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).