Two Thumbs

A lazy start tomorrow will help! Stay clear of steep lee terrain until it is possible to assess how much snow has accumulated and moved by the wind.

There will be some new wind slabs, especially in the South of the range.

Moderate

• The snowpack structure is well understood.
• We are uncertain about forecast snowfall amounts.
• We are uncertain due to the variability of wind effect on the snowpack.

No new avalanche observations.

From 12-13 Aug: Report of several loose wet and slab avalanches in neighbouring regions close to the main divide.

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.

All surfaces have gone through a melt-freeze cycle and the Northern half has softened in the sun, but will refreeze in clear nights. Only above approximately 2200m dry snow may have survived the warm weather. The crusts are mostly decomposed and the lower snowpack is well settled and consists of mainly meltforms or round crystals.

Snow depth varies from 40-50-cm, with deeper accumulations of 100-120cm in sheltered areas.

Northern end of range — north of Stag Saddle

The snowpack North of Stag Saddle is not well understood. We only have one observation from Monday 10 Aug from the area around Captains Peak and Mt Toby, reporting only slightly more snow than around Camp Stream or the Richmond Range, with very little old avlaanche debris observed. The group of recreationists did report a similar snowpack to the South.

A few showers, falling as snow above 500 metres, clearing about Mackenzie Basin by afternoon, but persisting as sleety showers in the north.

WIND AT 1000m: Southeasterly 30 km/h, but 50 km/h north of Mackenzie Basin. Becoming southeasterly 30 km/h everywhere in the evening.

WIND AT 2000m: Southerly 40 km/h, but 60 km/h north of Mackenzie Basin.

FREEZING LEVEL: 700m, rising to 1000m in the evening.

Most computer models predict around 5cm for the range, but with a Southeasterly, there are some indications a little more snow might fall. Already at 6pm on 15 Aug the Southern tip of the range has received 6-10 mm of rain in the valleys below Fox Peak and Mt Dobson ski fields (approximately 6-10cm of snow). 15cm of new snow might accumulate until Sun 16 Aug by midday.

All surfaces have had a solid melt-freeze cycle. Windward slopes will be stripped back to crust from any new snow by the morning. A slip or fall on steep terrain could have serious consequences. Many run out areas are now bare rock or scree.

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.