Avalanche Forecast

Issued: Jan 30th, 2018 4:35PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

Large and destructive avalanches are likely. Step way back and avoid avalanche terrain. Avalanche control is planned for Mt. Bosworth, Mt. Dennis Mt. Field and Mt. Whymper tomorrow. No activity permitted in these areas.

Summary

Weather Forecast

Wednesday will present a slight cooling trend and an easing of precipitation. However, Thursday will see the temperatures rise and the precip return. By Friday the storm will intensify a deposit up to another 30cm by the end of the weekend. Obviously, this will contribute to a rise in the danger rating.

Snowpack Summary

Recent storms have deposited 45-85cm of storm snow in the last 7 days. Increasing wind and steady snowfall today are loading 3 persistent weak layers of surface hoar and facets in the upper half of the snowpack: Jan 16 down 25-45cm; Jan 6 down 35-55cm; and Dec15 down 45-80cm. In snowpits, these layers are giving sudden test results.

Avalanche Summary

A major cycle is upon us. Avalanche control today produced results up to size 3.5 with deep fractures and wide propagations. Basically, avalanches could been seen anywhere a forecaster looked today.

Confidence

Due to the quality of field observations on Monday

Problems

Persistent Slabs

There are three weak layers 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. Avalanches are occurring on these layers and human triggering is almost certain.

Use conservative route selection, choose supported terrain with low consequence.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

2 - 3.5

Wind Slabs

Recent winds and new snow have formed slabs in leeward areas of alpine and treeline terrain, and caused natural avalanches. The slabs are plump and ripe for triggering, and will likely step down to persistent weak layers.

If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Valid until: Jan 31st, 2018 4:00PM