Wind slabs remain on north and west aspects. Exposed slopes have been stripped of loose snow, resulting in a sliding hazard. Recommend a cautious approach when travelling over slick surfaces. The consequences of an uncontrolled slide can be high. The weather starts to deteriorate over the next 24 hours. Cloud increases and showers may develop. Poor visibility may become a problem, making managing hazards challenging.
Wind slabs exist mostly on north-facing aspects. This wind slab has shown signs of strengthening, but triggering cannot be ruled out. Sheltered terrain features such as rocky catchments near ridgelines will also have wind slab deposits. Any loaded start zone lacking support will remain an area of concern and should be treated with caution.
No avalanche activity has been reported or observed over the past 24 hours.
Very little precipitation has affected the snowpack over the past 24 hours. A hard wind slab with a density inversion formed during the last storm event. These deposits have been gaining strength and heading in the right direction. Gale winds have also stripped and sublimated loose snow from ridgelines, exposing a slick rime crust (check photo). In the northwestern areas near Whakapapa, a facet crust combination weakness has been noted. At Turoa, a buried graupel layer has been identified, which has also been noted near Whakapapa. Snow cover exists on Mt Ngauruhoe and Mt Tongariro. These northern mountains are likely to have wind slabs also. If doing the Tongariro Crossing, you will be traveling over snow and ice with start zones at threshold. Recommend alpine gear and take avalanche precautions. The south-west areas have enough snow cover in start zones above 1500 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. Recent snowfalls have improved snow cover overall and lowered the threshold elevation in the northern and eastern areas (about 1600 metres elevation).
Saturday the 8th of August will be mostly cloudy, with isolated showers. The winds are light to moderate, westerly or northwest, over the next 24 hours. The freezing level is about 1600 metres. A ridge of high pressure lies over the North Island today, while a front moves onto the western South Island. The ridge moves away to the east of the North Island tomorrow, while the front affects the northern and western South Island.
Crusts exist, and at some locations they are very slick and icy. Winds have stripped ridgelines and windward terrain features, exposing hard icy crusts. 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.
High
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
