Avalanche Forecast

Issued: Jan 1st, 2019 4:00PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

Preemptive avalanche control is planned for Mt. Stephen, Mt. Field and the Simpson Slide Paths. No activities in these areas tomorrow. Expect a major system with significant snowfall starting late tomorrow.

Summary

Weather Forecast

A major system is heading for the forecast region starting late tomorrow. The models have varying data but upwards of 40cm is expected throughout Thursday and Friday. The system is accompanied by warm temperatures. Surprisingly, wind does not appear to be increasing when the front tracks through the forecast region, but this could easily change.

Snowpack Summary

Wind effect exists in the alpine and at treeline. Below treeline, the surface is faceted powder. This overlies the Dec. 10th layer of facets and depth hoar which is down 60-100 cm. In thin snowpack areas, the Dec. 10th layer is mixed in with the basal facets and October crust. In thicker areas, it is a distinct layer, with a stronger snowpack below

Avalanche Summary

No new avalanches observed or reported today however potential for human triggering remains.

Confidence

Intensity of incoming weather systems is uncertain on Thursday

Problems

Deep Persistent Slabs

A stiff slab overlying a weak lower snowpack comprised of facets and depth hoar can be found in most areas of the region (generally central and eastern) where a shallow snowpack exists. Give this weak snowpack some time to adjust to the storm load.

Be wary of slopes that did not previously avalanche.Watch for signs of instability such as whumpfing, or cracking.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Wind Slabs

Strong SW winds blew mid-storm on Dec. 29th creating touchy new slabs. While the cold temperatures that have followed have diminished the sensitivity of these slabs, they are still reactive with explosives in steep terrain.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 2nd, 2019 4:00PM