Watch for newly formed and reactive wind slabs as approach wind-exposed elevations and ridgetop features on Wednesday. Keep your guard up around steep, sheltered slopes in the north of the region, where persistent slabs are a lingering concern.
Light new snow amounts and elevated southwest winds have likely formed thin but touchy slabs over leeward (north to east) terrain, where recent wind slabs already exist. The most suspect terrain is immediately adjacent to ridges at treeline and alpine elevations. Note that cornices are large, looming, and could fail under the weight of a person or machine.
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A weak layer of feathery surface hoar may be found around 40 to 80 cm deep on northerly aspects around treeline and lower alpine elevations. This layer may be spotty and only found in sheltered terrain features. The latest avalanche activity was in the north of the region on March 6. The layer has been dormant in the south (e.g. around Coquihalla). Assess the layer in the snowpack prior to committing to avalanche terrain or adopt a conservative mindset to avoid the problem.
In the north of the region (e.g. Duffey, Hurley, Goldbridge), a deeper persistent weak layer of faceted grains near the ground presents a lingering concern on steep, shallow slopes in the alpine.
Tuesday night: Cloudy with continuing flurries bringing 5-10 cm of new snow. Moderate to strong west winds.
Wednesday: A mix of sun and cloud, mainly cloudy in the south of the region. Light to moderate northwest winds. Alpine high temperatures around -10.
Thursday: Mainly cloudy. Light variable winds. Alpine high temperatures around -12.
Friday: Cloudy with isolated flurries and up to 5 cm of new snow. Alpine temperatures dropping to around -15.
Pemberton SAR responded to a cornice collapse involvement in the Duffey Lake area on Monday when a large chunk of cornice released and collided with a rider in steep terrain on a lower elevation (1700m) feature. The impact of the cornice failed to trigger a slab but it did entrain loose snow that contributed to the full burial of the subject.
On Sunday there was a skier triggered size 2 persistent slab avalanche in the north of the region that is suspected to have run on weak facets that were buried in late November. It was on a northwest aspect at 2200 m and may have been a slope that had slid previously and was reloaded.
On Friday, explosives triggered cornices and 20 cm slabs within the recent storm snow, producing small (size 1 to 1.5) up to large (size 2) avalanches. The avalanches were on west to north aspects and at alpine elevations. A persistent slab avalanche was triggered by a rider in the northern part of the region, likely releasing on the February 22 surface hoar layer described in our Snowpack Summary. The avalanche was large (size 2) and occurred on a north aspect in the alpine.
Up to 15 cm of new snow is expected to accumulate in the region by Wednesday morning. Accompanied by strong south and west winds, the new snow is likely sufficient to have formed small but reactive new wind slabs that will bury previous wind slabs at higher elevations as well as surface hoar in more sheltered areas.
A weak layer of surface hoar crystals and/or faceted grains may currently be found around 40 to 80 cm deep on northerly aspects at treeline and lower alpine elevations. This layer may have been destroyed by strong wind immediately before burial on February 22nd, but it may still exist in sheltered terrain features. Where it exists, it has been reactive in some snowpack tests but not others, suggesting spatial variation. This persistent weak layer continues to warrant investigation conservative terrain use around large, steep, and sheltered terrain features. Check out the latest forecaster blog that offers a deeper dive into these conditions.
In the northern part of the region (i.e., Duffey/Hurley/Goldbridge), a deep instability may linger at the base of the snowpack. It has not produced an avalanche since February 17th. Human-triggering is unlikely, though if one were to trigger the layer, it would likely be in a thin, shallow, rocky spot. A large load, such as from a cornice fall, or sustained warm temperatures have the potential to trigger this layer.
