We are at the tail end of the largest storm of the winter. Heavy snow has fallen with gale force winds from nearly all directions. Moderate to strong winds from the NW quarter last night will have created a fresh wind slab problem.
Heavy rain at lower and mid elevations has created a wet snow hazard and if temperatures remain warm this will become increasingly reactive.
Temperatures have fluctuated widely during the storm and with no field observations there are many unknowns in the snowpack in the region. Though the avalanche hazard is settling, continue to treat any steeper terrain and runouts with caution. At lower and mid elevations continue to be wary of any slopes that are wet and unconsolidated.
A cautious approach is still advised in all avalanche terrain.
Over 2m of snow has fallen at higher elevations. Winds up to severe gale force have been observed from nearly all directions, most recently from the north. Expect reactive wind slabs at mid to high elevations particularly towards the main divide.
Significant rain has fallen up to 1900m. Rain at these lower and mid elevations has created a loose wet snow and wet slab hazard and if temperatures remain warm this will become increasingly reactive.
Weather has prevented any observations in the region for several days now. The large storm cycle will have produced widespread natural wind slab and wet snow avalanches. Reports from adjacent regions indicate large, wide spread natural avalanches have occurred.
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.
Fresh snow fall potentially over 2m has fallen in the region at higher elevations, amounts taper down at lower elevations with rain falling below 1900m-1600m as temperatures fluctuated. These temperature fluctuations have been large and coupled with winds from around the clock will see wide variations in the structure and depth of the storm snow. Unusually, at the end of the storm temperatures spiked rapidly, rain saturated the snow pack to approximately 1800m. This storm snow has fallen on a variety of bed surfaces - facets, wind pressed and wind stripped - poor cohesion is likely.
Previously above 1900m: A mix of faceted surface snow and wind pressed snow existed on south aspects. This snow has largely bonded well to the old snow surface and the upper and mid pack are generally showing settled characteristics as total snow depths have increased. With continued cold temperatures some near surface faceting had been observed. With the very strong winds experienced throughout the winter there is a high degree of spatial variability in the distribution of snow and there are still areas of unusually shallow snowpack at all elevations. The lower part of the snowpack appears consolidated and unreactive. Large cornices have also formed above 1800m.
Below 1900m rain last week had saturated the snow pack creating a very stout supportive rain crust. With cold morning temperatures there was a very slick snow surface. With continued cold temperatures and a shallow snow pack some facet development had been observed.
Today 29 Aug
Showers, turning to rain in the afternoon. Snow to 1100 metres.
Wind at 1000 metres: Northwesterly 50 km/h.
Wind at 2000 metres: Northwesterly 50 km/h, rising to westerly gale 70 km/h in the morning.
Wind at 3000 metres: Northwesterly severe gale 90 km/h, easing to gale 70 km/h for a time in the morning and early afternoon.
Freezing level: 1200 metres, rising to 1600 metres in the evening.
With severe gale force winds stripping snow at altitude and rain having fallen to 1800m there may be areas of slick frozen snow surface which with cold temperatures would present a sliding hazard. Take care. An ice axe and crampons could be necessary.
Low
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
