An avalanche accident fatality in southern East Tirol. Mostly moderate danger above 2200m.

 First avalanche fatality of this winter season

The course of the accident

Yesterday, 25.01.2023 a person lost his life in an avalanche beneath the Widerschwing on the Carnic Ridge. Four persons were involved in the avalanche, a group of 3 friends and a single person who followed the trio of friends through part of an ascending track. A few seconds before the avalanche triggered the trio heard a settling noise. The avalanche caught one of the trio and the single person in its path. Both persons were totally buried in snow masses. To the orographic right, a secondary avalanche triggered, thereby increasing the depths under which the two victims were buried. Through swift rescue assistance the person belonging to the trio was dug out of his 2.4-metre deep burial spot. The single person had no emergency equipment, and was not found until a probe located him at a depth of about 2 metres about 4 hours after the avalanche. Reanimation was undertaken. He was transported to the Innsbruck Clinic where he died the same day.

Overview of the avalanches below the Widerschwing. Rescue team is still engaged in probing. Inside the circle, both persons were ultimately found. The red arrow indicates the ascent track of the single person, the blue arrow, that of the trio. The main avalanche is right in the photo, the secondary release was left of it. The main avalanche is about 30 metres wide and 250 metres long. The secondary release measures a length of 75 metres to the main release. (photo: 25.01.2023)

To the right of the Alpine police, the two points of snow burial are visible, very close to each other. (photo: 26.01.2023) 

Investigations by the Alpine Police and Avalanche Warning Service were carried out with the help of a state helicopter. (photo: 26.01.2023)

Short accident analysis

Together with the Alpine Police we undertook the investigation today. The weak layer significant to the release consisted of faceted crystals which were embedded between two melt-freeze crusts that formed during the Christmas rainfall. This crust sandwich occurs only in a narrow band of altitude at 2200-2400m and demands attentiveness mainly on shady slopes. The previous periods of snowfall amounting to about 50cm were enhancing factors. Equally so was the heavy impact of the NE wind. Snowfall plus wind generated a slab atop the weak layer, which favoured the elongation of the fracture inside the weak layer.

Stability tests at the avalanche fracture. The terrain is 45° steep at that point. (photo: 26.01.2023)

One profile taken at the avalanche spot. The weak layer occurs between two melt-freeze crusts. The profile was taken orographically to the left of the secondary avalanche at 2350m. The steepness gradient was 33° there, the slope was west-facing.  Additional profiles can be found at lawis.at (profile from 26.01.2023)

In most parts of Tirol: moderate avalanche danger

Following an extended period of considerable avalanche danger, moderate danger currently prevails above 2200m in most parts of Tirol, below that altitude danger is low. The avalanche problems underlying the danger abide: a snowdrift problem and a persistent weak layer. The snowdrift problem requires attentiveness particularly in steep, shady ridgeline terrain.

Small slab near a ridgeline in northern Zillertal Alps (photo: 22.01.2023)

The persistent weak layer is distributed in diffuse ways. Avalanche prone locations are currently not very widespread. In steep terrain which until now is little tracked, a narrow band of altitude at 2200-2400m on shady slopes often evidences this problem. On west-facing and east-facing slopes we find problematic zones mostly above 2500m; even above 2300m particularly on west-facing slopes near ridgelines which are wind-loaded. Steep south-facing slopes have the problem above 2800m.

Snow profile, west, 2340m, 26° in the Glockturm Massif. There are numerous potential weak layers. Frequently there is no pronounced slab on top of it.  (profile from 26.01.2023) 

Slab avalanche on a south-facng slope at about 2900m near Schöntalspitze in Sellrain. The avalanche triggered on 25 January when a person was ascending. (photo: 26.01.2023) 

Powder snow and still too little snow for this juncture of the season

The last two rounds of precipitation brought us some snow, but for this point in the season there is still too little snow on the ground.

Snowfall on 19-21 January, particularly in the northern regions

From 21-24 January, southern regions received snowfall.

In bowls and with a little luck, a descent without hitting rocks is possible. Above view is typical of many regions in Tirol. (photo: 26.01.2023)

Last week enjoyed good powder and less rock contact in some regions. Eastern Tux Alps. 
(photo: 22.01.2023)

Where are conditions most wintery? Currently in southern East Tirol. (photo: 24.01.2023)

Super-light, fluffy snow and surface hoar

Due to the low temperatures and the NE air current, the snow fell as super-light, fluffy so-called “wild” snow wherever there was no wind. In extremely steep, sunny terrain, a sequence of loose-snow avalanches triggered in its wake. In the interim, wide expanses of surface hoar have formed in a certain band of altitude, particularly pronounced near the ceiling of high fogbanks.

