Avalanche Forecast

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. Uncertainty is due to the extreme variability of wind effect on the snowpack.

Friday Overnight: Snowfall, 5-15 cm of accumulation. Strong southwest winds. Alpine temperatures around -15 C.

Saturday: Continued snowfall, 10-20 cm of accumulation. Strong southwest winds. Alpine temperatures rising to -10 C. Snowing overnight, 10-30 cm accumulation. 

Sunday: Snowfall easing, 5-10 cm accumulation. Strong southerly winds. Alpine temperatures rising to -5 C.

Monday: Snowfall increasing again overnight, 10-25 cm of accumulation. Strong southwest winds. Alpine temperatures around -5 C.

Highway avalanche control near Shames produced several size 1.5 to 2 wind slab avalanches with explosive control on Thursday. 

On Thursday, operators north of Terrace reported a size 1 skier triggered persistent slab avalanche on an east aspect in an open area at treeline. This avalanche failed on a layer of surface hoar buried at the end of December. There has been no other reports of reactivity on this layer and it seems like a fairly isolated event. 

Overnight, 5-15 cm of new snow accompanied by southwest winds will have created wind slabs in open areas in the alpine and treeline. Continued snow and wind through out the day will build fresh, reactive wind slab in lee areas.

This new snow overlies a previously wind affected surface, comprised of older hard wind slabs, sastrugi, and areas scoured to the ground or old crusts. Near surface faceting, and in isolated areas surface hoar, above the old surface may increase the reactivity of newly formed wind slabs.

The early December rain crust is up to 10 cm thick, down 80-150 cm in the snowpack, and exists to an average of 1400 m in elevation. Up to 2 mm facets have been reported above this crust, and it is producing hard but sudden planar results in snowpack tests in areas north of Terrace. While this layer has generally gone dormant in the region, it still has the possibility of waking up with new snow load or warming, and wind slab avalanches may still have the potential to step down to this deeper layer in isolated areas. 

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Be aware of highly variable recent wind loading patterns.
• Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
• Keep your guard up at lower elevations. Wind slab formation has been extensive.