Persistent weak layer is still the dominant problem. Danger zones start at 2200 m.

 Danger zones hard to spot, even for experts

Avalanche danger in the western regions of North Tirol and in northern East Tirol above 2200m and above 2400m continues to be considerable. The underlying problem is the persistent weak layer. That means we are confronted with weak layers in the old snowpack which remain prone to triggering for an extended period of time. Specifically, we are seeing faceted crystals and depth hoar in layers near the ground. These layers often border up against thin crusts. Danger zones are found increasingly on W/N/E facing slopes above 2200m / 2400m and on south-facing slopes above about 2800m.

Typical of the current situation is the highly varied nature of snow depths, but also snow quality: transitions from deep to shallow snow fluctuate just as zones with good and poor snowpack stability. Yet it is also typical of the current situation that the danger zones are really hard to recognize, even for professionals. That means, experience in assessing avalanche danger, together with immense restraint in outlying terrain, are crucial factors when you are en route.

Weak layer of depth hoar near the ground which can easily be disturbed. Profile from 26.12.2022 
(for further details, see lawis.at)

Snow profile northern Zillertal Alps. 2250m. North. 32°. In stability tests here, no fracture could be generated. Profile from 28.12.2022 (for further details, see lawis.at)

Snow profile Sellrain Mountains. 2520m. NE. 25°. Fracture of snowpack near the ground in a faceted layer just beneath a thin melt-freeze crust. (for details, see lawis.at)

Becoming rare: remote triggerings of slab avalanches, like here in Kleines Königtal in the Gurgl Massif on 28.12.2022.

Danger zones are still found in the immediate vicinity of ski runs. Samnaun Massif. (photo: 29.12.2022)

More favorable: conditions in the southern regions of North Tirol (apart from northern East Tirol). The problem here is the lack of snow.

Snow depths: (way) below average for the time of year

Some of our observation stations have been in operation since the Avalanche Warning Service Tirol was established in 1960. We extend an enormous vote of thanks to our observers over many years. If you look at the current snow depths there, we have descended below the minimum ever recorded.

Observation station Obergurgl: maximum, medium, minimum overall snow depth until now. Magenta line is the season 2022-23. Never before since measurements have been recorded has there been so little snow on the ground.

Observation station Obertilliach: also here, overall snow depth for the season is below average.

Not much snow in open terrain. During a descent heightened risk of injury from rocks sticking out of the snow (or just barely concealed). Grieskogel Massif. (photo: 28.12.2022)

The thaw around Christmas included rain and had an awful impact on the snowpack in most regions of Tirol. Mieming Massif  (photo: 25.12.2022)

Last week’s weather in western regions: initially lots of precipitation including rainfall (up to 2300m). Minor cold front on 26-27.12. Then dry weather (for this juncture of the season) and above average temperatures.

Low and intermediate altitudes are frequently bare of snow. View towards Kaunergrat. (photo: 29.12.2022)

What’s next? Very high temperatures!

The ZAMG Weather Service predicts unusually high temperatures for the next few days. Thus, the year 2022 will end (and go down in history) as the warmest year in the history of measurements, which goes back more than 250 years. Last year also broke some temperature records. This year might break them again. Since there is hardly any snow on the ground at low and intermediate altitudes, the high temperatures will probably not have grave effects on avalanche danger levels. However, we expect increasingly frequent glide-snow and possibly wet-snow slides on sunny slopes and grass-covered terrain. Outside of that, the persistent weak layer will incrementally diminish, unless it becomes so warm and the air so moist that water penetrates down to the ground level layers and leads to heightened proneness to trigger. That is unpredictable at the moment, it simply remains a possible implication.

As a result of higher temperatures, glide-snow activity will increase again. (photo: 29.12.2022)

The entire team at Avalanche Warning Service Tirol wishes everyone good health and no accidents in the year 2023!

Good explosion triggerings and triggerings by persons confirm: snowpack still weak

Treacherous avalanche situation continues

Right off the bat: particularly in the western regions, but also in northern East Tirol, we have a tenacious problem with a persistent weak layer which is quite pronounced. This problem begins at about 2200m (generally at 2400m), to start with on shady slopes, later frequently on west-facing and east-facing slopes. Above about 2700m it is found increasingly on south-facing slopes.

This is confirmed by stability tests, also by slab avalanches which have been triggered by winter sports enthusiasts and in some regions by successful artificial triggerings through explosives over the last few days. The artificial triggerings were reported to us from the western regions where snowfall was heaviest.

Slab avalanches were triggered due to the well formed “slab” (snowfall, warmth, wind) which was quite extensive in places and occurs repeatedly in seasons when the snow depths are below average.

The situation is treacherous also because the avalanche prone locations in outlying terrain are difficult to recognize and distributed in highly irregular fashion. In addition, we observe high variations not only in snow depths, but also in snowpack stability.

