Lots of fresh snow and wind. High avalanche danger!
Over the last few days there has been snowfall in far-reaching parts of Tirol, focal point in the northwestern regions. Since Sunday, 14 March, about 100 cm of fresh snow has been registered there, more from place to place. In addition, strong-velocity winds were blowing amid unseasonably low temperatures. All in all, a combination which heightened dangers significantly. We currently assess avalanche danger above the timberline from Silvretta over Lechtal Alps to the Karwendel and in northern East Tirol as high .
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| 72-hr difference in snow depths. Most snow fell in northern / northwestern regions and in northern East Tirol (in southern Ötztal, depiction is erroneous). |
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| Beginning Sunday, 14 March, persistent, sometimes heavy snowfall, intermittent storm-strength winds. Days prior to that: variable conditions. Jöchelspitze station (Allgau Alps region) |
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| Front-runner in precipitation (typical in this weather scenario): Alplhütte station, Mieming Massif (Hydrographie Tirol) |
During the next couple of days, additional snowfall is expected. The distribution of precipitation will resemble that of the just completed period of snowfall.
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| 48-hr fresh snow forecast (Tuesday, 16.3, 7:00 am until Thursday, 18.3, 7:00 am) |
Problem zones: uppermost snowpack layers
As referred to in the letzten blog potential weak layers for slab avalanches can currently be found in the uppermost layers. On the one hand these are superficial layers near a recently blanketed-over old snowpack surface; on the other, potential weak layers inside the mass of fresh fallen snow.
Potential weak layers near surface of old snowpack
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| Blue: zones with a crust-sandwich due to variable weather starting Friday, 5.3. Potential weak layers in the old snow are located between the crusts. Orange: zones with older, loose powder as potential weak layer. |
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| Snow profile 2440m, SE, 23°; Weisskugel Massif. Relevant: uppermost layers. Top layer, crust, beneath that loose faceted crystals (profile from 12.03.2021) |
Potential weak layers inside the fresh snow mass
Loose powder and/or graupel can also constitute a weak layer for slab avalanches when it gets blanketed-over by drifts. For example, it is conceivable that during a short phase with little wind (visible in the Jöchelspitze graph above) loosely-packed fresh snow is deposited, subsequently added to by further snowfall with increasing wind impact, then gets blanketed-over by snowdrifts. Equally conceivable: massive graupel deposits during the snowfall. Both weak layers are short-lived, but merit close attention over the next few days.
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| Observable in far-reaching parts of Tirol: graupel inside the fresh snow. It only becomes a problematic weak layer when massively deposited. Mieming Massif (photo: 15.03.2021) |
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| Currently important at heightened altitudes: massive wind impact leads to wide-ranging snow transport. Northern East Tirol (photo: 14.03.2021) |
Caution in regions where snowfall was heaviest: increasingly frequent glide-snow at low altitudes.
At low altitudes (on sunny slopes at least up to intermediate altitudes): bare ground. There, in regions where heavy precipitation has been registered, more frequent glide-snow avalanches can be expected.
Loose-snow avalanches in extremely steep terrain
In springtime, solar radiation is already quite intense. As soon as the sun reappears (including diffuse light) the snowpack surface will rapidly become moist. We then expect increasingly frequent loose-snow avalanches on extremely steep slopes.
The smart approach: defensive conduct
Currently there is little information being supplied from backcountry terrain. We assume that some large-sized slab avalanches are triggering naturally during this period of snowfall. Winter sports enthusiasts need to act defensively when they are in backcountry where snowfall has been heavy. Rule of thumb: circumvent fresh snowdrifts in steep terrain for the moment. An update on the situation will be published on coming Thursday, 18 March 2021 at latest.
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