Winds are driving the avalanche danger. Seek out low density new snow that winds haven't transformed into a slab. Low consequence terrain is still advised while deeper persistent slab problems remain a real concern.
Weather Forecast
Saturday: Mainly cloudy with isolated flurries and a trace of new snow. Moderate to strong southwest winds. Freezing level near valley bottom with alpine high temperatures around -7.Sunday: Mainly cloudy with isolated flurries and a trace to 5 cm of new snow. Strong to extreme southwest winds. Freezing level near valley bottom with alpine high temperatures of -7.Monday: A mix of sun and cloud. Strong west winds. Freezing level near valley bottom with alpine high temperatures of -8.
Avalanche Summary
Only one new natural storm slab release (Size 1.5) has been reported since Thursday's storm. The slab depth was roughly 20cm and it occurred in the southeast of the region. Improving visibility may allow for more observations of recent activity.Looking forward, expect ongoing moderate to strong winds to promote lee loading as well as slab formation and reactivity even as snowfall tapers off.
Snowpack Summary
Up to 30 cm of new snow from Thursday has buried both a new layer of feathery surface hoar that has been developing in sheltered areas as well as sun crust on solar aspects. The new snow will need time to form a reliable bond to this previous surface. Moderate to strong winds have also been encouraging slab formation at higher elevations and continuously loading loose snow into deeper slabs in lee areas. Beneath the new snow, Previous southwest winds formed wind slabs that are now buried in lee terrain at higher elevations.An unstable weak layer from mid-December (predominantly feathery surface hoar crystals and/or a sun crust) is found at treeline and below treeline elevations. Slabs may fail on this layer under the weight of a person or machine. Deeper in the snowpack, an early-season rain crust and sugary facets exist. Storm slab releases could step down to these deeper layers to create a large and destructive avalanche. Although the snowpack structure is variable across the region, these persistent slab problems are generally widespread. Snowpack depths are across the region are similarly variable, but typically shallower in the east.
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.