Issued: Apr 6th, 2017 4:00PM

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

garth lemke, Parks Canada

Jasper.

Warm temperatures, rain below 2200m, and snow at higher elevations may incrementally push the problems closer to the tipping point. Thursday night's warm temperatures, with no freeze, may accelerate the potential for natural activity.

Summary

Weather Forecast

For the Icefields, Thursday night will have little overnight freeze and 7mm of precipitation. Friday's freezing level will be 2200m or higher, 7-10mm of rain in valley bottom and 10-15cm of snow in higher elevations by late Friday afternoon. Timing of this is uncertain. Temperatures will cool Saturday to Sunday -3 to -9 degrees Celsius.

Snowpack Summary

Good skiing between 1900-2400m in sheltered areas. Approximately 10-15cm of snow sits on a generally solid mid-pack. The mid-pack is bridging a weak base. The lower snowpack is a combination of weak facets and depth hoar mixed around a Nov rain crust. Below tree line a supportive 20cm melt freeze crust sits above a weak facet layer to ground.

Avalanche Summary

No Patrol or public reports on Thursday. Wednesday's helicopter flight from Jasper to Sunwapta Resort to Maligne lake reported no new avalanches noted and visibility was good. Tuesday's patrol at Bald Hills also did not note any new avalanches. Despite natural activity subsiding forecasters have low confidence in the deep basal weakness.

Confidence

Freezing levels are uncertain on Friday

Problems

Loose Wet

Friday will be warm and 7-10mm of rain below 2200m. This has potential to initiate the loose wet avalanche problem especially around steep and rocky areas. Caution is warranted for ice climbers in gully terrain.

Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. Make your travel plans to take advantage of overnight freezing.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Deep Persistent Slabs

This problem will persist. It can be triggered by large loads such as cornice failures. Triggering is most likely from shallow spots or on steep unsupported slopes. Friday's warm temperatures and snow may be pushing it closer to the tipping point.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Cornices

Cornice failure is hard to predict but is more likely with inputs like solar radiation, warm temperatures, and wind-loading. Some very large cornices out there so give them a wide berth.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Apr 7th, 2017 4:00PM