The northern congestion was short-lived and we are falling back into a south-westerly situation that is quite impressive: While there are warnings of heavy snowfall and high to even very high avalanche danger on the southern slopes of the Alps, the north can expect foehn-like mild swamp.
Initial situation
The polar vortex has a dipole-like structure with a center over northeastern Canada and a second center over Siberia. The Canadian cold air center induces the development of storm lows that start from the east coast of the USA into the Atlantic. We've seen this all before this winter, including the extremely low temperatures and massive snow events in parts of North America that don't normally get this. However, the current over the Atlantic is not a pure westerly flow, but is somewhat wavy due to a developing wedge in the western Atlantic, so that the south-westerly component is increasing. Between the two low pressure centers there is a powerful high pressure system that stretches over Russia and Scandinavia far to the north. This high is blocking the Atlantic current. A pronounced low on the western flank of the wedge cannot move any further east and has to move south. The trough extends across the Iberian Peninsula into the Mediterranean region and, as we know, we are dealing with waves, so the Alps are right in the line of fire on the front side of the trough as a kind of breakwater. Our colleague Orakel has already explained what this means for the south in terms of snow.
Foehn in the north, heavy precipitation in the south
"I'm so cold, I'm not used to it anymore!" - WeatherBlog has heard these and similar comments time and again over the last few days. The problem of normal January cold should now be a thing of the past. Before we get used to the cold, the Föhn will return in time in the north and ensure a continuation of the previous mild winter, at least where it makes it into the valleys to clear out the cold air close to the ground. In the south, it is (and remains) not excessively cold, but wet. A comparison of the climate diagrams of Innsbruck and Loibl in the Karawanken clearly shows the contrasts of the last few weeks. In terms of precipitation, Innsbruck is miles behind Loibl. In terms of the long-term average, the precipitation balance in Innsbruck is also clearly negative, but in Loibl even the long-term extreme values are clearly exceeded in the second half of January, not to mention the January average.
With the exception of the last few days, it has been warmer than average at both locations, with the 5-degree mark often being exceeded in Innsbruck thanks to the Föhn wind. If anyone now thinks that 5 degrees actually feels rather chilly, please bear in mind that this is the daily average temperature, not the daily maximum. December was already 1.5°C warmer than the long-term average throughout Austria, and in the higher regions it was even 3.1°C warmer than usual. If we now look at the course of January, February would have to develop an almost arctic character in order to reach a "normal" meteorological winter (= December, January, February) in terms of temperature. In view of the current situation, this is not to be expected for the time being, because as our colleague Orakel has already indicated ("never change a dumping system"), the current situation tends to maintain the system.
