Avalanche Forecast

Issued: Apr 13th, 2013 4:00PM

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

garth lemke, Parks Canada

Jasper.

Cool night and daytime temperatures are aiding with overall stability. Be vigilant for poor bonding of windslab to underlying temperature crusts. Human triggered avalanches remain possible with this condition.

Summary

Weather Forecast

Sunday through to Tuesday will be scattered flurries, light North switching to E winds, minimal precipitation, cold overnight maintaining cool daytime temperatures with freezing levels rising only to 1050m.

Snowpack Summary

Windslabs on lee aspects of exposed ridgecrests above treeline are covered by 5-10cm of new snow. Below 2100m the new snow sits on temperature and sun crusts. Cornices are big. Several natural cornice falls have been observed over the past 72hrs. Melt freeze crust carries well in AM and maintains into the PM.

Avalanche Summary

No new avalanches reported, but several large cornice failures reported in the past 72hrs. Several of these cornice falls did trigger deep persistent slabs with crowns up to 1m, and some were observed to initiate more recent storm/wind slabs with a depth of 10-40cm.

Confidence

The weather pattern is stable

Problems

Wind Slabs

Winds have formed windslabs on lee aspects below ridgecrests above treeline. These slabs are roughly 10-15cm thick sitting on previous crusts. It is possible to initiate from skier traffic where its bonded poorly to the underlying crust.

Use caution in lee areas in the alpine. Recent wind loading have created wind slabs.The recent snow may now be hiding windslabs that were easily visible before the snow fell.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Cornices are large and a hazard by their sheer mass. They can also be a significant trigger to deeper layers if they drop. Several failures were observed in the past 72 hours. Some triggered storm slabs on the slopes below up to size 2.

Do not travel on slopes that are exposed to cornices overhead.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Apr 14th, 2013 4:00PM