Surface hoar in the eastern Tux Alps (photo: 24.01.2023)

During this last week we often had perfect pre-requisites for the process of radiation recrystallisation. Amid very cold temperatures, very dry air and intensive solar radiation, the light-fluffy snow stays that way on the snowpack surface, while the snowpack beneath it becomes moist. Due to nocturnal outgoing radiation, a thin melt-freeze crust forms. If conditions are unfavourable, weak layers can be generated near the melt-freeze crusts. (photo: 25.01.2023)

Fog over Inn Valley. This helps to form surface hoar during nights with clear skies. (photo: 26.01.2023)

Outlook

The really tenacious fog in the northern regions (often extending up to 2000 m) is a major determinant of current weather. It’s cold, winds are frequently strong. Starting on Monday, 30 January, the weather will undergo a radical change. A W/NW air current will bring us wintery and stormy conditions.

Starting next week, avalanche danger levels will rise rapidly. Avalanche accidents will become more likely. Visible in above photo: an avalanche below Padauner Mountain in the northern Zillertal Alps on a shady slope near the timberline on 22 January. (photo: 24.01.2023) 

What’s safe + what’s dangerous: often right next to each other. Most fresh snowdrifts are prone to triggering.

Cold, loose powder constitutes an explosively reactive weak layer

To round out the last blog we want to call your attention to the fact that freshly generated snowdrift accumulations are, as a rule, prone to triggering. This is because of the weak layer consisting of loose, cold powder snow. In wind-protected terrain this is amazingly light, fluffy snow. It bonds extremely poorly with the snowdrifts deposited on top of it. For a brief spell, i.e. several days, the cold, loose powder snow is highly reactive, i.e. threateningly malicious, much like surface hoar which is blanketed by fresher snow. For that reason, one often sees glide cracks when one treads the snowdrifts, or hears settling noises. In isolated cases, even remote triggerings are possible. In addition, naturally triggered avalanches have been reported. This is generally a case of a small-sized slab, but near ridgeline terrain sometimes medium-sized releases.

Extremely varied zones: safe + unsafe lie cheek-by-jowl

The snowpack is highly varied throughout the land. This applies both to the snowpack surface; to the snowpack layering; and to the distribution. It is the consequence of extremely diverse weather conditions this winter. Currently it is also a function of the highly fluctuating degree to which snow depths have grown and to wind impact.

72-hr difference in snow depths

Wind distribution on 22.01.2023, 5:00 am

One of the measurement stations where snowfall was heaviest, Puitegg/Gehrenspitze in the Mieming Massif. The spot where the station is located seems to have been wind-protected. Whereas at the wind-measurement device on Gehrenspitze, strong velocity NE winds were blowing.

In some places, like here in Virgen in Osttirol, winds extended down to the valley floor.

 Fascinating: the 15mm of precipitation during the last two days resulted in less than 50cm of fluffy fresh snow due to the low temperatures. Station Wilde Krimml in the western Kitzbühel Alps

Freshly generated snowdrifts in steep terrain: AVOID THEM!

Hone your skills, sharpen your ability to recognize freshly generated snowdrifts on-site, and rigourously circumvent them in steep terrain. To an increasing degree, these avalanche prone locations are above the forested zones; however as we just pointed out, in some places the wind extended down to low lying areas. Danger zones can also lie in steep forest clearances at far lower altitude, for example.

Wind impact at the edge of a forest. Hahnenkamm near Reutte (photo: 21.01.2023)

High proneness to triggering wherever cold, loose powder snow has been covered by snowdrifts.
Bergeralm, central Stubai Alps (photo: 21.01.2023)

Wind influence even in low lying areas like here inside town limits of Matrei in Osttirol (photo: 21.01.2023)

Persistent weak layer persists

To round out the last Blog: the snowdrift masses which accumulated due to heavy wind can constitute a slab in zones where the snowpack previously was loose / low in tension. Increasingly this was in shady terrain starting at about 2000-2200m. Also in sunny terrain, whenever a new slab forms, the likelihood of faceted layers bordering crusts triggering is heightened. This occurs particularly at altitudes starting at 2300-2500m.

Yes, superb powder descents are also possible!

Safe and Unsafe often lie right next to each other. What matters here is experience in assessing avalanche dangers on-site. That’s how to distinguish safe from unsafe zones. Then, fabulous powder descents are on the agenda.

Swishing in the western Kitzbühel Alps (photo: 21.01.2023)

Fresh snowdrifts easily triggered by winter sports enthusiasts. Persistent weak layer in places starting at 2200m.

