Conditions are tricky with a complex mix of avalanche problems and weather factors. Err on the side of caution when dealing with such uncertainty.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
SATURDAY NIGHT: Passing frontal system brings 10-20 cm of new snow overnight with strong southwest winds.SUNDAY: Light flurries easing off throughout the day, moderate southwest winds, alpine temperatures around -4 C.MONDAY: Cloudy with isolated flurries, moderate to strong southwest winds, freezing level rising to around 1700 m.TUESDAY: Cloudy, moderate southwest winds, freezing level around 1900 m.
Avalanche Summary
A storm cycle occurred on Friday, producing numerous natural size 2-3 avalanches (including some triggered by cornice falls) and several size 1-2 skier-triggered avalanches. Activity tapered off on Saturday, but explosive control produced numerous size 2-2.5 avalanches. Earlier in the week, a size 3.5 avalanche on Mt. Hosmer was a sign the deep persistent slab problem may persist.New snow will form fresh storm slabs on Sunday, while warming and loading may stress cornices and deeper weaknesses.
Snowpack Summary
Warm temperatures from an alpine inversion have rapidly settled the most recent 40 cm of storm snow. Southwest winds over the past few weeks formed large cornices on alpine ridges. March has delivered regular storms with roughly 80-120 cm of snow sitting above crust and facet interfaces from February. Little is known about the reactivity of these interfaces, although no recent avalanches have been reported on these layers. Isolated basal facets still exist in shallow snowpack areas and can produce destructive full-depth avalanches. Possible triggers for these deeper weak layers include cornice falls, rapid warming, or strong solar radiation.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.