High freezing levels and continued rain will keep the avalanche danger elevated. The weather forecast is a tricky mix of changing freezing levels and uncertain precipitation amounts.
Confidence
Moderate - Freezing levels are uncertain on Thursday
Weather Forecast
Overnight: Freezing level at 2000 metres, slowly dropping by morning to 1200 metres. Expect 15-20 mm of precipitation that will be mostly rain, except at the highest elevations. Thursday: Daytime freezing level around 1500 metres, 5-10 cm of new snow above 1500 metres, moderate southwest winds. Friday: Overnight freezing down to valley bottoms, and then rising back up above 2000 metres. Mostly sunny with valley fog in the morning, and light southwest winds. Saturday: Freezing level remaining above 2000 metres, strong southwest winds, and 5-10 mm of precipitation.
Avalanche Summary
Widespread natural avalanches were reported up to size 3.0. Most of these were reported to be loose wet avalanches gouging and entraining mass as they travelled down the path. This avalanche cycle is likely to continue overnight,
Snowpack Summary
Heavy rain to mountain tops has soaked the upper snowpack and caused rapid settlement of the recent storm snow. The surface has been reported to be wet to at least 1800 metres, and moist to 2000 metres or higher. The forecast brief drop in freezing levels in the early morning may not have much effect on the snowpack when the daytime warmth brings the freezing level back up. 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.
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.
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.