Following good firn snow conditions, new burst of warmth + rainfall

In a nutshell...

After two days of flawless firn snow conditions and a daytime cycle of wet-snow avalanche danger, the weather is again becoming instable. On Saturday, 06.05, it will be a bit cooler, sunshine and clouds will alternate, showers and thunderstorms can pass through. On Sunday, 07.05, it will turn warm again, with a mixture of sunshine, clouds and thunderstorm showers. Thus, avalanche danger will vary greatly from region to region. Danger zones for wet-snow avalanches occur especially on steep shady slopes above 2600m wherever the snow is rather shallow. Where the reserves of cold are nearly used up inside the snowpack and there are faceted weak layers, naturally triggered avalanches are possible.

Review of recent days, outlook for the weekend

The snowpack was able to cool during the last few nights, a melt-freeze crust formed which was capable of bearing loads, it then softened up during the daytime all the way up to high alpine regions, depending on aspect, creating perfect firn-snow conditions.

Geisslehnscharte on 04.05: the long ascent was rewarded by perfect firn snow.

The small amount of information regarding snowpack conditions from profiles and snowpack models show that above 2600m on shady slopes, there are still reserves of cold in the snow cover. The deeper the snowpack is, the greater they are.

 

Snow profile from 04.05 on Geisslehnscharte: temperature variations inside the snowpack show that there are still reserves of cold. Snow depths are above average here.

At low altitudes and wherever there is less snow on the ground, even high-altitude shady slopes became wet for the first time this season. As we reported in the last blog, activity was at its highest on the weekend prior to 1 May. Also in the last few days, impressive photos have shown us the avalanches which released in this period.

 

Seen through the telescope: wet-snow avalanches at summit level, as seen here on Ochsenbug in East Tirol.

 

Large naturally triggered avalanche on the Seespitze, Schlick, Stubai Alps, presumably from Saturday, 29.04 or Sunday, 30.04.

 

Finally some good firn snow! But unfortunately it’s already passed. Due to weather developments in coming days, firn snow formation doesn’t stand a chance.

Following a night of clear skies on 3-4.05, the surface temperatures sank to -10°C. Due to higher daytime temperatures, it ascended noticeably (red arrow) and wasn’t above  to cool down as much at night on 5 May due to the high relative humidity.

A different weather station, an identical picture: following a night of clear skies on 3-4 May, the surface temperature descended to -10°C. Due to daytime warmth it rose visibly (red arrow) and wasn’t above  to cool down as much at night on 5 May due to the high relative humidity.

Reduced nocturnal outgoing radiation, thunderstorms, higher daytime temperatures are again weakening the snowpack, especially where it wasn’t yet thoroughly wet. Snow quality and snowpack stability will be poor to very poor. Danger zones for wet-snow avalanches occur esp. on steep shady slopes above 2600m where the snow is shallow. Where the temperature reserves inside ths snowpack are used up and there are faceted layers, naturally triggered avalanches will be possible.

To finish up, two photos of the snowpack:

Whereas in glacer zones there is still sufficient snow for winter sports...

...in others it’s hard to find the way down to the valley.