Avalanche Forecast

Issued: Dec 28th, 2018 4:00PM

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

Timothy Johnson, Parks Canada

Jasper.

While the new snow will refresh ski conditions, it will also bring the danger rating back up. Watch out for rapid loading with extreme winds on Saturday.

Summary

Weather Forecast

Up to 25cm of snow on Saturday. Temperatures are expecting to rise to -5 in the alpine and freezing levels to valley bottom through the day. Also, west winds are going to pick up to extreme in the alpine and strong at treeline and below. A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

New snow is forecast to fall on top of a settled snow in sheltered areas and wind pressed in exposed locations and near ridge crests. This will likely create a slab avalanche problem to watch. Below this the Dec. 11th persistent weak layer is buried 50-100cm. The deep persistent weakness lingers near the ground in the depth hoar and facets.

Avalanche Summary

Small avalanches have been failing to ground in facets in the last couple of days. However we haven't seen any large natural activity since last weeks storm which initiated several deep releases from the alpine up to size 3.

Confidence

Intensity of incoming weather systems is uncertain on Saturday

Problems

Wind Slabs

The new snow is forecast to come in with strong winds in the alpine which will create slabs.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Minimize overhead exposure during periods of heavy loading from new snow, wind.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Persistent Slabs

The new snow will fall on to settle snow from last week. Below this the interface with the old snow surface, buried up to a meter deep, is strengthening however, large triggers such as cornices have produced several releases recently.

Avoid thin, rocky or unsupported slopes.Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Deep Persistent Slabs

The base of the snowpack is weak and facetted. Likely trigger locations are around rocks, where cold air can penetrate to the base of the snowpack, and shallow snowpack locations.

Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 3.5

Valid until: Dec 29th, 2018 4:00PM