Avalanche Forecast

Issued: Mar 20th, 2017 4:19PM

The alpine rating is high, 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.

Avalanche control work on Monday produced numerous class 3 avalanches from alpine terrain. Stick to low angle supported terrain until the snow pack settles down.

Summary

Weather Forecast

Unsettled warmer weather for the next few days. Overnight -10.Â Tomorrow mainly cloudy with isolated flurries. Freezing level 2100m. Alpine highs 0 C. Ridge winds south 10-20 km/h. More sun to the north near the townsite. On Wednesday 5-10cm of new snow lesser amount near the townsite with more sunshine.

Snowpack Summary

The 50cm of snow that fell last week and into the weekend has formed 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.

Avalanche Summary

A widespread avalanche cycle took place over the weekend with crowns up to a kilometer long and in places 2m deep. The largestÂ 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 today produced numerous size 3 avalanches from the alpine.

Confidence

Freezing levels are uncertain on Wednesday

Problems

Wind Slabs

60cm of storm snow over the 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very 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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 4

Valid until: Mar 21st, 2017 4:00PM