7 AM update: The north island is looking like the hotspot on Monday, with lower freezing levels, heavy snowfall and strong northwest winds forming increasingly large and reactive wind slabs throughout the day. Further south and at lower elevations, warmer temperatures and rain mean wet loose avalanches will be the main concern. The underlying crust could make both wet loose and wind slab avalanches more likely.
Northwest winds and new snow may form fresh wind slabs at upper elevations. These slabs have formed over a smooth crust and as a result, they may not bond well.
Rain at lower elevations will weaken the upper snowpack and may create wet loose avalanches in steep terrain.
On Friday our field team observed evidence of a natural storm slab cycle to size 2. These avalanches were generally on northwest aspects at treeline. They ran on a crust that is now 20-70 cm deep.
Rain at lower elevations will soak the upper snowpack. At higher elevations, 10-25 cm of new snow will accumulate by the end of the day. Northwesterly winds will strip windward slopes and create fresh wind slabs in lee area. A crust can be found down 20-70 cm that extends to mountain tops on all aspects. Recent reports suggest this crust is bonding poorly to the snow above.
The remainder of the snowpack is consolidated and strong.
Sunday night
Mainly cloudy with wet snowfall or showers. Trace to 8 mm accumulation in most areas except Mount Cain which may receive up to 15 cm of new snow. Freezing levels in the south are 1500-2000 m, and 1100 m in the north. Ridge wind northwest 50 km/h gusting to 90 km/h.
Monday
Periods of wet snow mixed with rain, 10-20 mm of accumulation. Alpine temperatures reach a high of 2 °C. Ridge wind west 45 km/h gusting to 90 km/h. Freezing level up to 2000 m in the south, 1300 m in the north.
Tuesday
Cloudy with snowfall, 5-15 cm accumulation. Alpine temperatures reach a high of -1 °C. Ridge wind north 20 km/h gusting to 75 km/h. Freezing level 1100 metres.
Wednesday
Mainly sunny with cloudy periods and isolated flurries. Alpine temperatures reach a high of -8 °C. Ridge wind northeast 10-30 km/h. Freezing level at valley bottom.
More details can be found in the Mountain Weather Forecast.
