Avalanche Forecast

Issued: Dec 22nd, 2014 7:35AM

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

rbuhler, Avalanche Canada

Northwest Inland.

This forecast was created using limited field data. If you are out in the mountains, please consider sending us your observations or posting on our new website.

Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A frontal system is expected to bring around 10-15mm of precipitation to the North Coast inland on Tuesday. Another 5-10mm is possible Tuesday night into Wednesday morning. Freezing levels on Tuesday are expected to be 800-1000m with strong-to-extreme winds from the SW in the alpine. On Wednesday, precipitation should taper off in the morning with freezing levels around 500m and winds easing to moderate NW in the alpine. Christmas day looks to be a mix of sun and clouds with freezing levels near valley bottom and moderate winds in the alpine.

Avalanche Summary

We received a report on Sunday from the Hankin area of a natural size 1 slab avalanche.Â This occurred on a north aspect at treeline. The crown depth was around 20cm and it failed on the most recent rain crust.Â Check out the report here: http://goo.gl/WdmvxL

Snowpack Summary

The weekend storm slab is between 20-40 cm deep. Very strong winds have transported snow in the alpine and at treeline into pockets of windslab that may not be well bonded to the old surfaces. Below the new snow you'll likely find wind-scoured surfaces and old wind slabs in exposed terrain, and settled storm snow closer to treeline. Near the base of the snowpack, weaknesses such as the mid-November crust-facet layer are still of concern. I'd use extra caution around steep, unsupported high elevation terrain as avalanches at this interface could propagate over wide distances.

Problems

Storm Slabs

The new storm snow is adding to the storm loading from the weekend. Strong winds are loading leeward slopes in exposed terrain.

Avoid freshly wind loaded features.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

Deeply buried weak layers may release during periods of high loading from new snow and wind. Triggering of these deep layers is most likely from shallow snowpack areas such as areas around rock outcrops.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 23rd, 2014 2:00PM