Timing is everything on Wednesday. A clear, but windy start to the day will turn to rain and snow in the afternoon.
The avalanche risk will increase rapidly with the incoming weather. Plan to be out of avalanche terrain before it hits.
Windslabs will continue to form at higher elevations on the eastern half in the morning.
An afternoon southerly change accompanied by fresh snow, will rapidly build windslabs on slopes that face northwest and north.
Poor visibility will make it difficult to identify wind loaded slopes and manage terrain safely.
It's best to be well clear of avalanche terrain before the weather hits.
The storm may start with rain to high elevations. Expect the loose wet danger to increase with rain on snow.
As the storm snow accumulates, avalanches are possible where there was enough previous snow to make smooth sliding surface.
The weather models predict that this storm will probably deliver enough snow to cause a problem from Wednesday evening onwards.
A size 1.5 windslab was triggered by skiers in the Haszard Range on Monday. It was on an east facing slope at 2000m. Similar snow conditions exist on the Two Thumb Range.
If you see any activity on the Two Thumb Range, please make a public observation. It helps us to produce accurate forecasts.
Rain will soak the snowpack on Wednesday afternoon, turning to snow as the freezing level drops.
Ridge-lines and slopes exposed to the west winds, are heavily scoured and stripped back to slick crusts and scree on upper ridges.
Multiple crusts exist in the old snow on all elevations and aspects. Facets (sugary crystals) have begun to form around these crusts at upper elevations, but have not posed problems. At mid-lower elevations, the old snow is well settled and consists of mainly melt forms or round crystals.
Snow depth varies from 40-75cm, with deeper accumulations of 100-120cm in sheltered areas.
Photos are of the Camp Creek area on Monday
Rain in the afternoon. Snow lowering to 600 metres.
Wind at 1000 metres
Gale northwesterly 65 km/h. Changing southeasterly 40 km/h in the afternoon.
Wind at 2000 metres
Gale northwesterly 75 km/h, rising to severe gale 120 km/h in the morning. Changing southerly 40 km/h in the afternoon, and becoming southeasterly 40 km/h in the evening.
Freezing level
2300 metres, lowering to 1500 metres in the afternoon, and to 1200 metres in the evening.
Rain has softened crusts at lower elevations. Higher ground could still have a slick sliding surface . A slip or fall on steep terrain could have serious consequences.
Assess runout zones before committing to steep slopes, and carry equipment appropriate for firm alpine conditions, such as crampons and an ice axe. Conservative route selection remains the most effective way to manage these hazards.
Moderate
New Zealand Avalanche Advisory (NZ Mountain Safety Council)
