Avalanche Forecast

Issued: Jan 4th, 2014 9:29AM

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

slemieux, Avalanche Canada

South Rockies.

Summary

Confidence

Good

Weather Forecast

Tonight and Sunday: Arctic air is flowing over the interior regions bringing strong to extreme winds from the NW. These should ease slightly on Sunday. Mainly clear skies and freezing levels at valley bottom.Monday: Moderate to strong NW winds and clear skies. Freezing level is at valley bottom, however, an above freezing layer is expected to warm things up between 1700 m and 2500 m of elevation.Tuesday: A weak front is supposed to arrive from the coast with light precipitation and with cooler air moving in aloft again.

Avalanche Summary

A natural avalanche cycle happened following the storm. Avalanches up to size 2 were observed in the alpine and at treeline on all aspects. An avalanche size 2 would have ripped out in mellow terrain at treeline and is suspected to have run on a deeper facetted layer. More avalanches are suspected tomorrow with the reloading of slopes from wind and snow available for transport.

Snowpack Summary

Strong to extreme NW winds forecasted for tomorrow is why danger rating is staying up again in the alpine tomorrow. Limited winds today have left the storm snow available for transport and reloading of slopes tomorrow. New windslabs could grow quite thick near ridge top and most likely be very touchy. Storm snow is settling but beware of the possibility of sluffing in steep sheltered terrain. Even though avalanche problems are starting to be more specific, I would still show respect to the deeper persistent weak layers that are still showing sudden planar results and have been suspected to be active during the avalanche cycle. For example, a windslabs could trigger a deeper slab avalanche in steep rocky terrain where basal facets and depth hoar exist. The surface hoar layer or crust/facet combo down a 100 cm is the other deep persistent weak layer that is still a concern to avalanche professionals.

Problems

Wind Slabs

Snow available for transport and forecasted strong to extreme NW winds is likely to trigger more avalanches tomorrow. Storm snow is settling but could still be reactive in steep, unsupported terrain.

Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.>Avoid steep lee and cross-loaded features>Stick to simple terrain and be aware of what is above you at all times.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 5

Persistent Slabs

Depth hoar at base of snowpack and surface hoar or crust/facets combo layers down 100 cm could be triggered by a windslab avalanche or a sled airing onto a slope.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 5th, 2014 2:00PM