Main danger: loose-snow avalanches + small snowdrift accumulations in high-alpine shady ridgeline steep terrain

Ongoing quite favorable conditions, slight daytime increase in danger

The big message: currently (28.04) there are very few avalanche problems. Loose-snow avalanches on extremely steep slopes and small fresh snowdrifts in high-alpine shady terrain are the main dangers. During the course of the day the snowpack surface softens on sunny slopes and loses some of its firmness.

Loose-snow slides in extremely steep terrain. Stubai glacier. (photo: 28.04.2022)

Shallow slab in extremely steep shady terrain below Vordere Jamspitze, Silvretta, 2900m, N/NE. Encircled: thin crust which formed on 25.04. Below it, a thin weak layer formed in a short time due to big temperature contrasts (danger pattern “cold on warm”). This problem crops up only in very isolated cases, the slab which forms above the weak layer is usually not pronounced. Caution urged in immediate Ridgeline terrain.

Weather review

Last week did honor to the month of April. Repeated bouts of precipitation, often strong-velocity winds from varying directions, rather cool for this juncture of the season. Starting on 27.04 weather conditions improved. Very dry air.

Variable: as of 27.04. improved weather conditions. Pitztaler Gletscher

Complementing the above graph: middle row depicts snowpack surface temperature (gray), together with air temperature (red) and thawing point (blue). Good nocturnal outgoing radiation on 28.04 and 29.04.

12hr-snow depth difference 23.04. - 24.04.2022

The hot spot of precipitation on 24.04 was at the Timmelsjoch station in the Gurgler Massif.

 

More precipitation on 24.04-25.04

Powder snow and firn

There was a brief spell when superb powder and good firn was enjoyed, in some places immediately following on the heels of the other). Due to the dry air that might be true tomorrow, 29.04. Thereafter the powder will be blanketed by a crust also in high alpine terrain.

 

Powder snow at 3000 m in the Stubai Alps (photo: 28.04.2022)

A photo from the 18.04 “archives.” Great firn in the Zillertal Alps, still to be enjoyed on steep sunny slopes.

A glance beneath the snowpack

As mentioned before, we are currently concentrating on the potential near-surface weak layers which have formed over the last few days due to dp.4. This means high alpine shady terrain. Due to only minor amounts of recent snowfall (usually 10-20 cm) and based on reports and snowpack analysis, we assume the problems are quite isolated. Caution urged in immediate ridgeline, extremely steep high alpine terrain. The risks of taking a fall are higher than those of being buried in snow masses.

At 3040m, NE, Stubai Alps, only partial fractures could be generated near the crusts. Weak layers were not sufficiently pronounced to become a danger. (photo: 28.04.2022)

The poorest snow quality is currently to be found in shady terrain at 2300m. There the snowpack is thoroughly wet down to lower layers. That is where you break through most easily.

Isotherm snow profile at 2260m in the Silvretta from 26.04.2022

On 30.04 our last Avalanche Bulletin of the season (with forecast for 1 May) will be published. Blogs will be published whenever the snow and avalanche situation changes significantly.

Spring is here... (photo: 20.04.2022)

We thank all of you enormously for the numerous, valuable reports.

Mostly quite good conditions – Danger zones where snowpack is wet, esp. on very steep shady slopes above 2500m

Southerly foehn will bring some precipitation, esp. to southern regions

Following an extremely dry month of March, April has still not brought much precipitation. A bit is scheduled to arrive starting on Sunday, 24.04 due to foehn influence, especially in southern regions in Tirol (Gurgler Massif incl. East Tirol).

Main Alpine Ridge as weather divide on 21.04.2022: overcast skies in the south, mostly sunny in the north. Gurgler Massif

Clouds dominated last week near the Adlersruhe. The wind shifting to southerly is visible, then overcast skies following two sunny days.

