Two Thumbs

This storm has delivered mostly wind, some rain and very little snow. Frozen surfaces might pose the most significant risk tomorrow.

Just be aware that North of Stag Saddle, windslab avalanches will likely linger in more places and might be bigger.

We have no reports of any natural or human triggered avalanches in the last 2 days. The South of the Range has received very little snow so far. We have no reports or observations at all from North of Stag Saddle.

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

The snow depth in the range South of Stag Saddle is 40-60cm with some deeper pockets of 100-120cm in sheltered areas. With the rain on Thursday 30 July elevations below 1200-1300m have lost most of the snow. Initially, the rain might have reach to 2000m. Only a few cm of snow fell on Friday morning 31 July, mainly above 1700m.

The hurrican-force winds over the last 2 days (140km/h or more measured at Round Hill and Mt Dobson) from the Northwest have stripped (sublimated = snow turns directly into water vapor and "disappears" into the air) much of the old dry snow in the South of the range off the widespread crusts it was sitting on. Windward ridges are stripped back to rocks. Only in the sheltered higher bowls in the centre of the range & in the North on the Eastern half, some of the dry snow might have survived the wind and rain. Expect most surfaces to be stripped back to mostly supportive icy crusts. The skiff of snow from Friday morning has been blown away by the Southerly winds, and only some will have accumulated in sheltered pockets. Under the crust layers the snowpack is well consolidated.

Guides and ski fields have reported some sugary weak layers developing around the crusts. At present, this does not seem a problem in the South of the range.

The snowpack North of Stag Saddle is not well understood, with no direct observations. It is possible that above about 2000m very deep snow has accumulated in sheltered areas.

Isolated showers and snow to 400 metres, clearing to fine before dawn. Winds will be Southerly 30 km/h, dying out in the morning. However, at altitudes around 2000m, winds will still be strong to gale 65km/h before dying out.

However, only a few centimeters (maybe 5cm) of snow are forecast until Saturday morning.

Free air freezing level is at 500m, lifting to 900m in the afternoon.

We have received rain to higher elevations, then the temperatures dropped with much wind and refroze most surfaces. We expect a significant sliding danger, in particular in exposed terrain (=windward, steep & where you find signs of frozen rain under any new surface snow).

Ski crampons will be required! If you like to venture into more exposed terrain tomorrow, then bring an ice axe and boot crampons .

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.