Wind slabs will develop on mostly south-facing aspects. Snowfall accumulation will increase, providing more material for transport, increasing the size and volume of slabs. Over the next 24 hours, a storm system impacts the region, bringing blizzard conditions. Poor visibility and gale winds will make backcountry travel challenging.
Wind slab formation is likely as new snow starts to be transported. Loading aspects will be mostly south-facing. As snowfall accumulation increases, so will the hazard. Wind-driven snow deposits may also form near sheltered terrain features, such as ridgelines and rocky outcrops. As the storm system progresses, it will become more likely that even light loads could trigger an avalanche.
A loose wet avalanche problem will exist. As freezing levels lower, the rain will turn to snowfall; this problem will decrease and become less of a concern. For a period, rain will reduce the structural integrity of the snow surface. Steep slopes lacking support will be the locations of concern.
Multiple size 1 loose wet avalanches observed at 2700 metres on a north-facing slope near the Pari traverse crater lake area.
No significant precipitation has affected the snowpack over the past 24 hours. A brittle melt-freeze crust has formed, capping the new snow below 2000 metres. Below this crust, a facet weakness is developing, which may become problematic once loaded by forecasted snow. Facet weaknesses have also been noted around Whakapapa. Supporting these crust facet layers is the older consolidated snowpack. Snow cover exists on Mt Ngauruhoe and Mt Tongariro. The south-west areas of the region have enough snow cover in isolated start zones above 1600 metres, mostly on north and west aspects. South and east aspects remain sparse at lower elevations. In the northern areas, the threshold is at a higher elevation.
Tomorrow, the 24th of July, will have a few showers, turning to rain in the afternoon, possibly heavy. Snow to 1700 metres from the afternoon. The wind is increasing overnight, becoming strong to gale northerlies. The freezing level is 2000 metres, lowering to 1600 metres at night. A ridge of high pressure lies over the North Island today, while a front moves up the South Island. Tomorrow, the front makes its way across the North Island while a series of troughs and fronts move over the South Island from the southwest.
Melt, freeze, and rime crusts exist, presenting a sliding hazard. 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)