A brief review of the last few days:

From the evening of 23.12 through 25.12.2022 in western regions, the Danger Level was “high” - level 4. This was the “winter sports high” we wrote about.

Dias/Kappl weather station in the west where snowfall was heaviest. About 50cm of fresh snow at high altitudes. Rising temperatures during the snowfall. On 25.12 fine weather, then a small cold front with winds, subsequently improved weather.

At low and intermediate altitudes  rainfall melted the snow. Rainfall level was  mostly around 2300m. Above 2200-2400m 30-50cm of fresh snow was registered, mostly in western regions, more from place to place.

A few avalanches triggered by winter sports enthusiasts

We were lucky in Tirol that over the Christmas holidays no one suffered injuries from avalanches. We are aware of several avalanche releases which involved winter sports enthusiasts. Here a brief selection:

Avalanche release Lampsenspitze on 25.12.2022. NE, 2700m. The person could evade it.
(photo: 25.12.2022)

Another avalanche on the Lampsenspitze on 26.12.2022. East, 2840m. No one caught. (photo: 26.12.2022

Lukas Ruetz, one of our observers, researched avalanche releases with large-scale lens web cameras near the Pirchkogel and Hinteren Grieskogel. Red ellipse: naturally triggered avalanche at 10:40 am. Turquoise ellipse: naturally triggered avalanche at 11:10 am. Green ellipse: avalanche released by winter sports enthusiasts at 1:00 pm. 2600m, N and E.

Photo of Pirchkogel fracture / Hr. Grieskogel at 2660 N. Encircled: ascent and descent track of a winter sports enthusiast. All evidence points to the avalanche having been remotely triggered by the person in the area of the circle. (photo: 26.12.2022)

Underlying this theory regarding the above avalanche is the significantly rising temperature during the day, which had an impact on the characteristics of the “slab.”

Encircled: temperature leap on 25.12.2022. Kühtai weather station in the vicinity of avalanche.

 

In the immediate vicinity of the Pirchkogel avalanche, a slab avalanche was triggered as a winter sports enthusiast was descending near the encircled area. 2595m NE (photo: 26.12.2022)

An avalanche release on Tiefenbachferner glacier. 2830m, NE. The skier was able to ski out of the plummet path but did not report it to headquarters (tel. no. 140). Only after a big rescue operation was the emergency search terminated. (photo: 25.12.2022)

Avalanche release Rietzer Griesskogel on 27.12.2022. Avalanche was remotely triggered during the ascent. A person was partially buried. 2700m, SW

Avalanche release Weisser Knoten in the Glockner Massif on 27.12.2022. The fracture expanded orographically left. Appx. 2600m, E

Avalanche operation due to a glide-snow avalanche of artificial snow near Untermarkter Alm in Hochimst (photo: 27.12.2022). The operation was terminated in the evening after all signs pointed to no one having been buried. (Incidentally, on 05.12.2018 on the very same spot, another such glide-snow avalanche of artificial snow was triggered.) 

On Carnic Ridge: glide-snow slide on steep grass-covered slopes. (photo: 26.12.2022)

Winds were briefly blowing at very strong velocity at high altitudes. Above, snow transport in the Gurgl Massif. (photo: 26.12.2022)

Outlook

The regionally quite treacherous avalanche situation will continue. The recently formed “slab” is still quite pronounced, thus, virtually demanding expansion of a release upon fracture in the weak layer of the snowpack. For that reason we recommend level-headed restraint in outlying terrain. Besides, due to the poor snow situation, conditions for skiing and freeriding tours are  rather bad in general.

One more plea to all winter sports enthusiasts: 1st fine-weather day after windblown precipitation is accident-prone!

“Lump Risk” : the snowpack is prone to triggering - brilliant and fine weather - high likelihood of avalanche releases involving persons! Caution urged particularly in Tirol’s western regions above 2400 m.

Once the clouds and the fogbanks have dispersed, particularly in the northern regions, Christmas Day according to ZAMG Weather Service will be brilliantly beautiful. In the western regions where there has been 30 to 50 cm of fresh snow registered above 2400 m since 23.12, locally more, we now have a treacherous situation: “winter-sports high” avalanche danger. Atop an often weak old snowpack there is now fresh snow deposited, winds and warmth have formed a pronounced slab. For tomorrow, 25.12, we foresee an extremely trigger-sensitive snowpack in very steep terrain above 2400 m (the rainfall level over recent days). Increasingly on W/N/E facing slopes and in general near ridgelines. On south-facing slopes the snowpack is prone to triggering only in high alpine regions. Even remote triggerings are possible because the slab is so pronounced. Therefore: keep distances, especially on very steep W/N/E facing slopes at high altitude. Especially on north facing slopes.

