Regions
Northwest Inland.
Avalanche danger may be higher in the north of the region, where a buried weak layer has been recently reactive.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
The Jetstream clips the region, while directing the most intense precipitation north of the area. On Thursday, 5-10 cm snow is expected with the freezing level climbing to around 1500 m. Winds become strong from the south-west. Light snow is expected on Friday, with winds easing. There is a lull in the weather forecast for Friday night/ Saturday.
Avalanche Summary
Isolated wind slab avalanches were reported over the last couple of days. In the north of the region, a small natural avalanche that stepped down to the early January surface hoar on Sunday is a good reminder that this layer needs to remain a concern. Deeply buried persistent weak layers in the alpine also woke up in the north of the region over the weekend when several large avalanches released on basal facets. This weak layer was reported to be reactive to skier triggering from thin spots, as well as heavy triggers such as a smaller avalanches or cornice failures.
Snowpack Summary
Alpine areas are reported to be widely wind effected with wind pressed surfaces found in exposed areas and a mixture of hard and soft slabs present in lee features. A thin crust may cap moist snow at or just below the surface at lower elevations and on slopes that see direct sun. The upper snow pack is reported to be bonding well to a crust buried on February 12th, now 40 to 80 cm down, that extends up to around 2000 m. The early January surface hoar can be typically be found between 60 and 140 cm down. Although it is getting harder to trigger this layer, it remains a concern. Shallow snowpack areas also have a weak base layer of facetted snow just above the ground.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.