The storm is forecast to back off slightly on Monday, but the hazard remains considerable. Warmer temperatures could lead to harder, more dangerous wind slabs. Stick to low angle slopes or make the most of inbounds terrain.
Ongoing gale northwesterly winds will continue to build windslab on sheltered northeast through to southwest facing terrain. Rising temperatures could make for stiffer, harder windslab, increasing the chances that the slab fractures above you and making it more likely that you get caught.
Avoid steep, recently loaded slopes.
Loose wet avalanches are likely as rain on snow and warmer temperatures cause the new snow to lose strength.
Freezing levels are forecast to rise to 2000m near the Divide and 2500m elsewhere on Monday. Showers are also forecast about the Divide.
Watch out for wet sticky snow or rollerballing, as these are clear signs the snowpack is losing strength.
23/08: Ohau Ski Patrol reported a natural wind slab avalanche cycle in sheltered terrain near ridgeline, with several size 1 avalanches and one size 2 avalanche on northeast through to south facing slopes.
We still have limited field observations due to the ongoing storm. It looks like at least 20cm of new snow fell in the south of the forecast area on Sunday morning, but gale northwesterly winds through the day have stripped exposed areas back to a hard crust and loaded sheltered terrain. Snow totals are likely to be closer to 40cm near the Divide, with the same pattern of scoured surfaces and deeper drifts.
This sit on a well settled lower snowpack, with slick crusts on solar aspects and shady slopes below 2000m. Faceting has been observed in the lower pack, but after warm temperatures and lots of sun this should be limited to shady slopes above 2000m. We will be monitoring these layers as the storm brings additional load through the start of the week.
A few showers about the divide, mainly fine with areas of afternoon and evening high cloud elsewhere.
Wind at 1000 metres: Westerly gale 70 km/h, rising to northwesterly severe gale 90 km/h in the afternoon.
Wind at 2000 metres: Westerly severe gale 90 km/h.
Freezing level: 1500 metres but 1100 metres about the divide, lifting to 2000 metres everywhere in the morning and to 2500 metres away from the divide in the afternoon.
Gale northwesterly winds have scoured exposed areas back to slick crusts. Take an ice axe and crampons for travel at higher elevations.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
