Avalanche Forecast

Issued: Feb 18th, 2017 3:35PM

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 with cooling temperatures, but the lingering possibility of deep persistent slab avalanches warrants extra caution around big slopes.

Summary

Confidence

Moderate - The weather pattern is stable

Weather Forecast

SUNDAY: Cloudy, light southeast winds, alpine temperatures around -10 C.MONDAY: Cloudy, light southeast winds, alpine temperatures around -8 C.TUESDAY: Cloudy with sunny periods, light winds, alpine temperatures around -8 C.

Avalanche Summary

Recent avalanche observations are limited. On Thursday, a size 2 natural wind slab was reported on a northwest treeline aspect. During the warm storm earlier this week, a few small wet slabs were reactive to ski cutting in the Howsons and very large natural and explosive triggered avalanches were reported in northern parts of the region where deep persistent slabs have been more reactive.On Sunday, watch for reactive wind slabs at higher elevations. Also keep in mind that a basal weakness continues to drive a low probability/high consequence deep persistent avalanche problem for the region. Very large avalanches remain possible, especially in shallow snowpack areas.

Snowpack Summary

5-10 cm of recent snow sits above a rain crust and settling storm snow. Strong winds earlier in the week formed deeper deposits in exposed terrain at higher elevations. About 30-60 cm below the surface, you may find surface hoar that was buried on February 10th. There's a fair bit of uncertainty regarding the reactivity and distribution of this layer throughout the region. A stiff mid pack sits above weak sugary snow near the ground. This basal weakness woke up during the last storm and produced numerous large avalanches that released on the ground. The layer has recently been considered dormant but should still be monitored.

Problems

Deep Persistent Slabs

A weakness at the bottom of the snowpack is lingering and may be triggered in shallow snowpack areas or by the weight of smaller avalanches.

Avoid lingering in runout zones.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: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Wind Slabs

Watch for reactive wind slabs in exposed high elevation terrain. Wind slabs may "step down" to deeper more destructive layers, including surface hoar buried on February 10th.

Use ridges or ribs to avoid pockets of wind loaded snow.Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 19th, 2017 2:00PM