Highly variable conditions + stormy. Main danger: snowdrifts.

Second warmest winter in history

The meteorological winter 2019/2020 (01.12 - 29.02) is coming to an end. According to ZAMG Weather Service it is the second warmest winter in the 253-year history of measurement-taking. One measurement stands out: at Innsbruck Airport on 23 February in the evening the temperature was 20.5°C. (Only twice was this temperature exceeded in a meteorological winter: on 24.2.2008 and on 28.2.2019, when 20.6°C was reached).

According to Alexanderr Radlherr from ZAMG Weather Service: extraordinary, over 20° in the evening, wind-adjusted mixture of air masses without sun.

Storm winds once again

The ZAMG Weather Service warns of a short but intensive storm-low which will move over Tirol today and tomorrow (27-28.2). The northern rim of the Alps will be hardest hit. In the latter part of the night, the storm winds will slacken off from west to east, easing further on Friday morning.

Easily recognized: winds intensified significantly during the daytime. Simultaneously, snow depths decreased noticeably. Thus, snow was transported.

Maximum wind gusts

Fresh snow, again and again

Several times last week there was precipitation. Here the fresh snow from 26-27.2 is visible. Today (27.2) more fresh snow will be added to it. Most of it in the western regions (up to 30 cm, locally more).

Forecast of fresh snow for the next two days

Main danger stems from fresh snowdrifts

The combination of fresh snow, wind/storm plus cold temperatures inevitably leads to wide-ranging snow transport.

Snow plumes indicate snow transport. Silvretta (photo: 26.02.2020)

The snowdrifts which were generated and occur in very steep terrain at high altitudes are increasingly prone to triggering, especially behind abrupt changes in the terrain and on shady slopes. A potential weak layer for slab avalanches is found inside the mass of fresh snow, e.g. graupel, possibly also cold loose powder. In addition there is currently a layer of decomposed snow beneath thin crusts near the snowpack surface, above the treeline. Also there, in case of a deeper layer of fresh snow and drifts, a fracture is possible by appropriate loading, e.g. the weight of one sole skier. Avalanches show no great risk of great magnitude due to little fracture propagation tendency (medium-sized at most). In addition, in very isolated cases older layers of faceted crystals beneath crusts (above 2300 m on shady slopes) are prone to triggering.

Soft layers beneath crusts can be a weak layer for slab avalanches when snowdrifted masses are deposited atop them.

A similar situation in the profile above. In addition, there is here a further weak layer in the form of faceted crystals which seldom occurs, from the end of January. The last layer can be triggered only by large additional loading where snow is shallow.

Indicative of sunny terrain: stable layering with a sequence of crusts and and a snowpack riddled with melt-water canals.

The snowpack surface

What matters in this connection is the extremely irregular snowpack surface with which fresh snow and drifts have in generally bonded rather well.

Snowpack surface heavily wind-impacted. East Tirolean Tauern (photo: 22.02.2020)

Avalanche deposits from 03-04.02 in the Silvretta. (photo: 18.02.2020)

Breakable melt-freeze crusts in sunny terrain on the Main Tauern Ridge  (photo: 22.02.2020)

Really loose, cold powder was rare. Mostly it suffered impact from wind and solar radiation. Tonigenkogel (photo: 22.02.2020)

Striking on 23-24.02 was that rain fell up to high altitudes. At intermediate altitudes the snowpack was thoroughly wet, 0° everywhere. Subsequently during a star-studded night the snowpack surface formed a solid melt-freeze crust.

Last week’s weather: warm, variable, windy. Rainfall up to high altitudes.

Last weekend and at the beginning of the week, a westerly air current brought very mild Atlantic air masses to the Alps. On Saturday, 22.2 the air was still dry, supplying us with ample sunshine and a few harmless cirrus clouds. As Sunday approached the air became moister, a few compact cloudbanks dominated. On 23.2 in the evening the record-breaking temperatures were recorded. Thereafter it started to rain, extending mostly up to 2500 m, in some places up to 2900 m.

Reports of rainfall levels on 23.2 and 24.2 from our observers.

The westerly air current which prevailed brought a rapid shift from dry to moist air masses on Wednesday, 26.2, then colder air and snowfall. In the course of the day today (Thursday, 27.2) a cold front approached, bringing strong-to-stormy westerly winds and snowfall which are expected to persist until the early hours of Friday. According to ZAMG, the air current will shift to southwesterly next weekend and it will again become milder.

Variable: rain on 23.2 and 24.2, subsequently more minor precipitation, windy, good radiation on 24-25.2 due to dry air masses. On 27.2 winds intensifying.

Situation in the southern regions

The southern regions of the land hardly got any precipitation in the recent period. Only now when the air current is changing is the south getting some snow or rain. What is striking there is the hard snowpack surface, which has caused numerous personal injuries. In one case someone in snowboots on a 30° steep slope slipped, fell a ways and was killed.

