Avalanche Forecast

Issued: Dec 16th, 2018 4:00PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

The natural avalanche cycle was tapering off Sunday afternoon. However, it is still primed for human triggering and forecasters expect the danger to return to high with an incoming system starting Monday night.

Summary

Weather Forecast

Expect temperatures to rise to slightly above zero at valley bottom on Monday as another moderate system tracks through the forecast region. Temperatures will drop slightly into Tuesday as up to 20cm is deposited by the end of the day. Wind is expected to be moderate from the S/SW throughout Tuesday.

Snowpack Summary

40 - 60 cm of snow since Dec 10 forming a storm slab over facets and surface hoar. New windslabs are common on lee (mostly east) aspects. The lower snowpack is weak and facetted with some avalanches running to ground.

Avalanche Summary

Numerous natural and skier or explosive triggered avalanches over the past few days up to size 2.5 have been reported and observed. Avalanches may run further down slope than expected, so be cautious of overhead hazard.

Confidence

Intensity of incoming weather systems is uncertain on Tuesday

Problems

Storm Slabs

Up to 50cm of recent snow along with strong winds will have created storm slabs and wind slabs at all elevations. These slabs are still reactive to skier triggering. Ice climbers pay attention to overhead hazard.

Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

The mid and lower portions of the snowpack are weak and are now overloaded with critical levels of snow. We expect avalanches to step down to this deeper layer.

Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1.5 - 3

Valid until: Dec 17th, 2018 4:00PM