Warm temperatures and sunny breaks are on the menu for Friday. Use caution in steep open terrain and around large overhanging cornices.
Confidence
Fair - Due to the number of field observations
Weather Forecast
Friday: Cloudy with sunny breaks. The freezing level is between 2500-3000 m. Ridge winds are light to moderate from the west. Saturday: Cloudy with possible light snow. The freezing level lowers to around 1500 m. Winds are generally light from the W-NW. Sunday: Mainly cloudy with light snow. The freezing level is around 1200-1500 m.
Avalanche Summary
Observations have been essentially non-existent in recent days. This likely speaks more to a lack of observers rather than actual conditions. I'm confident recent storm loading has produced large storm slab avalanches at higher elevations, while loose wet or wet slab avalanche activity occurred at lower elevations where rain fell.
Snowpack Summary
The rain line during recent heavy precipitation generally hovered around 1700m, although there were periods where rain fell into the alpine. Above that elevation, heavy accumulations of moist, dense snow have been pushed by strong southwest winds into much deeper deposits on the lee side of ridgecrests and terrain breaks. This recent storm snow overlies a hard crust, which may have overlying surface hoar that was buried late January. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.
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.