Regions
Northwest Inland.
Tricky snowpack conditions exist and require a conservative and cautious approach to terrain, especially if you see signs of recent loading.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
WEDNESDAY: Flurries with accumulations up to 10 cm, 40-60 km/h southwest winds, temperatures around -8C.THURSDAY: Flurries with 5-10 cm accumulations, 20-40 km/h northwest winds, temperatures around -8C.FRIDAY: Cloudy with isolated flurries, 60-80 km/h northwest winds, temperatures around -10C.
Avalanche Summary
On Monday, a skier remote triggered a size 1.5 wind slab in the Hankin area on a north aspect at treeline (see MIN report). They also reported a whumpfing caused by collapsing facets at the bottom of the snowpack. Over the weekend, numerous size 1.5-2 avalanches were remote triggered in the northern parts of the region, also releasing on weak facets near the ground.Wind slabs will remain touchy throughout the week, as sustained winds will redistribute the new low density snow. The additional load of new snow will also keep deeper persistent weak layers reactive, making it possible to trigger larger avalanches.
Snowpack Summary
Moderate to strong winds are redistributing 10-30 cm of low density storm snow and forming touchy wind slabs in the lee of exposed ridges. The new snow has also buried a layer of feathery surface hoar (up to 15 mm in sheltered areas), making wide propagations possible. A weak interface that formed during the early December cold snap can be found about 40-60 cm deep underneath a hard wind slab. The layer consists of weak faceted (sugary) snow, and preserved surface hoar in sheltered areas. The snowpack is still shallow throughout the region and widespread faceting of the lower snowpack is likely in most areas. A thick rain crust that formed in early November is probably near the bottom of the snowpack and is likely surrounded by sugary facets. Basal facets and depth hoar (more sugary crystals) right at the bottom of the snowpack are reportedly widespread.
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.