 Main problem: fresh snowdrifts

Finally we have reached temperatures which are appropriate to the season. Currently we lie at the long-term mid-level of air temperature measurements for this juncture. Thus, the fresh fallen snow of recent days is frequently loose wherever there was no wind. And where wind was blowing, the fresh snow was swiftly transported. Freshly generated snowdrift accumulations are frequent, lying atop cold, loose fresh snow, a quite malicious (prone to triggering) weak layer which has existed in that state for only a few days. For that reason, winter sports enthusiasts can easily trigger avalanches; these are generally small but with ascending altitude increasingly medium-sized. Caution is urged most of all near ridgelines, behind abrupt discontinuities in the terrain and in steep gullies and bowls. Where winds are strong, even naturally triggered avalanches are conceivable. Currently, this applies to the eastern regions in particular.

Breathtaking snow plumes could be observed especially along the Main Alpine Ridge and in the typical foehn lanes at the beginning of the week. Stubai Glacier (photo: 16.01.2023)

Winds in the foehn lanes were conspicuous also below the treeline. Western Tux Alps (photo: 16.01.2023) 

Fresh, trigger-sensitive snowdrifts in the Kalkkögeln (photo: 16.01.2023)

Glide cracks in the snowpack can signal a potential snowdrift problem. Geigenkamm ( photo: 16.01.2023)

Starting on Sunday, 15 January, it turned colder. Winds from varying directions were blowing, predominantly at strong velocity.

Avalanches last week

On 12.01.2023, remote triggerings (one small and one medium-sized slab avalanche) were reported in the Samnaun Massif in the west. On the weekend (14-15 January) additional avalanches released which were provoked by a persistent weak layer. This occurred at altitudes above about 2200m in all aspects (for details see lawis.at). In the last few days it was the freshly generated snowdrifts which got triggered by winter sports enthusiasts. In isolated cases there were glide-snow slides on grass-covered slopes, particularly during and after the rain impact of 14 and 15 January.

Remote triggering in Samnaun Massif, 2750m, W (photo: 12.01.2023)

A slab avalanche that triggered near the ridgeline when skiers entered the slope. Greitspitze, Samnaun Massif along the Tirolean/Swiss border. 2700m, SE. Persistent weak layer (photo: 14.01.2023)

Slab avalanche in Rettenbachtal due to persistent weak layer. SE. 2200m (photo: 14.01.2023)

Slab avalanche near ridgeline when skiers entered the extremely steep east-facing slope at 2800m.
Persistent weak layer (photo: 14.01.2023)

Glide-snow slides in Ausserfern (photo: 14.01.2023)

The snowpack

There wasn’t really much fresh snow that fell this week. Mostly it amounted to 10-20 cm, more from place to place in the eastern regions. Frequently there was graupel embedded in the fresh snow. Along with the near-surface problem zones already mentioned (loose fresh snow as weak layer for the fresh snowdrifts deposited on top of it), there are also additional potential weak layers deeper down in the old snowpack. Generally these are faceted crystals near thin crusts or depth hoar/faceted crystals at ground level. In stability tests, partial fractures occurred in most results. Sometimes the entire snow cover was structured loosely; or else there was a slab. Nonetheless, there still exist zones which are prone to triggering, increasingly in terrain which has not yet been tracked. These are mostly shady slopes above 2200m and sunny slopes above 2500m. Transitions from shallow to deep snow are considered zones where there is heightened likelihood of triggering. The steeper the slope, the higher the chances a slab avalanche will trigger in the old snow.

A frequent guest during recent rounds of snowfall: graupel. Venediger Massif (photo: 18.01.2023)

Snow profile in Glockturm Massif: N, 2480m, 26° from 19.01.2023.
Quite typical: weak base, but still only partial fracture.

48-hr snow depth difference from 17.01.2023

48-hr snow depth difference from 19.01.2023

Quite unusual this winter: frequent rainfall up to high altitudes, e.g. here in the Arlberg region.

We continue to see below-average snow depths at all measurement stations (upper graph). Middle graph: measured fresh snow. Lower graph: this years’s temperature fluctuations and difference from medium values.

Heightened risk of falling into a crevice continues on the glaciers. Venediger Massif (photo: 12.01.2023)

Outlook

According to Geosphere Austria (formerly ZAMG), cloudy, windy, cold days lie ahead of us. The predominant snowdrift problem will persist. Caution: loose powder snow which has been blanketed by freshly generated snowdrift accumulations is still especially prone to triggering. For that reason, rigourously circumvent fresh snowdrift accumulations in steep terrain.

Rough-hewn picture of coming weather conditions...  Western Karwendel (photo: 19.01.2023)

Sequence of warm-cold fronts. Very windy. Ongoing: persistent weak layer and snowdrift problem.

