The first week of the year is going to see two different weather patterns over the continent. On W. Europe, a strong high-pressure system will be positioned between the UK and N. Atlantic, bringing mild and settled weather in Spain, Portugal, Ireland (and western part of the UK).
Instead, on the eastern side of the anticyclone, a deep low pressure system, positioned between Sweden and Finland, will lead very cold air (polar continental with values between -12/-14 °C at 850 hPa (1500 m a.s.l)) to move southward during the week (Figure1) towards central-eastern Europe. In addition, the cold air will cause the formation of a low-pressure system in the Mediterranean Sea (between S. Italy and Greece) which will lead to snow at low levels and (very likely, due to the cold temperatures) along the coast of the Adriatic Sea.
The cold wave should reach the maximum intensity between Thursday and Friday, instead Saturday and Sunday milder air from the Atlantic should move eastward, pushing the cold air towards E. Europe and Russia.
Thus, during the week, the continent will be ‘divided’ in two parts, with temperatures well below 0°C (also during the day) in Scandinavia, Balkans and Central Europe, with snow expected especially between Poland/E. Germany and Czech Republic, and between Serbia and central/northern Greece and central-S. Italy.
Instead, warm temperatures on the west (possible maximum values between 8-11 °C in Ireland and between 16-18 °C in S. Spain/Portugal), with settled conditions in both Spain, France, Ireland and the UK (except for some low clouds close to the coastal areas and valleys).
This morning (Figure1) the weather condition hasn’t changed from the weekend, with a strong temperature gradient between northern- eastern Europe and western-southern Europe. Values well below 0 °C are observed in Scandinavia, Russia and between Romania and the Baltic region, with peaks below -20 °C between Finland and Russia.
Meanwhile, in western Europe and in the Mediterranean region (where a high-pressure ridge is setting from Spain towards N. Atlantic) temperatures are above 10 °C, with peaks of 14-16 °C in Sardinia, southern France and Cyprus. To notice that the high-pressure ridge is causing mild conditions also in Iceland, with observed values well above 0 °C.
Regarding the precipitation, snow at low-levels/plains is observed between Norway and Sweden (mainly in the mainland) and between Poland and the Baltic countries. Some snow (showers) are observed also in the Alpine region and between Czech Republic and Romania (on the Tatra and Carpathians mountains).
The unsettled weather between the Alpine region and E. Europe is due to a cold front related to a low-pressure system moving southward from the Baltic region towards the Balkans. The pressure difference between central Europe and the Mediterranean region is causing strong winds in the Alpine region leading to the fohn effect in N.W. Italy (Figure2); this is leading to drier and milder conditions compared with the previous days.
Regarding the weather for Christmas day, the high-pressure ridge will set between France and the UK, leading the cold air mass (from Scandinavia and the Baltic region) to move southwards towards the Balkans and the E. Mediterranean region.
Thus, tomorrow the weather conditions will see warm temperatures in western Europe (especially between Spain and France and in Ireland), with maximum values above 10 °C (peaks of 15-18 °C are expected in S. Spain). Only between N. France, English Channel and Belgium (where fog/low clouds are possible) lower temperatures are expected.
Instead, moving eastward, the cold air will cause a decrease in temperatures in the Alpine region, in Italy (especially along the Adriatic coast) and E. Europe. However, the lowest temperatures are expected mainly in the Balkans, with maximum values close or below 0 °C between Romania, Bulgaria and Serbia. Also in Greece will be cold, with values below 10 °C mostly everywhere (except in Crete and Peloponnesus).
Most of the precipitation will occur this evening, when the cold front will be more active (and temperatures will still be slightly above 0 °C at low-levels), thus snow is expected mainly on the mountainous areas in E. Europe. However, during the night and tomorrow morning, the decrease in temperatures might lead to snow at low-levels/plains in the mainland between Romania, Bulgaria, Hungary and Serbia.
Finally, in Scandinavia, Baltic regions and Russia the weather conditions will still see low temperatures and some snow at low-levels/plains is expected between Poland, Belarus and Ukraine, as well as between Finland and N. Russia and in W. Norway.
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).
If we look at the minimum temperatures of this morning across Europe (Figure1), we can see how most of Central-Western Europe is observing minimum values well above 0°C (that this, almost 10 °C above the average in some areas between central Europe and S. Scandinavia).
Only in the Balkans, Russia and central-northern Scandinavia negative temperatures are observed, though with values still above the average (minimum temperatures below -10 °C are pretty normal in Russia and central Scandinavia at this time of the year, but these values are observed only between Lapland/ N. Sweden and N. Norway).
Very mild especially across the central-western Mediterranean region with values between 10-15 °C in central-southern Italy, eastern Spain and S. France. Colder, instead, in Greece with temperatures below or close to 0°C.
These temperatures are closer to the average of November than of December, and especially in W. Europe all the first week of December has been mild, with maximum values close to 20°C in the Mediterranean region. This was due to a high pressure system positioned on the western Mediterranean region, which has driven mild air from N. Africa/ mid-Atlantic towards W. Europe.
However, the weather condition (especially in Central Europe, Alpine region and S. Scandinavia) is going to change from this weekend due to an arctic maritime air mass which will move southwards on the eastern side of a high pressure ridge positioned between Spain (where mild conditions are expected) and the UK (Figure2).
The arctic air is visible from the satellite imagery of this morning (see the scatter clouds on the N. Sea, Figure3) and is moving southward due to a deep low pressure system positioned on the N. Sea between the UK and Norway. The strong pressure gradient between central-northern Europe and the Mediterranean region is causing fohn (a dry and warm wind) in N. Italy, with bright skies and mild temperatures. Finally, the high-pressure system is still positioned west of Spain and Portugal, causing settled and mild weather in the western Mediterranean region.
The arctic air mass will cause a decrease in temperatures, and snow at low levels especially in Central Europe and Scandinavia. However, it won’t be a relevant episode, but simply a way back to the average temperatures values for December. So, in the next week, no cold waves are expected and temperatures will be mostly close to average (or slightly below), but it will feel ‘colder’ due to the drop in temperatures compared with the previous week.
If we look at the minimum temperatures observed this morning in Europe (Figure1), it is clear how the coldwave has reached, from Russia/Ukraine, the Balkans, Central Europe and Northern Italy.
The lowest values are observed between Ukraine and Russia (-10/-12°C) and between Germany and Poland (-6/-8 °C). Temperatures close to (or slightly below zero) are observed also in eastern France, Po valley and Balkans.
The cold air will move westward during the day towards the UK and the Atlantic, instead still mild conditions are expected in Spain, Portugal, southern Italy and Greece. To notice how Scandinavia and Iceland, but also the Baltic states see very mild conditions (compare with the observed average for these areas), with 10-12°C observed in Iceland.
The mild conditions in Northern Europe are explained by the high-pressure system positioned over Scandinavia (Figure2), which causes cold air (Continental) from Russia to move towards the west and mild (Tropical) air from the low-mid Atlantic to move towards Iceland and Scandinavia. This condition should last for other 3/4 days.
Regarding the weather conditions (Figure3), bright conditions are observed in Central Europe and in the UK, instead more clouds with rainfall/ snow between Poland, Belarus and Russia due to the occluded front moving southwards (Figure2). Rainfall is observed also in south-east Europe (mainly Greece) and southern Italy. Finally, a long band of clouds is positioned on the Atlantic, from Iceland to Spain. This is the area between the continental (and drier) air coming from the east and the warmer (and moist) air on the Atlantic. This is causing some rainfall between Spain and Portugal and overcast conditions west of Ireland.