Attention: other alpine dangers (not avalanches)

 Springtime conditions

The beautiful weather and clear nights will give us classic springtime conditions starting on Sunday, 28 February. In early morning, conditions are favorable. Avalanche danger subsequently increases somewhat due to daytime warming and solar radiation. Naturally triggered avalanche activity has receded compared to last week. Winter sports enthusiasts can still trigger slab avalanches, particularly where the snowpack in steep terrain becomes moist/wet during the day. The main danger, however, is glide-snow avalanches, particularly in East Tirol where snowfall has been heaviest.

Other alpine dangers

Apart from the danger of avalanches, we are dedicating this forum to some other alpine dangers which currently require attention.


Danger of taking a fall on hardened surfaces

As a direct consequence of nighttime outgoing radiation and the hardening of snowpack surfaces, the risks of taking a fall atop hardened surfaces needs special consideration. It is advisable to make use of crust spikes or even climbing spikes (and ice pick) when called for.

When nocturnal skies have been clear, the snowpack is frozen in early morning, capable of bearing loads.

Danger from breaking cornices

Particularly in springtime, the danger of naturally breaking cornices increases. It is important to be aware of these risks so that one does not step unconsciously on one, which then breaks beneath the burden.

Cornices: beautiful in form, but treacherous (photo: 18.02.2021)

Danger from crevices

On Thursday, 25 February, someone on the Grossvenediger fatally fell into a crevice. The person was not roped up. Due to intensive precipitation in the southern regions, the impression may have arisen that snow depths on the glaciers is quite adequate. However, high speed winds prevailed during the periods of snowfall in high alpine regions in particular, transporting great masses of snow. The depths on wind-exposed glaciers are often below-average for this juncture of the season.

Rescue operation due to fall into a crevice on Grossvenediger (photo: 25.02.2021)

The broken snow bridge. Visible is the extremely thin covering. (photo: 25.02.2021)

Snow bridges over brooks

We are currently observing brooks and mountain streams slowly opening to view. These streams are carrying more water due to snowmelt. Snow bridges are thus thinner, prone to breaking. Therefore: caution when crossing brooks with lots of water. There is a danger of drowning. There is not always (as in this photo) a snow bridge over the stream.

Cables spanned tight on ascent to Adlersruhe

A very local danger, notable because of the popularity of this backcountry touring region, is currently found near the goods-lift up to the Adlersruhe. A very large slab avalanche from Lange Wand in the Grossglockner region destroyed this lift on 6 December 2020.

In foreground, a destroyed support pylon of the goods lift to the Adlersruhe. At left, Grossglockner. Just right of the top of the pylon, the starting zone of the damaging avalanche is visible. (photo: 17.12.2021)

At the moment, the cables of the goods lift in the central section lie buried in snow about 50-70 cm beside their normal course. They are currently tightly spanned. A possible peering out of the cable in case snowmelt continues is a huge danger to all skiers. This applies also to the mountain station of the lift where high spanning tensions are in play. This state of affairs has led the refuge manager at the Adlersruhe, Toni Riepler, to cordon off the endangered zone and mark it.

The damaging avalanche. Upper left: Grossglockner. At right along the ridge, encircled: the Adlersruhe.

Main danger: glide-snow avalanches. Heed daytime danger cycle!

 Numerous naturally triggered avalanches

Numerous avalanches unleashed naturally in Tirol during this last week. These occurred primarily on steep, sunny slopes up to altitudes of approximately 2700 m. Wet-snow and glide-snow avalanches were frequently observed below about 2400 m.

Deposits of fresh wet-snow avalanches on Fliesser Berg, south, 2100 m (photo: 23.02.2021)

Slab, glide-snow and loosely-snow avalanches in the Samnaun Massif.  At left edge of photo a glide crack is visible, indicator of potential glide-snow avalanche (photo: 23.02.2021)

A palpable threat to exposed transportation routes, Gschnitztal, photo: 23.02.2021

Naturally triggered avalanches in extremely steep south-facing terrain. Central Lechtal Alps
(photo: 23.02.2021)

Small glide-snow avalanche, huge effect. This avalanche buried the approach road to Kals. see also photo below (photo: 23.02.2021)

Avalanche deposits from above avalanche on Kalser Landesstrasse (photo: 23.02.2021)

Successful artificial triggerings 


Due to heightened potential danger to certain sectors of roads in East Tirol where snow has been heavy, avalanches were also artificially triggered from a helicopter. Since these were carried out at the right moment, they achieved great success, as the following video shows.

