Avalanche Forecast

Issued: Apr 19th, 2018 6:55PM

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

Rupert Wedgwood, Parks Canada

Jasper.

Avoid all slope with cornices overhead as there is plenty of evidence of them falling recently with significant consequences.

Summary

Weather Forecast

Cooler temperatures Friday with freezing levels at 1,900m close to Jasper and 2,300m at the Icefields, where it will be mainly cloudy with isolated flurries. Alp High -2 C low -6C Ridge wind SW 15 km/h gusting to 40 km/h. Limited Solar at the Icefields, but more near Jasper. On Saturday up to 10cm of fresh snow is forecast.

Snowpack Summary

Below 1,900m the snowpack is isothermal. Sun or temperature crusts extend to treeline and continued into the alpine on southerly slopes. Persistent slabs can be found on most aspects at treeline and above. These have been most reactive recently to large triggers like cornices. Soft windslabs have been developing and are up to 40cm deep.

Avalanche Summary

In the past 36hrs persistent slab avalanches up to size 3.5 have occurred from alpine terrain. Most are in the 2 to 2.5 range and are are being triggered by cornice failures or small windslab avalanches stepping down to these deeper layers. With freezing levels reaching treeline expect some loose avalanches on South to West facing slopes.

Confidence

Problems

Wind Slabs

Although mostly thin some wind slabs are up to 40cm thick in alpine terrain. Solar radiation and cornice collapses can trigger these events. Once triggered the potential to trigger deeper weaknesses exists resulting in larger avalanches.

Use caution on open slopes and convex rolls Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Pay close attention to the effect of solar radiation and daytime warming on the snowpack underfoot and overhead. Point release from rocks and cliffy terrain can trigger isothermal snow below. This will be of most concern in the late afternoon.

Use extra caution on solar slopes or if the snow is moist or wet.Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

These events require a significant force to trigger them such as a large cornice failure or avalanche debris from above. Once triggered they can be very large and run far into the valley below. Many slopes have already been triggered.

Avoid shallow snowpack areas where triggering is more likely.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Apr 20th, 2018 4:00PM