Indicative of the most recent period: the snowpack surface was frequently icy. Lienz Dolomites (photo: 21.02.2020)

At low and intermediate altitudes there is little to no snow. Sunny slopes are becoming increasingly bare. Southern East Tirol (photo: 22.02.2020)

More gliding snow for a brief period, generally little avalanche activity recently

Throughout Tirol, particularly in the southern regions, avalanche activity recently has been rare. Most of it came from moist or wet loose-snow avalanches. Increasing avalanche activity was observed in the rain-impacted regions on 24 February in the form of glide-snow avalanches.

Glide-snow avalanche in East Tirolean Tauern. (photo: 24.02.2020)

Glide-snow avalanche in Kleinvermunttal. (photo: 25.02.2020)

Don’t underestimate this risk: rooftop avalanches in Defereggental. (photo: 23.02.2020)

Also to be heeded, observed in isolated cases: breaking cornices.

Breaking cornice in the Tux Alps. (photo: 22.02.2020)

Talk to avalanche.report!

Thanks to the software developer Tobias Kupek (www.tkupek.eu) it is possible to interact with the avalanche report by voice via Google Assistant and as Alexa-Skill. In a conversation with the feature, you can ask for the current avalanche situation in a specific region, as well as get the danger levels explained.

How do I ask Google Assistant correctly?

To get the desired information from the Google Assistant, you can simply start with "Talk to Avalanche Report", from then on you will be guided by the Assistant.

It is also possible to ask directly for specific locations or topics, e.g:

"Ask avalanche report about the danger level in Innsbruck"

"Ask Avalanche Report for Stubai Glacier"

or

"Ask Avalanche Report what are the danger levels“

The information is then read out and a direct link to the website www.avalanche.report is available for more detailed information.

Possible question

How do I ask Alexa correctly?
Using Alexa you can activate the function with "Alexa, open avalanche report" and then be guided through the conversation. Possible questions are:

"What's the forecast for Stubai Glacier?"
"What are the danger levels?"

Alexa - https://www.amazon.com/dp/B084WWVPB1
Google Assistant - https://assistant.google.com/services/a/uid/000000f00e110a46?hl=en_us
Tobias Kupek – www.tkupek.eu

Small-spread fresh snowdrifts. Isolated old-snow problem. All in all, quite favourable conditions.

Current problems: small-spread snowdrifts, old snow

Quite favourable conditions currently reign in Tirol. Avalanche danger is moderate to low today (Friday 21.02.2020).

En route in Defereggental. On sunny slopes, springlike conditions often prevail, including corn snow during the descent. (photo: 18.02.2020)

Avalanche danger map for Friday, 21.02.2020

We currently have 2 avalanche problems to deal with: a snowdrift problem & an old-snow problem. The snowdrift problem is far easier to evaluate than the old-snow problem.

Snowdrift problem

What matters for the snowdrift problem is to pay heed to fresh snow transported by winds, most triggerable at high altitudes, particularly on shady slopes. The big advantage: if you have experience assessing avalanche dangers on-site, these drifted masses are easily recognized, thus, circumvented.

Fresh snow being transported by wind. If solar radiation is diffuse, the drifts tend to bond swiftly with the loose powder snow beneath them in this season. Silvretta (photo: 17.02.2020)

The likelihood of fresh snowdrifts triggering tends to increase with ascending altitude. Snow plumes in the Venediger Group (photo: 18.02.2020)

The most recent past: sometimes variable, often sunny, inordinately warm, frequently windy.

Similar situation on Patscherkofel. Visible in the graph: the generally low level of precipitation.

Cold fronts brought only small amounts of fresh snow.

Old-snow problem

The old-snow problem is more complex, and needs to be examined in more differentiated ways. These are faceted, loosely-packed snow crystals which lie deep inside the old snowpack and potentially constitute a weak layer for slab avalanches. However, the old-snow problem is not widespread; it is limited to little-tracked, very steep to extremely steep backcountry touring terrain.

On the one hand, we are dealing with expansive metamorphosis of snow launched by the danger pattern “cold on warm.” This process began with the rainfall on 3-4 February. The weak layer is not the same everywhere. Most often, our snowpack analysis uncovered significant layers at altitudes around 2300 m on north-facing slopes. Since this zone currently has little snow, the necessary ‘slab’ for a slab avalanche is lacking. Thus, there are relatively few avalanche prone locations.

Layer of faceted crystals between two rain crusts. The rain crusts formed on 3 February due to a briefly fluctuating snowfall level. The layer of faceted crystals subsequently formed between the crusts.

Visible in this snow profile from the Lower Inn Valley: only a partial fracture could be generated in the relevant layer. We received repeated reports particularly from the lowlands about settling noises, especially in flat terrain above the treeline, which emanated from this layer.

