Icy surface conditions throughout the Park make sliding danger the primary hazard on Monday.
On high northerly aspects, beware pockets of stiff windslab and go around convex rolls.
If the day begins to warm then loose wet avalanche hazard will rise on sunny slopes holding deposits of new snow.
Southerly snow blown onto firm north-facing slopes may have formed pockets of wind slab. Remember the indicative signs, including changes in the density of snow and firm pockets that sound hollow or drummy.
Any snow deposited on sun-facing slopes will sit over a slick melt-freeze crust sliding surface. Daytime heating may trigger loose-wet releases.
The big question mark is whether things will warm up sufficiently on Monday, and whether there is much new snow on sunny aspects.
Check conditions through the day and as you move through terrain.
A widespread loose wet avalanche cycle was observed prior to the present southerly blast, but nothing since.
Park user observations provide important information.
If you see anything, please report it in the public observations section of the NZAA website.
In most parts of the Park a largely isothermic snowpack is currently well frozen after 24hrs of southerly blast, with air temps down to -7 at 1650m. Currently, any stablity concerns exist primarily at surface/new snow interface level. A trace of southerly snow fell on the 15th and 16th driven by strong southerly winds. Isolated pockets of windslab might exist about ridge lines and downslope terrain features lee to the southerly wind and will sit on a very firm melt-freeze crust surfaces. Over the last few weeks winds from all around the compass have stripped higher elevation peaks and ridge lines back to either ice or very firm and now frozen snow. The threshold for avalanches is estimated at around 1500m in the west, tapering east.
Forecast for Monday 17 August
Fine, then showers developing in the evening.
Wind at 1000 metres
Southerly 35 km/h, easing to light before dawn.
Wind at 2000 metres
Southerly 60 km/h, easing to 35 km/h in the morning, then strengthening to gale 65 km/h in the evening.
Freezing level
600 metres, lifting to 1200 metres in the morning.
Elevated sliding danger currently exists on all elevations and aspects. Melt-freeze crusts are the primary snow surface type at present and a cold southerly wind will limit daytime warming and snow softening. Crampons and an ice axe are a good idea. Putting crampons on early increases your safety margin massively.
High
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
