Avalanche Forecast

Issued: Feb 16th, 2019 3:32PM

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.

Avalanche Canada shorton, Avalanche Canada

Two persistent weak layers in the snowpack continue to be a concern. Despite the moderate hazard, a cautious approach to backcountry travel is recommended.

Summary

Confidence

High - The weather pattern is stable

Weather Forecast

SATURDAY NIGHT: Light flurries of low density snow with trace accumulations, light northeast wind, alpine temperatures drop to -18 C.SUNDAY: Mix of sun and cloud, light north wind, alpine high temperatures around -15 C.MONDAY: Mix of sun and cloud, moderate northwest wind, alpine high temperatures around -15 C.TUESDAY: Cloudy with isolated flurries and trace accumulations, light northwest wind, alpine high temperatures around -12 C.

Avalanche Summary

Reports of human-triggered persistent slab activity continued on Friday. A few size 1.5 persistent slab avalanches were were remotely triggered on north aspects at treeline, failing on 50 cm deep surface hoar. Some larger (size 2) persistent slab avalanches were triggered on the same layer just outside the region boundary. Similar to persistent slab activity earlier in the week, these were mainly on northeast aspects between 1200 and 1900 m. I'd remain leery of the mid- and late-January weak layers especially at treeline elevations.Several smaller (size 1) wind slab and storm slab avalanches were reactive to human triggering on a variety of aspects on Friday.

Snowpack Summary

10-15 cm of recent low density snow sitting on the surface has been blown around by strong northeasterly winds, creating reverse-loading on some slopes. 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

An icon showing 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

An icon showing 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 17th, 2019 2:00PM