Avalanche Forecast

Issued: Feb 14th, 2016 7:10AM

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.

rbuhler, Avalanche Canada

Northwest Coastal.

Benign weather on Monday should lower the hazard throughout most of the region.The hazard may be higher than posted in the far north of the region where buried weak layers may still be reactive to human-triggering.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain on Tuesday

Weather Forecast

A ridge of high pressure is expected to keep the region mostly dry on Monday. Freezing levels are expected to stay below 900m with light alpine winds. A storm system is expected to reach the region on Monday evening or overnight and should continue through until Tuesday night. 15-30cm is expected between Monday evening and Tuesday afternoon. Freezing levels are forecast to reach around 1000m and alpine winds are forecast to be moderate from the southwest. Another 5-10cm is forecast for Tuesday overnight and Wednesday is currently expected to be mainly dry.

Avalanche Summary

No new avalanches were reported on Saturday. On Friday, a skier triggered a size 1.5 wind slab on a northwest aspect at 1600m elevation. The slab was 10-20cm thick and was triggered on a thin, rocky, unsupported slope. Explosives also triggered several size 1.5 cornices on west aspects around 1500m elevation. Wind slabs are expected to remain reactive to human-triggering on Monday in steep, unsupported leeward features and around loaded convexities. In the far north, deeply buried persistent weak layers may still be reactive to large triggers.

Snowpack Summary

Temperatures have been gradually dropping and the freeze/crust line has been dropping as well. Breakable crusts have been reported as low as 1000m in the south of the region. In the Shames backcountry on Thursday, there was a supportive crust above 1300 metres that had developed overnight, on Wednesday there was no crust at 1300 metres ( the highest point the observer reached), and there was 50 cm of recent storm snow, with the top 25 cm being rain soaked. This moist and wet storm snow was sitting on the old crust from the previous warm storm at the end of January. Compression tests resulted in moderate shears within the storm snow and on the old crust. The January 9th surface hoar/facet layer is down 70-200 cm across the region and remains a concern for commercial operations. In the north of the region, we continue to get reports of natural and remotely triggered avalanches on the early January persistent weak layer, large avalanches have released where this layer steps down to weak basal facets.

Problems

Wind Slabs

Recent snowfall and wind has formed soft slabs in leeward features in exposed terrain in the alpine and at treeline. Older, stiffer wind slabs may also still be reactive to heavy loading.

Be cautious as you transition into wind affected terrain.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Buried weak layers are still reactive in the snowpack, especially in the far north of region, and have the potential to produce very large avalanches. Thin spot triggering, cornice releases, and smaller avalanches all have the potential to step down.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a big line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Feb 15th, 2016 2:00PM