Looking at the temperatures observed this morning (Figure1), we can see how the values are quite different between W. Europe and Russia. On the Atlantic coast and western Mediterranean region (UK, France, Spain and central/southern Italy) very mild temperatures are observed with values between 10-15 °C in N.W. Spain, most of France and S. England. This mild condition is due to Tropical maritime air (coming from mid- Atlantic) moving on the northern side of a high-pressure system positioned between Spain and N. Africa (Figure2).
The mild air is moving eastward, and temperatures are increasing also in the Alpine region and in the Balkans. On the other hand, between Germany and Scandinavia a low pressure system (moving eastward) is causing unsettled and windy conditions in these areas.
In addition, very cold air (coming from Siberia) is moving westward between the northern side of the low-pressure system and the western side of an anticyclone positioned close to the Ural mountains (Russia). The minimum values in Scandinavia and Russia are between (-10/-20 °C) with peaks of -25 °C in some places. However, these temperatures are quite normal for this time of the year and especially in Scandinavia, December has observed mostly positive temperature anomalies; thus, there is nothing exceptional in the observed values.
These conditions are not going to change until the next week. Indeed, a strong anticyclone is going to set between Spain and the UK bringing settled weather and mild temperatures in Western Europe especially on Christmas day. Instead, on the eastern side of the anticyclone, the cold air (now positioned between Scandinavia and Russia) should move southwards towards the Balkans and Greece, decreasing the temperatures and causing snow at low-levels in some areas (although temperatures are not expected to reach the same values observed these days in Russia).