Stormy, snowy days – high avalanche danger in places

End of 2018 / Beginning of 2019: Stormy and Snowy

The start of the new year is storm-ridden (windspeeds of 180 km/hr in the southern Ötztal Alps) throughout Tirol, and there is lots of fresh snow in many places. In coming days the ZAMG weather service forecasts additional, at times very heavy snowfall, with the focal point east of Wipp Valley and northern East Tirol.

Illustrative of last week: the Hahnenkamm-Ehrenbachhöhe weather station in the Kitzbühel Alps. Weather deterioration starting on 30.12 amidst precipitation and wind.

Southern East Tirol ended up with practically no snow.

Snow plumes showcased wide-ranging snow transport throughout the land, as here in the northern Stubai Alps.  (photo: 01.01.2019)

Matrei Tauernhaus in the Venediger range during heavy snowfall and stormy winds. The stark gradients of snow depths towards the south are interesting. While here at the southern portal of the Felbertauern there was 40 cm of fresh snow on 01.01/02.01, in Matrei in East Tirol there was barely 5 cm.  (photo: 02.01.2019)

Extremely interesting,  quite seldom: the snow balls formed by the storm-strength winds in the free spaces in Kals (also behind the church).  (photo: 31.12.2018)

Snowpack development

A precise-as-possible depiction of snowpack layering is crucial before intensive precipitation. Currently the problem areas inside the snowpack are concentrated on the layers nearest to the upper surface. More deeply embedded graupel can also play an important role.

Yesterday on 02.01 during the snowfall: a thick layer of graupel was deposited in some places; this is now a potential weak layer for coming rounds of snowfall. Graupel was observed throughout Tirol. Kaiserbachtal  (photo: 02.01.2019)

Furthermore, covered powder snow is a temporary weak layer for the drifted masses which have been deposited on top of it. This can frequently be observed during intensive snowfall when temperatures are low.

Superficial slab on a gliding snowpack, recognizable by the glide cracks. Ausserfern  (photo: 29.12.2018)

The old-snow problem in the central sections of the snowpack referred to repeatedly in the most recent blogs seems in the interim to have shrunk to relatively narrow aspects and altitude bands. It is focused on the inneralpine regions, such as central East Tirol, where we assume potential problem zones on south-facing slopes between about 2400 and 2600 m and on north-facing slopes between about 2200 and 2600 m (in some places up to 2800 m). These zones are not usually cohesively connected over widespread areas.

A backcountry skier was ascending when an avalanche was triggered. The person remained unhurt. Gaishörndl, Villgratental.  Limited-terrain old-snow problem  (photo: 01.01.2019)

The snowpack’s proneness to triggering has diminished in these areas due to the temperature development, including warm phases. Nevertheless, we still have to expect these layers to fracture, at very least in the regions where precipitation has been heaviest. Deep persistent weak layers which formed on north-facing slopes on glaciers in autumn, can in all likelihood now be triggered only in highly unusual cases, i.e. through the additional loading of an avalanche which forms at altitudes above them in those regions where snowfall has been heaviest.

Typical of recent days: highly fluctuating temperatures. This was particularly striking in the northern regions, where  there was drizzling rain as far up as 2200 m for a brief interim.

The snowpack over the course of this last week was moistened on the surface: unbonded-snow avalanches on 27.12.2018 near the Pleisenspitze in the Karwendel. All in all, it had a positive impact on snowpack stability.  (photo: 28.12.2018)

Outlook

The ZAMG weather forecasting institute has issued a heavy snowfall warning for the morning of 04.01 until 07.01.2019, with more than 100 cm of fresh snow expected from region to region.

Eastern regions got the brunt of the snowfall.

Avalanche danger is increasing to high in the indicated regions. We expect increasingly frequent naturally triggered avalanches, particularly on leeward, very steep slopes adjacent to ridgelines and below rocky zones. The avalanches can easily reach large size (sizes 3-5) and even very large size (sizes 4-5).

Detailed forecast for the Venediger range: ongoing snowfall and continuing strong-velocity winds.

Already yesterday (02.01) and again today (03.01) several large-sized avalanches were triggered. Such releases occurred frequently in the regions along the eastern sector of the Main Alpine Ridge.

Naturally triggered avalanche in the Zillergrund. Further avalanches can be expected during the coming days in these regions, particularly where snowfall is heaviest.  (photo: 03.01.2019)

One thing is certain: during the next few days, massive traffic jams are on the agenda.

In the end, we appeal to all backcountry skiers and freeriders: whoever is en route in outlying terrain needs profound knowledge of avalanche risks and should behave highly defensively. We advise the inexperienced to remain on the secured and marked ski runs over the coming days.

