Wind slab development above 2000 metres elevation is possible. A loose wet avalanche problem will persist until the freezing level lowers. The weather remains changeable over the next 24 hours with showers and periods of poor visibility.
Wind slab development over the next 24 hours is possible. Any new snow will immediately get transported to west- and north-facing slopes. Wind slab deposits will form near sheltering terrain features and catchments. Triggering will be possible on steep start zones lacking support. Recommend a cautious approach to any freshly loaded slope, especially convex-shaped high in the path.
Loose wet avalanche activity is possible over the next 24 hours. Showers will continue to reduce the structural integrity of the surface layer. Any steep slope lacking support will become prone to loose wet avalanche activity. Visibility could be poor at the higher elevations, hindering slope assessment and navigation. Signs of a developing surface instability are roller ball and point release below cliff bands. Monitor foot penetration and precipitation.
Natural avalanche cycle overnight near Whakapapa, all small loose wet events above 2000 metres. Multiple loose wet avalanches were triggered during slope assessment this morning by Whakapapa ski patrol. Yesterday (13082026), Whakapapa ski patrol triggered a size 1 loose wet avalanche during slope assessment below 2000 metres.
No overnight freeze at Whakapapa with rain saturating the snowpack below 2000 metres elevation. The mid snowpack is made up of layers that are mostly enhancing stability, but a facet layer of unknown distribution may have survived. Uncertainty exists on what impact the rain has had on these layers. In the northwest around Whakapapa, the snow cover and threshold have been affected by this rain. Threshold is now about 1750 metres. Around in the southwest, the snowpack has also been saturated by rain over the past 48 hours. This has now refrozen, locking up and leaving a melt-freeze crust at the surface. Current snowpack seems to be draining well, with no signs of structural collapse observed. Any new snow at higher elevations will bond well to the old surface due to warmer temperatures. Buried crusts help maintain the structure of the snowpack. No significant weaknesses currently exist. Even after recent rain, snow cover will still exist on Mt Ngauruhoe and Mt Tongariro. 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. Threshold in the southwest remains at an elevation of about 1600 metres.
Saturday the 15th of August will be partly cloudy. A few showers until evening and snow lowering to 2100 metres. The winds will be moderate easterly tending southeast overnight. The freezing level is about 2200 metres elevation. A low and several associated fronts move slowly east across the upper North Island today and tomorrow. Meanwhile, another front approaches the far south of the country today, then moves north over the South Island and onto the lower North Island tomorrow.
Strong winds can strip exposed slopes, making the surfaces slick and icy. Numerous hazards, including exposed rocks and cliff bands, exist. It is recommended to carry an ice axe and crampons when venturing into the backcountry. Having strong alpine skills and competence is essential for navigating over slick surfaces, as the consequences can be severe.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
