Avalanche Forecast

Issued: Jan 23rd, 2017 3:53PM

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

shorton, Avalanche Canada

Northwest Inland.

Conditions are improving, but the consequence of triggering a large persistent slab avalanche warrants a cautious approach to steep open terrain.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

TUESDAY: Cloudy, light west winds, alpine temperatures around -8.WEDNESDAY: Cloudy, moderate southwest winds, alpine temperatures around -6.THURSDAY: Cloudy with isolated flurries, moderate to strong southwest winds, alpine temperatures around -4.

Avalanche Summary

Recent avalanche reports are limited to a size 1 skier triggered slab avalanche on a southeast aspect at 1350 m in the Howsons. Last week, a large deep persistent slab avalanche was reported in the Smithers area that released on weak snow near the ground. The avalanche occurred on a cross-loaded feature, and was likely triggered by a smaller wind slab stepping down to weak basal facets over a metre deep. Looking ahead, triggering wind slabs as well as lingering persistent slabs remains a possibility at higher elevations.

Snowpack Summary

5-20 cm of settled storm snow sits above a widespread rain crust up to about 1300 m. Recent winds have likely formed wind slabs on lee and cross loaded features. Several buried surface hoar layers have been reported 40-80 cm deep and have given variable results in snowpack tests. Many areas have hard slabs in the upper snowpack above weak sugary snow near the ground. Triggering a deep persistent slab above this sugary snow will remain a low probability high consequence scenario for some time.

Problems

Deep Persistent Slabs

Weak sugary snow exists at the bottom of the snowpack, creating the potential for full depth avalanches. Uncertainty revolves around what type of load is now required to trigger these deep persistent slabs.

Assess start zones carefully and use safe travel techniques.Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Wind slabs are likely lingering at higher elevations. If triggered, they have the potential to 'step down' and trigger large deep persistent slab avalanches.

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 24th, 2017 2:00PM