Tongariro

Wind slabs are lingering. Recent evidence has shown these wind slabs gaining strength, but weaknesses remain. Recommend early identification and a cautious approach to any loaded slope with catchment terrain features. The weather will be changeable over the next 24 hours; snow showers are possible with strong westerly winds at times.

No avalanche activity has been reported today, Sunday the 2nd of August. Multiple avalanches were triggered by Whakapapa and Turoa ski patrols during slope testing and assessment yesterday, the 1st of August.

On average, the last storm system brought 30cm to 40 cm of new snow at an elevation of 2000 metres. Wind-transported pockets are over 100 cm deep but becoming less reactive and showing signs of strengthening. Weaknesses do exist within these new snow deposits. A couple of days ago, a change in reactive density was observed in the new snow deposits at Whakapapa. Facet development has also been noted on shady aspects such as the Pinnacles at Whakapapa. Graupel has also been seen at 2000 metres elevation, buried and as a surface form. The older, deeper snowpack is consolidated and supportive. 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 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. This recent snowfall has improved snow cover overall and lowered the threshold elevation in the northern and eastern areas (about 1600 metres elevation).

Monday the 3rd of August will have a few snow showers. The winds are strong to moderate westerly, possibly strong in the northwestern areas. The freezing level is about 1700 metres elevation. A narrow ridge of high pressure dominates the North Island today, while westerlies build over the South Island. A cold front moves northeast over the South Island tomorrow and reaches central New Zealand tomorrow night, with cold southwesterlies following.

Despite the recent new snow, slick rime crusts remain. During the last storm, gale winds 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.

Moderate

• We have a good understanding of the snowpack structure and confidence in the weather forecast.
• We are uncertain about forecast snowfall amounts.