Avalanche forecast

Tongariro

New Zealand Avalanche Advisory
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Avalanche danger

High Alpine · above 2,300 m
3 · Considerable
Alpine · 1,800 m–2,300 m
2 · Moderate
Sub Alpine · below 1,800 m
2 · Moderate
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Highlights

Wind slab and cornice formation is likely on slopes with a south and east aspect. Avalanche hazard is increasing over the next 24 hours, considerably at higher elevations. A low-pressure system is approaching the region, bringing snowfall, strong to near gale winds, and poor visibility. Very difficult to assess and identify avalanche and alpine hazards in these conditions. Recommend delaying any backcountry travel until conditions improve.

Avalanche problems

  • Wind Slabs

    • All elevations
    Likelihood
    Possible
    Size
    2

    Wind slab formation will become a possibility as snow showers develop over the next 24 hours. Winds will transport new snow, loading east and south aspects. Snowfall accumulation may be intense for a period. Wind slab deposits are likely to form near sheltering terrain features and catchments. Triggering these wind slabs is more likely on steep, unsupported slopes. It's advisable to approach any freshly loaded slope with caution, especially those that are convex-shaped and positioned high in the path.

  • Cornices

    • All elevations
    Likelihood
    Possible
    Size
    1.5

    Cornice formation will be possible once accumulated snow starts to be moved around by increasing winds. This new snow will be transported, forming a cornice near south- and east-facing ridgelines. Failure will be possible once weight exceeds support. Natural triggers include more precipitation or the weight of a single person. Cornice fall is an effective natural trigger for any wind slab on the slope below. Recommend avoidance and maintaining a decent distance even after the storm event.

Recent Avalanche Activity

No reports in relation to avalanche activity over the past 24 hours. No natural or human-triggered avalanche activity has been observed over the past 24 hours.

Current Snowpack Conditions

No precipitation has fallen over the past 24 hours, affecting the snowpack. Turoa and Whakapapa are experiencing an isolated melt-freeze cycle. Only on solar aspects at the lower elevation, with no total collapse of the surface structure. The snowpack continues to consolidate with no significant weaknesses currently identified. Around Whakapapa, graupel deposits were observed. The gale southerly winds have stripped exposed south-facing slopes, leaving a rain or rime crust at the surface. This aspect is going to be loaded by the incoming wind-driven snow. An effective bed surface lacking any bonding characteristics (check photo of a slope example). Threshold is now about 1800 metres in the northwestern areas. Snow cover will exist on Mt Ngauruhoe and Mt Tongariro. Snow and ice are present on the Tongariro Alpine Crossing. Alpine skills and equipment are essential to hike this track. If doing the Tongariro Crossing, you will be traveling over snow and ice with exposure to start zones at threshold. Recommend alpine gear and take avalanche precautions. The threshold in the southwestern areas remains at an elevation of about 1600 metres.

Mountain Weather

Sunday the 23rd of August will have showers, turning to rain and possibly heavy for a time in the morning. Snow to about 1700 metres. The winds are strong north-westerly but near gale overnight, then tending westerly and easing slightly. The freezing level is about 2000 metres, lowering to 1600 metres Sunday evening. A northwest flow strengthens over New Zealand today, and a front affects the western South Island, while a ridge of high pressure remains to the north of the North Island. Tomorrow, a series of fronts move north over the country, followed by an unsettled westerly flow.

Sliding Danger

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.

Forecast Confidence

Moderate

  • The snowpack structure is well understood.
  • We are uncertain due to rapidly changing freezing levels.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

Regions covered