Extra caution is still required around and below cornices. Avoid sun-exposed slopes if the sun makes an appearance on Sunday.
Weather Forecast
Increased cloud will develop throughout Sunday with 10-20cm of new snow expected between Sunday night and Monday morning. A mix of sun and cloud and occasional light flurries are forecast for the rest of the period. Ridgetop winds should be moderate from the southwest with Sunday night's system and then become light. Freezing levels should sit at 2000m on Sunday, 1600m on Monday and 1500m on Tuesday.
Avalanche Summary
In recent days, natural cornice releases and explosives control triggered size 2.5 persistent slabs in the Duffey area. A few size 2 wet slabs were also reported. Lots of loose wet sluffing was also observed. Cooling temperatures on Saturday will mean that natural sluffing and cornice releases will become less likely, but with all the heat in the snowpack, it will still be possible for human-triggering of cornices. It may still be possible for a cornice release to trigger a deep weakness in the north of the region. Once the snow surface develops a widespread supportive crust layer, it will become unlikely to trigger any deep weaknesses.
Snowpack Summary
A melt-freeze cycle is reported to be widespread to mountaintops except for shaded true north aspects above 2200m. The last few nights have seen some limited overnight crust formation which has quickly broken down the following morning. With freezing levels dropping on Saturday, a surface crust has likely formed at higher elevations and hasn't completely broken down during the day. Large cornices are lingering above many alpine slopes. Below the snow surface, there is a layer of concern in the northern half of the region. Professionals are tracking a thick layer of facets down over 1m which likely resulted in a couple deep persistent avalanches which were reported on Thursday. Deep persistent weaknesses and natural cornice failures will remain a concern until there is a substantial period of cooling.
Problems
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.