Tongariro

Wind slabs exist on east and north aspects. Loose wet avalanche activity will increase when the sun appears. The weather continues to be changeable, with an improving trend tomorrow morning before clouds return and winds increase. Poor visibility may return later tomorrow. Recommend keeping an eye on cloud cover and elevation.

No avalanche activity was observed or reported over the past 24 hours. Recent weather conditions have been preventing comprehensive observations.

Rain has affected the snowpack, which then refroze once freezing levels fell. Precipitation continued, with rain turning to snowfall above 1600 metres. New snow accumulation is about 12 to 15 cm at 2000 metres elevation. Around Whakapapa, wind slabs have been observed up to 40 cm in depth on north and east aspects at the higher elevations. Around Turoa, the distribution of the new snow is even. The older snowpack has matured, having gone through multiple melt-freeze cycles over the past week. In the southwest near Turoa, the snowpack is displaying a consolidated character, although isothermal conditions are present at lower elevations near Turoa and Whakapapa. At the lower elevations, snowpack erosion and a lifting snowline have occurred. Waterfall holes and free-flowing water under unsupportive snow in gullies are an increasing hazard. Waterfall holes are a serious spring hazard and are mostly found in gullies at the lower elevations. Ice fall has recently been observed near Turoa. This unpredictable, dangerous hazard is more likely to occur during rapid warming events. The threshold is about 1900 metres in the northwestern areas. Isolated slopes in the southwest are still above the threshold at 1700 metres.

Monday the 21st of September will have increasing cloud in the morning, with isolated showers. The winds will be moderate south-westerly tending westerly, and increasing, becoming strong. Will be stronger in down-slope locations in northern areas of the region. The freezing level is about 1400 metres but rising over the next 24 hours to 3000 metres. A front spreads up the North Island today. Another front spreads north up the South Island from Monday afternoon.

Surface crusts can form rapidly and be icy and dangerous. Rime events can occur anytime conditions align, leaving a robust crust in its wake. Even at sunset, a refreeze can happen quickly. Loss of footing can lead to an uncontrolled slide. Numerous impact hazards exist, including exposed rocks and cliff bands. Recommend carrying an ice axe and crampons when venturing into the backcountry. Strong alpine skills are essential for navigating slick surfaces, as the consequences can be severe.

Low

• We are uncertain about forecast precipitation amounts.
• We are uncertain about how the timing or intensity of solar radiation will affect the snowpack.