Current situation and trend
The April weather persists:
Current unstable and (for backcountry skiers) infelicitous weather conditions will persist for a bit. Nonetheless, a marked change is about to take place in air masses, according to forecasts of ZAMG: the southerly foehn system is expected to collapse on Friday, 26 April. A cold front will then take its place and spread throughout Tirol from the west. Subsequently, winds will taper off and precipitation will set in, as rainfall up to nearly 2500 m to start with, but then the snowfall level will descend to about 1800 m. Following that outburst, unstable April weather is expected to continue.
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| Conditions were perfect til Easter Monday. As of 23 April, barrier cloud in the south, accompanied by storm-strength winds. |
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| A striking southerly-foehn scenario |
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Effects of southerly-foehn scenario on the snowpack: massive melting
together with deeper snowpack at high altitudes along Main Alpine Ridge |
The snowpack is becoming wetter and more prone to triggering:
Intense warmth, diffuse radiation, moist air masses - those are the ingredients which make the snowpack wetter. This is occurring in all aspects, but fascinatingly enough, primarily on shady slopes. There, the snowpack has become deeply wet mostly up to intermediate altitudes, but this level is now extending up to high altitudes where (unlike on sunny slopes) there has not yet been any water-seepage, i.e. any re-freezing cycle, that makes the snowpack sluggish. The consequence is heightened proneness to triggering of the snowpack on shady slopes in particular. Due to the rainfall forecast to start tomorrow (Friday, 26 April) this will be amplified a further notch.
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At low and intermediate altitudes, the snowpack is already transforming to
sluggish “summer-firn” snow. Allgäu. (photo: 24.04.2019) |
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Visible increasingly often: a water-soaked snowpack surface.
appx. 2000 m, north, Main Alpine Ridge. (photo: 23.04.2019) |
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Snow profile on a shady site, exposed to wind all winter long. North, 2340 m. The snowpack is isotherm.
Beneath a crust, depth hoar and faceted crystals were able to be triggered in our snowpack analysis. |
Increasing avalanche activity:
The heightened trigger sensitivity of the snowpack as a result of progressing water seepage into the snow also has an effect on avalanche danger: in some regions, danger level 3 - “considerable” - is being reached. We are observing increasingly frequent avalanches, following a period of remarkable calm. Not only loose-snow and glide-snow avalanches, but gradually also isolated naturally triggered slab avalanches are being registered, the latter primarily on shady slopes.
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The startlingly large expanse of a naturally triggered slab avalanche at this altitude (1900 m). North-Northwest.
Areas
of Untere Gamswaid near Bach in Ausserfern. In the background,
loose-snow avalanches as the trigger mechanism of the (entire?) slab.
(photo: 24.04.2019)
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| A slab triggered by an avalanche explosion displaced the Kaunertal Glacier Road. (photo: 21.04.2019) |
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Relatively fresh loose-snow avalanche in shady terrain.
Altitude zone around 2500 m. North. Northern Stubai Alps. (photo: 24.04.2019) |
Currently it is possible to observe the ways in which tiny impulses can unleash huge effects.
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This small glide-snow slide swept the thoroughly wet snow into the plummet path.
In the next photo, the plummet path can be seen with avalanche deposit. Silvretta. (photo: 23.04.2019) |
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| The avalanche that goes with the picture above. (photo: 23.04.2019) |
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| Ice chunks from a frozen waterfall as trigger of a wet loose-snow avalanche. Silvretta. (photo: 23.04.2019) |
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| Deposit of a glide-snow avalanche below Gorfenspitze in Paznauntal, triggered about 3:00 pm on 24.04.2019 |
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| Heightened activity of glide-snow avalanches also in Zillertal (photo: 24.04.2019) |
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| The avalanche deposits belonging to the photo above. Recognizable: avalanches can extend all the way to green zones. Zillertal Alps. (photo: 24.04.2019) |
Some other items of interest:
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| Observable in concavities: sand/dust from the Sahara. Silvretta. In the regions subjected to precipitation along the Main Alpine Ridge and in East Tirol, the Sahara stuff was deposited regularly over wide areas. (photo: 23.04.2019) |
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| Snowfall at low altitudes? Or the flight of pollen from willows as a result of foehn wind? Inn Valley. (photo: 21.04.2019) |
