Avalanche Forecast

Issued: Mar 21st, 2017 4:00PM

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

rupert wedgwood, Parks Canada

Jasper.

Wind transportation and solar radiation will both rapidly increase the avalanche danger

Summary

Weather Forecast

Freezing level remaining at 1900 overnight with light SW winds. Gradual cooling tomorrow afternoon with highs of -5 in the alpine and winds increasing to strong. Snow flurries to 5cm for upper elevations. Nearer to the townsite some sunny skies and warmer temperatures

Snowpack Summary

Wind slabs up to 1.5m's thick at and above treeline. Large cornices loom above. Below the slab is a mid-pack with several crusts and persistent instabilities of facets and surface hoar. Closer to the ground a weak base around the November rain crust and depth hoar below. More time is needed for the snowpack to strengthen after the recent loading.

Avalanche Summary

A widespread avalanche cycle took place over the weekend with crowns up to a kilometer long and in places 2m deep. The largest are size 3.5 and have run full path several stepped to basal layers near ground. From treeline less activity and more in the class 2-2.5 range. Control work on Monday produced numerous size 3 avalanches from the alpine.

Confidence

Freezing levels are uncertain on Thursday

Problems

Wind Slabs

60cm of storm snow over the past week has formed a dangerous windslab. Wide crowns up to 2m and a km long have been seen across the range. In shallow areas several of these stepped to ground. All are running a long way into the valley.

Use caution in lee areas in the alpine and treeline. Storm snow is forming touchy slabs.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Cornices

Large cornices on lee features some visibility detaching. Those that have released are triggering large avalanches from alpine terrain

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

The widespread observations of large and deep avalanches indicates strongly that many of the weekends avalanches went on this layer particularly where the snowpack is shallow and in rocky start zones.

Be careful with low angle slopes that may not normally be a concern.Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Valid until: Mar 22nd, 2017 4:00PM