Avalanche Forecast

Issued: Feb 12th, 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 Wind Slabs.

Ian Jackson, Parks Canada

Banff Yoho Kootenay.

Natural activity is tapering, but we are still seeing sporadic large avalanches with small triggers. The next system is forecast to come in with lots of wind. If this wind comes, we expect it to rise the alpine hazard again on Tuesday

Summary

Weather Forecast

Warmer temps are moving in with another system off the coast. Expect alpine temps to be in the -5 to -10 range and dropping to -15 to -20 on Wednesday. Expect 5-10 cm of new snow Tuesday afternoon through Wednesday. Winds will spike to strong from the SW on Tuesday and then ease on Wednesday and Thursday. Skies should clear on Thursday.

Snowpack Summary

Moderate to strong winds last Saturday redistributed the recent storm snow forming wind slabs at higher elevations. The three main mid-pack concerns are the Jan 16th, Jan 6th, and Dec.15 weak layers. These are a mix of facets, crusts and surface hoar and can be found 70cm to 150cm deep in the snowpack and have been producing very large avalanches

Avalanche Summary

The bulk of the recent avalanche cycle has tapered off. However, avalanche control with explosives today in Kootenay NP showed conditions are still touchy with avalanches to size 2.5, one of which was triggered with just the bag hitting the slope before the explosion occurred. Another size 3 natural was witnessed today on Quartz Ridge.

Confidence

Wind speed and direction is uncertain on Tuesday

Problems

Persistent Slabs

Three weak layers exist in the mid 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. These layers are sensitive to triggering both naturally and by human triggering.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Be wary of slopes that did not previously avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 3.5

Wind Slabs

Much of the recent storm snow has now been effected by moderate to strong winds at higher elevations. Strong winds are forecast for Tuesday, expect new slab formation and possible triggering of the persistent layer.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 13th, 2018 4:00PM