Artificially triggererd avalanche to ensure safety of Kalser Landesstrasse  (video: 24.02.2021)

A list of recent avalanches involving persons and rescue operations

Several avalanches were reported which involved persons and required rescue operations as a result of the unclear situation. According to our information, there were no injuries. Here is a rough list:

 

17.02.2021 11:50 am:     Nederkogel, Gurgler Massif, southeast, 2650m, 
20.02.2021 09:50 am:     Lämpermahdspitze, northern Ötztal and Stubai Alps, east, 2400m

20.02.2021 11:35 am:     Vordere Brandjochspitze, Karwendel, southeast, 2250m

20.02.2021 --:-- am :      Kesselspitze, northern Ötztal and Stubai Alps, northeast, 2300m

21.02.2021 1:15 pm:     Hohe Warte, western Tux Alps, north, 2250m

23.02.2021 5:40 pm:     Arzler Reise, Karwendel, south, 1950m

24.02.2021 11:00 am:     Foppmandl, central Stubai Alps, northeast, 2350m

24.02.2021 12:15 pm:    Kleiner Kaserer - Wildlahnertal, western Tux Alps, southwest, 2100m

24.02.2021 3:15 pm:     Arztaler Hochleger, western Tux Alps, 2200m, south

25.02.2021 7:45 am:      Zirmeggenkar, Gurgler Massif

25.02.2021 12:45 pm:     Riffelsee Talabfahrt, Weisskugel Massif

25.02.2021 2:15 pm:     Schafkar, Lechtal Alps, southeast, 2300m

25.02.2021 3:50 pm:     Gleierschköpfe, Karwendel

Nighttime operation Arzler Reise, Karwendel (photo: 23.02.2021)

Avalanche rescue operation Arztal-Hochleger (photo: 24.02.2021)

Avalanche Foppmandl (photo: 24.02.2021)

Slab avalanche Kleiner Kaserer, Wildlahnertal (photo: 24.02.2021)

Avalanche Zirmeggenkar (photo: 25.02.2021)

Slab avalanche Schafkar (photo: 25.02.2021)

Systematic snowpack analysis as basis of danger evaluation

Over recent days we have concentrated our efforts on observations of the increasing degree to which the snowpack is moistening or becoming thoroughly wet. In the context of a large-scale exploratory tour of the terrain with the help of a state helicopter we were able to systematically examine and analyze the snowpack. 

A landing at weather station Gallreideschrofen,  Pitztal (photo: 23.02.2021)

We utilized this opportunity to also verify the snowpack simulations which had been programmed at some of the weather stations. The results amazed us: reality and model fit together perfectly.

Steady rise in temperature, adequate nocturnal outgoing radiation and cooling, daytime moistening of snowpack - Gallreideschrofen station.

Snow profile in vicinity of Gallreideschrofen weather station, east-facing slopes, 2190m, isotherm snowpack, i.e. thoroughly wet and 0°C. Potential weak layers inside the snowpack 

Snowpack simulation: at left, red triangles and squares show potential weak spots based on wet-snow indicators; at right, simulated snow profile for Gallreideschrofen location.

A few metres distant from above snow profile, a 23° NW slope: the snowpack still has cold reserves, i.e. the warmth is not yet harming the snowpack on shady slopes at that altitude.

Map of EUREGIO region with wet-snow indicators for selected stations and simulated south-facing slopes: the redder the color, the more instable the spot

Dust blown northwards from the Sahara desert provided a special fascination, turning the atmosphere quite hazy on 22 - 24 February.

Dust from the Sahara can frequently be found on or near the snowpack surface, stemming from the beginning of February. This reinforces the absorption of warmth in the snowpack, thereby increasing the degree to which it becomes wet. (photo: 23.02.2021)

Outlook for the next few days

The springlike conditions, including a daytime cycle of avalanche danger, will remain intact to start with. A weak cold front will reach Tirol on Friday night and lead to an improvement of the situation, i.e. a lesser daytime danger cycle than was the case this last week. Starting on Sunday, 28 February, a new, stable high-pressure front is expected to reach Tirol.

The main danger will be glide-snow avalanches which can slide across steep grass-covered slopes. These avalanches can release at any time of day or night, even when there is a melt-freeze crust capable of bearing loads. For that reason, our recommendation: circumvent / avoid all zones below glide cracks. In East Tirol where snowfall has been heaviest, glide-snow avalanches can still grow to dangerously large size and place hiking trails or forest roads at risk.

Glide-snow avalanches which have already released and glide-snow fractures, Northern Massif above Innsbruck (photo: 24.02.2021)

For winter sports enthusiasts the rule of thumb is: plan backcountry tours well, i.e. time allotment is all-important following nights of clear skies. Apart from the glide-snow problem, conditions are good. During the morning there is also danger of taking a fall on the hard-frozen snowpack surface. Near combs and ridges, cornices are in danger of breaking.

