Avalanche Forecast

Issued: Dec 22nd, 2012 9:53AM

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

ghelgeson, Avalanche Canada

South Columbia.

Summary

Confidence

Good

Weather Forecast

Saturday night: 5 - 10 cm Sunday: Moderate SW ridge top winds easing throughout the day. Isolated afternoon flurries. 1500m temp: -5 Freezing level: SurfaceMonday: Light S ridge top winds. 1500m temp -14 at day break, warming to -5 in the afternoon. No snow. Freezing Level: SurfaceTuesday: Light S ridge top winds. Treeline temp -6. No snow. Freezing Level: Surface

Avalanche Summary

We're starting to see the effect of the big winds midweek. More reports of large natural avalanches came in today. A few different operations reported naturally triggered slab avalanches to size 3, pulling out of N through E facing terrain in the alpine. Out of the wind, there's still some sluffing in the new snow too.

Snowpack Summary

An average of 150 cm of storm snow fell in the last 10 days across the region. Winds picked up Wednesday/Thursday of this week and wreaked havoc on wind exposed terrain both in the alpine and at the upper treeline elevations. Wind slabs and touchy cornices are now a serious concern on north through east facing slopes. Sluffing of the new snow is still a concern in steep wind sheltered terrain. There are some reports of a suncrust down around 100 cm in steep south facing features. The mid-pack is reported to be settling well. I haven't heard of any test results on the late November surface hoar in the last few days. The early November crust, near the base of the snowpack has also been inactive as of late. It's important to note that professionals are still cautious about these lingering persistent slab problems, but the likelihood of triggering is low. Be wary of steep complex terrain with a shallow snowpack, where triggering a persistent weakness is more likely.

Problems

Wind Slabs

Wind slabs in the Alpine are a serious concern. I suspect they're susceptible to human triggering and when they fail, they will go big. Watch for wind slabs immediately below ridge crest and in the lee of mid slope terrain features like ribs

Slopes above treeline still need a few days to stabilize. Those without significant experience and expert terrain management should avoid alpine terrain.>If you see signs of wind loading, or you feel the snow stiffen under your skis or machine, back off and head to wind sheltered terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 6

Cornices

New snow and wind has fueled significant cornice growth. The right chunk of falling cornice has the potential to kick off a wind slab avalanche.

Give cornices a wide berth when traveling on ridges.>Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 3

Valid until: Dec 23rd, 2012 2:00PM