Avalanche Forecast

Issued: Dec 19th, 2018 4:00PM

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

jonas hoke, Parks Canada

Jasper.

Avalanche danger will spike again on Thursday with incoming snow and wind. Be particularly cautious of slopes that haven't had recent avalanche activity.

Summary

Weather Forecast

Stormy weather is expected through Thursday. Up to 35cm of snowfall is forecast to fall between Wednesday evening and Friday morning with gusting strong westerly winds. A detailed mountain weather forecast is available from Avalanche Canada.

Snowpack Summary

Up to 40 cm of new snow has been blown into fresh wind/storm slabs by moderate SW winds. The Dec. 11th persistent weak layer (facets, crust and isolated surface hoar) has been buried by up to 80cm of fallen snow and continues to produce whumfs under foot and sudden results in test profiles. The deep persistent weakness lingers near the ground.

Avalanche Summary

Expect another round of natural activity on Thursday with incoming heavy snowfall. On Wednesday, explosive work in previously controlled terrain produced a few size 1-1.5 loose snow and slab avalanches. A few large (up to size 3) natural storm and persistent slab avalanches occured at treeline and in the alpine during the most recent storm.

Confidence

Problems

Persistent Slabs

This layer now sits under close to a meter of snow, any terrain that has not had previous activity on this layer should be given a wide berth.

Watch for signs of instability such as whumpfing, or cracking. Minimize overhead exposure during periods of heavy loading from new snow, wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 3.5

Wind Slabs

Moderate SW winds and new snow continues to build fresh wind/storm slabs, particularly near ridge-tops.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.The new snow will require several days to settle and stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

Several recent large avalanches have been the result of the entire snowpack failing on or near the ground due to the weak snowpack structure surrounding this interface.

Be aware of the potential for wide propagations.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3.5

Valid until: Dec 20th, 2018 4:00PM