Avalanche Forecast

Issued: Jan 28th, 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.

ian jackson, Parks Canada

Banff Yoho Kootenay.

A juicy storm is forecast to arrive and we are expecting a widespread avalanche cycle Monday/ Tuesday. Now is a good time to stay out of avalanche terrain!

Summary

Weather Forecast

Rising temps, increased winds and up to 30 cm of snow Monday and overnight into Tuesday will likely cause a natural avalanche cycle if the current forecast comes true. Tuesday and Wednesday the temps will cool, and the winds will die, but we are still expecting another 10-20 cm.

Snowpack Summary

Alpine winds have created wind slabs in leeward areas up to 1m thick. 25-55 cm of settled snow from recent storms has formed a soft slab over 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 size 2.5 natural was observed in the the Sunshine backcountry today. Low visibility meant that fewer new avalanches were observed, but several close calls in the last few days: - size 3 at treeline in Kootenay resulting in a 2.7 m burial who was rescued with no injuries! - size 1.5 near Vermillion peak that buried a skiier to his chin

Confidence

Timing, track, or intensity of incoming weather system is uncertain

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 likely.

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

Wind Slabs

Recent winds and new snow have formed slabs in leeward areas of alpine and treeline terrain, and caused natural avalanches and small cornice failures. These slabs are starting to bond but can still be triggered and may step down to persistent 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 29th, 2018 4:00PM