Avalanche Forecast

Issued: Mar 8th, 2016 4:00PM

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

Ian Jackson, Parks Canada

Banff Yoho Kootenay.

We have seen avalanches failing on the deeper persistent weak layers daily. Although these are generally isolated to thin snowpack areas, the snowpack right now deserves some respect.

Summary

Weather Forecast

Cool temps, light winds and convective flurries continue on Wednesday and then a big system is forecasted starting Wednesday overnight and Thursday. Models are showing 20 - 30 cms with moderate to strong SW winds and freezing levels rising to ~ 1900m. The danger ratings will rise rapidly if it materializes.

Snowpack Summary

10-20 cm of new snow over the last couple days, becoming moist below 1700m. Buried sun crusts on solar aspects. Recent West winds have formed soft slabs in lee areas of the alpine. A firm upper snow pack sits over a generally weak mid-pack of facets and depth hoar. In shallow areas snowpack tests results are typically collapses near the ground.

Avalanche Summary

Two size 2 - 2.5 natural avalanches overnight Monday in the Sunshine area. These were on N aspects in the alpine and were triggered by small loads (10-15cms of new snow with light winds). Additionally, a couple recent close calls: Monday a skier accidental size 2.5 on the Collie Glacier and on Sunday a skier accidental size 2.5 near Bow Summit.

Confidence

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

Problems

Deep Persistent Slabs

The mid-pack facets remain weak, especially in thin or rocky areas. Avoid steep or unsupported terrain, and watch for signs of instability such as whumphing and cracking. This weakness will be present for some time.

Caution around convexities or areas with a thin or variable snowpack.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Wind Slabs

Recent W winds and new snow have created soft slabs in leeward ares near ridge crests. Pay attention to the snow surface conditions while touring - you can usually detect wind slabs easily and avoid these spots.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Mar 9th, 2016 4:00PM