Avalanche forecast

Two Thumbs

New Zealand Avalanche Advisory
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Avalanche danger

High Alpine · above 1,800 m
2 · Moderate
Alpine · 1,200 m–1,800 m
2 · Moderate
Sub Alpine · below 1,200 m
1 · Low
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Highlights

Small windslabs have proved to be easily triggered by a person's weight.

Take extra care to evaluate windloaded slopes before committing.

Avalanche problems

  • Wind Slabs

    • All elevations
    Likelihood
    Possible
    Size
    2

    Windslabs have formed on north, northeast and east facing slopes. They could easily be triggered by a skier on Saturday.They are likely to be mostly small and confined to areas sheltered from the SW wind around ridges and terrain features. It i possible that larger windslabs are present in isolated slopes.It would be wise to avoid wind loaded features that are steep enough to slide. Pay particular attention to the consequences of a small avalanche knocking you off your feet.

  • Loose Dry

    • All elevations
    Likelihood
    Possible
    Size
    1

    Small loose dry avalanches are possible throughout the range on very steep slopes, particularly in sheltered areas where the snow sits over a firm crust. Although these are expected to be small, the consequences could be major depending on where you get carried.

  • Loose Wet

    • All elevations
    Likelihood
    Unlikely
    Size
    2

    Cold temperatures should keep the loose wet danger away on Sunday.

    However, if it warms up more than expected, a loose wet cycle could happen on steep sunny slopes. Particularly where new snow sits on a solid crust.

    Keep an eye out for signs of the snow heating like rollerballing. Be prepared to change plans to avoid consequential sunny avalanche terrain if you notice it getting too warm.

Recent Avalanche Activity

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

Over 20cm of new snow fell in the north above 2100m on Friday with 20mm of rain soaking the snowpack at lower elevations. This precip amount tapered to almost nothing at the south end of the range.

A further 15cm of snow came in throughout the range on Friday and Saturday. The snow has been redistributed by strong southwest winds. Windward ridges are stripped with loaded areas up to 50cm deep.

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

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.

Mountain Weather

Fine, with morning frost, possibly severe in sheltered places.

Wind at 1000 metres

Light.

Wind at 2000 metres

Light.

Freezing level

600 metres, lifting to 1200 metres in the morning.

Sliding Danger

While the new snow should go some way toward easing the sliding danger. Snowfall amounts are low particularly in the south. The old crusts may still be exposed and slick in plases.

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

Iceaxe and crampons are recommended.

Forecast Confidence

Moderate

  • We are uncertain due to the variability of wind effect on the snowpack.
  • We are uncertain about how the timing or intensity of solar radiation will affect the snowpack.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

Regions covered