Avalanche Forecast

Issued: Jan 4th, 2014 9:32AM

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

slemieux, Avalanche Canada

Kootenay Boundary.

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 (AFL) 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 leaving a trace of precipitation and with cooler air moving in aloft again.

Avalanche Summary

Multiple natural avalanches in the storm snow up to size 2.5 were reported yesterday on NW-W slopes. 2 natural avalanches size 2.5 were suspected to have been triggered on a surface hoar layer on a steep N-NE facing aspect at 1900 m. Sledders and skiers also triggered several storm and windlabs up to size 2 without any involvement. There was also results from explosive control in the storm slab up to size 2.5. These mostly were triggered on NW and SW slopes.

Snowpack Summary

Intense W-NW wind event in the region created windslabs on lee slopes in the alpine and at treeline. These windslabs are quite thick near ridge top and will still be touchy, especially later during the day on S facing slopes where sun will have been shining and with temperatures starting to warm up at higher elevations. Some slab formation was also observed below treeline in the top 5-20 cm with some cracking around the skis. Storm snow has started settling but beware of the possibility of sluffing in steep sheltered terrain. Even though avalanche problems have started localizing, I would still show some respect to the deeper persistent weak layers that are more stubborn but also more widespread and complex. The 2 natural avalanches size 2.5 that are suspected to have slid on the early December SH layer down is a good reminder of that. This layer would be more sensitive on N and NE aspects and is now down 90 cm. Basal facets weakness in shallower/rockier areas are also still mentioned by avalanche professionals.

Problems

Wind Slabs

Touchy windslabs exists lee of N-NW winds in alpine and at treeline. Forecasted strong NW winds for tomorrow will keep loading these slopes. Storm snow is settling but could still be reactive in steep unsupported terrain.

Travel on ridgetops to avoid wind slabs on slopes below.>Carefully evaluate terrain features by digging and testing on adjacent, safe slopes.>Be cautious of sluffing in steep terrain.>

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

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

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