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.
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.
High
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.
Approximately 15–20 cm of new snow fell above 1850 m between 13–14 July, accompanied by severe NW winds that later shifted to the SW. In exposed terrain, the strong winds stripped the new snow back to the ground or to slick rain crusts.
Wind loading created pockets of dense wind slab on east through south aspects, with slab depths of approximately 30–50 cm.
In some locations, these wind slabs overlie weak faceted snow, making them potentially reactive to additional loading.
Below 1850 m, precipitation fell as rain, forming a widespread rain crust on all aspects.
Showers developing in the morning about the Divide, otherwise fine with morning frosts and high cloud.
wind at top
Northwesterly 70 km/h.
freezing level
Lowering to 2000 metres overnight.
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
