Up to 40cm of fresh snow has fallen accompanied by winds up to gale strength from the NW. Prior to the storm there was already large amounts of loose dry snow available for transport. These factors will have combined to produce a wind slab hazard at higher elevations. With rain falling up to 1700m there may be wet slab hazards at lower elevations. Conitnue to exercise caution when moving through avalanche terrain.
The combination of periods of fresh snowfall and gale force winds from the NW 1/4 plus existing large amounts of loose dry snow available for transport has created a widespread windslab hazard. Slopes lee to the NW will be of particular concern but unstable pockets may exist on specific terrain features on all aspects at higher elevations.
With significant rainfalls up to 1700m and freezing levels remaining high, a wet slab hazard may exist on slopes below 1700m.
Wet slab avalanches were observed yesterday at Albertburn Saddle 1600m during the storm. Wind slab activity is anticipated to have occurred during the storm. Previously, widespread size 1-2 natural wet avalanches were observed on Monday and Tuesday on steeper solar aspects as the days warmed.
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.
Approximately 15-30cm of new snow fell above 1700m over the past day and a half this snow is likely to been re-distributed by yesterday's strong NNW winds and there is likely to be areas of wind pressed and wind scoured snow. Previously 20-40 cm of loose dry snow had fallen over the weekend. This snow has generally well bonded to the old snow surface.
Before this, on 1st - 4th of August, very strong winds from the west and south have significantly stripped any exposed faces and features; other downwind areas in the lee have been left with variable surface conditions and multiple layers of very dense hard slab ranging from 10-60cm thick. This slab now appears very stubborn and unreactive. Large cornices have also formed above 1800m.
The snowpack remains relatively shallow for the time of year. 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 lower part of the snowpack also appears consolidated and unreactive, 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.
Showers, some heavy before dawn with snow to 1700 metres, becoming few and far between in the morning, clearing in the evening.
Wind at 1000 metres; Northerly 55 km/h easing to 35 km/h before dawn, then dying out late afternoon.
Wind at 2000 metres: Gale northerly 75 km/h, easing to northwesterly 45 km/h before dawn, then dying out late afternoon.
Wind at 3000 metres: Gale northwesterly 70 km/h, easing to 45 km/h before dawn, then dying out early evening.
Freezing level: 1900 metres.
Exposed areas such as ridgelines on west and south aspects may have been stripped back to old ice layers by strong winds. Depending on your objective, an ice axe and crampons could be necessary.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
