Bulletin d’avalanche

Tongariro

New Zealand Avalanche Advisory
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Danger d’avalanche

High Alpine · above 2,300 m
3 · Marqué
Alpine · 1,800 m–2,300 m
3 · Marqué
Sub Alpine · below 1,800 m
2 · Modéré
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Périmé — ce bulletin a expiré last month. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Wind slabs have developed. Currently, the situation is complex with new snow avalanche problems. This storm system has delivered a decent amount of new snow. Intense snow transport has occurred, resulting in significant wind slabs over the past 24 hours. Snow showers are expected to continue overnight with clearing Sunday morning. New snow instabilities exist. Time is required for weaknesses to strengthen and consolidate. Recommend a conservative mindset if you do venture into the alpine backcountry.

Problèmes avalancheux

  • Wind Slabs

    • Toutes altitudes
    Probabilité
    Likely
    Taille
    2.5

    Wind slabs have formed. Strong to gale winds have redistributed the new snow over the past 24 hours. The loading aspects were mostly south- and east-facing, but wind direction has changed, expanding the area of concern. Wind-driven snow deposits may also form near sheltered terrain features, such as ridgelines and rocky outcrops. Wind slab size and volume are significant over 100 cm in depth at 2000 metres elevation. Weaknesses are present, with triggering likely by light loads on start zones that are steep and lacking support.

  • Cornices

    • Toutes altitudes
    Probabilité
    Possible
    Taille
    1.5

    Cornice formation has occurred. 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. 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.

Recent Avalanche Activity

Debris from size-1 natural avalanches has been observed by the Whakapapa and Turoa ski patrols today (25072026).

Current Snowpack Conditions

Over the past 24 hours at 2000 metres elevation, about 40 cm of new snow has fallen. This new snow was immediately redistributed, forming deposits over 100 cm in depth on south and east aspects (Turoa). It is expected that the newly formed wind slabs above 2000 metres will be significant in depth and mass. 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 have enough snow cover in start zones above 1600 metres for avalanches to run freely (threshold). In the northern areas, the threshold is at a higher elevation, but this is also changing fast.

Mountain Weather

Sunday the 26th of July will be cloudy with a few showers, clearing and becoming fine in the morning. The winds will be moderate to light south-westerly, tending southeasterly throughout Sunday. The freezing level is at 1200 metres, lowering to 900 metres over the next 24 hours. A broad trough over Aotearoa/New Zealand moves east across the country today, followed by a cold southwest flow. Tomorrow, a low is expected to move east across the northern North Island, and another low develops near the Chatham Islands. Meanwhile, a ridge spreads onto the South Island.

Sliding Danger

Slick 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 snowfall amounts.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

Régions couvertes