Avalanche Forecast

Issued: Jan 21st, 2018 4:00PM

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

ian jackson, Parks Canada

Little Yoho.

The snowpack this year is complex with multiple weak layers. Avalanche control last week showed that these layers can be triggered in certain areas, but variable results make it difficult to forecast where. Conservative terrain selection is a must!

Summary

Weather Forecast

We are in the influence of a SW flow with a series of storms moving in off the coast. Expect light snow ~ 5 cm per day for the next three days. Temps will be cool in the -5 to -15 range and winds generally light to moderate from the SW.

Snowpack Summary

Recent winds have developed windslabs on alpine and treeline lee slopes. In sheltered areas the upper snowpack has 30-50cm of soft slab over the Jan 6 surface hoar. The Dec. 15 surface hoar layer is still a concern and is 60-80 cm down and well preserved at treeline and below.

Avalanche Summary

No new avalanche activity reported in this forecast region, however, a size 2 windslab was triggered by a skiier in the lake louise ski hill backcountry. This was in semicircular bowl (approximately 2400m NE aspect).

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

Recent snow and wind are have created new windslabs on lee slopes at alpine and treeline elevations. The winds have been from many different directions over the past few days and have formed these slabs on numerous aspects.

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.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

The Dec 15 layer is a concern mainly at treeline around Field, Emerald Lake and Little Yoho - this is a very specific band, although avalanches initiated could run into areas below treeline.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Valid until: Jan 22nd, 2018 4:00PM