Avalanche Forecast

Issued: Jan 15th, 2018 4:00PM

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

aaron beardmore, Parks Canada

Banff Yoho Kootenay.

By definition, the danger rating is moderate. However, the Dec 15th layer continues to be very sporadic and temperamental in its reactivity and distribution. Exercise caution near steep rolls at treeline.

Summary

Weather Forecast

The temperature inversion will continue until Tuesday morning. Expect alpine temperatures to remain near 0 degrees. A cooling trend is expected thereafter. Cloud cover and the start of light precip will begin late on Tuesday. Accumulations of up to 10cm are expected by the end of Thursday. Wind will pick up to moderate from the SW throughout Tues.

Snowpack Summary

Continued warm alpine temperatures and clear skies moistening the upper snowpack on steep S-W aspects. 30-50cm over the Dec.15 persistent weak layer of facets and surface hoar. This Dec 15th layer is becoming reactive to skiers at treeline and above and producing easy to moderate snowpack test results. Below this is a heavily faceted snowpack.

Avalanche Summary

Avalanche control produced results up to size 2.5 today on Hwy 93S and the Sunshine Road. The larger avalanches were produced on uniform terrain features at treeline where the Dec 15th surface hoar was present. Overall, the control mission produced 'hit and miss' results, which speaks to the variability and distribution of the Dec 15th layer.

Confidence

Problems

Wind Slabs

Wind slabs are present in the alpine and near ridge crests at treeline in isolated areas. Watch for the changing feel of the snow under your feet and be wary of areas with denser surface snow over weaker snow.

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

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

This layer continues to be the cause of much uncertainty with forecasters. Easy test results and report of significant whumps and cracks show the potential for this to be a dangerous problem. It is present and reactive in some areas, not in others.

Choose conservative lines and watch for clues of instability.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Jan 16th, 2018 4:00PM