Two Thumbs

Strong Northerly wind, some rain or maybe some snow above 1800-2000m for Wednesday (12 Aug).

Watch the weather in the morning and once the precipitation and wind starts travel away from steep, lee terrain.

Consider loose wet avalanches on South-east aspects!

No avalanche observations from the Two Thumbs Range. Guides got high on Beuzenberg Peak today and did not observe any new loose wet activity.

In neighboring Cass Valley no loose new loose wet avalanches were reported today on 11 Aug as well.

In Aoraki / Mt Cook National Park closer to the Main Divide loose wet activity was observed on Monday 10 Aug

If you see any activity on the Two Thumb Range, please make a public observation. It helps us to produce accurate forecasts.

Southern end of range — south of Stag Saddle

Ridge-lines and slopes exposed to the south-west, have been heavily scoured, and mostly stripped back to old crusts, or even bare rocks and scree on upper ridges. Firm crusts and areas of wind-affected snow are widespread, with the most scoured and variable conditions found in the high alpine, and at the southern end of the range.

Sheltered terrain above 1600m continues to hold soft snow.

Sunny slopes have been softening from late morning.

Snow depth varies from 40-70cm, with deeper accumulations of 100-120cm in sheltered areas.

Small facets (weak sugary crystals) have begun developing around crusts in the upper snowpack and between layers of old wind slab, particularly on shallow shaded slopes. At present, these are not posing a significant problem. Below the crusts, the lower snowpack is well settled.

Northern end of range — north of Stag Saddle

The snowpack north of Stag Saddle is not well understood, with no direct observations. We expect that deep snow will have accumulated in sheltered areas above 1800m.

Cloudy periods. Rain developing in the morning, more persistent and heavier from the afternoon. Snow lowering to 2000 metres.

WIND AT 1000m:Northerly 40 km/h, rising to gale 70 km/h in the morning.

WIND AT 2000m: Northerly gale 65 km/h, rising to severe gale 90 km/h in exposed places in the morning.

FREEZING LEVEL: 1800m, lifting to 2300m in the afternoon.

The weather tomorrow is hard to judge with high uncertainty of when the precipitation will start, how much rain there will be and at what elevation it may snow. Computer generated models predict approximately 10mm of precipitation across the range - mostly from the late afternoon and into the night to Thursday.

The only thing that seems certain is that the winds from the North will get strong.

Firm snow surfaces, exposed ice and rocks are widespread and will present a greater hazard than avalanches in areas previously exposed to the south-west gales. A slip or fall on steep terrain could have serious consequences, particularly above bluffs, in gullies or where runouts are confined.

Take extra care when travelling on hard snow, 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

• The snowpack structure is well understood.
• We are uncertain if precipitation will fall as rain or snow.
• We are uncertain due to the timing of the incoming weather system.