Avalanche Forecast

Issued: Apr 19th, 2017 4:00PM

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

rupert wedgwood, Parks Canada

Jasper.

Large cornices are very unstable and can trigger big avalanches if they fall. Avoid all terrain below cornices

Summary

Weather Forecast

Freezing Levels will descend to 1,200m near town providing good overnight snowpack freezing at treeline and above. Sunshine during the morning followed by rain, at lower elevations, will soften and weaken the snowpack in the valley bottom. Up to 7cm of snow is forecast. The freezing level will rise to 2,150m and winds will be SW light to moderate.

Snowpack Summary

9cm of snow within the past 48 hrs with moderate SW winds building slab on lee alpine ridge lines. Melt freeze crust up to 2000m. Dryer surface snow on northerly aspects, above 2000m, over a solid mid-pack bridging the weak base. The bottom of the snowpack consists of weak facets and depth hoar mixed around the Nov rain crust.

Avalanche Summary

No new avalanches observed or reported.

Confidence

The weather pattern is stable on Friday

Problems

Wind Slabs

Moderate SW winds have built windslabs on alpine lee slopes. If triggered, these could step down to the deep persistent slab resulting in large avalanches.

Minimize overhead exposure during periods of heavy loading from new snow, wind.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The deep instability could be triggered by large loads such as a cornice failure or a surface avalanche. Human triggering is most likely from shallow spots or on steep unsupported slopes.

Be cautious in shallow snowpack areas where triggering is more likely.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

The snowpack will warm during the day with rain, at lower elevations, and solar radiation at all elevations. As the change occurs the danger will increase from low in the morning, in the valley bottom, to considerable by mid or late afternoon.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Start and finish early before the surface crusts melt.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 20th, 2017 4:00PM