With rain initially, the loose wet hazard will be the main problem in the morning with storm slab increasing in the afternoon/evening as the freezing level drops.
Over 100mm is forecast tomorrow; expect changing conditions.
Keep out of runout zones, including tramping terrain and valley floors.
Heavy rain tomorrow will keep the loose wet hazard likely tomorrow. If you end up in deep, wet snow, keep out of steeper terrain.
Keep out of runout zones, including tramping terrain and valley floors.
Significant snowfalls at higher elevations have increased the storm slab hazard on slopes lee to the NW, and more new snow is forecast tomorrow. Freezing levels are initially high (2200m) but dropping later in the day. Higher elevations will have significant falls from 5 days of weather.
With new snow from the last few days and now rain at higher elevations, Wet slab avalanches are possible with heavy rain forecast again tomorrow.
A natural avalanche cycle is expected to have occurred during the storm.
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.
52mm of rain fell in Arthur's Pass on Tuesday, with Gale NW winds and a freezing level up to 2200m. Earlier in the week, up to 250mm of precipitation has fallen in western areas of the Park since Friday night, accompanied by fluctuating freezing levels. Most areas below ~2100m will have received a snow-rain-snow combination, followed by snow falling to ~1000m on Sunday afternoon. 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 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.
Rain, with heavy falls. Snow lowering to 700 metres in the evening. Winds Gale northwesterly 85 km/h, rising to severe gale 120 km/h late morning. Easing to westerly 40 km/h early evening, dying out at night. Winds 2200 metres, lowering to 1200 metres in the evening.
Wind stripped ridge lines and northerly slopes scoured back to old rain crusts will present a sliding hazard. An ice axe and crampons are recommended.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
