Avalanche forecast

Aoraki/Mt Cook

New Zealand Avalanche Advisory
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Avalanche danger

High Alpine · above 2,000 m
3 · Considerable
Alpine · 1,500 m–2,000 m
3 · Considerable
Sub Alpine · below 1,500 m
1 · Low
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Highlights

The storm is forecast to clear on Thursday. The snowpack has been through a lot and most accidents happen in the first 24 hours after a clearance.

Stick to safe, low angle terrain and give the snow time to settle.

Avalanche problems

  • Wind Slabs

    • All elevations
    Likelihood
    Likely
    Size
    2

    Days of snow and gale NW winds will have built wind slab on NE through to SW slopes in the alpine and high alpine. These slabs are most likely in sheltered areas near ridgeline but could also be mid slope wherever snow has been deposited.

    These slabs will be largest near the divide, but slabs large enough to bury a person are still possible in the eastern part of the forecast area.

    A southwesterly change on Thursday afternoon could see new slabs building on northerly aspects above 1800m.

  • Storm Slabs

    • All elevations
    Likelihood
    Possible
    Size
    2

    Storm slab avalanches in sheltered areas are still possible as the new snow settles, especially as temperatures warm on Thursday afternoon.

  • Loose Dry

    • All elevations
    Likelihood
    Likely
    Size
    1

    With sun and warming temperatures on Thursday afternoon, a loose wet avalanche cycle is likely on solar aspects.

Recent Avalanche Activity

Observations are still limited by bad weather, but two size 3 suspected wind slab avalanches were visible from Aoraki Mt Cook Village on SE facing slopes in the Hayter and Stewart Stream drainages off the Divide on the 14th.

There was also a widespread loose wet avalanche cycle below 1800m on the 13th and 14th.

Please let us know via the Public Observations link if you see any slides.

Current Snowpack Conditions

Around 120cm of new snow has fallen around the divide, tapering to around 100cm on the Liebigs, and 25cm in the eastern part of the forecast area above 1800m, with a mix of rain and new snow down to around 1500m. This has been redistributed by gale NW winds which will have built deeper drifts in sheltered east and south facing slopes. Freezing levels have fluctuated from between around 1500m and 2000m, leaving wet snow at lower elevations and density inversions in the storm snow in the Alpine and High Alpine.

This sits on a well settled snowpack, with as much 2m of snow near the divide, tapering to 120cm at upper elevations in the Liebig, Gammack and Burnett Mountains, tapering to roughly 50cm at 1700m.

In the eastern part of the forecast area, this snowpack was capped with a variable rime crust around 1cm thick, with another crust down around 6cm. Any surface hoar that developed during the cold, clear conditions on the weekend has probably been destroyed by gale NW winds on Monday morning, but faceting below these two crusts has probably survived. We are monitoring these layers to see how they respond to new load during this storm.

Mountain Weather

Showers, with snow to 1400 metres, clearing to fine towards midday.

Wind at 1000 metres: Northwesterly 40 km/h, easing to southwesterly 30 km/h in the morning.

Wind at 2000 metres: Westerly 40 km/h, rising to gale 65 km/h for a time in the morning.

Wind at 3000 metres: Westerly gale 75 km/h, rising to severe gale 95 km/h for a time in the morning, easing to southwesterly 50 km/h in the afternoon.

Freezing level: 1600 metres, lifting to 2100 metres in the evening.

Sliding Danger

Exposed areas will likely be stripped back to a slick crust by strong NW winds. Below 1800m there may be slick rain crusts. Take an ice axe and crampons for any travel above the snowline.

Forecast Confidence

Moderate

  • We are uncertain due to a limited number of field observations.

New Zealand Avalanche Advisory (NZ Mountain Safety Council)

Regions covered