Avalanche Forecast

Issued: Mar 24th, 2017 4:00PM

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

garth lemke, Parks Canada

Jasper.

We are in a low probability high consequence situation. Natural activity has subsided but any slope that did not slide should be treated with utmost caution. Be vigilant if the sun comes out which could destabilize the snow rapidly.

Summary

Weather Forecast

Saturday to Monday will be -3 to -12, clouds and flurries, 5cm of snow, and light to moderate SW winds. Sunday may be more sun than clouds.

Snowpack Summary

Large looming cornices are present. Wind, persistent, and deep basal slabs found at and above treeline. Mid-pack has several weaknesses yet is providing bridging strength above the weak base. Basal layer is facets and depth hoar, with a rain crust from November. On southerly slopes a melt freezing crust is developing as the pack warms.

Avalanche Summary

No patrol on Friday and nothing new reported. Thursday several fresh slab avalanches were recorded at treeline and alpine. Such as a class 3 triggered by a falling chunk of cornice on a NE facing slope, a size 2 from a S facing slope likely triggered by solar radiation, and a skier may have triggered a size 2 on a N slope near Boundary lake.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Cornices

Large cornices on lee features with some visibly detached and looking precarious. Those that have released are triggering large avalanches from alpine terrain. Give them a wide berth.

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

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

The lower snowpack is weak with a crust from November surrounded by loose facets and depth hoar. This weakness is most developed in shallow snow with rocky terrain. A cornice failure triggered a size 3 on a NE treeline feature near Parkers ridge.

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

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Snow is being transported at treeline and above. Slabs exist near ridge tops and open treeline spots. Avalanches to size 2.5 have been observed. Lower elevation features such as glacial moraines have slid to size 2 in isolated areas.

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Valid until: Mar 25th, 2017 4:00PM