Bollettino valanghe

Tongariro

New Zealand Avalanche Advisory
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Pericolo valanghe

High Alpine · above 2,300 m
2 · Moderato
Alpine · 1,800 m–2,300 m
2 · Moderato
Sub Alpine · below 1,800 m
2 · Moderato
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In sintesi

Wind slab formation will occur once the new snow starts to move around due to increasing winds. Enough new snow has accumulated today. This has increased the amount of loose material for transport. The weather remains changeable with an improving trend throughout the day Wednesday, the 5th of August. Periods of poor visibility are expected, making navigation and hazard management difficult.

Problemi valanghivi

  • Wind Slabs

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    Probabilità
    Possible
    Dimensione
    2

    Wind slabs may form over the next 24 hours. Locations will be mostly north-facing aspects, but redistribution of the new snow may occur as winds shift direction. Wind slab may also form at the lower elevations. New snow has accumulated today below 1800 metres, providing material for slab formation once winds increase. Sheltered terrain features such as rocky catchments near ridgelines will also have wind slab deposits. Any loaded start zone lacking support will be an area of concern and should be treated with caution.

  • Cornices

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    Probabilità
    Unlikely
    Dimensione
    1.5

    Cornices by nature lack support, and triggering remains possible for some time. Failure will be possible once weight exceeds support, such as additional snow loading, rain, or human activity. Recommend avoiding and maintaining a decent distance from these formations, even after a storm event.

Recent Avalanche Activity

No natural or human-triggered avalanche activity has been reported over the past 24 hours.

Current Snowpack Conditions

Yesterday’s rain and rime event in the southwest (Turoa) left a surface crust which has now been buried by today’s new snow. New snow has also accumulated at Whakapapa. Very cold conditions today with a lowering freezing level have resulted in low-density snow. This new snow will be easily transported once winds increase. In the northwestern areas near Whakapapa, a facet crust combination weakness has been noted. Questions remain on distribution and reactivity once stressed by subsequent loading. Snow cover exists on Mt Ngauruhoe and Mt Tongariro. If doing the Tongariro crossing, you will be traveling over snow and ice. Recommend alpine gear and precautions need to be considered. The south-west areas have enough snow cover in start zones above 1500 metres for avalanches to run freely (threshold). In the northern areas, the threshold is at a slightly higher elevation, but this is also changing fast. This recent snowfall has improved snow cover overall and lowered the threshold elevation in the northern and eastern areas (about 1600 metres elevation).

Mountain Weather

Wednesday the 5th of August will have showers, heavier with hail and falling as snow in the morning, then easing through the afternoon with increasing fine spells. The winds are strong to moderate southerlies. Overnight, the freezing level drops to 400 metres, then rises to 800 metres in the morning. A front moves over the North Island today, bringing a cold southerly flow. A high pressure builds over the South Island today and expands to cover the country tomorrow.

Sliding Danger

Slick rime crusts exist. Winds can strip ridgelines and windward terrain features, exposing hard icy crusts. 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 uncertain about forecast snowfall amounts.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

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