Avalanche Forecast

Issued: Mar 13th, 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.

An intense but short-lived storm last night and an expected dose of snow tonight, will keep windslabs fresh at Treeline and above. Triggering a windslab could have high consequences with the deep persistent slab problem still lingering.

Summary

Weather Forecast

Another 5 cm is expected to arrive Sunday night with light to moderate SW winds. Following this freezing levels are expected to drop a bit to 1300m while the light to moderate westerly flow bring trace amounts over the next couple of days .

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. 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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Another 10 cm with moderate to strong W winds has contributed to windslab and cornice development. With more snow expected Sunday night expect these slabs to develop further and remain touchy for a few days.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 14th, 2016 4:00PM