From region to region, there is still a lot more snowfall on the way...Lampsenspitze. Northern Stubai Alps  (photo: 03.01.2019)

Numerous trigger-sensitive snowdrifts above timberline. We recommend enormous restraint in steep terrain.

Caution: 

Similar to 25.12.2018, the first day of the new year 01.01.2019 as "first fine-weather day" following a period of stormy snowfall is also an accident-prone day.

Snowfall and storm winds:

During the last two days in North Tirol and in northern East Tirol, there has been snowfall accompanied by formidable winds. The focal point of the snowfall was in the Lower Inn Valley and in northern East Tirol, where at high altitudes there was mostly 50 cm, but also as much as 100 cm of fresh snow registered.

Top windspeed velocities of 100 km/hr were not seldom in the mountains of Tirol in recent days. A great deal of snowfall was transported.

Trigger-sensitive snowpack:

Starting at the upper rim of the timberline the snowpack is prone to triggering. This has been corroborated by reports from skiers in these regions on New Year's Eve who observed both settling noises and glide cracks. In the Kitzbühel Alps on 31.12, skiers triggered an avalanche in shady terrain north of the 3S-Station near Jochberg. Nothing serious occurred. At 17:25 a report arrived at headquarters that near the Unterfaister Niederalm near Söll, an avalanche was released. We do not yet have any additional details

We also know that yesterday, 30.12, graupel showers moved over the land. Graupel, which is to say, powder snow blanketed by snowdrifts, currently comprise a rather wide-ranging and primal weak layer for slab avalanches. Secondarily, the faceted layers in the vicinity of crusts can also be triggered. Their typical altitude band: 2200 m to 2700 m, especially in the inneralpine regions and in the northern and central sectors of East Tirol. This includes all aspects. The altitude band in sunny terrain above about 2400 m is especially endangered.

To sum it up:
Whoever is currently in outlying terrain needs to have extensive avalanche knowledge and be defensively active, particularly above the timberline. Freshly generated snowdrift accumulations in steep terrain should be circumvented!

Outlook:

Wintery conditions are coming, also in southern East Tirol. For those engaged in winter sports, the conditions above the timberline are frequently treacherous. Additional information will be supplied in the course of the week.

Avalanche events of recent days

This blog entry is intended to provide a brief overview of the avalanche events of the last few days. For details, please consult here: most of these events occurred in the regions which are currently ranked with "considerable danger" (in addition in the Arlberg region).

In those regions in an altitude band between 2200 and 2700 m, there is an old snow problem in all aspects: in the middle section of the snowpack and near to the ground there are repeated layers of unbonded, faceted crystals, often in the vicinity of crusts. These loosely-packed crystals are the weak layer, on top of which is deposited a snowpack bearing formidable effects of wind from recent days. Snowdrifts, a weak layer and the additional weight of skiers and freeriders, and sometimes even the additional burden of solar radiation are the pre-requisites of the slab avalanches which were observed.

Avalanche accident Hohe Mut on 25.12. This was a very large slab avalanche. A snowboarder lost her life. A second person was able to escape to the orographic right. Fracture zone 2600 m, SW, parts 40°. Also visible is a second, remotely-triggered avalanche at the right upper edge of the photo. (photo: 26.12.2018)

Hohe Mut: view from the path of the avalanche towards Rotmoostal  (photo: 26.12.2018)

Hohe Mut: this snow profile was taken near the fracture of the avalanche. It reveals superficial snowdrifts and beneath that, a sequence of crusts and faceted crystals.  (photo: 26.12.2018)

Hohe Mut: place of burial (photo: 26.12.2018)

Some of the avalanches reported were remotely triggered:

Rastkogel: left of the avalanche, skiers escape the path. On the right, a slab avalanche triggers. (photo: 26.12.2018)

Avalanches on Zischgeles, presumably triggered by skiers and remotely triggered  (photo: 26.12.2018)

Avalanche Hoher Burgstall on 27.12: a backcountry skier was ascending when an avalanche triggered.  (photo: 27.12.2018)

Avalanche accident Weisser Knoten in the Grossglockner region. Four persons involved, no injuries.  (photo: 25.12.2018)

Glide-snow avalanches are a potential problem primarily where snowfall has been heavy, such as here in the Arlberg region.  (photo: 26.12.2018)

In southern East Tirol, in photo the Villgraten mountains, the snowdrifts are less deep than further north.  (photo: 25.12.2018)

In extremely steep terrain, a skier triggered this superficial avalanche today (27.12) below the Talsenhöhe in the Kitzbühel Alps, fresh snow, snowdrifts on top of a hardened rain crust. The person was apparently able to escape. (If the avalanche had been registered by calling tel. no. 140, we could have spared ourselves the expensive and arduous search party.)

