Lots of snow in the south
Following a week of highly variable conditions with some snowfall, sunshine, varying wind impact and low temperatures, it’s time to concentrate on the forecasts of the ZAMG Weather Service for the coming days: Tirol will increasingly be caught in the grips of a southerly airstream. Large amounts of precipitation in southern regions and strong to storm-strength southerly winds can be expected.
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| In southern regions, immense precipitation is anticipated. |
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| Winds have already shifted to some extent, are blowing at strong-to-storm strength in the classic foehn lanes. |
For that reason, a warning of heavy snowfall in Tirol’s mountains between Friday, 01.02 at 9:00 am and Saturday 02.02 at 6:00 pm was published by the ZAMG Weather Service.
“The axis of the precipitation will be all of East Tirol and the Zillertal Alps, the focal point is in the mountains of Defereggen, Carnic Ridge, Lienz Dolomites and Schober group. In the East Tirolean Gailtal and bordering Lesachtal, 100-150 cm of fresh snow is expected; in Hohe Tauern and Zillertal Alps 75-100 cm; and between the Brenner mountains and the rear Ötztal 50-75 cm. According to current forecasts, the snowfall level will be at low lying areas in East Tirol throughout the major period of precipitation until Saturday afternoon. It is likely that between 800 and 1500-1800 m, isothermic conditions of 0 degrees will prevail. Wet snow in low lying areas will be the consequence. On Saturday night, the precipitation will calm significantly, and subsequently temperatures will drop measurably.”
Prior to massive precipitation, it is always important to have a look at (and inside) the snowpack. The distribution of snow depths in Tirol is subject to a striking north-south curve: lots of snow in the north, (very) little in the south.
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| Analysis of the overall snow depths in Tirol: in the central and southern parts of East Tirol there has been very little snow to date. As of tomorrow, 01.02.2019, that is where the brunt of the snowfall is expected. |
If you look at the snowpack structure, a marked north-south curve jumps into view. In the northern regions, a generally densely-compacted snowpack is prevalent, the weak layers “only” on the surface. In the southern regions, on the other hand, there are several potential weak layers for slab avalanches inside the shallow snowpack.
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| Snow profile Thurntaler - Unterwalder Alm on 26.01.2019. NE; 2200 m; 35 degrees. The arrows point to the most significant weak layers in the snowpack: depth hoar lies embedded between hard crusts. Near to the upper surface there is loosely-bonded decomposed snow and surface hoar. (profile: Bernhard Grüner) |
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| Snow profile in the eastern Deferegger Alps (Blitz Schupfe); south, 2200 m; 31 degrees. The faceted crystals between crusts are relatively well bonded here. A stability test showed no fracture. Only avalanches close to the uppermost surface are likely here. (profile: Daniel Kleinlercher on 24.01.2019) |
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| View into the snowpack near Golzentipp in the Lienz Dolomites region: surface hoar atop a thin mass of fresh snow, beneath that a melt-freeze crust, beneath that faceted, loosely-bonded crystals: surface hoar and faceted crystals constitute two potential weak layers for slab avalanches in case of further loading. (photo: 27.01.2019) |
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| Snow profile on Carnic Ridge in the Lienz Dolomites region. Easily distinguishable through colors: fresh snow and beneath that, weak old snow. (photo: 31.01.2019) |
Particularly in the central and eastern parts of East Tirol, we are faced with a quite widespread old-snow problem at various altitudes and in various aspects. As potential weak layers, loosely-bonded, faceted crystals and depth hoar are the foremost candidates. In the region of the Lienz Dolomites, the old-snow problem begins on shady slopes above approximately 1200 m, in eastern and western aspects above about 1600 m, in southern aspects above about 2000 m.
In the central part of East Tirol, the most endangered area lies between about 1800 and 2500 m in W/N/E aspects. (Special caution is urged also at the edges of forested areas below 1800 m.) On south-facing slopes, in addition, beneath a thin, surficial melt-freeze crust which formed in mid-January, a thin, faceted weak layer formed within a quite narrow altitude band on very steep south-facing slopes at about 2300-2500 m. (The latter was also observed in other parts of Tirol.)
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| Observed with increasing frequency: due to the danger pattern cold-on-warm (dm.4) a loose layer of faceted crystals has been forming beneath a melt-freeze crust since mid-January at altitudes between about 2300 and 2500 m on very steep south-facing slopes. (In this profile in the northern Stubai Alps at 2730 m, south, 38 degrees, no fracture has yet propagated inside the faceted layer.) (profile: Lukas Ruetz am 25.01.2019) |
In addition, the snowpack surface, except on very steep, sunny or wind-impacted slopes, largely consists of loosely-bonded, cold fresh snow. There is also widespread covered surface hoar, excluding in heavily wind-impacted terrain where it has been windswept.
