Avalanche Forecast

Issued: Feb 14th, 2019 5:20PM

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

mbender, Avalanche Canada

North Columbia.

A persistent slab problem treeline and below continues to produce avalanches treeline and below. A conservative approach to terrain selection is recommended.

Summary

Confidence

High -

Weather Forecast

THURSDAY Night: Mainly cloudy with isolated flurries, light to moderate southeast wind, alpine temperature -9 C.FRIDAY: Scattered flurries, accumulation 5-10 cm , light to moderate southwest wind, alpine temperature -8 CSATURDAY: Flurries, accumulation 5-10 cm, light north wind, alpine temperature -10 CSUNDAY: Mix of sun and cloud, light northeast wind, alpine temperature -15 C

Avalanche Summary

On Wednesday a few size 1-1.5 wind slab avalanches were triggered naturally in the alpine on northwest and northeast aspects. Avalanche activity on Monday and Tuesday has been reported as naturally triggered size 1-2 wind slabs between 2000 and 2300 m on all aspects and also a few skier triggered size 1 and 2 persistent slab avalanches on northeast aspects between 1200 and 1900 m. On Saturday, a snowmobiler died in a large (size 2) slab avalanche in the Oventop Creek drainage (report here). It was triggered by the rider at 2100 m on a south aspect. The crown fracture varied from 15-100 cm deep, suggesting wind loading was a factor in the incident.

Snowpack Summary

There are two prominent, touchy weak layers in the snowpack that have been responsible for a several dangerous avalanches in the past 2 weeks. The upper layer was buried at the end of January and lies approximately 40 cm below the surface. The lower 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.

Any steep opening in the trees should be treated as suspect.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid convexities as well as steep, open and/or sparsely treed slopes at and below treeline.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Wind slabs have been reported on all aspects in exposed areas. Wind slabs at treeline elevations have the potential to step down to a persistent weak layer resulting in large avalanches.

If triggered, wind slabs may step down to deeper layers and result in even larger avalanches.Wind from a variety of directions has formed wind slabs in unusual locations at and above treeline.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Feb 15th, 2019 2:00PM