Bollettino valanghe

Two Thumbs

New Zealand Avalanche Advisory
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Pericolo valanghe

High Alpine · above 1,800 m
2 · Moderato
Alpine · 1,200 m–1,800 m
1 · Debole
Sub Alpine · below 1,200 m
1 · Debole
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In sintesi

Small windslabs have formed around ridges and terrain features. Lower down, the snowpack might warm tomorrow for small loose wet avalanches to develop.

Take extra care to evaluate windloaded & sunny, steep slopes before committing.

Problemi valanghivi

  • Wind Slabs

    • Tutte le quote
    Probabilità
    Possible
    Dimensione
    1.5

    Windslabs are likely to be mostly small and confined to areas sheltered from the SW wind around ridges and terrain features. Triggering by a single skier is still expected to be possible. It is also possible that larger windslabs are present in isolated slopes. Pay particular attention to the consequences of a small avalanche knocking you off your feet.

    The windslab danger will decrease with the warming temperatures.

    The danger rating will stay at moderate above 1800m to account for the possibly higher snow depth in the North of the Range - and therefore higher consequence (larger) avalanches.

  • Loose Wet

    • Tutte le quote
    Probabilità
    Possible
    Dimensione
    1

    Tomorrow, warmer temperatures are forecast with no clouds. The sun may have enough power to start a loose wet cycle on steep sunny slopes. Particularly where new snow sits on a solid crust. Keep an eye out for signs of the snow heating - like roller-balling. Be prepared to change plans to avoid consequential sunny avalanche terrain if you notice it getting too warm.

Recent Avalanche Activity

A natural windslab was observed on Pk 2211, NE of Erebus. E aspect, Sz 1.5-2. likely ran during the storm on Friday or Saturday.

Multiple size 1 (too small to bury a person) windslabs were deliberately released by ski cut on Saturday 24 July. They were on north east facing terrain below 2000m. These slabs failed on the previous snow surface prior to the storm which was a solid melt freeze crust.

If you see any activity on the Two Thumb Range, please make a public observation. It really helps us to produce accurate forecasts.

Current Snowpack Conditions

The snow depth in the range South of Stag Saddle is 40-60cm with some deeper pockets of 100-120cm in sheltered areas. The Two Thumbs still have good snow cover to elevations around 1100m.

The dry snow that fell throughout the range on Friday and Saturday has been redistributed by strong then moderate southwest and west winds at higher elevations. Windward ridges are stripped with loaded areas up to 50cm deep. Even at lower elevations, katabatic (cold air falling down the mountain) winds caused by the cold overnight temperatures, have moved the surface snow around. The snowpack below is capped by a crust of several layers that is highly variable over the terrain. In places it is thin and breakable with skis and in other places it forms large areas of solid concrete-like patches. Under the crust layers the snowpack is well consolidated.

Guides and ski fields have reported some sugary weak layers developing around the crusts. At present, this does not seem a problem in the South of the range.

The snowpack North of Stag Saddle is not well understood, with no direct observations. It is possible that above about 2300m very deep snow has accumulated.

Previous gale force wind from the northwest and southwest has left old crusts and rock exposed on ridges and upper elevations.

Mountain Weather

Tuesday 28 July 2026: Fine weather with possibly severe morning frosts. Light winds are expected at elevations below 2000m, while above the South-West winds of 30km/h will die out during the morning. The free-air freezing level is forecast to be at 1600m and then lifting to 2000m in the afternoon

Sliding Danger

The winds that have continued over the last few days will have stripped many areas back to the old crust. Some very firm patches exist in the range.

Come prepared for a possible high sliding danger and assess each slope. Expect lots of rocks in the runouts.

Ski crampons should be in the pack! Ice axe and crampons are recommended.

Forecast Confidence

Moderate

  • We have a good understanding of the snowpack structure and confidence in the weather forecast.
  • We are uncertain due to a limited number of field observations.
  • We are uncertain due to the variability of wind effect on the snowpack.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

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