Avalanche Forecast

Issued: Feb 17th, 2019 3:49PM

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

shorton, Avalanche Canada

North Columbia.

Two persistent weak layers in the snowpack continue to be a concern. A cautious approach to backcountry travel is recommended.

Summary

Confidence

High -

Weather Forecast

SUNDAY NIGHT: Clear with cloudy periods, light northwest wind, alpine temperatures drop to -18 C.MONDAY: Mix of sun and cloud, moderate northwest wind, alpine high temperatures around -14 C.TUESDAY: Cloudy with some isolated flurries with up to 5 cm of snow, moderate northwest wind, alpine high temperatures around -12 C.WEDNESDAY: Mix of sun and cloud, light north wind, alpine high temperatures around -10 C.

Avalanche Summary

On Saturday, skiers triggered a few small (size 1) storm slabs and wind slabs as well as one larger (size 2) persistent slab avalanche. The persistent slab avalanche was triggered on a north aspect at 2100 m and failed on a 60 cm deep surface hoar layer. On Friday, a few size 1.5 persistent slab avalanches were were remotely triggered on north aspects at treeline, failing on 40-60 cm deep surface hoar layers. Some larger (size 2) persistent slab avalanches were triggered on the same layers just outside the region boundary. More persistent slab activity occurred earlier in the week, predominantly on northeast aspects between 1200 and 1900 m.

Snowpack Summary

10-15 cm of low density snow has been blown around by strong northerly winds, creating reverse-loading on some slopes. Two prominent weak layers have been responsible for a several dangerous avalanches in the past two weeks. The upper layer was buried at the end of January and lies approximately 40 cm below the surface. The deeper one was buried mid-January and lies approximately 75 cm below the surface. Both comprise a mix of surface hoar and facets and may lie on top of a sun crust on southerly aspects. Both layers are potentially reactive and in any given location, one or both could potentially exist in the snowpack. Wide propagation has been noted, meaning avalanches have the potential to be large (up to size 3). These weak layers are most prevalent at treeline and below, but may also be found in sheltered areas in the alpine.Average snow depths are approximately 300 cm. Very sporadically, failures have occurred near the base of the snowpack in or close to this region. These releases have almost all been from high alpine areas, possibly triggered close to rocky features.

Problems

Persistent Slabs

There are two persistent weak layers in the snowpack, buried approximately 40 cm and 75 cm below the surface. Activity is most pronounced at treeline elevations.

Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.Any steep opening in the trees should be treated as suspect.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Wind slabs have formed on various aspects as the wind has shifted direction over the past few days.

If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Avoid freshly wind loaded features.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 18th, 2019 2:00PM