Mostly favorable conditions – Focus on thoroughly wet snowpack on shady slopes at 2500m

Low avalanche danger for the most part last week, with just a slight daytime cycle which heightened danger to moderate. Only on Friday, 15.03, was there a brief wet-snow cycle. So our focus is now on shady slopes at 2500m. As the wetness penetrates deeper, increasingly frequent loose-snow and mostly small-to-medium slab avalanches will be the result. Due to the character of April weather, forecasts that reach over several days are doomed to failure, should this happen. We simply have to observe the situation each day, since even minor weather changes can cause huge effects on the wetness of the snowpack. Keep an eye on diffuse radiation and high air moisture and warm temperatures. Other than that, all is quiet in outlying terrain.

Following snowfall, more frequent loose-snow avalanches

A classic pattern is the sure-fire appearance of loose-snow avalanches in extremely steep terrain following snowfall at this time of year. Due to presumably modest amounts of fresh snow, as forecast by ZAMG Weather Service for Sunday, 24.04, the loose-snow avalanches will probably remain mostly small.


Below-average snow depths

As noted in the Blog on 31.03, snow depths for this juncture of the season are below average. Here are a few impressions of present conditions...

Haggen in Sellraintal (photo: 12.04.2022)

Haggen in Sellraintal - photo for comparison, mid-April 2021

Bare ground up to high altitudes at low and intermediate altitudes and on sunny slopes - Lüsental
(photo: 18.04.2022)

Crocuses in bloom - spring arrives. Gurgler Massif (photo: 20.04.2022)

Review of one-day wet-snow cycle on 15.04.2022

As referred to above, and also mentioned in the last Blog, on 15.04 we faced a wet-snow problem. Instead of the anticipated isolated naturally triggered avalanches, they turned out to be numerous. The situation was facilitated by rainfall. Here are a few impressions of that...

Rainfall set in on Friday, 15.04, at Hahnenkamm station in the Kitzbühel Alps. On 16.04 the wet-snow cycle came to an abrupt end on shady slopes, due to dropping temperatures (NE air current).

Wet loose-snow avalanches released frequently on 15.04. East Tirol, Deferegger Alps

Flight of Christophorus crew to an avalanche on the Glungezer north flank, western Tux Alps. 2300m.
No one was buried. (photo: 15.04.2022)

On a north-facing slope at 2300-2500m, numerous naturally triggered avalanches.
Wildlahnertal, northern Zillertal Alps (photo: 18.04.2022)

Arrows: naturally triggered avalanches. Pink shading: naturally triggered slab, north flank of Nederkogel, Gurgler Massif (photo: 20.04.2022)

(Daytime) wet-snow problem & diminishing persistent weak layer

 Snowpack becoming moister

With clouds moving in during the night of 14.04-15.04, the snowpack will not cool down during the nocturnal hours. Particularly in an altitude belt around 2300m the moistness will then sink down to deeper layers which have been dry until now. Thereby, the snowpack will lose firmness. The likelihood of moist or wet snow slides, primarily triggered by winter sports enthusiasts, in isolated cases also naturally triggered, thus increases.

The curve of surface temperatures is flattening visibly. The thaw point rose for the first time above 0°C. This is an indicator of the snowpack rapidly becoming thoroughly wet at the place the profile is made.

Even at 3000m the snowpack was superficially moist where the profile was made
(Glacier Ski Area Sölden, 14.04 late evening).

Caution urged particularly where diffuse radiation leads locally to intensified energy seepage and thereby reinforces the melting process. It is clear that snow quality is currently deteriorating.
 

Glide cracks in the snowpack as red flags of potential glide-snow avalanches. As more water seeps into the snowpack, the likelihood of a release increases. (photo: 12.04.2022)

Diminishing persistent weak layer

In our last last Blog we pointed out the development of superficial weak layers above 2600m. This problem has receded in the interim. This applies currently most of all to W/NW to N to E/NE aspects. Caution urged especially on very steep to extremely steep slopes where many snowdrift accumulations were deposited last week. This is a problem which is extremely difficult to evaluate and pinpoint. A view into the snowpack down to the area of the colored layer of Sahara dust from mid-March is helpful.

