New snow and strong winds are expected. Wind slabs will build on top of potentially weak layers in the snowpack.
Surface hoar and other weak crystal types have developed during the recent cold, clear weather. As new snow loads these weak layers, avalanche danger is expected to increase.
A good plan is to wait for the storm to pass and allow conditions to settle before heading into serious backcountry terrain.
Wind slab danger is increasing on E–S aspects above 1800 m. Surface hoar and weak faceted snow were previously observed on shaded aspects.
As denser new snow accumulates on top of these weak layers, avalanche danger is expected to increase quickly. Careful assessment will be required as the storm develops.
Loose wet avalanches are likely when rain falls onto the current snowpack. The freezing level is forecast to rise to around 2000 m on Tuesday, increasing avalanche danger on all aspects below this elevation.
Limited observations due to low cloud and precipitation.
Approximately 90 cm of new snow fell in the Ohau area last week at 1800 m, tapering to around 45 cm at 1500 m. Many slopes are only just reaching the threshold for avalanche activity, and shallow snowpack areas may still contain hidden rocks and hazards.
Two buried rime crusts have been observed approximately 20–30 cm below the surface, although their depth varies depending on local wind loading. Solar-exposed slopes have developed varying degrees of melt-freeze crust, with faceting observed beneath these crusts, while surface hoar was observed on sheltered shaded aspects.
Incoming NW winds and forecast snowfall over the first few days of the new week are expected to increase avalanche hazard, with wind slab development likely on affected slopes.
Isolated showers, becoming widespread and heavier with thunderstorms possible about the divide in the afternoon and evening.
Wind at top
Northwesterly 70 km/h.
freezing level
2000 metres.
Firm snow conditions were present on west-facing slopes near ridgelines, with a potential sliding hazard on steep terrain.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
