Avalanche Forecast

Issued: Nov 29th, 2016 4:17PM

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

cam_c, Avalanche Canada

Northwest Coastal.

There is low confidence in this forecast due to limited observations. As always, and especially when confidence is low, it is essential to supplement this information with your own observations. And don't forget to post them to the MIN!

Summary

Confidence

Weather Forecast

Expect another 10-30 cm by Wednesday morning (depending on elevation and proximity to the coast) accompanied by strong to extreme southerly winds and freezing levels spiking at around 1400m. Wednesday should be relatively dry, cool and calm with alpine winds easing to moderate westerlies and freezing levels dropping to 600 m. Light snowfall is expected for Thursday with 5-10 cm of accumulation, moderate southwesterly alpine winds, and freezing levels rising throughout the day. The next major system is expected to make landfall early Friday morning with heavy snow, extreme winds and freezing levels as high as 1500 m.

Avalanche Summary

Skiers in the Shames area reported natural and skier accidental avalanche activity up to size 1.5, and skier controlled up to size 2.0 on Friday, but there have been no new reports since then. These avalanches are suspected to have released on a buried layer of decomposing surface hoar that is sitting on a firm supportive crust down about 50-80 cm in the alpine.

Snowpack Summary

Another 10-20cm since Monday morning adds to the 20-50 cm of fresh snow from Sunday. Recent reports from the Shames area suggest a touchy weak layer of surface hoar buried mid-November and is now probably down about 50-80 cm and sitting on a firm supportive crust, making it particularly sensitive to triggers. Some earlier information came from Wesach that suggested the buried surface hoar problem exists there as well. This weak layer has been reactive to light loads like individual skiers and riders. There is very little snow in the north of the region at Ningunsaw and Cassiar. Snow that is on the ground in these areas may be facetting and developing a weak basal layer.

Problems

Storm Slabs

Although settling and strengthening rapidly, forecast snow and wind is expected to keep storm slabs fresh and touchy. Watch for particularly deep and weak wind slabs on the downwind side of ridge crests and terrain features in exposed areas.

Be alert to conditions that change with elevation.Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Shaded slopes in the alpine are the most likely spots to encounter this problem. Slopes that have already avalanched may be the safest spots after the next storm moves in.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Make observations and assess conditions continually as you travel.