When analysing the snow we conce pntrate currently on superficial layers down to the layer of Sahara dust, easily recognised in the photo. Weak layers have recently formed precisely at that point. In isolated cases they are malignant and prone to triggering. Stubai Alps (photo: 12.04.2022)

  

Arrow points to the colored layer of Sahara dust. Beneath it a soft layer of faceted crystals is recognizable. In some places a thin layer of faceted crystals has formed above the Sahara layer. Near the surface there is frequently graupel. 

This is a photo of the profile above: upper arrow points to a graupel layer, lower arrow to the layer of Sahara dust from mid-March. The initiated fractures were not completed. (photo: 14.04.2022)

Fresh snow forecast from Friday, 08.04 until Sunday 10.04.2022. A pronounced layer of graupel kernels was deposited in many places during this period of precipitation.

Recent avalanches: triggered exclusively in weak near-surface layers

A few pictures follow of recently reported avalanches in Tirol. What all the releases have in common: weak near-surface layers triggered them due to dp.4 (cold on warm) or dp.9 (graupel).

Western Liebenerspitze, Ötztal Alps, 3200m, SW (photo: 10.04.2022)

Ridgeline slab Wildebene, Arlberg region; 2570m, NW (photo: 11.04.2022)

Slab avalanche on 12.04 near Knotenspitze, northern Stubai Alps.

Three naturally triggered slab avalanches on 12.04 on Marzellkamm, Ötztal Alps, 2930m-3050m, NE (photo: 13.04.2022)

What’s next?

In northern regions, ample clouds and some precipitation; in southern East Tirol, it will be pretty dry. That's how the ZAMG Weather Service forecast looks until Easter Sunday, 16.04. Temperatures are currently dropping, on Easter Monday they will rise again.

In case there is serious snowfall anywhere, numerous loose-snow avalanches can be expected in extremely steep terrain as soon as skies brighten again. Otherwise, springtime conditions will continue, including a daytime avalanche danger cycle. All in all, we then expect quite favorable conditions.

Abfahrtsgenuss im Gschnitztal (Foto: 12.04.2022)

All signs point to Danger Pattern 4 (cold on warm) at high altitudes

Following snowfall, trigger-sensitive weak layer highly probable due to dp.4

Weak layer caused by dp.4 (cold on warm)

In our last Blog we referred to the “small snowdrift problem at high altitudes” and the possible development of Danger pattern “cold on warm” (dp.4). Back then on 07.04 we had no information about the development of a malicious weak layer. In the interim reports keep coming in about slab avalanches in a superficial weak layer due to Danger Pattern dp.4.

Based on current information we can narrow down the problem zones due to dp.4 to the following:

• Regions where recent snow was heavy, particularly Silvretta, Arlberg region, Karwendel, regions along the Main Alpine Ridge and northern East Tirol
• Shady slopes between 2600 and 2800m
• Sunny slopes above 2800m, even more above 3000m

On the monthly graph from the Pitztal Glacier station we recognize not only the start of precipitation on 31.03 but also the temperature leaps which followed, including brief period of high wind impact.

Weak layer due to dp.9 (covered graupel)

Just as conceivable, however, are massive deposits of graupel which were blanketed by the recently generated snowdrift accumulations in all aspects. Graupel precipitation was repeatedly observed during the last round of precipitation. Similar to dp.4, we assume that problem zones are evident above about 2600m.

Some reports about avalanches

Avalanche releases were reported from Wildebene and Albonakopf in the Arlberg region, from Felderkogel in the Ötztal Alps, from Grossglockner in the Glockner Massif and from Grosser Geiger (SW, 3200m) in the Venedig Massif. In addition, a report came in today (11.04) about large-scale settling noises in the Venedig Massif above 3000 m.

