Avalanche Forecast

Issued: Apr 18th, 2017 4:00PM

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

Mark Herbison, Parks Canada

Jasper.

Rising freezing level and prolonged solar radiation will increase the avalanche hazard on solar aspects at all elevations.

Summary

Weather Forecast

Mix of sun and cloud with 5cm of snow by Wednesday morning. Freezing level rising to 1900m with an alpine high of -4 and 20-30km/hr southwest winds.

Snowpack Summary

5cm of snow within the past 24hrs with moderate SW winds building slab on lee alpine ridge lines. Melt freeze crust up to 2000m. Dryer surface snow on northerly aspects over a solid mid-pack bridging the weak base above 2000m. 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

Freezing levels are uncertain on Wednesday

Problems

Wind Slabs

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

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 3

Cornices

There are some very large cornices out there, give them a wide berth. Cornice failure is hard to predict but is more likely with inputs like solar radiation, high freezing levels and wind-loading.

Give cornices a wide berth when travelling on or below ridges.Avoid travel on slopes that are exposed to cornices overhead.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 19th, 2017 4:00PM