Avalanche Forecast

Issued: Mar 12th, 2016 4:00PM

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

Tim Haggarty, Parks Canada

Banff Yoho Kootenay.

Recent wind effect treeline and above combined with some incoming snow may keep the hazard elevated into the middle of the week. Monitor surface snow for slab conditions and use a probe to keep tabs on the strength of the mid and lower snowpack.

Summary

Weather Forecast

Following near treeline freezing levels and an expectedÂ warm, gusty, wave of precip Saturday night, temperatures should drop overnight with treeline temps only climbing to -5C values for Sunday under a weak, dirty ridge. Up to 10cm is expected to arrive with moderate winds at treeline Monday as the cool temperatures persist.

Snowpack Summary

20-40 cm of snow now sits above crusts to 1800m and all solar slopes. Recent moderate S-SW winds with strong gusts have formed slabs in lee areas.Â The snowpack is highly variable but in the 150cm average found at TL, a firm upper pack sits over a weak mid-pack of facets. In thin snowpack areas tests results are typically collapses near the ground.

Avalanche Summary

Numerous avalanches to size 2.5 occurred Thursday morning after the passing of the storm. Most appeared to be windslabs in lee or cross-loaded alpine areas, many of these failed on crusts seen on S and W aspects, a few notable examples of deep persistent slabs were seen on east and north aspects.

Confidence

Intensity of incoming weather systems is uncertain on Monday

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 whumpfing and cracking.

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

2 - 3

Wind Slabs

Recent W winds and new snow have created soft slabs in lee areas and cross-loaded features.

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: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 13th, 2016 5:00PM