Attentive observer on Pfuitjöchl. This avalanche is a moist unbonded-snow avalanche resulting from solar radiation and daytime warming.  (photo: 26.12.2018)

Outlook:

The old-snow problem will remain upright for a while. For that reason, we recommend all backcountry skiers and freeriders to avoid terrain which is very steep in the infamous zones.

Elsewhere, conditions are in general quite favourable. Only the snow quality leaves much to be desired.

As a consequence of the intensifying winds forecast by the ZAMG weather services for the weekend, however, increased attentiveness will be demanded by the fresh snow, particularly at higher altitudes.

Avalanches involving persons, one fatality. Cause: fresh snowdrifts and weak old snow.

At headquarters in Tirol today we were informed about 6 avalanches in which people were involved: Glorer Refuge and Marchkinkelle in East Tirol; Rettenbachferner Glacier, Serleskamm, Giggijoch and Hohe Mut in North Tirol. The last of these took human life. According to initial information of the Alpine Police, it was a large-scale release below the Hohe Mut in open ski terrain. This suggests a marked old-snow problem. Tomorrow, 26.12, we will investigate the incident together with the Alpine Police. For initial details, please click here:

Avalanche Hohe Mut on 25.12.2018. The ellipse shows the slope where the accident took place below the Hohe Mut in Obergurgl in open skiing terrain.

Strong-to-stormy wind influence in the mountains was striking on 25.12. In many places, snow plumes were observed in the vicinity of ridgelines. According to ZAMG weather headquarters, the winds are expected to slacken off.

The main danger in the coming days will stem from freshly generated snowdrifts which need to be assessed critically in steep terrain. Particular caution is essential at altitudes between about 2200 and 2700 m, since long-persistent weak layers are evident inside the snowpack near crusts there. Special attention is also called to the terrain adjacent to ridgelines, in gullies and bowls, where unbonded powder snow or fresh snow harbors deposited graupel which can serve as a (short-lived) weak layer for slab avalanches.

 Snow transport on Hohe Tor above Kals (photo: 25.12.2018)

Cornices on the Navis Kreuzjöchl in the Tux Alps  (photo: 25.12.2018)

Caution: beautiful weather after stormy period is particularly accident prone

The forecasts of the ZAMG weather service were correct. There has been much rainfall and snowfall in far reaching regions of Tirol. In addition, storm-strength NW winds were blowing in many regions at high altitude.

All in all over the last few days in the western regions of the land, there was at least 50 cm of fresh snow registered at high altitude, frequently 70 cm in the southwestern regions, and from place to place as much as 100 cm.

Disparites in overall snow depth. Some weather stations are at altitudes where there was persistent rainfall.

Precipitation distribution from 23.12 to 24.12, morning, for comparison

The rise in temperatures (rainfall up to 2000 to 2600 m) combined with precipitation and snowfall together with storm winds have weakened the snowpack. Up to intermediate altitudes, increasingly frequent wet unbonded-snow and glide-snow avalanches were reported. At high altitudes, naturally triggered avalanches released. These were large-sized,  triggered in all aspects, primarily in the western and southwestern regions of the land. The major activity was between yesterday 23.12 and today, 24.12, during the morning.


The weak layer was the graupel registered over wide-ranging areas yesterday on 23.12 . In addition, the faceted crystals near the crusts also played a role in the release of slab avalanches (sh. Schneeprofile).
The fact that some slab avalanches were also triggered on south-facing slopes at altitudes between 2300 and 2700 m points to the generation of danger pattern "cold on warm" since the beginning of December.

Upshot: particularly at altitudes between about 2200 and 2700 m in the middle part of the snowpack, or else near ground level, there are persistent weak layers, i.e. the beginning of an old-snow problem, which could prove triggerable over the coming few days. At higher altitudes, the covered (that is, drifted) powder snow could prove to be a weak layer, particularly adjacent to ridgelines on very steep, wind-protected slopes. Atop these weak layers, deep, brittle drifted masses have been deposited which increasingly in transitions from shallow to deep snow and, in general, wherever the snow is shallow, can be triggered.

Due to the quite widespread danger zones and the period of pleasant weather conditions which is being forecast over the Christmas holidays, we expect heightened likelihood of avalanche accidents. Today, on 24.12, we were informed at headquarters of one in Söll and one in the Axamer Lizum, the latter near to a ridgeline in very steep terrain on an east-facing slope at about 2200 m. Both proved relatively harmless, according to our current information. We hope these avalanche releases will inspire backcountry skiers to ski defensively on Christmas Day and in the days following. Don’t forget: experience shows that the first day of pleasant weather following a stormy period is particularly prone to accidents.