 Highly variable conditions

The best way to describe the current weather, snow and avalanche situation is with the phrase “highly variable.” Last week was marked by a sequence of warm and cold fronts, repeated snowfall, most of it in the western regions and in northern East Tirol, maximum 50-75 cm, but generally 30-50 cm. Strong to storm-strength winds were always blowing, initially from the south, then from the west.

The strong-velocity winds transported masses of snow at high altitudes, and that is precisely how the terrain now looks: windblown zones alternate with wind-loaded zones (gullies and bowls). The overall impression that there is simply too little snow for this juncture of the season is not illusory.


Highly variable: the snowpack

Heavily wind-impacted snow cover in the eastern Lechtal Alps (photo: 12.01.2023)

 

Similar shot in the northern Zillertal Alps (photo: 11.01.2023)

Storm above the timberline. Venediger Massif (photo: 10.01.2023)

In the Kitzbüheler Alps (photo: 11.01.2023)

Cornices forming on the ridgeline. Samnaun Massif (photo: 10.01.2023)

Highly variable: the weather

Galzig on the Arlberg numbered among the stations with the most snowfall registered.  Besides the striking rise in snow depth on 9-10 January, the up-and-down temperatures are clearly visible. In addition there were repeated bouts of precipitation, sometimes as rain all the way up to the Galzig.

72-hr snow depth change on 09.01 and 12.01.2023

In the high mountains, strong to storm-strength winds from varying directions were blowing.

Highly variable: the snowpack


The results of stability analysis: a snowpack of medium stability tended to dominate. But reports of settling noises and glide cracks, particularly at altitudes of 2000-2400 m, have become more frequent over the last few days. The weak layer was usually a thin, loose, generally faceted layer above or below thin surface-near melt-freeze crusts. Atop of that lay the fresh snow and snowdrifts of recent days. Elsewhere there were loose layers near ground level. These were found most of all in wind-protected bowls over widespread terrain, and were quite cohesive. Graupel was often discovered inside the layers of fresh snow and snowdrifts.

Snowpack analysis on Stubai Glacier. Highly variable weather conditions are reflected in the snowpack: a sequence of hardened and softened layers, wind-crusts and melt-freeze crusts, and repeated layers of expansively metamorphosed crystals. (photo: 11.02.2023)

Profile near Löchelspitze in the Allgau Alps: the recent round of fresh snow is visible, beneath that a sequence of crusts, harder and softer layers. (photo: 11.01.2023)

The snowpack surface is wildly irregular. Samnaun Massif (photo: 10.01.2023)

Highly variable: avalanche activity


Over the course of this last week, a number of avalanches were observed: loose-snow, glide-snow and slab avalanches. All in all, there were not so very many. The loose-snow and glide-snow avalanches released mostly after the snowfall on 9-10 January when weather conditions improved and temperatures rose. Slab avalanches were mostly medium-sized. One interesting release was reported from the Saumspitze in the Arlberg region, where a large-sized slab avalanche triggered naturally in early afternoon on 6 January in shady high alpine terrain. On the previous day, lots of snowdrifts were deposited there as a result of the strong westerly winds. At the time of the avalanche the wind had slackened off significantly, but the temperature had risen.

Large-sized naturally triggered slab avalanche below the Saumspitze (photo: 06.01.2023)

In an avalanche release near the Stubai Wildspitze on 10 January, 5 persons were buried by a slab avalanche. Two persons were injured, one person suffered from hypothermia. The investigations of the Alpine Police showed that at the time of the accident 19 persons were in the zone of a large wind-hole digging snow-spots for protection. The slab avalanche triggered at a width of about 30 metres and a length of about 10 metres. Thanks to a swift rescue operation, the worst was avoided.

Slab avalanche Stubai Wildspitze at about 3150 m. The circles roughly depict the zones where the snow-spots were dug. (photo: 11.01.2023)

 
Our own on-site snowpack analysis produced an interesting picture: while the recent snowfall was being deposited, inside the masses of fresh snow and snowdrifts were repeated packages of graupel. We found up to 3 different layers of graupel on-site. With a high degree of probability, these layers of graupel were the likely cause of the avalanche. The bowl-like terrain favoured the deposit of thick graupel layers due to the sliding of these grains from extremely steep into flatter areas. The report of one observer on-site was also interesting. In the entire area there were 25 artificial triggerings through explosives but with very little success.

In this profile at the uppermost fracture point of the avalanche there were two thin layers in which graupel grains were deposited. Beneath them, also a very thin layer atop a very thin melt-freeze crust.
(profile from 11.01.2023)

The tiny ellipse at left shows the point of the accident from an overview (c) tiris

Highly variable: that’s how it will continue...


Just the way this last week wrapped up, that’s the way the next week will unfold: highly variable.