Dangerous surface conditions currently. An icy rime crust is present above 1400 meters, primarily on southern and eastern aspects. A high level of alpine skills will be necessary to navigate these conditions. Wind slabs may develop on southern aspects. A frontal system affects the region over the next 24 hours. Visibility will be poor, and the weather unpleasant. Recommend delaying any alpine travel until conditions improve.
Wind slabs will form as new snow starts to be transported above 1700 metres in elevation. This wind slab will develop on mostly south aspects. Eastern aspects may also have wind-transported deposits. Triggering will be possible on higher-angle slopes. Terrain features such as gullies and rocky outcrops will act as catchments. Types of locations where loading tends to occur.
Loose wet avalanche activity will increase as rain breaks down the snow surface structure. Fluctuating freezing levels will result in rain at higher elevations at times. Loose wet activity will be greater on northern aspects, where the older wind slab is located. The surface penetrability and rain intensity will be higher on north-facing slopes.
No natural or human-triggered avalanche activity has been observed or reported over the previous 24 hours.
On southern aspects, on southern slopes, a strong and hazardous rime crust is the primary feature of the snowpack. This crust is resistant to rain saturation and may take time to break down. Older, wind-driven snow deposits have been gaining strength but are now becoming wet. The current snowline is approximately 1400 metres in elevation, with an estimated threshold slightly higher at around 1500 metres in elevation. This threshold indicates the minimum snow cover needed to cover surface irregularities, and avalanches can run freely.
Tomorrow, the 14th of July, will have showers, some heavy and possibly thundery before dawn, easing in the afternoon. Snow to 1900 metres. The winds are strong north-westerly overnight, easing over the next 24 hours. The freezing level is about 2000 metres, but rising through the day. A broad trough moves across the South Island today, then moves over the North Island tomorrow, followed by a disturbed northwest flow. A front pushes onto the southwest of the South Island during the second half of tomorrow.
Rime crust on southern aspects is slick, hard, and unforgiving. These types of conditions demand a high level of skill and competency. The consequences of a fall and slide will be severe. Plenty of hazards, such as exposed rocks and cliff bands, exist. It is essential to carry the appropriate gear, crampons, and an ice axe. Be prepared and read the surface conditions as you travel. Recommend a conservative mindset.
Low
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
