Rising avalanche danger due to fresh snow+wind
During the last week, uninterrupted low avalanche danger prevailed throughout the European region Tirol-South Tirol-Trentino. All in all, including 17 January, it lasted for eleven days. On 18 January avalanche danger will increase somewhat as a cold front passes through. Winter sports enthusiasts then need to exercise caution towards new snowdrift accumulations. They will be easiest to disturb on W/NW - N - E/NE facing slopes, since the snowpack surface there is loose and riddled with loosely packed snow crystals beneath thin crusts. These can prove a possible weak layer for the freshly generated snowdrifts. Intermediate altitudes will be the focus, including sparsely wooded, steep forest areas and wind-protected slopes at high altitudes; but also very steep ridgeline slopes. In the northern regions where precipitation will be heavier (current forecast: up to 25 cm) potential danger zones will occur more frequently than in southern regions, with less snowfall.
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| Once again a picture-perfect week of beautiful weather and low avalanche danger. Central East Tirol (photo: 13.01.2020) |
Short weather overview and forecast
Last week was marked by high-pressure weather conditions and unseasonably mild temperatures. Most striking was the dryness of the air, accompanied by strong southerly winds, observed particularly in classic foehn lanes along the Main Alpine Ridge. The high-pressure front will last until Friday, 17 January, and be replaced by a cold front on 18 January. This will bring some snowfall throughout the land and lower temperatures more typical of January. Subsequently, according to ZAMG Weather Service forecasts, a new high-pressure front will reestablish itself.
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| One of the weather stations where a great deal “happened” - located in a classic foehn lane where strong winds were blowing. Something else unusual: the extremely dry air masses on 12-14 January. |
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| Forecast for snowfall expected by Saturday 4:00 pm |
Below-average snow depths for the season in some places
Current snow depths (maxima, minima, medium values) show that in northern regions the snow depths are below average for this juncture of the season, in southern regions snow depths are slightly above average, compared to long-term measurements.
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| The magenta-colored line shows the current snow depth for the observer in Ausserfern. It is below average. |
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| After way-above-average snow depths in November, only slightly-above-average currently in southern East Tirol. |
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| Bare ground on the valley floor, snow in the mountains. Axamer Lizum (photo: 14.01.2020) |
The snowpack and its layering
As mentioned in the last blog, snow quality steadily deteriorated during the long period of fine weather. At high altitudes it showed extraordinary wind impact, on sunny slopes and at low altitudes melt-freeze crusts more or less capable of bearing loads, in wind-protected shady terrain very loosely-packed crystals (expansively metamorphosed). Beneath the crusts were frequently loose crystals, less on sunny slopes up to high altitudes. The snowpack was moist down to deep layers as a result of the relatively high temperatures. The situation there resembled conditions in springtime.
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| Heavy wind impact left its marks on the snowpack in glaciated terrain. Possible danger of falling due to hardened surfaces throughout Tirol. Grossglockner (photo: 15.01.2020) |
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| Wind “sculpted” its works of art, often leaving behind rough hewn snowpack surfaces. Defereggental (photo: 16.01.2020) |
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| Conditions like in springtime on steep south-facing slopes. (photo: 10.10.2020) |
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| Joys of corn snow at 2700 m in mid-January. East Tirol (photo: 15.01.2020) |
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| Widespread: melt-freeze crusts. Defereggental (photo: 16.01.2020) |
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| “Burled powder” composed of expansively metamorphosed crystals adjacent to thin melt-freeze / wind crusts in shady terrain at 2000 m. (photo: 16.01.2020) |
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| Good tour planning helps to target the good backcountry snow. Silvretta (photo: 10.01.2020) |
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| On the banks of streams, large surface hoar crystals can be found. (photo: 09.01.2020) |
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| Typical profile of heavily wind-influenced shallow snow: hard wind crusts, a layer of loosely-packed crystals beneath them. |
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| Wherever loose snow is on the surface, the least favorable situation occurs as soon as fresh snow is deposited on it. |
Further profiles can be viewed
here.
Avalanches last week
Things were very tranquil...
Rockfall misinterpreted as an avalanche
An interesting tidbit about an ‘avalanche’ which released near the Madlenerspitze in the Silvretta. Alpine Police research showed that a rockfall had swept along some snow and buried parts of a path. No persons were involved.
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| Rockfall near Madlenerspitze. (photo: 10.01.2020) |
Fresh snowdrifts - a brief concern over limited zones
Strong winds in the foehn lanes along the Main Alpine Ridge generated mostly small-sized (but trigger-sensitive) snowdrift accumulations. Danger zones easily recognizable and not widespread.
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| Wind in Gschnitztal (photo: 13.01.2020) |
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| A small, skier-triggered avalanche due to fresh snowdrifts in Gschnitztal (photo: 13.01.2020) |
Gliding slides and glide-snow avalanches
In isolated cases, glide-snow avalanches were also observed.
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| For the most part, there was not much activity near glide cracks. (photo:12.02.2020) |
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| Glide cracks in the snowpack: potential danger of glide-snow avalanches. East Tirol Tauern (photo: 10.01.2020) |
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| Great snapshot: gliding snow including dynamic slide. (photo: 14.01.2020) |
Otherwise notable:
Yesterday, 15 January, Austria’s highest wind station was installed at the Adlersruhe below the Grossglockner. It is already delivering data.
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| Technicians install weather station at Adlersruhe. (It was mistakenly reported that it cost several hundred thousand euros. Actual costs amounted to €10,000). (photo: 15.02.2020) |
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| Data from the new Adlersruhe weather station |
