Wind Slab problem exists following recent snowfall accompanied by severe NW gale-force winds. Fresh wind slabs may be reactive, particularly in wind-loaded terrain.
At lower elevations, a firm rain crust has formed, creating a potential sliding hazard on steep terrain.
Wind slab danger exists on east to south aspects above 1800 m.
Denser new snow has been deposited onto underlying weak layers, and these wind slabs may be reactive to the weight of a person. Further investigation is required to determine the distribution and reactivity of this problem.
Careful assessment and conservative decision-making will be required.
Small loose wet avalanches are possible on steep sunny slopes during the day.
14 July – Multiple size 1 loose wet avalanches triggered by a rain-on-snow event were observed from Ohau Ski Field. Cornice failures were also observed along the ridgeline.
About 15–20 cm of new snow fell above 1850 m between 13–14 July, accompanied by severe NW gale. In exposed terrain, the wind stripped the new snow back to the ground or to slick rain crusts.
Wind loading formed pockets of dense wind slab on east through south aspects, with depths of approximately 30–50 cm.
In some locations, these wind slabs are sitting on weak faceted snow and may remain reactive to additional loading.
Below 1850 m, precipitation fell as rain, forming a rain crust across all aspects.
Fine, with severe frosts in the morning, then a few evening showers about the Divide.
wind at top
Westerly 60 km/h.
Freezing level
Lowering to 2200 metres evening.
Firm snow conditions are present on west-facing slopes near ridgelines and at lower elevations where a rain crust exists. These hard surfaces may present a sliding hazard, particularly on steep terrain.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
