Avalanche Forecast

Issued: Dec 4th, 2013 4:01PM

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

Lisa Paulson, Parks Canada

Banff Yoho Kootenay.

10-20 cm was received in the forecast area earlier in the week, with the greatest amounts in the Eastern part of the region. Cold temperatures will remain and expect a gradual weakening of the snowpack support.

Summary

Weather Forecast

The alpine temperatures will dip to -30 by Friday, but become slightly warmer by the weekend to -20C for a high. Winds will remain light from the North. The Arctic high pressure will be in the region for the next several days.

Snowpack Summary

10-15 cm fell with moderate- strong North winds as the Arctic air moved in 2 days ago. Some reverse loading of slopes may have created some new windslabs in the alpine. There is 65-85 cm at our treeline study plots and some mid-pack support for skiing. Field tests still show failures on the Oct 27 crust where it exists or on the basal facets.

Avalanche Summary

In the last 24 hours, a size 2 avalanche occurred on a NW aspect of Copper Mountain, just west of Banff, at about 2350 m. It started as a point release which then triggered a 80 m wide slab that failed near ground, down 100-150 cm.

Confidence

Problems

Persistent Slabs

The October melt freeze crust and basal depth hoar are a a concern and avalanches may step down to basal layers. This is primarily a concern on steeper features especially if they are windloaded.

Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.Conditions are greatly improved, but be mindful that deep instabilities are still present.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Wind Slabs

Reverse loading has created new slabs on southerly aspects. Although less reactive with the colder temperatures, watch out for lingering wind slabs on N-NE aspects.

Be careful with wind loaded pockets while approaching and climbing ice routes.The new snow will require several days to settle and stabilize.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 5th, 2013 4:00PM