Wind slabs may continue to form with ongoing gale southerlies and blowing snow on Tuesday
Evaluate the snow and terrain carefully, avoiding steep, recently loaded features of concern
Reactive wind slab formation may continue on Tuesday, building on recent wind loading from the past few days. More likely above 1700m, on northwest to southeast facing aspects.
Strong to gale southerly winds and 40-50 cm of recent storm snow mean recent wind slabs could easily be over 100cm in depth.
Evidence of multiple Sz 2-3 natural storm and wind slab avalanches was observed to have run during the July 30-31st storm. Around the Forbes and Richardson Mountains these ran on mostly SE aspects between 1900-2100m. Image below shows one on Mt Earnslaw east aspect.
If you see any recent avalanche occurrences or have any relevant snowpack information or photos, you can share them via the Public Observations link on the NZAA home page.
Up to 50cm of new snow fell between July 30 and 31. Initially, with strong northwest winds on the 30th, this also had a good going-over with strong southerly winds on the 31st to 1st and again on the 3rd August. Exposed slopes, ridgelines and features, mostly west facing, have been stripped back to old layers and rock. Large cornices may also be forming along ridgelines. Although there were numerous naturals during the storm, some investigation through the Richardson range on the 1st showed this new load was bonding relatively well.
Previously the snowpack was still shallow, approximately 60- 70 cm below 1700m and 120cm at 2000m. Crevasses are still very open, and many rock features are still visible, particularly on west-facing aspects.Although the pack appears consolidated, the Aspiring region is very large, and there is still limited data. Caution should still be taken, particularly in steeper, more extreme terrain where unknown weaknesses may exist.
Mt Aspiring National Park Forecast
Forecast for Tuesday
Mostly cloudy with isolated snow showers, clearing and becoming fine in the afternoon.
Wind at 1000 metres Southwesterly 50 km/h, gusting severe gale 100 km/h from morning. Turning southeasterly 60 km/h in the afternoon, dying out at night.
Wind at 2000 metres Southwesterly severe gale 100 km/h. Turning southeasterly severe gale 90 km/h in the afternoon, easing to 30 km/h at night.
Wind at 3000 metres Southwesterly severe gale 100 km/h, turning southeasterly in the morning. Becoming 50 km/h in the evening, easing to 30 km/h at night.
Freezing level 300 metres.
Issued: 2:48pm Mon 3 Aug
Exposed areas such as ridgelines on west aspects may have been stripped back to old ice layers by recent strong winds. Depending on your objective, an ice axe and crampons could be necessary.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