We also found faceted crystals as a result of the extended period of fine weather prior to 28 January, particularly in W/N/E aspects. Due to the warmth which has prevailed since then, we assume that these layers can only be triggered in W/NW to N to E/NE facing terrain between 2600 and 3000 m. The prerequisite: large additional loading in zones where the snow is shallow or in transitions from shallow to deeper snow.

Thin faceted layer between two melt-freeze crusts at 2875 m on extremely steep NW slope in Silvretta. The lower melt-freeze crust formed until 18.01, the upper until 28.01. Two persons were in the immediate vicinity of this snow profile when a slab avalanche triggered.

Avalanche for the above profile. Snow profile location and location of persons when the avalanche triggered are circled. Haagspitze - Silvretta - Bieltal side (photo: 17.02.2020)

Fracture point of the avalanche on 17.02. Haagspitze including descent track. The avalanche released when one person was in the upper part of the fracture zone. (photo: 17.02.2020)

Apart from this avalanche, we are aware of only one other avalanche due to the old-snow problem (despite the marvellous weather last weekend, 15-16 February). This underscores our assumption that there are relatively few danger zones where avalanches can be triggered in the old snow. This one was in freeriding terrain of the Sölden ski area on a very steep east-facing slope at 2500 m. This avalanche also caused no injuries or damages.

Avalanche on 16.02 in freeriding terrain of Sölden Ski Area (photo: 17.02.2020)

Entry track for avalanche on 16.02 in freeriding terrain of Sölden Ski Area (photo: 17.02.2020)

Quite typical of the current situation in steep sunny terrain: sequence of hard crusts and soft layers near the surface, also in varied form in middle part of the snowpack. The soft layers are frequently riddled with frozen melt-freeze canals and blanketed by several hard layers. Thus, little likelihood of triggering.

Short review of last week’s weather

As an addendum to the above weather graphs, here a verbal description of the weather by our apprentice Marco Knoflach:

“At the beginning of last weekend (15-16 February) an intermediate high took shape which brought us springlike conditions in the middle of February. As a result of the westerly-to-southwesterly air current, very dry and mild air masses were fed our way. The zero-degree level ascended to 3500 m on Sunday, 16 February. In addition to the very mild air, strong foehn winds in the classic foehn-exposed wind lanes made the mercury climb a further notch. Highest temperatures released by the ZAMG Weather Service for the period 15-17 February were approximately 10 degrees above average. On Monday night (18.02.2020) a cold front swiftly moved in, and in its wake came drier and colder air masses. On Wednesday (19.02.2020) the next cold front passed through, before a brief intermediate high calmed the conditions today (20.02.2020).”

A swiftly moving cold front passed through this week. View from Senderstal towards the northwest. (photo: 19.02.2020)

Weather and Avalanche Outlook
“According to ZAMG Weather Service, on Thursday night (21.02.2020) a weak cold front will brush past us, lowering temperatures, bringing brisk-to-strong winds and light showers. On the coming weekend, an outlier of the high over the Azores will generate the weather, again creating springlike conditions.”

This forecast connotes a quite favourable avalanche situation. To an increasing degree, caution will be necessary towards moist glide-snow and loose-snow avalanches. The diffuse old-snow problem with isolated danger zones will persist. The relevant sector (W/NW - N - E/NE) will shrink further, thus transferring the problem to north-facing slopes. This depends on the actual weather which prevails and will be evaluated on each given day. (If lots of water seeps down into the loose layers of the snowpack, that would increase the likelihood of triggering.)


Images from last week

Numerous high-altitude refuges are open for business, here the Jamtalhütte in the Silvretta. (photo: 18.02.2020)

Glide-snow and loose-snow avalanches

During these days of inordinate warmth for this juncture of the season, more numerous glide-snow slides and avalanches are observed. Saile. (photo: 18.02.2020)

Gliding snow masses also over a roof. St. Jakob im Defereggental. (photo: 20.02.2020)

Higher temperatures stimulate wet loose-snow avalanches. Längental. (photo: 15.02.2020)

Deposits from wet/moist loose-snow avalanches. Silvretta. (photo: 17.02.2020)

Nature’s artistry in the snow. Result of a moist snowpack surface. (photo: 17.02.2020)

The snowpack surface

Snow dunes after snowfall+wind. (photo: 18.02.2020)

Snowpack showing the mighty effects of wind. Venediger Group. (photo: 18.02.2020)

Bizarre snow sculpture after rainfall, then snowfall and wind erosion. Ötztal. (photo: 15.02.2020)

During the recent snowfall, there was graupel mixed in again. Jamtal. (photo: 18.02.2020)

Snowpack examination to generate a snow profile: the basis of our danger level analysis. Senderstal. (photo: 19.02.2020)