Avalanche Forecast

Issued: Apr 21st, 2018 4:00PM

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

Jonas Hoke, Parks Canada

Jasper.

Good skiing remains on on sheltered and shaded slopes. Recent persistent slab activity is a sign that ski mountaineering season is not here quite yet.

Summary

Weather Forecast

A building ridge of high pressure brings a warming trend that likely marks the end of winter.Sunday will be partly cloudy, with the freezing level rising to 1800m, an Alpine High of -4C, and light to moderate NW winds.The warming trend begins in ernest Monday, with Clear skies forecast through the week, and the freezing level surpassing 3000m by Thursday.

Snowpack Summary

Windslabs are up to 40cm deep. 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 cornice failures. Below 1,900m the snowpack is going isothermal on a daily basis.

Avalanche Summary

Report of a large persistent slab avalanche (size 2.0) on the NE slopes of Lectern, initiating in the alpine and running in to treeline.Last weeks avalanche activity is still visible in many location - a good reminder to avoid steep terrain that has not had recent avalanche activity (especially on Northerly aspects).

Confidence

The weather pattern is stable

Problems

Persistent Slabs

Avoid travel on steep slopes that have not had recent avalanche activity. These events have been most reactive to large triggers, such as a cornice failure or smaller avalanche, but may be reactive to the weight of a skier in the wrong place.

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

Wind Slabs

SW winds Saturday have added to the existing wind slab and cornice problem. Although mostly thin, some wind slabs are up to 40cm thick in alpine terrain. Once initiated the potential to trigger deeper weaknesses exists resulting in larger avalanches.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Stay well to the windward side of corniced ridges.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

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

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

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Valid until: Apr 22nd, 2018 4:00PM