Caution: glide-snow avalanches possible at any time of day or night. Hiking trails, forest roads at risk

Snowpack forfeits firmness due to water seepage

As a result of above-average temperatures and solar radiation, a progressive wetness of the snowpack can be observed. This applies particularly to sunny slopes below 2600 m, shady slopes below 1800 m.

Indicative of the current situation: steadily rising temperatures over the last few days. Snowpack-surface temperature is subject to daytime cycle, reaching 0 degrees by late morning. Intensive solar radiation.

The water seeping into the snowpack reaches the ground to an increasing degree. The snowpack is then isotherm, thus, the temperature from ground level to the surface = 0°C.

Snow profile Jöchlspitze, Ausserfern: isotherm snowpack, almost 1700 m in 6° steep south-facing terrain

The lower the altitude, also the steeper and more sun-exposed the slope, the more massive the process of wetness. The situation is correspondingly better at higher altitudes.

Yesterday, 21 February, the snowpack in the Karwendel, 38° gradient south-facing slope at 2680 m only superficially wet. There are still reserves of cold there, thus, the snowpack will hold out longer before becoming destabilized.

Glide-snow avalanches can release at any time. Exposed transportation routes, hiking trails, forest roads at risk

More water at the interface between ground and snowpack means a lesser amount of friction with the smooth ground, thus, heightened likelihood of the entire snowpack gliding over the ground. For that reason we have seen increasingly frequent glide-snow avalanches throughout the land since yesterday (20.02). What these avalanches have in common: the gliding process at ground level continues even during the nocturnal hours when the snowpack surface freezes so that it can bear loads. That means, glide-snow avalanches can release even in the middle of the night! In regions where snowfall has been heaviest, e.g. East Tirol, these avalanches can grow to large size and place not only exposed transportation routes at risk, but also hiking trails and forest roads.

Glide-snow avalanche near an ascent track. Defereggental (photo: 21.02.2021)

Endangerment of ascents and descents in southern East Tirol due to glide-snow starting zones, not visible from the valley. Extremely treacherous! (photo: 21.02.2021)

Fresh glide-snow avalanche due to inceased water seepage into the snowpack, Schmirntal, western Tux Alps. (photo: 22.02.2021)

A thoroughly wet snowpack also furthers slab avalanche releases. Heed daytime cycle.

If there are weak layers inside the snowpack consisting of expansively metamorphosed (faceted) crystals, water seepage can weaken them further. As a result, slab avalanches can trigger. Currently this applies to steep E-S-W facing slopes below about 2400 m. If the starting zone is large enough, dangerously large slab avalanches are also possible. Contrary to glide-snow avalanches, slab avalanches are subject to the daytime danger cycle to a significant degree: from early morning following nights of clear skies, generally favourable conditions, thereafter steadily increasing likelihood of triggering for the rest of the day.  

Slab avalanche Rotgabele (Schober Massif). It can be derived from the photos (and this corresponds to the current situation in East Tirol) that the deeper layers of the snowpack are stable, i.e. no fracture reaches these layers by large additional loading from the avalanche which was unleashed. (photo: 21.02.2021)

Area where the Rotgabele avalanche was deposited - danger of path damage (photo: 21.02.2021)

Similar situation on Wolgemuthalm (Gschlöss). Avalanche deposit on approach path (photo: 22.02.2021)

Wet loose-snow avalanches

During the last few days, increasingly frequent wet loose-snow avalanches have been observed in sunny, extremely steep terrain. Below the Brandjoch in the Northern Massif, for example, a winter sports enthusiast was overtaken by a loose-snow avalanche, swept along and injured. The danger of wet naturally triggered loose-snow avalanches has subsided in the interim. Artificial triggering by skiers is still conceivable, however, if the snowpack surface is sufficiently wet.

Loosely-packed slides visible where the arrows point. These were triggered naturally. One person was swept along. Brandjoch, SE, extremely steep (photo: 20.02.2021)

Only isolated danger zones remaining for dry-snow slab avalanches

As mentioned in the last blog, there are only few isolated danger zones remaining for dry-snow slab avalanches. These can be triggered most easily in extremely steep, shady terrain wherever the snow is shallow or in transitions from shallow to deep snow. Instructive for this situation is an avalanche release in Wildlahnertal, near Hohe Warte in the western Tux Alps where a descending skier was caught in a slab avalanche, swept along and partly buried (uninjured). 

Avalanche release in rocky, extremely steep terrain. Hohe Warte (photo: 21.02.2021)

Summary: 

Apart from the glide-snow problem, favourable conditions reign widespread in the early morning hours after nights of clear skies. During the daytime, danger of wet-snow and glide-snow avalanches increases. Caution: avalanches can plummet all the way to the valley floor.

