Touchy and growing storm slabs will keep avalanche danger elevated this week. Riding should be great, but a conservative approach is recommended. Stick to simple terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Tuesday: Periods of snow 10-15 cm. The freezing level is near 1400 m and winds are moderate to strong from the SW. Wednesday: 10 cm of snow should accumulate before tapering off throughout the day. The freezing level is near 1400 m and ridge winds ease from moderate W-NW to light. Thursday: Periods of snow. The freezing level remains near 1400 m and wind increase to moderate from the SW.
Avalanche Summary
Numerous intentionally-triggered size 1-1.5 storm slabs were reported on Sunday. Most of these were from unsupported and wind-loaded features. Additionally, there were reports of loose dry sluffing in steep terrain, and a couple natural size 2 storm slabs from big alpine slopes. These fresh storm slabs should increase in size and likelihood and become much more widespread as they build throughout the week.
Snowpack Summary
30-40 cm of new storm snow sits on a crust on solar aspects and lower elevation terrain, and surface hoar on shady and sheltered slopes. Touchy new wind slabs are likely in exposed lee terrain at and above treeline. A weak layer of surface hoar and/or a sun crust buried February 21 is now 40-75cm below the surface. Where it exists, this layer may become reactive to human triggers as the overlying slab develops. The surface hoar and/or crust layer buried February 10 is now down 75-120cm. This layer was less reactive over the weekend with cooler temperatures, but remains a concern for large triggers like cornice falls or a smaller slide in motion. Cornices are large and potentially weak and should be avoided if possible.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.