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| In every place where the snowpack surface was not impacted by the wind or by the sun, there is cold, loosely-bonded powder snow or, as seen in this photo, surface hoar. The surface hoar has been covered by some fresh snow in many places. (photo: 25.01.2019) |
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| Fresh snow from the beginning of the week (27-28 January) cloaks central and southern East Tirol in wintery garb. (photo: 29.01.2019) |
Weak layers near the surface further to the north
If we cast a glance further north, we observe a quite favourably layered old snowpack over widespread areas. (Only in the central Stubai Alps are there persistent deep weak layers in some places. In the interim, however, they are probably triggerable only in highly unfavourable conditions.) Nevertheless, in the northern regions there are weak layers near the upper surface in the form of cold, loosely-bonded powder snow, surface hoar or light-fluffy snow. Due to the wind impact, which occurred often during the week, at least at high altitudes, this snow was transported, so that area-wide, cohesive, loosely-bonded layers become more and more seldom with ascending altitude. This means that atop these weak layers, large-scale slab avalanches will be the exception rather than the rule. (Caveat: regions which have been wind-protected until now, e.g. sparsely wooded zones, are excluded.)
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| Loosely-bonded, cold snowpack surface in the southern Ötztal Alps (photo: 29.01.2019) |
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| A loosely structured snowpack surface in Kelchsau in the Kitzbühel Alps (photo: 27.01.2019) |
Consequences
Fresh snow accompanied by strong-to-stormy winds transporting the snow will burden the snowpack measurably. Accordingly, avalanche danger will increase rapidly in the regions where precipitation is heaviest and will increase to “high” at latest on Saturday, 2 February. We expect numerous naturally triggered avalanches. These will be most frequent in the regions which have remained wind-protected to date, e.g. in sparsely wooded areas at the timberline or cliff bowls which have been protected from wind until now. The largest avalanches, comparatively, will take place in NW to N to NE aspects. Due to the shallow snow depths overall, extremely large-sized avalanches are not expected.
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| View from Golzentipp towards the south, the ridge on the Italian border and the region where the greatest amounts of snowfall are anticipated in coming days. We expect not only high activity of naturally triggered slab avalanche, but also the largest-sized avalanches. (photo 27.01.2019) |
Since the snowfall will be moist up to approximately 1800 m, we will also be confronted with increasingly frequent glide-snow avalanches. These could glide over steep, grass-covered slopes and put exposed transportation routes at risk in some spots.
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| Glide-snow avalanches on steep, grassy slopes, particularly wherever there has been heavy snowfall and the snow is wet or where there has been heavy rainfall into the snowpack. Zillertal. (photo: 19.01.2019) |
Caution is also urged towards trees which fall over due to the burden of snow on the branches, or branches which break off under the weight of snow.
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| Apart from the danger of avalanches in the regions where snowfall has recently been heavy, this is also a risk... Stubaital (photo: 30.01.2019) |
For participants in winter sports, extremely treacherous and highly dangerous conditions prevail in the regions where snowfall has recently been heavy.
Further to the north, where there is less snowfall, restraint is also urged. Snowdrift accumulations continue to be highly trigger-sensitive, can be unleashed by one sole skier. The above-described area-wide distribution of a weak layer near the upper surface is here the case with regard to wind impact to date.
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| Strong to storm-strength winds will also transport much snow over the next few days, generating some dangerous snowdrift accumulations. Tux Alps (photo: 27.01.2019) |
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| In the Kitzbühel Alps over the last few days, several avalanches were triggered by skiers in the weak layers near the upper surface, e.g. surface hoar. (photo: 27.01.2019) |
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| Shooting cracks, as in photo in the Tux Alps, indicate a snowpack which is prone to triggering: snowdrifts atop surface hoar or loosely-bonded, cold powder. (photo: 25.01.2019) |
Review
This last week 24.01.-31.01.2019
As already mentioned, this last week has been highly varied. Whoever planned the tour carefully was able to enjoy lots of sunshine and rather good conditions, depending on selected terrain.
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| In a nutshell: variable. Station Puitegg in the Mieminger Massif |
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| Repeated bouts of snowfall in Tirol |
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| Unexpected masses of snow (up to 60 cm) over limited terrain near Kelmen in Ausserfern. (a precipitation cell of just a few kilometers probably due to a convergence) (photo: 29.01.2019) |
This last month: January 2019
The month of January 2019 will go down in history with a few medals, according to the ZAMG Weather Service:
Northern regions registered above-average amounts of snowfall (about 150% of the average). It was one of the ten heaviest-precipitation months of January in the last 160 years. The 15-day overall sum of fresh snow between 1 and 15 January was record-breaking in some places, e.g. amounted to 451 cm in Hochfilzen. This corresponds to an event which takes place even more seldom than once in 100 years. In the south (southern regions of East Tirol) on the other hand, only 20% of the mean amount of snowfall was registered this month.
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| Precipitation in January 2019: comparison with precipitation average 1981-2010. One hundred percent corresponds to the average. Evaluation with SPARTACUS data through 20.01.2019. (source: ZAMG) |
Viewing temperatures, it was also a cold January. In the mountains it was the coldest January for more than 30 years. The lowest temperature measured in Tirol was on 11.01.2019: -25.5°C at 3437 m on the high Brunnekogel of the Pitztal Glacier.
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| Temperatures January 2019: divergencies from average temperature 1981-2010. Evaluation with SPARTACUS data through 29.01.2019 (source: ZAMG) |
