While the north-western Alps are drowning in snow, there is no sign of winter in the lowlands. January temperatures are often around 5 degrees above the long-term average and it has only seriously snowed above around 600 meters so far. There seems to be no end in sight to the wet and mild westerly slide - or is there?
Masses of snow due to westerly conditions
Since mid-December, a strong north-westerly flow has been transporting one disturbance after another directly from the Atlantic to Europe. During the last week in particular, this has caused so much snow that reports of "winter chaos" and avalanche danger in Austria have even made it into the daily news. The temperature sensors of one or other measuring station, which are normally installed around 3 m above the ground, were or are snowed in and spectacular images of immense snow drifts are making the rounds.
Not since 1999 have there been similar amounts of fresh snow over such a short period of time, resulting in road closures, cut-off villages, valleys and entire federal states (Vorarlberg could not be reached from any side at short notice). Avalanche warning level 4 for four consecutive days was also last seen in the avalanche winter of 1999. In general, the current weather situation is very similar to that of February 1999 (catastrophic avalanche in Galtür), only it was colder then.
Possible polar vortex split and change in the general weather situation
The next cold front is due tomorrow (Friday, 13.1.12). This time, however, the north-east will be ahead in terms of fresh snow. An increasingly strong wedge is developing upstream (west) of the low belonging to the front, which should bring us bright weather at the weekend, especially on Sunday.
The wedge, in combination with advancing stratospheric warming, is causing a potential change in the circulation pattern. The westerly flow is blocked and disturbances from the Atlantic are deflected to the north or have to sneak into Europe far to the south. The polar vortex increasingly loses its previously quite uniformly round shape and becomes an irregularly billowing structure with two distinct cold poles separated by a high-pressure bridge between our wedge and one over Siberia.
This means that Europe will be influenced by colder air masses from the east, which, in contrast to the mild Atlantic air, should also provide a winter feeling in the lowlands. Masses of fresh snow to add to the cold are not in sight for the time being, and it is unlikely to snow heavily again until the middle/end of next week at the earliest, but as usual, this is all still in the realm of the crystal ball.