With a webcam from  Lucknerhaus the recent naturally triggered slab avalanches are recognisable. The lower avalanche triggered today, 11.04, at midday.  (c) foto-webcam.eu

Avalanche Felderkogel. The release was remotely triggered. N, 2700-2750m (photo: 10.04.2022)

Heightened caution during the next few days

As a result of expected higher temperatures and solar radiation, the snowpack will be briefly weakened and the likelihood of slab avalanches triggering will be heightened. We assume that the weak layer will no longer be a threat once it has become thoroughly wet. Thus, the problem will last a little longer on shady slopes. This depends on coming weather developments, including diffuse radiation, and cannot as yet be pinned down to a certain length of time. Winter sports enthusiasts with lots of experience in evaluating avalanche dangers on-site can easily recognize a potential problem through snowpack analysis and stability tests, and react accordingly. Of course we are grateful for your reports, at lawine@tirol.gv.at

April weather generating variable snow+avalanche conditions

 Conditions: variable!

The first week of April has been highly variable. To start with, formidable amounts of snow with little wind, but strong where there was impact. All this at low temperatures. Subsequently less and less sunshine, with rainfall up to 2000 m, particularly in North Tirol. Rising temperatures.

You had your work cut out for you when laying a track last weekend. Rieserferner Massif
(photo: 02.04.2022)

72-hr snow depth difference, 03.04.2022. Up to 50 cm of snowfall in some high altitude places.

Powder Alarm in the Tux Alps. In extremely steep terrain, loose-snow avalanches could be easily triggered in regions where there was lots of fresh snow. Sluff Management was the word of the day.
(photo: 03.04.2022)

Initially quite cold, then increasingly warmer. Repeated bouts of precipitation, starting 07.04 at latest strong wind impact in the mountains.

One of the few really windy spots on 03.04. (southern East Tirol)

No serious avalanche problems

Loose-snow avalanches

The main danger was loose-snow avalanches immediately following snowfall. Diffuse solar radiation was just as responsible as impulses from winter sports enthusiasts. The releases were mostly small, sometimes medium-sized.

Loose-snow avalanches on Carnic ridge (photo: 06.04.2022)

Loose-snow avalanches on Schrankogel in the Stubai Alps (photo: 04.04.2022)

A loose-snow avalanche triggered by a winter sports enthusiast (photo: 04.04.2022)

Glide-snow slides and avalanches in regions where snowfall was heavy

Wherever snow fell on steep bare grass-covered slopes, there were increasingly frequent glide-snow slides, in isolated cases large-sized. In the interim, such activity has receded.

Gliding snow on grass-covered slopes. Tux Alps (photo: 02.04.2022)

 

(Small) snowdrift problem at high altitudes

In spite of strong winds starting on 07.04.2022 it can be assumed that the transported snow was a problem only at very high altitudes. In any case, the likelihood of these snowdrift accumulations triggering increased with altitude. Potential weak layer: probably the graupel which was deposited during showers in North Tirol on 06.04. And in high alpine regions, also the loose fresh snow (on 07.04) could form a weak layer. Avalanche prone locations occur particularly behind protuberances in very steep terrain. A possible development that we also kept an eye on: Danger Pattern “cold on warm” (dp.4). Starting on 31.03, a possible weak layer might have formed between the formerly moist old snowpack surface and the cold fresh fallen snow in a certain altitude and aspect belt. However, no worrisome developments of this nature have been recorded to date.

Snow transport at 3000m and above. Stubai Alps

Just beneath the surface in some places: a pronounced layer of graupel. Stubai Alps (photo: 07.04.2022)

Over small spaces, snowdrift accumulations atop graupel could be triggered. Stubai Glacier
(photo: 07.04.2022)

What’s the outlook?

The ZAMG Weather Service forecasts for Friday, 08.04, and Saturday, 09.04, ongoing variably cloudy skies including precipitation. Temperatures are expected to drop. Initially the snowfall level will descend from 2000 m to below 1000m. What is striking: strong-to-stormy winds in the mountains will persist. The snowdrift problem will be at the forefront, requiring attentiveness at high altitudes in particular. In addition, following snowfall and diffuse solar radiation, loose-snow avalanches can again be expected on extremely steep slopes.

Storm-strength winds in the mountains. Stronger in the north than in the south...

72-hr fresh snow forecast, as of 07.04.2022