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
3 · Considerable
Sub Alpine · below 1,800 m
2 · Moderate
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Highlights

Wind slabs are forming. Multiple avalanche concerns and a complex situation are developing associated with the current storm system. Snowfall accumulation and snow transport will continue over the next 24 hours. The storm system continues to bring blizzard conditions to the alpine areas of the Tongariro region. Poor visibility and gale winds will make backcountry travel challenging. Recommend delaying any travel in the alpine backcountry until conditions improve.

Avalanche problems

  • Wind Slabs

    • All elevations
    Likelihood
    Likely
    Size
    2.5

    Wind slab development is occurring as strong to gale winds redistribute the new snow. Currently, the loading aspects are mostly south-facing but are likely to change as winds shift direction. Wind-driven snow deposits may also form near sheltered terrain features, such as ridgelines and rocky outcrops. As the storm system progresses, deposit size and volume will increase. Sensitivity to triggering will increase where light loads could trigger a weakness.

  • Cornices

    • All elevations
    Likelihood
    Possible
    Size
    1.5

    Cornice formation is likely as increasing snowfall and strong to gale winds provide optimal conditions. Cornice formations will be isolated to south- and east-facing ridgelines. Cornices will be touchy to light loads through the storm cycle. Failure will be possible once weight exceeds support, triggering wind slab on the slope below. Recommend avoidance and maintaining a decent distance even after the storm event.

  • Loose Wet

    • All elevations
    Likelihood
    Unlikely
    Size
    1.5

    A loose wet avalanche problem will exist until the freezing level lowers. Rain is expected to turn to snowfall. As the freezing level lowers, wet snow will refreeze, reducing the loose-wet hazard. For a period, rain will reduce the structural integrity of the snow surface below 1800 metres. Steep slopes lacking support will be the locations of concern.

Recent Avalanche Activity

No recent natural or human-triggered avalanches have been reported or observed over the past 24 hours. Poor visibility and adverse weather have been limiting observations.

Current Snowpack Conditions

About 10 cm of new snow has accumulated at 2000 metres elevation today, 1500 hours (Turoa). This new snow has been transported to south and east aspects. This new snow is overlaying the crust and a developing facet layer. Facet weaknesses have also been noted around Whakapapa and may have been affected by a recent warming spike and gale winds. The older deeper snowpack is consolidated and supportive. 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.

Mountain Weather

Tomorrow, the 25th of July, showers continue, some heavy, with possible hail, easing in the evening. Snow lowering to 800 metres in the afternoon. The winds are strong to gale North-westerly, turning to south-westerly gale in the afternoon. The freezing level is 1900 metres elevation but lowering to 1200 metres over the next 24 hours. A broad front over the South Island makes its way north onto the North Island today, while a series of troughs and other fronts follow behind, moving over the South Island from the southwest. Tomorrow, a broad trough moves east across Aotearoa New Zealand, followed by a cold southwest flow.

Sliding Danger

Melt-freeze and rime crusts exist, presenting a sliding hazard. The strong to gale winds will strip any new snow, exposing these crusts on ridgelines and windward terrain features. 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

Forecast Confidence

Moderate

  • We are confident the likelihood of avalanches will increase with the forecast weather.
  • We are uncertain about forecast precipitation amounts.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

Regions covered