New snow tomorrow will increase the wind slab hazard during the day. Good assessment skills of the quickly changing snowpack conditions are important for any backcountry travel tomorrow. The snowpack is still recovering/draining from all the rain this week and the danger rating could quickly change with rain or more snow than forecast.
New snow tomorrow and a lowering freezing level will increase the wind slab hazard during the day. A hard crust from the rain this week will give a good bed surface, so check the bonding of any new snow to this crust.
With the freezing level lowering, the loose wet hazard is decreasing. If the freezing level is higher than expected, the loose wet hazard will increase quickly, as the snowpack is still draining from this week's rain.
A natural avalanche cycle is expected to have occurred during the storm during the week.
Park user observations provide important information. Please help us.
If you see anything, please report it in the public observations section of the NZAA website.
Partly cloudy with showers, mainly about the Main Divide. Snow to 1300 metres. Winds westerly 50 km/h. Freezing level lowering to 1300 metres evening.
Conditions are changing. Low sliding hazard at present.
Moderate
500+ mm of rain has fallen in western areas of the Park in the last week; part of this was snow to Arthurs Pass Village on Thursday, which melted when the rain returned. This has been accompanied by fluctuating freezing levels. Most areas below ~2100m will have received a snow-rain-snow combination, followed by snow falling to ~900m on Thursday. Snow totals remain to be determined once the storm concludes but the threshold for avalanches in western areas of the Park close to the divide is probably around 1500m, tapering to the east. A series of rain on snow events over the past weeks mean rain percolation channels will be well established in the snowpack below ~1800m and new channels will be forming to the highest elevations during this storm's heavy rain precipitation. Strong to gale winds from the northerly half will have formed windslabs on south- through east-facing slopes and around terrain features. The underlying snowpack was well consolidated prior to the storm and once drained is unlikely to hold deeper layers of concern for avalanche hazard.
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
