Loose, wet avalanche activity on sun-exposed slopes cannot be ruled out. Rime and melt freeze crusts exist. It is essential to have strong alpine skills and competency when travelling over a slick surface with high consequences. The weather is expected to be stable over the next 24 hours, with periods of clear skies and light winds, although isolated showers may occur.
Loose wet avalanche activity on solar aspects during the warmest period of the day cannot be ruled out. The surface structure will be reduced on slopes being impacted by solar radiation. High freezing levels and a warm snowpack will also increase the chance of structural breakdown of the surface snow. Be alert to signs such as increased foot and ski penetration and roller ball activity.
No human or naturally triggered avalanches have been reported or observed over the past 24 hours.
A minimal amount of precipitation has affected the snowpack over the previous 24 hours. Little change to the snowpack recently, other than a melt freeze crust developing in the southwest areas. This crust is improving snowpack stability but increasing the uncontrolled sliding hazard. Elevated temperatures and high water content have contributed to the bonding process at the higher elevations. The snowpack is displaying signs of consolidation, and difficult to find any significant weaknesses currently. A rime crust has also formed in the southwest areas, limiting snow transport. A few days ago, snowfall accumulation was noted on Mt Ngauruhoe and Mt Tongariro. The south-west areas of the region have isolated start zones above 1600 metres, mostly on north and west aspects. South and east aspects are still sparse at the lower elevations. Only isolated start zones at 1800 metres have enough snow cover for avalanches to run freely. Check the photo of Mangawhero headwall at Turoa, taken on the 15th, two days ago. In the northern areas, the threshold is at a higher elevation.
Saturday, the 18th of July, will be mostly cloudy with isolated light showers, drizzly about the southern and western faces. Winds are moderate westerlies, possibly strong at times above 2300 metres elevation. The freezing level is high for winter at about 3000 metres elevation, lowering to 2500 metres tomorrow evening. A ridge of high pressure covers much of the North Island today, while a westerly flow affects the South Island. Tomorrow, a west to southwest flow covers Aotearoa/New Zealand, and a front south of the country moves north onto the far south.
Recent formation of melt-freeze and rime crusts has increased the risk of sliding hazards. Windward and exposed areas were stripped by gale-force winds during the last storm cycle, exposing an icy rime crust on slopes above 1600 metres. Numerous hazards, such as exposed rocks and cliff bands, remain present. It is essential to carry the appropriate gear, including crampons and an ice axe. Having the right skills will help reduce the chance of an accident.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