Christmas Day will be an accident-prone day, particularly in the western regions.

Turbulent weather: snowfall, rainfall, wind & warmth. Increase of avalanche danger to “winter sports high”

Significant increase in avalanche danger

Warm front and cold front

A warm front will bring instabile, stormy and very mild mountain weather our way on Friday, 23.12.2022, according to ZAMG Weather Service Innsbruck. In places there will be intensive precipitation, in many places below about 2000 m as rain. Precipitation will be most intensive in the western part of North Tirol: 30-50 mm is expected there on 23.12. This correspondes to about 30-50 cm of fresh snow. On Christmas Eve, 24.12, a cold front will follow on its heels. In the morning, frequent snowfall and rainfall in North Tirol and in the northern regions of East Tirol. In the afternoon it will slacken off. Southern East Tirol will get hardly any precipitation.

Forecast fresh snow over the next few days. Precipitation gradient from west to southeast.

Precipitation will frequently be accompanied by strong to storm-strength winds.

Snowfall level at midnight, 23 December

Snowfall level will ascend during the course of the day. Above: snowfall level at 4:00 pm on 23.12.2022

Precipitation and wind forecast for one region where it will be heaviest. Precipitation will begin during the night of 22.12 and persist until Christmas Eve. Strong winds. Fluctuating temperatures.

Impact on avalanche danger

Currently we expect a significant increase in avalanche danger during the course of the day. If the forecast amounts of precipitation occur, Danger Level 4 (high) will be reached in the afternoon / early evening. This is a so-called “winter-sports high” – the snowpack is weak and prone to triggering; there are numerous danger zones; the likelihood is great that winter sports enthusiasts can trigger slab avalanches. In addition, we expect naturally triggered avalanches. Most will be medium-sized (typical magnitude of skier’s avalanche). Especially on shady slopes, these can grow to large size. Here are the reasons:

• Wherever it snows, the snow will initially fall at lower temperatures. During the snowfall temperatures will rise. Thereby, warm snowfall will be deposited atop colder snowfall, i.e. a “slab” on a potentially weak layer. Depending on how much the temperature rises, the snowpack will be weakened with varying swiftness. Small-to-medium avalanches will release naturally, more and more as the temperature rises. The “slab” will release ever larger masses of snow. That slab also heightens the likelihood of remote triggerings.
• The old snowpack is weak in many places. This is increasingly the case on west-facing, north-facing and east-facing slopes above 2200 m. Fractures in the weak layers inside the old snowpack are possible from the impulse of naturally triggered superficial avalanches in the fresh fallen snow. On the other hand, this is possible “only” through the weight of fresh fallen snow. The old snowpack on north-facing slopes above 2200m is least favourable of all. On west-facing and east-facing slopes the old snowpack is triggerable above about 2400m. On south-facing slopes, this is the case mostly in high alpine terrain. If fractures occur in the old snowpack, the avalanches can grow to large size.
• In zones with rain impact the snowpack is moist or thoroughly wet already and will become wetter still. The snowpack will forfeit its firmness. We expect numerous wet loose-snow avalanches but also increasingly frequent glide-snow releases. Due to the shallow snowpack, most of these will be small sized, in isolated cases medium sized.

Impressions of the current situation

Cracks in the snowpack: the alarm signal for a trigger-sensitive snowpack. Sattelberg, 14.12.2022. The photo is more than a week old. In the meantime we have received few reports of glide cracks and whumpf noises.

At low and intermediate altitudes the snowpack is moist. (2nd graph above with temperature, thawing point and snow-surface temperature). The winds have intensified.

Due to higher temperatures and recent rainfall, increasingly frequent wet loose-snow avalanches and glide-snow slides have been observed.

Wet snowslide, north side of Kitzbühler Horn (photo: 20.12.2022)

Knobby powder snow - now gone, due to the rise in temperatures, Tux Alps (photo: 18.12.2022)

Profile near Hochzeiger, north, 2340 m. Weak layer near the ground which can fracture upon loading.

Sequence of hard and soft layers. Axamer Lizum, west, 2260 m, 28°. At this spot no thorough fractures were generated in our stability tests. (photo: 22.12.2022)

Winds have already intensified and transported snow at high altitudes. Above, snow plumes in the Gurgl Massif. (photo: 22.12.2022)

Treacherous and accident-prone days lie ahead for winter sports enthusiasts. Immense restraint is called for.

On Sunday, Christmas Day, 25.12, the weather will improve. It will remain mild. Please heed this warning: in the regions where the most snowfall occurs we will have a very tense avalanche situation. That is - as we all know - when most of the avalanche accidents occur, in that brief time window. Therefore, act defensively. The inexperienced are advised to remain on the secured ski runs.

