Avalanche Forecast

Issued: Feb 3rd, 2018 4:00PM

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

snow safety, Parks Canada

Banff Yoho Kootenay.

Avalanche control on highway 93N Sunday, avoid travel on Hector, Andromache, Dolomite, Helen Lake trail, Observation, Silverhorn, Noyes and Waterfowl Lake Gullies. Dangerous avalanche conditions persist in the forecast region.

Summary

Weather Forecast

Valley bottom temperatures will drop Saturday night with a slight inversion forecast for Sunday, alpine temps expected around -12 to -17. A brief break in precipitation Sunday will bring clears skies before another small system moves in Monday. Winds are expected to remain in the light to moderate range through Sunday.

Snowpack Summary

15-25cm of new snow and moderate winds have developed new storm slabs in the upper snowpack. The main concern in the snowpack continues to be the three persistent weak layers of surface hoar and/or facets that are found between 50 and 100cm down. We continue to observe sudden test results, whumphing and large propagations on these layers.

Avalanche Summary

Natural activity reported Saturday on Bourgeau Left, limited observations due to visibility but the powder cloud reached the Sunshine parking lot (suspect a size 3). Big avalanches with explosives over the last few days show that snowpack remains prime for triggering. Some avalanches ran full path and put dust or debris on roads.

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 the 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

Expected Size

2 - 3.5

Storm Slabs

15-25cm of new snow has developed a reactive storm slab at higher elevations, If triggered this layer has the potential to step down to deeper instabilities. Stick to non-avalanche terrain until things have a chance to settle

Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Feb 4th, 2018 4:00PM