Hazard is expected to slowly drop with the cooling over the weekend but avalanche problems are expected to linger for a while longer. Extra caution is required around and below cornices, and on steep sun exposed slopes during the heat of the day.
Weather Forecast
A mix of sun and cloud is expected for Saturday with freezing levels dropping to around 2000m and moderate westerly winds in the alpine. Mostly cloudy conditions are forecast for Sunday with light southwest winds in the alpine and afternoon freezing levels around 2000m. A storm system is forecast to reach the south coast on Sunday evening. 15-20mm of precipitation is expected by Monday evening. Freezing levels are forecast to start around 2000m at the beginning of the storm and drop to around 1500m by the end of the storm on Monday.
Avalanche Summary
On Thursday, loose wet sluffing up to size 2 was reported throughout the region. A couple cornice releases were also observed but no slab avalanches were reported. On Wednesday, a natural size 2 was reported on a south aspect at 2000m. Skiers triggered a size 1.5 avalanche on a south aspect at 2200m. These avalanches were 10-40cm deep with the most recent snow sliding on a crust. Loose wet avalanches up to size 2.5 and cornice releases up to size 3 were also reported. 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 and sluffing. These problems are expected to linger until the region gets a substantial refreeze and a widespread crust forms on the snow surface.
Snowpack Summary
A moist/wet snow surface is reported to be widespread to mountaintops except for shaded true north aspects above 2600m. 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 is expected to form at higher elevations and not completely break down during the day. Large cornices are lingering and are expected to remain weak until there is a substantial period of cooling. Below the snow surface, the mid snowpack is generally well-settled throughout with no notable persistent weaknesses.
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.