Avalanche Forecast

Issued: Jan 22nd, 2017 3:46PM

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

MONDAY: Cloudy with sunny periods, light west winds, alpine temperatures around -8.TUESDAY: Mainly cloudy, light west winds, alpine temperatures around -10.WEDNESDAY: Cloudy with isolated flurries, moderate southwest winds, alpine temperatures around -8.

Avalanche Summary

Recent avalanche reports are limited to evidence of natural activity that occurred during last week's storm. This includes a large deep persistent slab avalanche in the Smithers area that released on weak snow near the 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

Last week's storm delivered 20-30 cm in the Smithers area and up to 40 cm or more in deeper areas to the north and west. Freezing levels reached up to around 1600 m, which has left a hard rain crust at lower elevations. Wind slabs may linger at higher elevations, and have potential for wide propagations where they sit above preserved surface hoar from earlier this month. Most areas continue to have a shallow and weak snowpack. Snowpack depths are around 120-150 cm at treeline, with hard slabs in the upper snowpack above weak sugary snow near the ground. Triggering a deep persistent slab will remain a low probability high consequence scenario.

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.

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

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 23rd, 2017 2:00PM