Increasingly favorable situation, slight daytime cycle of rising danger

Coming soon: a stable high-pressure weather front

According to ZAMG Weather Service forcasts, high-pressure conditions will increase ongoingly over the next few days. On Friday, 19.02, a cold front over Germany will send some clouds to Tirol. Starting on Saturday, 20.02, a stable high-pressure weather front will take over the reins. The zero-degree level is expected to lie at 3000 m. Light winds will prevail in the mountains.

The models all agree: in the coming week, no fresh snow in Tirol.

Increasingly favorable avalanche situation

Superficial avalanche problems continually decreasing

These prospects will have a thoroughly favorable effect on the avalanche situation. Potential superficial avalanche problems we have observed over the last few weeks, e.g. snowdrifts, superficial old-snow problem, will recede into the background. Most of all, this is because over widespread areas only shallow slabs have formed during the last week atop potential weak layers. The energy now is  reinforcing the bonding between slab and weak layer.

Snowdrift problem on 13.02.2021: the very loosely-packed fresh snow (fluffy powder) was transported by winds, generated very trigger-sensitive snowdrift masses for a short time. Grieskogel Massif.

Since 7 February, potential weak layers have formed only on the uppermost surface. Warmth and solar radiation are now having positive effects on the situation. In the second crust in the above picture, a slightly yellowish hue is visible. This is from the recently deposited layer of sand from the Sahara.
South, 2200 m, western Tux Alps. (photo: 16.02.2021)

A very short excursion to avalanche danger of recent days from the perspective of avalanches being triggered by low additional loading. At first glance this fits both with danger level 3 (considerable) and danger level 2 (moderate). The reason: avalanche danger levels are published in accord with a number of different parameters.

• On the one hand, snowpack stability (and likelihood of avalanches triggering) is fed into this algorhythm: snowdrifts could be easily triggered.
• On the other, it is a matter of the distribution of avalanche prone locations. These occurred increasingly in ridgeline terrain and behind protruberances, in other words, were not widely distributed.
• In addition, both type of avalanche and size of avalanche play a huge role. We assumed small slab avalanches with a more shallow potential fracture depth.

What was decisive was the not-very-widespread avalanche prone locations and the small size of avalanches by and large. Thus, the ultimate rank of: moderate danger, in accordance with the criteria of the European Avalanche Warning Services.

Fresh drifted mass which triggered on a faceted weak layer (based on dp.4- cold on warm) in the Grieskogel Massif. (photo: 12.02.2021)

Snow profile taken near the spots photographed above. Visible are the potential weak layers near a melt-freeze crust. Fractures were incomplete.

A similar picture in the central Lechtal Alps. Weak layer with incomplete fracture, a slightly marked slab on top of that. South, 2230 m.

Only a few other danger zones

What remains are avalanche prone locations on steep, smooth surfaces (especially on grass-covered slopes in East Tirol where snow was heaviest) where glide-snow avalanches can still trigger. This applies increasingly to steep sunny slopes. Glide-snow avalanches frequently ‘announce’ their triggering by glide cracks in the snowpack surface. For that reason, we advise: if possible, no stops near/below glide cracks.

Glide-snow avalanches on steep grass-covered slopes. Central East Tirol. (photo: 11.02.2021)

In addition, a few avalanche prone locations where persistent, long-enduring weak layers at mid-level in the snowpack could be triggered. These last danger zones are likely to trigger only in spots where snow is shallow, in transitions from shallow to deep snow and then, in extremely steep terrain, by large additional loading. Most likely to trigger are W/NW to N to E/NE aspects between 2000 m and 2400 m. Furthermore we received reports from our South Tirolean colleagues of two avalanches 1-2 weeks ago in extremely steep S/E facing slopes along the Main Alpine Ridge at about 3000 m. Also there, they were isolated avalanche prone locations. 

In addition, at high altitudes (above 2400 m) a small-spread snowdrift problem was noted, especially in shady terrain near ridges.

Worthy of note: this is only the very first daytime cycle of avalanche danger due to daytime warming and the springlike temperatures. Do not fail to get your daily information from the Avalanche Bulletin.

Snow quality is improving

Currently (18.02.2021) melt-freeze crusts dominate. Only in very steep sunny terrain, particularly at intermediate altitudes, is the snow transforming to firn. Firn snow, or more correctly, corn snow, will occur more frequently on sunny slopes at high altitudes during the coming days. Making a daytime tour time-plan is helpful in this regard, so that the snow has not softened by the time you begin your descent.

Firn snow at about 2000 m, south, Karwendel (photo: 18.02.2021)

Short review of the last week

A brief intermezzo of very low temperatures, now history.

Initially (very) cold, now getting warmer...

A similar picture in East Tirol...
On 16 February the snowpack became moist. Uppermost layers thus bonded. The snowpack became more prone to triggering for a short time.

On wind-protected spots, good powder...

On the weekend, often good powder (photo: 12.02.2021)