Avalanche Forecast

Issued: Feb 1st, 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 and Wind Slabs.

stephen holeczi, Parks Canada

Banff Yoho Kootenay.

There's plenty of loose snow available for transport, and big winds are forecast for Friday and Saturday. This in conjunction with incoming snow will likely induce another avalanche cycle.

Summary

Weather Forecast

Fridays big story will be the forecasted alpine winds in the 70 - 100kmh range and rising temperatures in front of the next system. Banff is forecast only for a couple cm, and Lake Louise in the 10cm range. By Saturday night Banff could see 10cm and regions near the divide could see 20+ cm. We expect another avalanche cycle given this forecast.

Snowpack Summary

40-80 cm of snow over the last seven days has overloaded 3 persistent weak layers of surface hoar and facets in the upper half of the snowpack: Jan 16 down 30-50cm; Jan 6 down 40-70cm; and Dec15 down 50-100+cm. A major avalanche cycle occurred Monday/Tuesday with avalanches running fall path on these layers and some stepping down even deeper.

Avalanche Summary

Natural activity has tapered slightly, but big results with explosives over the last few days to size 3.5 proves that these layers are prime for triggering. Some avalanches ran full path and put dust or debris on roads. Many slopes haven't slid yet, and any additional input (snow/wind/human) will overload the snowpack.

Confidence

Problems

Persistent Slabs

Three weak layers exist in the upper snowpack: Jan 16, Jan 6, and Dec 15. All are a mix of sun crust, surface hoar and facets depending on your aspect and elevation. Destructive avalanches have occurred on these and will continue over the few days.

Avoid all avalanche terrain.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 3.5

Wind Slabs

With plenty of loose snow around, incoming wind will form slabs quickly, adding to existing ones. The slabs are plump and ripe for triggering, and will likely step down to persistent weak layers.

Avoid all avalanche terrain.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 2.5

Valid until: Feb 2nd, 2018 4:00PM