Diffused persistent weak layer starting at 2000m – Some releases triggered by winter sports enthusiasts

Top priority: persistent weak layer still treacherous – danger zones also on sunny slopes

The persistent weak layer is still treacherous. It starts at about 2000m altitude, occurs mostly on shady slopes to begin with, with increasing altitude also on sunny slopes. This has been confirmed by several avalanches in the last few days which involved winter sports enthusiasts. As described in our last blog, we are dealing with below average amounts of snow on the ground. Avalanches triggered by winter sports enthusiasts are generally small-sized for that reason. Wherever winds have recently generated more snow, the avalanches are medium-sized. Caution: Because of the shallow snow, avalanches currently cause not only a risk of being swept along and forced to take a fall, but also heightened danger of injuries from protruding rocks.

Avalanche on Hoher Burgstall. Since it was uncertain whether persons were involved, an avalanche rescue operation was ordered. No one was buried. Please report negative avalanches to headquarters! Tel. no. 140. Thanks. (photo: 17.12.2022)

Avalanche Lampsenspitze (photo: 17.12.2022)

Avalanche triggering Hochgurgl (photo: 17.12.2022)

Slab avalanche near ski area St. Jakob i.D. (photo: 17.12.2022)

Due to higher temperatures, increasingly frequent glide-snow slides. Ausserfern (photo: 17.12.2022)

Unchanged: persistent weak layer starts at 2000 m - Fresh drifts at high altitude

 Peristent weak layer, still not enough snow

Starting at about 2000 m there are weak layers of faceted crystals inside the old snowpack. These often border against a crust. Frequently, a “crust sandwich” is observed: a weak layer between two crusts. For a slab avalanche, a hardened, deeper layer is required atop the weak layer, the so-called “slab.” Since there is still so little snow in many regions of Tirol, the slab is not pronounced. Due to the cold temperatures from 10-13 December, this snow has now changed, forfeited some of its firmness and thereby become less prone to triggering. That’s the reason behind the current decrease in avalanche danger from Level 3 (considerable) to Level 2 (moderate) above approximately 2000 m. 

Nevertheless, in wind-loaded gullies and bowls as well as ridgeline and pass areas above 2000 m, caution is still imperative. Wherever there is more snow, slabs can be triggered by winter sports enthusiasts. This is increasingly the case on shady slopes above 2000 m. At higher altitudes it also applies to sunny slopes.

    

Typical of the current snowpack layering: a sequence of crusts and softer layers (photo: 14.02.2022)

A crust sandwich on a 33° steep south-facing slope at 2250m in the western Verwall Massif. For slab avalanches, the slab is still lacking.

Typical of the current situation: not much snow. Nonetheless, avalanches can still be triggered by winter sports enthusiasts. In above photo: a small ridgeline slab in the Silvretta. (photo: 15.12.2022)

The slab of the previous photo, up close. Ridgeline fracture. Small avalanche. (photo: 15.12.2022)

The snow profile for the above photo: a faceted layer beneath a thin crust as weak layer: 2385m, NE, 35°. Profile from 15.12.2022

Ridgeline slab on a shady slope in the eastern Deferegger Alps (photo: 14.12.2022)

Not much snow

Little snow in the Tux Alps. Thus, heightened danger of injuries during a descent (photo: 15.12.2022)

Insufficient snow in the western Verwall Massif (photo: 15.12.2022)

A bit more wintery in northern East Tirol, but frequently one breaks through to the ground.
(photo: 12.12.2022)

We recommend...

It’s best on snowy grass-covered slopes, where there are no massively drifted areas or very steep zones. What matters more: the danger of injuries from “sharks” (rocks hidden beneath the surface) is far less.

Relatively more relaxed descents in spite of insufficient snow: photo from 11 December in Ausserfern.
The snow situation in the Kitzbühel Alps is better by comparison.

Instead of skiing tours or treks in outlying terrain, this slot in time might be used for advanced education, for example, training in beaming devices, first-aid, avalanche courses including equipment checks.

During an Avalanche Commission course, a variety of avalanche emergency situations were trained for with helicopter support, as visible above. (photo: 15.12.2022)

What’s the outlook?

According to ZAMG Weather Service we are about to get two minor bouts of precipitation, one from the southwest in a warm front, one from the northwest in a cold front. Anticipated amounts hover around 10 cm. On the weekend, conditions will improve: from Saturday to Sunday, clear nighttime skies are anticipated.

Precipitation on 15.12 starting in late afternoon

Thurntaler Measuring Station: Snowfall started in the evening. Winds were blowing above transport velocity. Fresh snowdrifts accumulated only at high altitudes (in contrast to the beginning of the week), were prone to triggering mostly on shady ridgeline slopes.

Snow forecast for 16.12.2022

Initially, not much change is expected in the avalanche situation. The treacherous persistent weak layer will stay with us. In addition, freshly generated snowdrifts at high altitudes need sharp attentiveness.