Avalanche Forecast

Issued: Dec 9th, 2018 4:00PM

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

grant statham, Parks Canada

Banff Yoho Kootenay.

Snow is in the forecast for the week, starting on Sunday night. Accumulations up to 20 cm are possible by the middle of the week. Pull in the reins once there is new snow on the ground, as the fresh stuff won't bond well to the current snow surface.

Summary

Weather Forecast

The weather pattern is changing for the week ahead, with flurries starting overnight on Sunday but only minor accumulations for Monday. Temperatures should remain in the -5 to -12 range. Expect more snow through the week, although we doubt the models slightly and expect perhaps up to 20 cm by the end of the week.

Snowpack Summary

No new snow in several days. Old wind slabs 10-40cm deep linger in immediate lee areas of the alpine. The October 26th crust/facet layer is ~30 cm above ground. In many areas the entire snowpack is faceting and becoming quite weak. Snow depths range from 50-85 cm at 2000 m.

Avalanche Summary

No new avalanches reported or observed today, but as recently as Saturday someone triggered a nasty looking size 2 on the SE slopes of Cirque Fore-Peak at 2700m above Helen Lake. Two skiers were caught on the flanks of a slab 20-40cm deep, 80m wide, running up to 250m with no burial but they some lost equipment.

Confidence

Forecast snowfall amounts are uncertain on Tuesday

Problems

Wind Slabs

These are getting quite old but are up to 40 cm deep in the immediate lees of alpine features. Although small in size, these slabs can provide the push to get the deep persistent slab problem initiated.

If triggered the wind slabs may step down to deeper layers resulting in larger avalanches.

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

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 1.5

Deep Persistent Slabs

It is still possible to trigger this layer but it will be in isolated, steep spots and often adjacent to thin rocky areas. Be cautious in steep terrain where a stiffer, more cohesive slab exists over the weak faceted snow at the base of the snowpack.

Be aware of thin areas that may propogate to deeper instabilites.Whumpfing is direct evidence of a buried instability.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1.5 - 2

Valid until: Dec 10th, 2018 4:00PM