Solar radiation on new snow and a rising freezing level quickly increases the Loose Wet hazard. A small Loose Wet slide could be enough to trigger a stubborn Wind Slab at upper elevations.
Mid August sun on light new snow and a rising freezing level will react quickly causing roller-balling first then possible small Loose Wet avalanches especially on sunny slopes in the heat of the day. Be aware of this hazard if traveling uphill in these areas.
Wind Slabs are more dense and contain smaller snow particles due to being tossed around and beaten up by the wind. These Wind Slabs will be found mostly on Northern 1/2 aspects above 1700m, near ridge tops and in sheltered zones. Cornices indicate wind direction and are currently soft and easy to collapse. Watch for denser, hollow sounding pockets of fresh snow on steep slopes above 30 degrees. Cross loaded slopes have been reported in the backcountry around the forecast area 16/08.
Several small Wind Slabs reported at both Porters and Mt Olympus 17/08
Snow coverage across the forecast area is super variable. Up to 150cm in some areas down to rime covered rocks. Warm temperatures will have settled the upper pack somewhat, almost creating a spring like snowpack leaving a firm surface after overnight freezes. Around 10cm of cold dry snow fell on the 15th and 16th August. This fell onto a very firm surface. Moderate Southerly wind pushed a lot of this snow onto North and Western aspects. Soft cornices were observed on Western aspects above Tarn Basin 16/08. Cold temperatures are creating a weaker layer underneath this new snow however this is not widespread in the forecast region. This is a layer to monitor over time to see which way it will go.
Thursday: Fine with morning and evening frosts. Cloud developing north of the Rangitata River in the afternoon. Light, westerly winds developing at night. Freezing level 2300 lowering to 2000m in the morning.
Friday: Fine. Westerly winds turning Northwest and increasing in the afternoon. Freezing level 2100m rising to 2600m in the afternoon.
Even after new snow, the previous surface is just beneath. Ice axe and crampons are highly recommended. Ski Crampons will be required if adventuring on skis or snowboard.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
