Overview of precipitation
The forecasts of the ZAMG Weather Service were fulfilled precisely. Most of the snow fell in the furthermost western regions, as well as in the northern Regions of Tirol. The snow station on the Seegrube above Innsbruck won the prize for maximum precipitation.
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| Overall snow depths at the Seegrube station have increased by more than 150 cm since 21.12. |
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| The 72-hr forecast of new snow for 23 - 26.12.2019 for Tirol and immediate surroundings. |
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| Deep winter at the Alpl hut in the Mieming Massif at 1540 m (photo: 25.12.2019) |
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| Ski-run vehicles battling with 60 cm of fresh snow on Tiefenbach Glacier on 25.12. |
Generally storm-strength winds were typical of East Tirol in general. Precipitation fell especially on 21.12 (further south even more).
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| Typical of East Tirol: station St. Veit Zischke in Defereggental. |
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| Some fresh fallen snow, but most of all, snow reserves from mid-November: on the path to Taishörndl in Villgratental (photo: 22.12.2012) |
The snowpack
The fluctuating temperatures during the most recent period of precipitation led to a vascillating snowfall/rainfall level: for a brief spell on 24.12 at 1800 m, before dropping frequently to 1000 m on 25.12. Due to previous warm weather, a slightly moist or isotherm snowpack can be assumed above about 2000 m. In addition, we see lots of graupel kernels inside the fresh snow, but no unified or pronounced layer for slab avalanches. Nevertheless, greater nests of graupel from place to place, which would encourage slab avalanches, cannot be ruled out (especially below rock falls).
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| Isotherm snowpack, graupel in the upper part. Mieming Massif (profile from 25.12.) |
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| Similar conditions in Lech, just across the Tirolean border: a thin melt-freeze crust formed near the surface from a previously rain-impacted layer. |
What matters most at the present juncture are not the embedded patches of graupel, but the faceted layers near the melt-freeze crusts on sunny slopes above 2400 m (somewhat higher on south-facing slopes, presumably above 2600 m). Avalanches can trigger particularly in transition zones from shallow to deep snow in very steep terrain, frequently only by large additional loading.
A potential weak layer for slab avalanches could also exist in the fresh fallen, now blanketed powder snow.
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| Fresh snowdrifts require caution, especially near ridgelines on shady slopes. (photo: 26.12.2019) |
Regarding the danger pattern (dp.4) referred to in the last blog, it seems that no significant weak layer has formed to date. The forecast temperatures seem to have halted this process.
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| Also widespread: snow padding. Rietzer Grieskogel (photo: 26.12.2019) |
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| The snow cover frequently shows pronounced effects of wind. Zillertal Alps. (photo: 26.12.2019) |
Avalanches that released
Numerous observer reports reached us on 26 December with the following picture: frequent naturally triggered avalanches on 24.12 in the latter part of the day; for example, a naturally triggered avalanche from the rear Kaunertal which plummeted all the way to the valley floor. In the rear Ötztal, reports of naturally triggered avalanches which have been blanketed in the interim. All in all, the number of naturally triggered avalanches throughout Tirol seems to have been rather limited.
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| Avalanche in Ferwalltal (fracture zone appx. 2800 m, north) (photo: 26.12.2019) |
Artificially triggered avalanches (through explosives) had widely varied results: some generated positive effects, others didn’t trigger any avalanches.
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| Explosives triggered these avalanches in the Sölden ski area, adjacent to ridgelines, NE, 3200 m (photo: 26.12.2019) |
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| Another slab avalanche triggered by explosives - Wilde Grube, Stubai Glacier (photo: 26.12.2019) |
Avalanches involving persons
Tirolean headquarters reported several avalanches on 26 December involving persons. They caused only minor injuries.
Here a summary:
- Pürgleslenke in Innervillgraten
- Schleinitzmulde in the Schober Massif
- Wasserkar - Gaislachkogel in Sölden ski area, south, 2900m
- Schwarzkogel in Sölden ski area
- Red ski run no. 38 Ischgl - Silvretta Skiarena
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| Avalanche on Schwarzkogel, E/SE, 2850 m. A person (not depicted) was thrust against the snow shed (photo: 26.12.2019). |
We were also informed of an avalanche triggered by a ski-slope vehicle in Paznauntal. No one was injured.
Avalanche releases of the last few days can also be found here:
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| Avalanche on the Diritissima of Hafelkar above Innsbruck on 24.12, south, 2200 m |
Increasingly relevant: glide-snow avalanches
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| Glide yaw in the foreground, glide-snow avalanche in the background, Paznauntal (photo: 26.12.2019) |
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| Avalanches in the Northern Massif: the red line traces the open fracture of a glide-snow avalanche. Loose-snow avalanches released at the spots marked by arrows. The magenta-colour marks a slab avalanche, somewhat covered by fresher snow. (photo: 26.12.2019) |
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| A latent threat: gliding snow in southern East Tirol (photo: 26.12.2019) |
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| Frequently observed: gliding snow on shady slopes below 2000 m. Ausserfern. (photo: 20.12.2019) |
What’s next?
On 27.12 skies will be heavily overcast in North Tirol and northern East Tirol, accompanied by a small amount of snowfall (rainfall below 600-1000 m). At high altitudes, brisk NW winds will be blowing. Subsequently, according to latest ZAMG Weather Service forecasts, a powerful high-pressure zone will prevail. Temperatures will rise. A still strong-velocity northerly wind will be blowing in East Tirol in particular, subsequently slacken off.
These anticipated weather conditions will have a positive effect on avalanche danger levels. But the risk of glide-snow avalanches will tend to grow larger over the next few days.
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| Joys of powder snow, Niltal, East Tirol (photo: 24.12.2019) |
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| Starting 28.12, fine weather like in the photo of Langschneid in Defereggental is anticipated (photo: 26.12.2019) |
