Wind slabs will form as the storm system approaches the region. Still plenty of loose snow available for transport. The combination of old loose and new snow will form wind slabs as winds increase. The first weather feature is likely to bring deteriorating weather first thing Thursday. Wind will increase, and snowfall will develop.
Wind slabs exist on west and north aspects. A new wind slab avalanche hazard will form on the opposite aspects over the next 24 hours. Any new or old loose snow will be transported to south- and east-facing slopes. Sheltered terrain features such as rocky catchments near ridgelines will also have wind slab deposits. Freshly loaded start zones lacking support will be areas of concern and should be treated with caution.
Multiple size 1 avalanche events in Turoa’s backcountry yesterday (28072026). These were wind slab events near sheltered rocky sub-ridges on west or north aspects. Check photos.
No precipitation has affected the snowpack over the past 24 hours. Low-volume wind slabs were forming yesterday (28072026). The older loose snow was being transported to north- and east-facing aspects. Light winds today, the 29th, and clear skies are prime conditions for surface breakdown, but freezing levels and recent cooling winds have counteracted the process. On average, the last storm cycle brought half a metre of new snow to the region at an elevation of 2000 metres. The older, deeper snowpack is consolidated and supportive. No step-down into the older snowpack was observed during testing over the past few days. Snow cover exists on Mt Ngauruhoe and Mt Tongariro. If doing the Tongariro crossing, you will be traveling over snow and ice. Alpine gear and precautions need to be considered. The south-west areas have enough snow cover in start zones above 1600 metres for avalanches to run freely (threshold). In the northern areas, the threshold is at a slightly higher elevation, but this is also changing fast. This last snowfall has improved snow cover overall and lowered the threshold elevation in the northern areas and east (about 1600 metres elevation).
Tomorrow, Thursday the 30th of July, will have cloudy periods with some morning and evening fog. A few showers will develop in the morning, with snow falling above 1300 metres. The freezing level is about 1600 metres. Today, a ridge of high pressure over the country moves slowly eastwards as a front approaches from the Tasman Sea; meanwhile, a northwest flow builds over the South Island. Tomorrow, the front moves onto New Zealand.
Slick rime crusts are present, posing a sliding hazard. Moderate winds are stripping any loose snow, exposing these crusts on ridgelines and windward terrain features. Numerous hazards, such as exposed rocks and cliff bands, remain. Carrying an ice axe and crampons is recommended in the backcountry. It is essential to have strong alpine skills and competence when travelling over slick surfaces with high consequences.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
