...
PDFs for the latest extended range forecast (the diagram is updated every Monday and Thursday). Each panel shows the PDF of the same forecasts valid for four subsequent weeks.
Further reading:
Ferranti L, Magnusson L, Vitart F, Richardson DS. How far in advance can we predict changes in large-scale flow leading to severe cold conditions over Europe?
Q J R Meteorol Soc 2018;144:1788–1802. https://doi.org/10.1002/qj.3341